ĐẠI HỌC QUỐC GIA HÀ NỘI TRƯỜNG ĐẠI HỌC KHOA HỌC TỰ NHIÊN ĐÀO THỊ HƯỜNG ỨNG DỤNG CÁC PHƯƠNG PHÁP PHÂN TÍCH QUANG PHỔ HIỆN ĐẠI NGHIÊN CỨU ĐẶC TÍNH HẤP PHỤ CỦA KHÁNG SINH HỌ FLUOROQUINOLONE TRÊN NHƠM OXIT BIẾN TÍNH BẰNG POLYME MANG ĐIỆN LUẬN VĂN THẠC SỸ KHOA HỌC Hà Nội - 2020 ĐẠI HỌC QUỐC GIA HÀ NỘI TRƯỜNG ĐẠI HỌC KHOA HỌC TỰ NHIÊN ĐÀO THỊ HƯỜNG ỨNG DỤNG CÁC PHƯƠNG PHÁP PHÂN TÍCH QUANG PHỔ HIỆN ĐẠI NGHIÊN CỨU ĐẶC TÍNH HẤP PHỤ CỦA KHÁNG SINH HỌ FLUOROQUINOLONE TRÊN NHƠM OXIT BIẾN TÍNH BẰNG POLYME MANG ĐIỆN Chun ngành: Hóa phân tích Mã số : 8440112.03 LUẬN VĂN THẠC SỸ KHOA HỌC NGƯỜI HƯỚNG DẪN KHOA HỌC: TS PHẠM TIẾN ĐỨC PGS.TS NGUYỄN VĂN RI Hà Nội – 2020 LỜI CẢM ƠN Với lòng biết ơn sâu sắc, em xin trân trọng cảm ơn TS Phạm Tiến Đức PGS.TS Nguyễn Văn Ri giao đề tài tận tình hướng dẫn, bảo để em hoàn thành luận văn Em xin chân thành cảm ơn thầy cô môn Hóa phân tích, anh, chị, em bạn phịng thí nghiệm Hóa phân tích ln nhiệt tình giúp đỡ em suốt trình thực luận văn Em gửi lời cảm ơn đến gia đình, bạn bè, bạn sinh viên học viên nhóm phân tích người thân u tạo điều kiện giúp đỡ em suốt thời gian học tập hoàn thành luận văn Hà Nội, ngày tháng Học viên Đào Thị Hường năm 2020 MỤC LỤC CÁC KÝ HIỆU VIẾT TẮT DANH MỤC CÁC BẢNG DANH MỤC CÁC HÌNH MỞ ĐẦU 10 CHƯƠNG TỔNG QUAN 12 1.1 Giới thiệu nhôm oxit 12 1.1.1 Cấu tạo tính chất nhơm oxit 12 1.1.2 Điều chế nano nhôm oxit 13 1.1.3 Ứng dụng nano nhôm oxit 17 1.2 Giới thiệu polyme mang điện 18 1.2.1 Polystyrene sulfonate (PSS) 18 1.2.2 Poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (PAMPS) 20 1.3 Giới thiệu kháng sinh fluoroquinolone 22 1.3.1 Các phương pháp phân tích CFX 24 1.3.2 Phương pháp xử lý CFX 26 CHƯƠNG NỘI DUNG VÀ PHƯƠNG PHÁP NGHIÊN CỨU 29 2.1 Đối tượng nghiên cứu 29 2.2 Mục tiêu nghiên cứu 29 2.3 Nội dung nghiên cứu 29 2.4 Thiết bị, dụng cụ, hóa chất 30 2.4.1 Thiết bị 30 2.4.2 Dụng cụ 30 2.4.3 Hóa chất 30 2.4.4 Pha chế hóa chất 31 2.5 Phương pháp nghiên cứu 32 2.5.1 Phương pháp tổng hợp nhôm oxit 32 2.5.2 Điều chế polyme PAMPs 32 2.5.3 Quá trình biến tính nano nhơm oxit polyme mang điện 33 2.5.4 Quá trình xử lý kháng sinh CFX thuộc họ fluoroquinolone 33 2.5.5 Phương pháp nghiên cứu đặc tính hóa lý vật liệu nano nhơm oxit 34 2.5.6 Phương pháp UV-Vis nghiên cứu biến tính hấp phụ 37 2.5.7 Phương pháp đo tổng nito 38 2.5.8 Phương pháp khối phổ cao tần cảm ứng plasma (ICP-MS) 38 2.5.9 Lấy mẫu, tiền xử lý bảo quản mẫu nước thải bệnh viện 38 2.5.10 Phương pháp xử lý số liệu 39 2.5.11 Cơ chế hấp phụ 40 CHƯƠNG KẾT QUẢ VÀ THẢO LUẬN 44 3.1 Xây dựng đường chuẩn cho xác định CFX phương pháp UV-Vis 44 3.1.1 Chọn bước sóng đo phổ 44 3.1.2 Xây dựng đường chuẩn 45 3.2 Đặc tính hóa lý vật liệu hấp phụ 46 3.2.1 Đặc tính hóa lý nano α-Al2O3 46 3.2.2 Đặc tính hóa lý polyme PAMPS 49 3.3 Khảo sát trình biến tính vật liệu nano α-Al2O3 polyme mang điện 52 3.3.1 Khảo sát biến tính vật liệu nano α-Al2O3 PSS 52 3.3.2 Khảo sát biến tính vật liệu nano alpha nhơm oxit PAMPs 54 3.3.3 Đánh giá q trình biến tính vật liệu nano alpha nhôm oxit polyme mang điện 56 3.4 Khảo sát điều kiện hấp phụ CFX lên vật liệu hấp phụ 57 3.4.1 Khảo sát yếu tố ảnh hưởng 57 3.4.2 Nghiên cứu chế hấp phụ CFX lên vật liệu biến tính 63 3.5 Ứng dụng xử lý mẫu thực 72 KẾT LUẬN 74 TÀI LIỆU THAM KHẢO 75 CÁC KÝ HIỆU VIẾT TẮT Ký hiệu viết tắt BET FT-IR Tiếng Anh Brunauer - Emmett - Teller Fourier-transform infrared spectroscopy Tiếng Việt Phương pháp BET Phổ hồng ngoại FT-IR XRD X-ray diffraction Phương pháp nhiễu xạ tia X ZP Zeta potential Thế zeta HPLC High Performance Liquid Chromatography Sắc ký lỏng hiệu cao LOD Limit Of Detection Giới hạn phát LOQ Limit Of Quantity Giới hạn định lượng CFX CiproFloXacin Kháng sinh Ciprofloxacin PAMPS Poly(2-Acrylamide-2-Methyl-1Propanesulfonic acid) Polymer Poly(2-acrylamide2-methyl-1-propanesulfonic acid) Polyme polystyrene PSS PolyStyren Sulfonate SEM Scanning Electron Microscope Kính hiển vi điện tử quét Transmission Electron Kính hiển vi điện tử Microscope truyền qua TEM UV-Vis ICP-MS Ultral Violet – Visible sulfonate Phổ hấp thụ phân tử vùng tử ngoại, khả kiến Inductively Coupled Plasma Phổ khối cao tần cảm ứng Mass Spectroscopy plasma PAMNA PAMPS-Modified Nano Vật liệu nano alpha nhôm Alumina oxit biến tính PAMPS Vật liệu nano alpha nhôm PMNA PSS-Modified NanoAlumina AP After Polymerization Sau polymer hóa BP Before Polymerization Trước polymer hóa oxit biến tính PSS DANH MỤC CÁC BẢNG Bảng 0.1 Một số ứng dụng nhôm oxit 17 Bảng 0.2: So sánh hấp phụ vật lý hấp phụ hóa học 27 Bảng 0.3 Độ hấp thụ quang CFX với nồng độ khác bước sóng 277nm 45 Bảng 0.4: Các yếu tố mơ hình động học trình hấp phụ CFX vật liệu PMNA 67 Bảng 0.5: Các yếu tố mơi hình động học hấp phụ bậc bậc hấp phụ CFX PAMNA 68 Bảng 0.6: Các thông số sử dụng mô hình bước hấp phụ CFX PMNA 70 Bảng 0.7: Các thơng số mơ hình hấp phụ đẳng nhiệt CFX vật liệu PAMNA 71 DANH MỤC CÁC HÌNH Hình 1.1: Sơ đồ chuyển pha nhôm oxit theo nhiệt độ 13 Hình 1.2: Cấu trúc alpha nhơm oxit nước Các hình cầu màu xanh nguyên tử oxy, hình cầu đỏ nguyên tử nhơm hình cầu màu xám hidro 13 Hình 1.3 Cơng thức cấu tạo PSS 19 Hình 1.4 Cơng thức cấu tạo PAMPs 20 Hình 1.5: Cơng thức cấu tạo Ciprofloxacin với giá trị pKa1 = 6,09 pKa2 = 8,74 24 Hình 2.1: Thiết bị UV-Vis phịng thí nghiệm khoa Hóa -ĐHKHTN-ĐHQGHN 38 Hình 3.1 Phổ hấp thụ phân tử UV-Vis kháng sinh CFX 44 Hình 3.2 Đường chuẩn phân tích xác định CFX phương pháp UV-vis 45 Hình 3.3: Phổ XRD vật liệu nhơm oxit 47 Hình 3.4: Hình ảnh TEM vật liệu α-Al2O3 48 Hình 3.5: Đường hấp phụ giải hấp N2 vật liệu nano α-Al2O3 48 Hình 3.6: Phổ dao động phân tử FT-IR vật liệu nano α-Al2O3 49 Hình 3.7: Q trình polyme hóa AMP để điều chế PAMPs 50 Hình 3.8: Kết phổ 1H-NMR mẫu trước polyme hóa (BP) sau polyme hóa (AP) 50 Hình 3.9: Kết phân tích GPC mẫu PAMPs 51 Hình 3.10: Ảnh hưởng pH lên trình hấp phụ PSS lên vật liệu nano alpha nhôm oxit 52 Hình 3.11: Ảnh hưởng nồng độ PSS ban đầu đến trình hấp phụ PSS lên vật liệu nano α-Al2O3 53 Hình 3.12: Phổ FT-IR PMNA 54 Hình 3.13: Ảnh hưởng pH lên trình hấp phụ PAMPs lên vật liệu nano αAl2O3 54 Polymers 2020, 12, 1554 of 14 by applying the Langmuir equation The variables of k2 and n were determined by trials and error method At the high salt concentration (10 mM), the k1,CFX value which was found to be × 104 (g/mg−1 ) was11 times greater than that at low salt concentration (0.1 mM) It implies that the active sites for adsorption of CFX increased with decreasing salt concentration In other words, the higher value of k1,CFX obtained, the stronger was the electrostatic attraction induced CFX-adsorption The maximum adsorption capacity at 0.1 mM was times higher than that at 10-mM NaCl The nCFX was the same while the value of k2,CFX changed insignificantly for all cases The error bars shown the standard deviations of different replicates were reasonable and close to solid line, indicating that the model was suitable to represent adsorption isotherm of CFX onto PMA Based on the fitting parameters, it can be found that the CFX-adsorption occurred onto PMA surface by a monolayer than the multilayer formation that is similar trends in previous publications [36–38] Table Fit parameters for the adsorption isotherms of CFX onto PSS-modified Al2 O3 (PMA) at different NaCl concentrations (pH 6) The maximum adsorbed amount is Γ∞, PSS , the equilibrium constants are k1,CFX , k2,CFX for first layer and multilayer, respectively, n the number of clusters of CFX molecules C NaCl (mM) Γ∞,PSS (mg/g) k1,CFX (104 g/mg) k2,CFX (g/mg)n−1 nCFX 0.1 10 28.02 19.92 13.02 22 1260 1249 1250 1.4 1.4 1.4 3.4 Adsorption Kinetic of CFX onto PMA The CFX-kinetic adsorption onto PMA was studied with three different CFX initial concentrations of 10, 50, 250 mg/L, under the optimum adsorption conditions Table shows the rate constant (K), adsorption capacity (qe ) and correlation coefficients (R2 ) of the pseudo-first-order and pseudo-second-order models The effectiveness of model was evaluated through the R2 values As can be seen, the pseudo-second-order model fit the adsorption kinetic of CFX better than the pseudo-first-order one, indicating that the adsorption kinetic of CFX onto PMA is in accordance with pseudo-second-order The linear fits based on the experimental data are shown in Figure Table Parameters of adsorption kinetics of ciprofloxacin (CFX) onto PMA Ci (mg/L) 10 50 250 Pseudo-First-Order Pseudo-Second-Order K1,k (1/min) qe (mg/g) R2 K2,k (g/mg.min) qe (mg/g) R2 0.146 0.131 0.124 1.835 4.879 13.865 0.9863 0.9984 0.9686 0.225 0.106 0.014 1.904 4.930 14.992 0.9990 0.9991 0.9969 Figure shows that adsorption kinetics of CFX onto PMA at three initial CFX concentrations fitted by pseudo-second-order achieved high R2 values (>0.9969) The value of K2 decreased from 0.225 to 0.014 when the initial CFX concentrations increased from 10 to 250 mg/L The decrease in the adsorption rate constant represents the adsorption kinetics for higher initial concentration of CFX because of limited number of adsorption sites of PMA Our results here are similar to adsorption of organic molecules onto surface modified adsorbents [17,19,25,36] Polymers 2020, 12, x FOR PEER REVIEW Polymers 2020, 12, 1554 10 of 15 10 of 14 10ppm 50 ppm 250 ppm 120 y = 0.5252x + 1.2234 R² = 0.999 t/qt min.g/mg 100 80 60 y = 0.2028x + 0.386 R² = 0.9991 40 y = 0.0667x + 0.3087 R² = 0.9969 20 0 50 100 150 200 Adsorption time (min) Figure Pseudo-second-order model for CFX-adsorption kinetic onto PMA with three initial CFX concentrations Figure Pseudo-second-order model for CFX-adsorption kinetic onto PMA with three initial CFX 3.5 concentrations Regeneration Study The regeneration of adsorbent is a key kinetics role to ofevaluate the stability reusable property Table Parameters of adsorption ciprofloxacin (CFX) ontoand PMA The various type of desorption solutions including 0.1-M NaOH, 0.1-M HCl and methanol (MeOH) Pseudo-second-order were used to conduct the Pseudo-first-order desorption process Almost CFX could desorb using NaOH one time then it Ci (mg/L) K 1,k (1/min) q e (mg/g) R K 2,k (g/mg.min) qe (mg/g) R2 it is decreased rapidly with the next desorption The desorption when using HCl was about 50% then 10 1.835 0.9863 0.225 1.904 decreased slightly 0.146 with the more desorption time On the other hand, CFX could not desorb0.9990 when 50 0.131 4.879 0.9984 0.106 4.930 0.9991 using MeOH (not shown in detail) 250 0.124 13.865 0.9686 0.014 14.992 0.9969 PMA after desorption was used to conduct CFX-removal again to evaluate the generation potential Figure shows that adsorption kinetics of CFX onto PMA at three initial CFX concentrations of the adsorbent (Figure 9) Figure shows that the CFX-removal after regeneration still reached fitted by pseudo-second-order achieved high R2 values (>0.9969) The value of K2 decreased from greater than 80%, and it changed insignificantly after three times of reuse For NaOH, the CFX-removal 0.225 to 0.014 when the initial CFX concentrations increased from 10 to 250 mg/L The decrease in the slightly decreased after reuse of the adsorbent The results show that PSS desorption could be occurred adsorption rate constant represents the adsorption kinetics for higher initial concentration of CFX simultaneously with CFX desorption When using MeOH, CFX-removal decreased too much at the because of limited number of adsorption sites of PMA Our results here are similar to adsorption of third time of CFX-removal The MeOH solution cannot be used for CFX desorption that may be organic molecules onto surface modified adsorbents [17,19,25,36] explained by the unsaturated adsorption of modified PMA Because CFX-adsorption occurs on the positively charged PMA surface, the highest desorption will take place with a basic solution On one 3.5 Regeneration Study hand, HCl can produce negatively charged ions (Cl− ), so that a competition of adsorption occurs of adsorbent is a On keythe roleother to evaluate theinteraction stability and reusable property that The can regeneration promote the CFX-adsorption hand, the of MeOH with CFX onThe the various type of desorption solutions including 0.1-M NaOH, 0.1-M HCl and methanol (MeOH) were adsorbent is hydrophobic interaction that is not strong enough to desorb the CFX from the adsorbent used to conductstudy the desorption process Almost CFX could desorbfor using NaOH one time then it is The generation indicate that the PMA is reusable adsorbent CFX-adsorption decreased rapidly with the next desorption The desorption when using HCl was about 50% then it decreased slightly with the more desorption time On the other hand, CFX could not desorb when using MeOH (not shown in detail) Polymers2020, 2020,12, 12,x1554 Polymers FOR PEER REVIEW 11ofof15 14 11 100 Removal (%) 80 60 40 Ads 1st 20 Ads 2nd Ads 3th Figure9.9.Regeneration Regenerationofofadsorbent adsorbentwith withremodification remodificationand andwithout withoutremodification remodificationusing usingdifferent different Figure solutions NaOH, HCl, MeOH Error bars show standard deviation of three replicates solutions NaOH, HCl, MeOH Error bars show standard deviation of three replicates 3.6 Application for CFX-Removal from Hospital Wastewater PMA after desorption was used to conduct CFX-removal again to evaluate the generation The of optimum conditions for CFX-removal applied forCFX-removal the treatment after of an regeneration actual wastewater potential the adsorbent (Figure 9) Figure were shows that the still sample in this part There are many complicated pollutants in real wastewater that strongly influences reached greater than 80%, and it changed insignificantly after three times of reuse For NaOH, the to performance of adsorbent experimental real that sample CFX-removal slightly decreasedTherefore, after reusethe of the adsorbent evaluation The resultsof show PSS treatment desorptionis important Actual samples of wastewater were takenWhen from using a hospital in CFX-removal Hanoi The wastewater could be occurred simultaneously with CFX desorption MeOH, decreased samples were then kept stored at low temperature in a cooling refrigerator desorption days of the too much at the third time of CFX-removal The MeOH solution cannot be usedwithin for CFX experiment Samples were pretreated by filtering to remove the tinyPMA particles As seen by the results, that may be explained by the unsaturated adsorption of modified Because CFX-adsorption the optimum conditions for CFX-removal were obtained when the SMN dosage was kept at 5amg/mL occurs on the positively charged PMA surface, the highest desorption will take place with basic and the pH wastewater wascan 7.0 (checked pretreatment) contact 90 for real sample solution Onofone hand, HCl produce after negatively chargedand ions (Cl−), time so that a competition of a treatment application adsorption occurs that can promote the CFX-adsorption On the other hand, the interaction of MeOH In this we try to CFX from the actual wastewater 10 shows that with CFX onsection, the adsorbent is remove hydrophobic interaction thathospital is not strong enoughFigure to desorb the CFX the high containing manystudy contaminants thethe UVPMA spectra was significantly reduced from the background adsorbent The generation indicate in that is (A1) reusable adsorbent for CFXafter treatment with PMA, indicating that PMA can remove not only CFX, but also many contaminants adsorption that appear in wastewater This trend is similar for the case of the addition of mg/L of CFX into a real sample (A2) By CFX-removal efficiency achieved greater than 75% when using PMA 3.6 Application forcalculations, CFX-removalthe from Hospital Wastewater while only 30% of pollutant molecular was removed by using alumina without surface modification The optimum conditions for CFX-removal were applied for the treatment of an actual Our results again indicate that PMA is a novel adsorbent and high performance for antibiotic removal wastewater sample in this part There are many complicated pollutants in real wastewater that from wastewater solution strongly influences to performance of adsorbent Therefore, the experimental evaluation of real sample treatment is important Actual samples of wastewater were taken from a hospital in Hanoi The wastewater samples were then kept stored at low temperature in a cooling refrigerator within days of the experiment Samples were pretreated by filtering to remove the tiny particles As seen by the results, the optimum conditions for CFX-removal were obtained when the SMN dosage was kept at mg/mL and the pH of wastewater was 7.0 (checked after pretreatment) and contact time 90 for real sample a treatment application Polymers2020, 2020,12, 12,x1554 Polymers FOR PEER REVIEW 12of of15 14 12 Abs 1.6 1.2 0.8 0.4 240 250 260 270 280 Wavelength (nm) 290 300 Real sample (A1) Real sample with 5ppm standard solution added(A2) A2 treatting with non-modified alumina A2 treatting with PMA A1 treatting with PMA Figure 10 UV-Vis spectra of CFX in the hospital wastewater samples before and after treatment The Figure 10 UV-Vis spectra of CFX in the hospital wastewater samples before and after treatment The (A1) real sample and the (A2) real samples with ppm of CFX standard solution added were treated (A1) real sample and the (A2) real samples with ppm of CFX standard solution added were treated using alumina and PMA Baseline subtraction was conducted at the wavelength of CFX maximum using alumina and PMA Baseline subtraction was conducted at the wavelength of CFX maximum absorbance, 272 nm absorbance, 272 nm Conclusions In this section, we try to remove CFX from the actual hospital wastewater Figure 10 shows that This paper reports a new study of PSS adsorption onto alumina particles and application in the high background containing many contaminants in the UV spectra (A1) was significantly reduced CFX-removal from water environment The adsorption of PSS increased with increasing ionic strength after treatment with PMA, indicating that PMA can remove not only CFX, but also many due to the both electrostatic and non-electrostatic interactions and the adsorption capacity reached to contaminants that appear in wastewater This trend is similar for the case of the addition of mg/L 11.0 mg/g The removal of CFX achieved greater than 98% while the maximum adsorption capacity of CFX into a real sample (A2) By calculations, the CFX-removal efficiency achieved greater than of 28.02 mg/g was achieved under the optimum conditions of pH 6, contact time 90 and adsorption 75% when using PMA while only 30% of pollutant molecular was removed by using alumina without dosage of five milligrams per milliliter The maximum CFX-adsorption capacity was found to be surface modification Our results again indicate that PMA is a novel adsorbent and high performance 25 mg/g The PMA was applicable for CFX-removal from an actual hospital wastewater with the for antibiotic removal from wastewater solution removal efficiency of 75% Our results indicate that PSS adsorption plays a key role to form a novel PMA for antibiotic removal from aqueous solution 4.adsorbent Conclusions Author Contributions: T.D.P and D.B.L.; data curation,particles T.H.D and formalin analysis, This paper reportsConceptualization, a new study of PSS adsorption onto alumina andN.T.N.; application CFXT.H.D., N.T.N and C.L.N.; investigation, T.D.P and D.B.L.; methodology, T.D.P and M.N.N.; project administration, removal from water environment The adsorption of PSS increased with increasing ionic strength due D.B.L.; resources, T.H.D and N.T.N.; software, C.L.N and N.H.L.; supervision, T.D.P and M.N.N.; validation, to the both electrostatic and non-electrostatic interactions and the draft, adsorption toT.D.P; 11.0 T.D.P and M.N.N.; visualization, T.D.P and D.B.L.; writing—original T.H.D.,capacity M.N.N., reached D.B.L and writing—review & editing, T.H.D., D.B.L and T.D.P.than All authors have read and agreed to the published versionof of mg/g The removal of CFX achieved greater 98% while the maximum adsorption capacity the manuscript 28.02 mg/g was achieved under the optimum conditions of pH 6, contact time 90 and adsorption Funding: is funded by Vietnam Academy of Science and Technology (VAST)was under GranttoNumber dosage ofThis fiveresearch milligrams per milliliter The maximum CFX-adsorption capacity found be 25 TÐANQP.03/20-22 mg/g The PMA was applicable for CFX-removal from an actual hospital wastewater with the Acknowledgments: Thi75% Huong Dao wouldindicate like to thank theadsorption financial support Vingroup Innovation removal efficiency of Our results that to PSS playsfrom a keytherole to form a novel Foundation and Toshiba Scholarships for Masters Course Study adsorbent PMA for antibiotic removal from aqueous solution Conflicts of Interest: The authors declare no conflict of interest Author Contributions: Conceptualization, T.D.P and D.B.L.; data curation, T.H.D and N.T N; formal analysis, T.H.D., N.T.N and C.L.N.; investigation, T.D.P and D.B.L.; methodology, 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polyelectrolyte onto nanosilica synthesized from rice husk: Characteristics, mechanisms, and application for antibiotic removal Polymers 2018, 10, 220 [CrossRef] [PubMed] Pham, T.D.; Nguyen, H.H.; Nguyen, N.V.; Vu, T.T.; Pham, T.N.M.; Doan, T.H.Y.; Nguyen, M.H.; Ngo, T.M.V Adsorptive removal of copper by using surfactant modified laterite soil J Chem 2017, 2017 [CrossRef] © 2020 by the authors Licensee MDPI, Basel, Switzerland This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/) Journal of Molecular Liquids 309 (2020) 113150 Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq Adsorption characteristic of ciprofloxacin antibiotic onto synthesized alpha alumina nanoparticles with surface modification by polyanion Ngoc Trung Nguyen, Thi Huong Dao, Thanh Tu Truong, Thi Minh Thu Nguyen ⁎, Tien Duc Pham ⁎ Faculty of Chemistry, VNU University of Science, Vietnam National University, 19 Le Thanh Tong, Hoan Kiem, Hanoi 100000, Viet Nam a r t i c l e i n f o Article history: Received March 2020 Received in revised form 10 April 2020 Accepted 12 April 2020 Available online 14 April 2020 Keywords: Ciprofloxacin Nanoalumina Poly(styrenesulfonate) Adsorption Surface modification a b s t r a c t In the present study, we reported the first adsorption characteristic of Ciprofloxacin (CFX) antibiotic onto synthesized alumina nanoparticles with surface modification by a polyanion Strong polyanion poly(styrenesulfonate) (PSS), was used for surface modification of synthesized alumina nanoparticles The alumina which was structural alpha phase, was confirmed by X-ray diffraction (XRD) The functional vibration groups of Al\\O and\\OH was characterized by Fourier transform infrared spectroscopy (FT-IR) The sphere morphology and particle size of about 40 nm was evaluated by Transmission electron microscopy (TEM), while the specific surface area of 6.08 m2/g was determined by Brunauer–Emmett–Teller (BET) method Surface modification of nanoalumina with PSS enhanced a significant increase in CFX removal from aqueous solution Some important parameters which influenced to the CFX removal including pH, contact time and adsorbent dosage, were systematically optimized Under experimentally selected parameters, the removal efficiency and adsorption capacity of CFX using PSS-modified nanoalumina (PMNA) reached maximum of 97.8% and 34.5 mg/g, respectively Adsorption isotherms of CFX onto PMNA were fitted well by the two-step adsorption model while adsorption kinetics of CFX followed the pseudo-second order Based on the change in surface charge monitored by zeta potential, surface modification by FT-IR and adsorption isotherms, we suggest that CFX adsorption onto PMNA was induced by both electrostatic and non-electrostatic interactions but electrostatic attraction was dominant The PMNA were reusable with high removal efficiency for CFX N96% Removal efficiency for CFX in an actual hospital wastewater sample using PMNA achieved over 75% Our results indicate that PMNA is a new and excellent adsorbent for antibiotic removal in wastewater treatment © 2020 Published by Elsevier B.V Introduction Organic pollutants in wastewater effluents become one of the most serious environmental problem in Vietnam [1] Antibiotic is one of major constituents in wastewater because many kinds of antibiotics are widely used for various bacterial infections Among different families of antibiotics, Fluoroquinolones (FQs) group is recently used for both human and animal medicines because of their high broad antibacterial spectrum Ciprofloxacin (CFX), which is belonged to second generation of synthetic FQs, has emerged as a serious contaminant despite of the low concentration in aquatic environment [2] The CFX residual in the water environment is not only harmful threats to the ecosystem but it also results in the growth of antibiotic-resistant genes and bacteria There are several techniques employed for antibiotic degradation or removal including photocatalysis [3], advanced oxidation [4], biological ⁎ Corresponding authors E-mail addresses: nguyenthiminhthu@hus.edu.vn (T.M.T Nguyen), tienducpham@hus.edu.vn, tienduchphn@gmail.com (T.D Pham) https://doi.org/10.1016/j.molliq.2020.113150 0167-7322/© 2020 Published by Elsevier B.V degradation [5] and adsorption [6–9] Since adsorption is one of the most common technique in developing countries due to high effectiveness and economic efficiency, the use of the low-cost adsorbents from the nature resources or the agricultural wastes increases significantly in which natural soils [10], mineral clays [11] and metal oxides [12] attract much researches of scientific communities Alumina is a wellknown material in industrial and environmental concerns There are different crystal alumina phases, but alpha alumina (α-Al2O3), which could be easily synthesized in the laboratory, is highest thermal stability [13] Since the α-Al2O3 has small specific surface area as well as low charge density, the direct application of the material for antibiotic removal is unapplicable Therefore, the surface modification of synthesized α-Al2O3 by the environmental-friendly chemicals is necessary to enhance the removal effciency for antibiotics Recently, some scientific projects indicate that the adsorptive removal of antibiotics is significantly increased by the surface modification of solid surfaces with a charged polymer (polyelectrolyte) [14,15] A comprehensive understanding of adsorption characteristics of polyelectrolyte onto particles is of great importance to control charging behavior of these systems and increase removal efficiency for antibiotics N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 Therefore, the adsorption of polyelectrolyte onto different particles and their applications for organic pollutants removal is still an interesting topic Poly(styrenesulfonate) (PSS), which contains a pH-independent sulfonate group, carry negative charge in aqueous solution In acidic medium, the formation of the PSS molecules can strongly remain on the positively charged alumina surface, resulting a high density of negative charge on alumina surface [16,23] To the best of our knowledge, the removal of CFX by adsorption technique using synthesized nano α-Al2O3 with the surface modification by PSS has not been investigated Adsorption isotherms which are represented by Freundlich and Langmuir models are frequently used to predict adsorption mechanisms However, adsorption behavior of CFX onto PSS modified alumina surface is complicated so that the common models cannot be employed The two-step adsorption model proposed by Zhu et al [17], possibly describe adsorption isotherms of CFX onto PSS-modified nanoalumina (PMNA) since this model were successfully described some types of adsorbates and represented the growth of polyelectrolyte bilayers [18–20] This report is the first study in which we examined the adsorptive conditions of CFX onto PMNA after conducting PSS adsorption onto syntheized α-Al2O3 The nano α-Al2O3 was successfully fabricated by solvothermal method and its structure, morpholgy and surface characteristics were throughly determined by physico-chemical methods Adsorption isotherms and kinetics of CFX on PMNA were experimentally constructed and predicted by modeling Adsorption mechanisms were proposed on the basis of the changes in surface charge of the adsorbent by zeta potential measurements, the differences in surface functional groups before and after adsorption by FT-IR and adsorption isotherms The reused potential of PMNA after CFX removal was also studied to examine the regeneration of the adsorbent The application for CFX removal in an actual wastewater sample collected from a hospital was also carried out by using PMNA Materials and methods 2.1 Materials Nano α-Al2O3 was synthesized based on solvothermal method, followed a previous procedure with a minor modification [21] Two common chemicals including Al(NO3)3.9H2O and NaOH were employed to fabricate alumina Aluminum hydroxide was obtained by slowly titrating NaOH into Al(NO3)3 solution in a plastic vessel, followed by well stirring White precipitation of aluminum hydroxide was formed and then separated by centrifugation at 6000 rpm (Digisystem, Taiwan) The precipitate was washed several times with ultrapure water in order to reach neutral pH The sample was dried in a thermal oven at 80 °C within 24 h Finally, the obtained white powder was calcined at 1200 °C for 12 h in a thermal furnace to achieve the nano αAl2O3 2.3 Characterization methods The synthetic alumina particles were characterized by XRD, FT-IR, TEM and BET methods The XRD pattern was recorded with an X-ray diffractometer (Bucker D8 Advanced) with CuKα radiation The intensities were recorded with 2θ from 20 to 80° with every step of 0.03° The FT-IR spectra were conducted using an FTIR Affinity-1S spectrometer (Shimadzu, Japan) The FT-IR spectra of synthesized α-Al2O3, PSS-modified nanoalumina (PMNA) and PMNA after CFX adsorption were recorded at the atmospheric pressure to evaluate the change of functional groups The size distribution and morphology of synthesized alumina was estimated by using TEM (H7650, Hitachi, Tokyo, Japan) The BET method was applied to examine the total specific surface area of alumina using a surface area analyser (SA 3100, Beckman Coulter) The N2 adsorption isotherms were performed in a cell with outgas condition of 150 °C for h The zeta potential was measured to evaluate the charge of synthesized α-Al2O3, after pre-adsorption with PSS and after removal of CFX by using Zetasizer Nano ZS (Malvern) The zeta potential (ζ) was determined from Smoluchowski's equation [22]: ζ¼ Sodium hydroxide (NaOH) pellets and aluminum nitrate Al(NO3) were supplied from Merck, Darmstadt, Germany Ciprofloxacin hydrochloride monohydrate (CFX) (CAS 86393-32-0) with HPLC grade (purity N98%) was purchased from Tokyo Chemical Industry, Japan Powder of sodium poly(styrenesulfonate), (PSS) with high molecular weight of 1000 kg/mol, was delivered from Sigma Aldrich The chemical structures of CFX (A) and PSS (B) were shown in Fig The solution pH was examined by a pH meter (HI 2215 Hanna, Woonsocket, RI, USA) while the ionic strength was monitored by adding NaCl (Merck, Darmstadt, Germany) The glass electrode was calibrated with buffer solutions every day All solutions used in this study were conducted with ultrapure water using an ultrapure water system (Labconco, Kansas City, MO, USA) with a resistivity of 18.2 MΩ 3.9H2O 2.2 Synthesis of alpha alumina nanoparticles ue η εrs εo ð1Þ where ζ the zeta potential (mV), ue the electrophoretic mobility (μm cm/sV), η the dynamic viscosity of the liquid (mPa·s), εo the electric permittivity of the vacuum (8.854 × 10−12 F/m), and εrs is the relative permittivity constant of the electrolyte solution 2.4 Adsorption studies Batch adsorption mode was used to carry out all adsorption experiments in 15 ml Falcon tubes at 25 ± °C controlled by an air conditioner The adsorptive removal of CFX onto synthesized nanoalumina was carried out in triplicates A stock solution of 1000 mg/L (1000 ppm) PSS was prepared by dissolving 0.2500 g PSS into a 250 mL volumetric flask and filled up with ultrapure water Fig The chemical structures of (A) Ciprofloxacin; (B) Polystyrenesulfonate N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 For PSS adsorption onto alpha alumina particles, mg/ml of nano αAl2O3 adsorbent suspension was thoroughly mixed with different PSS concentrations from mg/ml to 200 mg/ml, followed by well shaking for h in order to form PSS-modified nanoalumina (PMNA) adsorbent [23] The PMNA adsorbent was washed with ultrapure water to reach neutral pH before using for adsorptive removal of CFX in Falcon tubes The concentrations of PSS after adsorption were quantified at the wavelength of 263 nm by a spectrophotometer (UV-1650 PC, Shimadzu, Kyoto, Japan) with a couple quartz cuvettes of a cm optical path length To investigate CFX adsorption, 10 mg/l of CFX was added into the PMNA adsorbent in a 15 ml Falcon tubes before adjusting pH solution and shaking for different contact time The effective parameters for CFX removal including adsorbent dosage, pH and contact time, were systematically investigated by changing one parameter while other parameters were fixed to find the optimum conditions For adsorption isotherms, CFX with the different concentrations increasing from 10 to 800 mg/l which were added to PMNA suspensions, were conducted triplicates All adsorption isotherms were performed under optimized conditions of pH, adsorbent dosage and contact time After reaching the equilibrium, the adsorbent was separated using a refrigerated centrifuge (MR23i, JOUAN, France) at 10.000 rpm for 10 The CFX concentrations in the supernatants were quantified at a wavelength of 276 nm using a spectrophotometer (UV-1650 PC) Before measuring all unknown samples, the standard solutions of CFX concentrations were constructed with very high correlation coefficient (R2 = 0.9999) to secure the accuracy The removal efficiency (%RE) of CFX is determined by Eq (2) Removal efficiency %ị ẳ C i −C f  100 Ci ð2Þ where Ci and Cf are the initial and final concentrations of CFX (mg/l), respectively The Cf is used for calculation of RE to find optimum experimental conditions of adsorption The adsorption capacities of CFX onto PMNA were calculated by using the following equation ẳ C i C e 1000 m 3ị where Γ is the adsorption capacity of CFX (mg/g), Ce is the equilibrium concentration of CFX (mg/l) and m (mg/ml) is the adsorbent dosage All adsorption experiments were conducted with triplicates Ce shows the different concentrations of CFX for calculation of Γ when conducting adsorption isotherms We employed the two-step model to fit adsorption isotherms of CFX onto PMNA The adsorption isotherms were described by using general isotherm equation The general isotherm equation is shown as follows: þ k2 C en−1 n Γ¼ þ k1 C e ỵ k2 C en1 k1 C e ð4Þ where Γ is the adsorption capacity (mg/g), Γ∞ is the maximum adsorption capacity (mg/g), k1 (g/mg), k2 (g/mg)n-1 are equilibrium constants for the first-layer adsorption and clusters of multilayer adsorption, n is adsorption layer Results and discussions 3.1 Characterization of synthesized alumina nanoparticles The XRD pattern of the synthesized alumina is shown in Fig The peaks with reflection at 2-Theta at 35°, 38°, 43.5°, 66°, 68° and 77° with high intensities corresponding to planes (104), (110), (113), (300), (116), (311) confirmed the alpha phase and crystalline structure of the synthesized alumina nanoparticles [244] The FT-IR spectra of the synthesized α-Al2O3 shown in Fig indicates that specific peaks of O-Al-O bonds in the α-Al2O3 structure were assigned at 638, 594 and 470 cm−1 The sharp peak appeared at 470 cm−1, represented the bending vibration of Al\\O in Al\\OH Fig XRD pattern of synthesized alumina particles N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 However, the removal of charged organic pollutants, surface charge density of alumina is more important than the surface area because the electrostatic interaction between the alumina and CFX molecules plays important role for adsorption of charged molecules Therefore, to enhance the removal efficiency for CFX, surface modification of synthesized nanoalumina is necessary All the above results of XRD, FT-IR, TEM and BET indicate that αAl2O3 nanoparticles were successfully fabricated with a simple procedure, that was applicable for polyelectroyte adsorption and adsorptive removal of antibiotics 3.2 Surface modification of α-Al2O3 by PSS adsorption Fig FT-IR spectrum of synthesized α-Al2O3 particles group [25] The peak of 594 cm−1 confirmed the stretching vibration of Al\\O bond In addition, the\\OH stretching vibration in aluminum hydroxide at 3479 cm−1 disappeared because Al(OH)3 was calcined at very high temperature (1200 °C) to form α-Al2O3 The average of particle size and morphology of nano alumina were examined by TEM The TEM image shown in Fig demonstrated that average particle size of α-Al2O3 particles were approximately 40 nm As can be seen, the alumina was sphere-shaped particles The specific surface area of synthesized α-Al2O3 was evaluated from N2 adsorption-desorption on the particles The specific surface area was found to be 6.08 m2/g (Fig 5) Basically, the adsorbents with high surface area are preferable for adsorption of organic contaminants [8,26] The effect of pH and ionic strength on adsorption of PSS onto nano α-Al2O3 was studied to optimize the conditions of surface modification (Figs and 7) The solution pH was monitored in a range of 2–10 whereas adsorption isotherms were examined at two different NaCl concentrations As seen in Fig 6, adsorption capacity of PSS onto nano α-Al2O3 was highest at pH 3, then it decreased slightly to mg/ml at pH When increasing pH solution, adsorption of PSS tend to decrease significantly due to the decrease of positive charge of α-Al2O3 at pH b PZC (point of zero charge) At pH 3, the PSS adsorption is slightly higher than that at pH Nevertheless, at pH 3, the dissolution of alumina influenced the reproducibility of results so that the error bar indicated the standard deviations were high As the results, the surface modification of nano αAl2O3 was not stable On the other hand, although the PSS adsorption at pH was not highest, the standard deviations of the experimental replicates was smallest, indicating that the reproducibility was the best In addition, at pH N 7, the increasing repulsive forces between negative molecules of polyanion PSS and the alumina surface which remain Fig Influence of pH on adsorption of PSS onto nanoalumina surface Error bars show the standard deviation of three replicates Fig TEM image of synthesized α-Al2O3 particles Fig Adsorption-desorption isotherms of N2 on synthesized nanoalumina Fig Adsorption of PSS onto synthesized nanoalumina at different NaCl concentrations (PSS concentrations range from mg/ml to 200 mg/ml, pH 4, mg/ml adsorbent suspension α-Al2O3, contact time 120 min) Error bars show the standard deviation of three replicates N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 progressively negative in basic solutions It suggests that surface modification of alumina particles with PSS is more sufficient when conducted at low pH values Thus, adsorption of PSS should be conducted at pH An increase in adsorption of PSS on alumina surface was demonstrated with increasing salt concentration to 100 mM at pH 4, suggesting that both electrostatic and non-electrostatic interactions controlled adsorption of PSS onto nanoalumina (Fig 7) At high salt concentration, hydrophobic and lateral interactions also attributed to adsorption due to stronger interactions between hydrophobic groups in polymer structure These results were in good agreement with the previous literature [18] To fabricate PSS-modified nanoalumina (PMNA), the absorbed amount of PSS onto synthesized nanoalumina should be maxima Therefore, the conditions that used to modify nano α-Al2O3 are 100 mM NaCl, pH and 100 mg/l PSS 3.3.2 Effect of adsorbent dosage The total surface area and surface charge density of nano α-Al2O3 are strongly influenced to the amount of adsorbent in adsorption technique To investigate the influence of the adsorbent dosage on CFX adsorption, different amount of the PMNA adsorbent varied from 0.1 to 15 mg/ml was used for treatment of 10 mg/l of CFX The effect of PMNA adsorbent dosage to CFX removal is shown in Fig Fig shows that an increase of the adsorbent dosage, the removal efficiency for CFX increased significantly from 0.1 to mg/ml It could be due to the enhancement of the total surface area and charge density of nanoalumina with increasing adsorbent dosage, thus the CFX removal using PMNA increased At higher amount of the adsorbent dosage than mg/ml, the removal efficiency for CFX varied insignificantly due to saturation of surface charge density Therefore, mg/ml PMNA is the optimum adsorbent dosage for the CFX removal from aqueous solution 3.3 Optimization of CFX removal from aqueous solution using PSS-modified nanoalumina (PMNA) 3.3.1 Effect of pH The solution pH plays the most vital factor because it influences the species form of CFX while the negative charge of PSS-modified nanoalumina (PMNA) is independent on pH The charging behavior of CFX can influence adsorption to the PMNA adsorbent A constant CFX concentration of 10 mg/l was kept in all experiments, pH values were adjusted in a range of 3–10 by using 0.1 M HCl and 0.1 M NaOH Fig shows that the CFX removal increased from pH to and decreased significantly in basic conditions (pH N 8) Since CFX has two pK of 6.1 and 8.7, the charging behavior of CFX vary with pH solution [27] The CFX molecules present mainly in positive ions from pH to due to protonation of amine groups Electrostatic attraction between positive CFX molecules and negatively charged PMNA surface decreased with increasing pH, especially at pH N 6.0 Nevertheless, at pH 6, removal efficiency of CFX reach maximum This could be explained that adsorption is possibly controlled by both electrostatic attraction and non-electrostatic interactions (hydrophobic interaction, hydrogen bonding, Van der Waals forces) because CFX appeared as zwitterionic species in the neutral pH ranges At pH N 8, CFX became more negative while PMNA surface is still highly negative, thus the repulsive forces induced to a rapid decrease in removal of CFX The highest removal efficiency for CFX was obtained about 97% at pH This pH value is nearly similar to neutral pH that is close to pH of wastewater, indicating that we can remove CFX from actual wastewater without pH adjustment This is not the case for removal of CFX using graphene oxide/sodium alginate aerogel since maximum adsorption capacities was achieved at pH [28] Therefore, pH is more suitable for treatment of CFX residual in actual wastewater samples when using PMNA Fig Effect of pH on removal of CFX using PMNA (Initial concentration of 10 mg/l CFX, adsorbent dosage mg/ml, contact time 120 and mM NaCl) Error bars show the standard deviation of three replicates 3.3.3 Effect of contact time The equilibrium process of CFX adsorption is influenced by contact time that represents the required time to achieve the equilibrium To study the effect of contact time to CFX removal, different contact time intervals ranging from 10 to 180 min, were used to conduct with 10 mg/L CFX at pH 6, mM NaCl and mg/ml adsorbent Fig 10 represents the contact time effect on adsorption of CFX using PMNA at different time intervals As seen in Fig 10, the removal efficiency of CFX grew up with increasing contact time The adsorption process of CFX onto PMNA reached equilibrium after 90 min, at which the removal efficiency was N90% After that, the CFX removal changed insignificantly because the Fig Effect of adsorbent dosage on removal of CFX by using PMNA (Initial concentration of 10 mg/l CFX, pH 6, contact time 120 and mM NaCl) Error bars show the standard deviation of three replicates Fig 10 Effect of contact time on removal of CFX by using PMNA (Initial concentration 10 mg/l CFX, pH 6, dosage mg/ml and NaCl mM) Error bars show the standard deviation of three replicates N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 adsorption of CFX onto PMNA could be saturated The adsorption time of CFX onto PMNA is much shorter than that of clay minerals in which need 24 h as sufficient time for CFX adsorption [27] Thus, contact time of 90 is relatively efficient for adsorptive removal of CFX from aqueous solution when using PMNA 3.3.4 Adsorptive removal of CFX using nanoalumina with and without surface modification by PSS The removal of CFX by batch adsorption technique using nanoalumina and PSS-modified nanoalumina (PMNA) were conducted at the similar conditions of pH 6, contact time 90 and mg/ml adsorbents Fig 11 shows that removal efficiency for CFX increased dramatically from 33.57% to 97.8% after surface modification of nanoalumina with PSS The surface charge of PMNA is highly negative due to presence of numerous PSS molecules on adsorbent surface while nanoalumina is low positively charged surface The CFX removal increased significantly due to main contribution of electrostatic interaction By contrast, the low surface charge density of bare nanoalumina induced low efficiency for CFX removal It implies that charge density of adsorbents is more important than specific surface area in this case, that closes to the adsorption of oxytetracyline onto surfactant modified alumina [29] Therefore, PSS-modified nanoalumina (PMNA) to be a new and promising adsorbent for antibiotic removal 3.4 Adsorption isotherm of CFX on PSS-modified nanoalumina (PMNA) Adsorption isotherm is important to predict mechanisms as well as the potential of adsorbent The adsorption isotherms of CFX onto PMNA under optimum conditions were conducted at different NaCl concentrations (pH 6) while the initial concentrations of CFX were changed from 10 to 800 mg/l The influence of ionic strength on the CFX adsorption onto PMNA is clearly observed based on adsorption isotherms at 0.1 and 10 mM NaCl (Fig 12) Fig 12 shows that the adsorption capacity of CFX decreased with increasing salt concentration with all initial concentrations of CFX At high ionic strength of 10 mM, the high number of Na+ cations (counter ions) induced a decrease of electrostatic attraction of PMNA and CFX molecules The electrostatic attraction between positive species of CFX+ ions and negatively charged PMNA surface is dramatically decreased when increasing salt concentration [29] Although nonelectrostatic interactions such as hydrophobic interaction, lateral interaction and hydrogen bonding could be occurred at high ionic strength, their contributions to adsorption of CFX onto PMNA were negligible On the other hand, when reducing salt concentration (0.1 mM), the electrostatic attraction was the main driving force that attributed to an enhancement of CFX adsorption This implies that CFX adsorption onto PMNA is mainly controlled electrostatic attraction rather than non-electrostatic interactions Fig 12 Adsorption isotherms of CFX onto PMNA at two NaCl concentrations Points are obtained from experimental results while solid lines are fitted by the two-step model Error bars show the standard deviation of three replicates As shown in Fig 12, the experimental data of CFX adsorption onto PMNA could be employed by the general isotherm Eq (4) The fit parameters were summarized and shown in Table At the higher salt concentration (10 mM), the k1 value was found to be × 104 (g mg−1) while at lower salt concentration (0.1 mM), k1 was about times higher In addition, the maximum adsorption capacity at 0.1 mM was 2.1 times higher than that at 10 mM NaCl This indicates that the total sites for adsorption of CFX increased with decreasing salt concentration The error bars shown the standard deviations of different replicated were acceptable, indicating that the model is suitable for fitting at different salt concentrations The values of n which represent the aggregation number of surface were insignificantly In other words, CFX adsorption took place onto PMNA surface by both monolayer and the multilayer formation 3.5 Adsorption kinetic of CFX onto PSS-modified nanoalumina (PMNA) Adsorption kinetic of CFX onto PMNA was studied at two initial CFX concentrations The pseudo-first and pseudo-second orders models are employed to describe adsorption kinetics of CFX onto PMNA The pseudo-first-order adsorption kinetic is K 1;k logðqe −qt Þ ¼ logqe − t 2:303 ð5Þ The pseudo-second-order adsorption kinetic was described by Eq (6) t 1 ¼ þ t qt K 2;k :q2e qe ð6Þ Table shows the rate constant, adsorption capacity at the equilibria and the correlation coefficients (R2) of the pseudo-first-order and Table The fit parameters for adsorption of CFX onto PMNA CNaCl (mM) ГCFX (mg.g−1) k1 (104 g.mg−1) k2 (g.mg−1) n 10 0.1 34.5 16 20 700 600 1.9 Table The parameters of adsorption kinetics of ciprofloxacin (CFX) onto PMNA Fig 11 Removal efficiency of CFX using nano α-Al2O3 nano α-Al2O3 modified with PSS (PMNA) Error bars show standard deviations of three replicates Ci (mg/L) Pseudo-first order Pseudo-second order K1,k (g/mg min) qe (mg/g) R 20 100 0.1306 0.7790 3.7426 8.5417 0.9820 0.9114 K2,k (g/mg min) qe (mg/g) R2 0.063 0.016 3.9385 9.3196 0.9998 0.9993 N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 pseudo-second-order models The value of R2 was used to evaluate the effectiveness of models Table shows that the pseudo-second-order model achieved the closer fit than the pseudo-first-order one The results indicate that the pseudo-second-order model matched the adsorption data, since the solid lines taken by model fitting is much better to the experimental points than that of the pseudo-first-order model Adsorption kinetics of CFX onto PMNA at two initial CFX concentrations fitted by pseudo-second-order achieved very high R2 value (N0.9993), were shown in Fig 13 The value of K2,k decreased from 0.063 to 0.016 when increasing the initial CFX concentration The rate constant which represents the adsorption kinetics, decreased for higher initial concentration of CFX because of limited number of adsorption sites on nanoalumina Our results here are similar to adsorption of CFX adsorption kinetics onto protein-modified nanosilica in which the pseudo-second-order was the best fitting model [30] 3.6 Adsorption mechanism of CFX using PSS-modified nanoalumina (PMNA) In this session, adsorption mechanism of CFX onto PSS-modified nanoalumina (PMNA) is suggested based on charging behavior of nanoalumina, with PSS modification and after CFX adsorption by measuring ζ potential, the functional groups modification by FT-IR and adsorption isotherms of CFX Fig 14 shows that a high positive value of the ζ potential of synthesized nano α-Al2O3 acidic conditions (ζ = +49.5 mV) implies the highly positive charge After surface modification by PSS adsorption, a charge reversal of the adsorbent was occurred so that the surface charge of PMNA caused to negative (ζ = −25.60 mV) because of the polyanion PSS molecules that covered the surface of nano α-Al2O3 The presence of numerous sulfonate groups in PSS molecules maintained the negative surface charge of PMNA at the plateau adsorption level However, the negative charge of PMNA surface was decreased after adsorption of CFX The results from ζ potential measurements confirmed that the CFX adsorption onto PMNA was induced by electrostatic attraction Adsorption mechanism of CFX onto PMNA is also discussed by the FT-IR spectra of PMNA and PMNA after CFX adsorption (Fig 15) The stretching vibration of C\\S of PSS molecules at 676 cm−1 disappeared in spectrum of α-Al2O3 (shown again in Fig 15) after PSS adsorption In addition, the symmetric and asymmetric bands of PSS at 1039 and 1185 cm−1, respectively could not be observed after PSS molecules were occurred onto nano α-Al2O3 [16] Moreover, the intensity peak for α-Al2O3 at 1639 cm−1 also increased after PSS adsorption It suggests that the adsorption of PSS onto α-Al2O3 surface was controlled by both hydrophobic and electrostatic interactions that agree well with PSS adsorption onto different sized α-Al2O3 particles [23] On the other hand, Fig 15 also shows that the significant changes of PMNA spectra were observed after adsorption of CFX onto the adsorbent surface The functional vibration of CFX in bottom of Fig 15 at 1385 cm−1 shifted to the shorter wavenumber of 1396 cm−1 because amine group of piperazine moiety is protonated [31] It suggests the presence of electrostatic driving force between the pronated amine groups and the negatively charged PMNA surface Furthermore, the peak of 1624 cm −1 represented for the ketone C_O stretching vibration shifted to longer wavenumber (1639 cm −1 ) due to the reinforcement of the ketone C_O bond, which was involved by the presence of hydrogen bonding between the ketone group and the adjacent carboxylic group [32] A hydrogen atom of carboxylic acid groups possibly makes a new hydrogen bonding with an oxygen of sulfonate groups on PSS The results are similar to the adsorption isotherms, and the changes in surface charge Based on these results, we confirmed that the electrostatic driving force between CFX ions and oppositely charged PMNA surface induced a greater contribution to CFX adsorption onto PMNA 3.7 Comparison of the adsorption capacity and the efficiency of PMNA with other adsorbents for CFX removal Fig 13 The pseudo-second-order kinetic model for CFX adsorption onto PMNA Recently, various studies have reported the CFX removal using various adsorbents However, the CFX removal through adsorption technique using PSS modified nano α-Al2O3 (PMNA) has not been investigated Table shows that the PMNA used in this work has the highest removal efficiency (97.8%) and adsorption capacity (34.5 mg/g) for CFX removal compared to other kinds of adsorbents The PMNA is a new, high performance adsorbent with simple fabricated procedure without using any organic solvent However, for practical applications, the regeneration of PMNA is necessary to estimate the regeneration of the adsorbent After adsorption of 10 mg/l CFX, we used 0.1 M HCl to conduct CFX desorption for 30 The recoveries of CFX were varied from 90.1% to 98.4% After CFX desorption, the suspension was centrifuged to collect PMNA Prior to reactivation with PSS solution, the adsorbent was cleaned with ultrapure water The PMNA then was recycled to remove 10 mg/l CFX under the conditions in Section 3.3 Fig 16 shows the CFX removal using PMNA after four re-cycles of the regeneration The removal efficiency for CFX decreased slightly but it was still higher than 96% after four recycles It implies that PMNA is not only high performance but also to be reusable adsorbent 3.8 Adsorptive removal of ciprofloxacin in hospital wastewater sample using PSS-modified nanoalumina (PMNA) Fig 14 The zeta potential of nano α-Al2O3, PSS-modified nano α-Al2O3 (PMNA) and PMNA adsorbent after adsorption of CFX antibiotic The application of adsorption method using the new adsorbent PMNA for treatment of antibiotic in real wastewater sample N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 Fig 15 The FT-IR spectra of alumina nanoparticle, alumina modified with PSS (PMNA), PMNA after CFX adsorption and CFX antibiotic is great of importance to evaluate the effectiveness of the material because different organic pollutants and other impurities in wastewater may be competitively adsorbed onto the PMNA A hospital wastewater sample in Hanoi was initially collected and pretreated by filtration before treatment The optimum conditions for CFX removal from the actual water sample were pH 6, contact time 90 and mg/ml PMNA adsorbent The UV–Vis spectra of this real wastewater sample and after addition of mg/l standard solution of CFX were shown in Fig 17 Although adsorption process is strongly influenced by many interferences in the water sample, the absorbance of CFX at the specific wavelength 276 nm decreased significantly when using PMNA The high removal efficiency of about 75% for CFX using PMNA was achieved while only 30% removal efficiency was obtained for Table Adsorption capacity and removal efficiency of PSS-modified nanoalumina (PMNA) and other adsorbents for removal of Ciprofloxacin antibiotic Adsorbent Adsorption capacity (mg.g−1) Removal efficiency (%) Reference Activated sludge Silica nanoparticles Graphene oxide/sodium alginate composite Schorl PSS-modified nanoalumina (PMNA) 0.24 30 2.51–3.78 78–91 78 NI [33] [15] [34] 8.49 34.5 NI 97.8 [36] This study NI: No Information using nanoalumina without modification Since CFX was competitive against other pollutants, the efficiency of CFX removal when using PMNA is still suitable because the concentration of antibiotics in wastewater is basically low The results again indicate that PMNA have great potential to CFX removal from wastewater from hospital Conclusions In this paper, we have reported the first study of adsorptive removal of ciprofloxacin (CFX) onto synthesized α-Al2O3 nanoparticles with the surface modification by poly(styrenesulfonate) (PSS) The characterization of alumina nanoparticles was thoroughly examined by XRD, FT-IR, TEM and BET methods The α-Al2O3 nanoparticles was modified with 100 mg/l PSS at 100 mM NaCl and pH to obtain PSS-modified nanoalumina (PMNA) We successfully optimized the conditions for CFX removal using PMNA as pH 6, contact time 90 and adsorption dosage mg/ml The maximum adsorption capacity and removal efficiency of CFX were found to be 34.5 mg/g and 97.8%, respectively Adsorption isotherms of CFX at different salt concentrations were in accordance with the two-step adsorption model Kinetic study indicated that the CFX adsorption followed the second-order model On the basis of adsorption isotherms, the differences in surface charge of adsorbent before and after adsorption by zeta potential measurements and the change in functional groups by FTIR, we suggest that the CFX adsorption onto PMNA was mainly promoted by electrostatic attraction The high removal efficiencies of 96% after four regenerations were achieved when using PMNA to remove CFX in aqueous solution An actual hospital wastewater sample was well treated with a high efficiency N75% for CFX antibiotic by using PMNA This study reveals that PMNA is a new and novel adsorbent for antibiotics removal from aqueous solution CRediT authorship contribution statement Ngoc Trung Nguyen: Software, Formal analysis, Data curation, Writing - original draft, Writing - review & editing Thi Huong Dao: Formal analysis, Data curation Thanh Tu Truong: Resources, Visualization Thi Minh Thu Nguyen: Methodology, Validation, Writing - review & editing Tien Duc Pham: Conceptualization, Methodology, Validation, Investigation, Resources, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration Declaration of competing interest Fig 16 Efficiency for removing CFX using PMNA after being reused four times Error bars show standard deviations of three replicates The authors declare that they have no conflict of interest N.T Nguyen et al / Journal of Molecular Liquids 309 (2020) 113150 Fig 17 The UV–Vis spectra of CFX of the wastewater samples collected at a hospital before and after treatment using PMNA adsorbent References [1] H.A Duong, N.H Pham, H.T Nguyen, T.T Hoang, H.V Pham, V.C Pham, M Berg, W Giger, A.C Alder, 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Chính đặc tính nêu mà CFX kháng sinh luận văn lựa chọn nghiên cứu Trong thực tế có nhiều phương pháp phân tích đặc tính kháng sinh CFX số phương pháp phân tích kháng sinh 1.3.1 Các phương pháp phân. .. nhôm oxit Nano nhôm oxit tổng hợp phương pháp khác sau sử dụng phương pháp phân tích vật lý hóa học nhằm nghiên cứu đặc tính 13 sản phẩm Dưới phương pháp tổng hợp phân tích đặc tính nano nhôm oxit