Đánh giá một số yếu tố ảnh hưởng đến hiệu quả khử mặn nước biển của hệ thống lọc nước sử dụng màng lọc thẩm thấu chuyển tiếp (FO)

ĐẠI HỌC QUỐC GIA HÀ NỘI TRƢỜNG ĐẠI HỌC KHOA HỌC TỰ NHIÊN Phạm Thị Phƣơng Thảo ĐÁNH GIÁ MỘT SỐ YẾU TỐ ẢNH HƢỞNG ĐẾN HIỆU QUẢ KHỬ MẶN NƢỚC BIỂN CỦA HỆ THỐNG LỌC NƢỚC SỬ DỤNG MÀNG LỌC THẨM THẤU CHUYỂN TIẾP (FO) Chuyên ngành: Kỹ thuật môi trường Mã số: 60520320 LỜIVĂN CẢM ƠN SĨ LUẬN THẠC Ngƣời hƣớng dẫn khoa học: PGS.TS Nguyễn Quang Trung TS Lê Văn Chiều Hà Nội - 2016 LỜI CẢM ƠN Trong trình thực nghiên cứu đề tài, em nhận sư quan tâm giúp đỡ nhiệt tình, đóng góp quý báu nhiều cá nhân tập thể tạo điều kiện thuận lợi cho em hoàn thành khóa luận Lời đầu tiên, em xin chân thành cảm ơn tới thầy hướng dẫn PGS.TS Nguyễn Quang Trung – Trung tâm Đào tạo, Tư vấn Chuyển giao công nghệ, Viện Hàn lâm Khoa học Công nghệ Việt Nam TS Lê Văn Chiều – Trường Đại học Việt Nhật, Đại học Quốc gia Hà Nội tận tình hướng dẫn em suốt thời gian thực đề tài Em xin cảm ơn tận tình dạy dỗ, bảo thầy côKhoa Môi trường, Trường Đại học Khoa học Tự nhiên, Đại học Quốc gia Hà Nội Em gửi lời cảm ơn tới tập thể cán Phòng thi nghiệm trọng điểm An toàn thực phẩm Môi trường giúp đỡ, tạo điều kiện cho em hoàn thành khóa luận Tuy có nhiều cố gắng thời gian kiến thức có hạn nên tránh khỏi thiếu sót, khiếm khuyết.Rất mong nhận góp ý, chỉnh sửa quý thầy cô Và cuối cùng, em xin cảm ơn gia đình, người thân bạn bè quan tâm, động viên giúp đỡ em suốt trình thực đề tài Em xin chân thành cảm ơn! Hà Nội, ngày 28 tháng 12 năm 2016 Học viên Phạm Thị Phương Thảo DANH MỤC CHỮ VIẾT TẮT AB Amoni bicacbonat (AB) A3C Amoni sắt (II) citrat (A3C) A2S Amoni sắt (II) sunphat (A2S) A3C Amoni sắt (III) sunphat (A3S) CAc Axit citric CTA Xenlulose triaxetat DS Dung dịch lôi (Draw solution) FO Thẩm thấu chuyển tiếp (Forward Osmonis) FS Dung dịch đầu vào (Feed solution) GMH g/(m2.h) Jw Thông lượng nước (Water flux) Js Thông lượng chất tan thấm ngược (Reverse solute flux) LMH L/(m2.h) LPRO RO sử dụng lượng thấp (Low power RO) MBR Thiết bị phản ứng màng sinh học (Membrane bioreactor) MD Chưng cất màng (Membrane Distillation) MED Chưng cất đa hiệu ứng (Multi Effection Distillation) MF Vi lọc (Microfiltration) MNPs Hạt nano từ tính (Magnetic nanoparticles) MSFD Chưng cất bay nhiều giai đoạn (Multistage flash distillation) NF Lọc nano (Nanofiltration) OMBR Thiết bị phản ứng sinh học màng – màng lọc thẩm thấu (Osmosis membrane bioreactor) PET Polyester PPA Polyacrylic axit PSf Polysylfone RO Thẩm thấu ngược (Reverse Osmosis) SRSF Tỉ số dòng thấm ngược chất tan (Specific Reverse Solute Flux) TDS Tổng chất rắn hòa tan (Total disolved solid) TFC Composit màng mỏng (Thin – film composite) TrOCs Các hợp chất hữu lượng vết môi trường (Trace Organic compounds) UF Siêu lọc (Ultra-filtration) DANH MỤC BẢNG Bảng So sánh công nghệ khử mặn nước biển[11] 12 Bảng Bảng tổng hợp số dung dịch lôi sử dụng màng FO khử mặn [12,13,16,31,34-36] 23 Bảng Đặc tính phức chất sử dụng hệ thống lọc FO 29 Bảng Điều kiện thí nghiệm hệ thống FO 36 Bảng Điều kiện thí nghiệm hệ thống NF 37 Bảng Giá trị thông lượng nước thông lượng chất tan thấm ngược thu dung dịch lôi khác với nồng độ 50 Bảng Hiệu thu hồi dung dịch lôi sử dụng màng NF-90 54 DANH MỤC HÌNH Hình Bản đồ xâm nhập mặn vùng Đồng sông Cửu Long (Tháng 3/2016)[3] Hình Thành phần nguyên tố nước biển Hình Sơ đồ nguyên lý vận hành công nghệ MSFD Hình Sơ đồ mô tả hoạt động công nghệ RO 10 Hình Sơ đồ mô tả hoạt động công nghệ ED 11 Hình Sơ đồ nguyên lý phương pháp tách nước sử dụng màng FO [21] 17 Hình Màng TFC sử dụng công nghệ FO có cấu tạo lớp[7] 18 Hình Cấu tạo màng TFC sử dụng công nghệ FO kính hiển vi: (A) Mặt lớp Polyamide; (B) Mặt lớp PSF [7] 19 Hình Mặt cắt ngang màng TFC sử dụng công nghệ FO kính hiển vi: (A) Lớp vải PET không dệt; (B) Hình ảnh phóng to hình dạng dày, gần giống bọc, gần lớp hoạt động [7] 20 Hình 10 Vị trí lấy mẫu nước biển xã Thạch Trị, huyện Thạch Hà, tỉnh Hà Tĩnh ngày 16/11/2016 32 Hình 11 Hệ thống lọc FO quy mô phòng thí nghiệm 36 Hình 12 Modun gắn màng lọc FO 37 Hình 13 Hệ thống loại bỏ dung dịch lôi để thu hồi nước 38 Hình 14 Độ dẫn điện phức sắt khác nồng độ khác sử dụng chất lôi thí nghiệm FO 42 Hình 15 Ảnh hưởng dung dịch lôi khác đến pH: (a) dung dịch Amoni sắt (II) sunphat, (b) Amoni sắt (III) citrat, (c) Amoni sắt (III) sunphat 44 Hình 16 Ảnh hưởng dung dịch lôi khác đến TDS: (a) dung dịch Amoni sắt (II) sunphat, (b) Amoni sắt (III) citrat, (c) Amoni sắt (III) sunphat 46 Hình 17 Sự thay đổi thông lượng nước thấm qua màng (Jw) với nồng độ muối loại dung dịch lôi khác 47 Hình 18 Sự thay đổi thông lượng chất tan thấm ngược (Js) thấm qua màng với nồng độ muối loại dung dịch lôi khác (khi dung dịch đầu vào nước deion) 48 Hình 19 Sự thay đổi tỉ số dòng thấm ngược chất tan (SRSF) thấm qua màng với nồng độ muối loại dung dịch lôi khác (khi dung dịch đầu vào nước deion) 49 Hình 20 Biểu đồ thể số thông số vận hành màng FO với nồng độ tối ưu dung dịch lôi khác 51 Hình 21 Giá trị thông lượng nước qua màng với mẫu nước đầu vào khác 52 Hình 22 Giá trị thông lượng chất tan thấm ngược với mẫu nước đầu vào khác 53 MỤC LỤC MỞ ĐẦU CHƢƠNG – TỔNG QUAN 1.1 Tình trạng thiếu nƣớc sinh hoạt Việt Nam 1.2 Thành phần nƣớc biển 1.3 Tổng quan công nghệ khử mặn nƣớc biển 1.3.1 Các công nghệ khử mặn nước biển 1.3.2 So sánh công nghệ khử mặn 12 1.4 Hệ thống lọc nƣớc sử dụng màng thẩm thấu chuyển tiếp (FO) 14 1.4.1 Cơ sở khoa học tượng thẩm thấu chuyển tiếp 14 1.4.2 Nguyên lý hoạt động 16 1.4.3 Vật liệu màng 17 1.4.4 Chất lôi lý tưởng cho trình thẩm thấu chuyển tiếp 20 1.4.5 Các nghiên cứu dung dịch lôi phương pháp thu hồi 22 1.4.6 Ứng dụng công nghệ FO xử lý nước 24 1.5 Cơ sở khoa học lựa chọn dung dịch lôi phƣơng pháp thu hồi màng NF nghiên cứu 29 1.5.1 Cơ sở khoa học lựa chọn dung dịch lôi nghiên cứu 29 1.5.2 Cơ sở khoa học lựa chọn phương pháp thu hồi màng NF 30 CHƢƠNG – ĐỐI TƢỢNG, NỘI DUNG VÀ PHƢƠNG PHÁP NGHIÊN CỨU 32 2.1 Đối tƣợng phạm vi nghiên cứu 32 2.1.1 Đối tượng nghiên cứu 32 2.1.2 Phạm vi nghiên cứu 33 2.2 Giả thuyết nghiên cứu 33 2.3 Nội dung nghiên cứu 33 2.4 Phƣơng pháp thực nghiệm 34 2.4.1 Vật liệu, hóa chất thiết bị 34 2.4.2 Mô hình thực nghiệm 35 2.4.3 Tiến hành thí nghiệm 38 2.4.4 Các thông số tính toán 40 CHƢƠNG – KẾT QUẢ NGHIÊN CỨU VÀ THẢO LUẬN 42 3.1 Đặc tính đặc điểm phức chất sắt 42 3.2 Kết khảo sát ảnh hƣởng dung dịch lôi (về nồng độ loại dung dịch) đến số thông số vận hành hệ thống lọc FO 43 3.2.1 Ảnh hưởng dung dịch lôi đến pH 44 3.2.2 Ảnh hưởng dung dịch lôi đến TDS 45 3.2.3 Ảnh hưởng dung dịch lôi đến thông lượng nước (Jw), thông lượng chất tan thấm ngược (Js) tỉ số dòng chất tan thấm ngược 47 3.2.4 So sánh số thông số vận hành hệ thống lọc FO với dung dịch khác 50 3.3 Ảnh hƣởng nồng độ dung dịch đầu vào đến hiệu lọc qua màng FO 52 3.4 Ảnh hƣởng chất lôi khác đến hiệu thu hồi nƣớc qua màng NF 54 KẾT LUẬN VÀ ĐỀ XUẤT 55 TÀI LIỆU THAM KHẢO 57 PHỤ LỤC - Định hƣớng thu hồi liti dịch cặn thải hệ FO 61 PHỤ LỤC - Một số hình ảnh trình thực nghiên cứu 63 PHỤ LỤC - Một số kết nghiên cứu 65 PHỤ LỤC – Các công trình công bố có liên quan đến luận văn 68 MỞ ĐẦU Tính cấp thiết đề tài Nước nhu cầu thiếu đời sống người Việc cung cấp đầy đủ nước đảm bảo chất lượng số lượng thách thức quốc gia Trong báo cáo chung công bố ngày 14/4/2015, Tổ chức Nông Lương Liên Hiệp quốc (FAO) Hội đồng Nước giới (WWC) cảnh báo, tác động môi trường sống tượng biến đổi khí hậu, nhiều quốc gia phát triển phải đối mặt với nguy nước diện rộng năm tới Theo hai tổ chức này, không cải thiện, giới phải đối đầu với khủng hoảng nghiêm trọng nước dân số giới tăng nhanh chóng với dự báo đạt tỷ người vào năm 2050 Một báo cáo gần Ngân hàng Thế giới ước tính, tới năm 2030, nhu cầu nguồn nước người vượt lượng cung tới 40% Theo Liên hiệp quốc, có 2,6 triệu người toàn cầu không tiếp xúc với điều kiện vệ sinh tỷ người không dùng nước Cứ 20 giây lại có trẻ em tử vong bệnh liên quan đến tình trạng thiếu nước điều kiện vệ sinh phù hợp Tại Việt Nam, có khoảng 41 triệu người dân nông thôn chưa có nước (theo quy chuẩn kỹ thuật quốc gia chất lượng nước sinh hoạt Bộ Y tế ban hành năm 2009) Chỉ có 8% dân số nông thôn có nước máy nhà có đường ống dẫn nước vào sân, 82% lấy nước từ nguồn đãđược cải thiện bên nhà, 10% phải lấy nước từ nguồn chưa cải thiện (theo báo cáo ADB - Ngân hàng Phát triển châu Á) Bên cạnh đó, mục tiêu Chiến lược Quốc gia cấp nước vệ sinh nông thôn Thủ tướng Chính phủ phê duyệt định 104/2000/QĐ/TTg ngày 25/8/2000 đặt mục tiêu đến 2020 “tất dân cư nông thôn sử dụng nước đạt tiêu chuẩn quốc gia với số lượng 60 lít/người/ngày”, đồng thời nêu rõ cần thử nghiệm phát triển công nghệ xử 74 75 76 Novel draw solutes of iron complexes easier recovery for forward osmosis process Nguyen Quang Trung, Le Van Nhan, Pham Thi Phuong Thao, Le Truong Giang Center for Training, Consultancy and Technology Transfer (CTCTT), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet Street, Cau Giay District, Hanoi City, Vietnam Corresponding Author: Dr Nguyen Quang Trung Center for Training, Consultancy and Technology Transfer (CTCTT),Vietnam Academy of Science and Technology 77 (VAST).No.18 Hoang Quoc Viet Street, Cau Giay District, Hanoi City, Vietnam.Tel: 0084-948109977; E-mail: nqt79@yahoo.com Abstract Forward osmotic membrane is a new process for produce fresh water from salty water The study of draw solute is one of essentials in the development and application of FO technology, draw solution should be good at drawing water and easy at recovery In this paper, three complex draw solutes such as ammonium iron (II) sulfate, ammonium iron (III) sulfate and ammonium iron (III) citrate with different concentrations were studied The physical properties such as pH, conductivity and TDS have simultaneously been investigated pH of most ammonium complexes were decreased whereas TDS increased with increasing of draw solution concentrations We found that high water flux of these iron complexes were reported in ranged from 8.88 to 11.24 LMH which higher than ammonium bicarbonate draw solution In addition, more than 90% iron complexes draw solutions were recovered by NF-90 membrane, which plays an important role in FO process to produce fresh water substitute ammonium bicarbonate This study provides direct evidences for the ability of permeate water from feed solution to draw solution, which shows the potential applications of iron complexes in FO process Key words: iron complex, FO membrane, NF, water flux, reserve salt flux Introduction Along with the rise of sea level, the status of salinity is happening in many countries in the world including Vietnam, which is seriously impacted on agricultural production and living life in these areas Results, many people will be lacked clean water to use in their daily life in the world To cope with these issues, technologies of seawater treatment were found by scientists in the world Desalination can be defined as any processes that remove salts from water At present, two types of technologies that are widely used around the world for desalination could be broadly classified as either thermal technology or membrane technology These technologies need energy to operate and produce fresh water According to Xiang Zheng et al (2015), membrane technology was popular applied for industrial wastewater treatment in China with around 6.7 million m of wastewater per day (2.4 billion m3 per year) treatment capacity applies membrane technology Xianbin (2013) used RO membrane filtering system for seawater desalination in the first phase of the Hongyanhe Nuclear Power Plant in China The system has maximum capacity of 16,000m3/day and purifies some 5.8 million m3 of seawater per annum for power generation and domestic water Forward osmosis (FO) membrane is valuable technology, which driven clean water permeates from feed solution to draw solution by the osmotic pressure difference across a semi-permeable membrane With the low operation cost, the FO membrane technology was widely applied in wastewater treatment (Achilli et al 2009), brackish water and seawater desalination (Mc Cutcheon et 78 al 2006), food processing (Garcia et al 2009, Petrotos et al 2001), and power generation (Achilli et al 2009, Seppala et al 1999) According to Sherub et al (2013), the major factors affecting the performances of forward osmosis includes membrane properties, draw solution properties, feed solution properties and the operation conditions To find out the suitable draw solutes becomes particularly crucial for FO process Klaysom et al (2013) and Ge et al (2013) indicated that the ideal draw solute should be taken the principal traits such as: high solubility, minimal reverse draw solute leakage, easy regeneration, nontoxicity, low cost, and compatibility with membrane The inorganic salts were investigated as draw solutions in the FO process in the previous studies due to their low cost and hight osmotic pressure potential, which creats a high flux (Achilli et al., 2010; Alnaizy et al., 2013) According to Kiriukhin and Collins (2002), the low charge and small hydrated radius of monovalent and divalent ions in the draw solution can result in a high reverse flux of salts, such as 0.6M NaCl (7.2 GMH), 0.6M NH4HCO3 (18.2 GMH) when deionized (DI) water was used as the feed solution On the other hand, a high mount of energy as the pressure-driven, which was required by the reverse osmosis (RO) membrane to produce freshwater and recover these draw solutions (Zhao et al., 2012) In the past few decades, many studies were reported in the development of suitable draw solutions for FO process; and a few reviews on draw solutions have been published to date (Chekli et al 2012; Ge et al 2013) Draw solutions can be generally classified as volatile compounds, organic compounds, inorganic compounds and novel synthetic compounds including MNPs and polymer hydrogel Some of draw solutions showed justifiable water flux such as: 2-methylimidazole-based organic compounds (Yen et al., 2010), switchable polarity solvents (Stone et al., 2013), ferric and cobaltous hydro acid complexes (Ge et al., 2014) and poly (sodium 4-styrenesulfonate) (Tian et al., 2015) However, high reverse salt flux and relatively energy-intensive regeneration make them impractical in FO desalination Therefore, identifying novel draw solutes with characteristics of high water flux, low reverse salt flux, and easy recovery is necessary in FO process Thus, in this study, a series of Ammonium complexes were investigated as draw solutes in FO process on the parameters such as water flux, reserve flux, solute rejection, and the results of FO process after hour experiment Exploration of suitable draw solutes plays an important role to develop the further advancement of FO process and even commercialization of FO membrane (Ren et al., 2014; Shaffer et al., 2015) Methods 2.1 Materials Laboratory-grade chemical reagents were purchased from Sigma-Aldrich Corporation, Germany The properties of these complexes were showed in the Table Deionized water was produced by an ultrapure water system (Purelabflex-3, ELGA, UK) The pressure of these iron complexes were calculated as the most suitable concentration of each complex following the formular: P = R.T.C (bar) Where: P: pressure (bar), R = 0.082, T = 273 + t(oC), C (M) is the concentration of complex as 0.1M, 0.4M, 1.0M and 1.5M were the most suitable concentrations of Ammonium Iron (II) Sulfate, Ammonium Iron (III) Citrate, Ammonium Iron (III) Sulfate and Ammonium bicarbonate complexes in forward osmosis and NF processes, respectively 79 Table The properties of complexes used in FO process Complex Ammonium Iron Ammonium Iron Ammonium Iron (II) Sulfate (A2S) (III) Sulfate (A3S) (III) Citrate (A3C) Formula (NH4)2Fe(SO4)2·6H NH4Fe(SO4)2·12 2O Ammonium Bicarbonate (AB) (NH4)5Fe(C6H4O7)2 NH4HCO3 FeNH4(SO4)2 C6H8O7.xFe3+.yNH3 NH4HCO3 262.97 79.056 g/mol Fe3+ NH4+ H2O, or NH4[Fe(H2O)6](SO4 )2·6 H2O Chemical (NH4)2Fe(SO4)2·6H formula 2O Molar 284.05 g/mol 482.25 g/mol mass (anhydrous) (dodecahydrate) 392.13 g/mol (hexahydrous) Cations Fe2+ and NH4+ Fe3+ and NH4+ Solubility 269 g/L 1240 g/L in water (hexahydrate) Very soluble in water 11.9 g/100 mL (0°C) 21.6 g/100 mL (20°C) 36.6 g/100 mL (40°C) Density 1.86 g/cm3 1.71 g/cm3 n.i 1.586 g/cm3 Pressure 2.44 (bar) 9.77 (bar) 24.44 (bar) 36.65 (bar) 2.2 Characterizations of iron complexes The pH values, TDS and electrical conductivity of the iron complexes solutions were determined by pH, TDS and conductivity sensors (LAQUA pH/Ion/Cond Meter F74BW, HORIBA, Japan)at different concentrations as 0.05, 0.10, 0.15 and 0.20 M (A2S), as 0.05, 0.10, 0.15, 0.20, 0.40, 0.50 and 1.00 M (A3S) and 0.05, 0.10, 0.15, 0.20 and 0.40 M (A3C), respectively 2.3 Experimental setup The experimental setup was showed in Fig.1 The active layer of FO membrane was oriented to face the feed solution in order to reduce internal concentration polarization (CP) and thus obtain high water flux, and the support layer facing the draw solution The total membrane surface area was 32 cm2 During experiments, the feed and draw solutions on both sides of the FO membranes were re-circulated by using two separate pumps with the same flow rate of 1.2 L/min, respectively The system was operated at laboratory conditions Each treatment was repeated three times during hour at room temperature 80 (around 25 ± 5oC) pH, TDS and conductivity sensors (LAQUA pH/Ion/Cond Meter F74BW, HORIBA, Japan) were used to monitor any changes in the containers of feed and draw solutions period 15 per time during experiments The initial volume of draw solution was 0.2 L, and a 0.2 L feed solution glass was placed on digital scale balance (Sartorius, Goettingen, Germany) to monitor the weight and volume changes at specified time intervals (Figure 1a) After FO test, the diluted draw solution was recovered for reuse through NF-90 membrane by using a cross flow module as Fig.1b at room temperature NF-90 (DOWN) membrane was made from polyamide materials which can used in pH ranged from 2-11 with 6.68 LMH/bar of pure water permeability The filtration experiments were repeated three times using fresh membranes The selection of the most appropriate experimental concentration for each complex is made before comparing test results between complexes H2O Draw solution Feed solution Pump a „v FO Membrane 81 Pump NF membrane Pump Diluted draw solution Valve Valve H2O Draw Solution H2O b Fig.1 Re-cycle system using Forward Osmosis membrane in desalination Water flux, reserve flux and solute rejection were determined according to the studies of Hau et al (2015) and Enling et al (2015) as methods below: The water flux (Jw) across the FO membrane was calculated from the volume ∆V change of feed solution using Equation: Jw = A∆t Where: ∆V (L) is the volume of water permeated from feed solution to draw solution over a predetermined time ∆t (h) during FO tests, A (m2) is the effective FO membrane area Iron complexes salts dissociated and conductive in their draw solution, some ions from draw solutions will permeate to feed solution through FO membrane The conductivities measured from the feed solution at certain time, which relative to concentration of draw solution and were considered as the reserve salt flux base on a standard concentration – conductivities curve The reserve salt flux (GMH) was determined by the Equation: 82 Js = Ct Vt −Co Vo Am ∆t -1 Where: Co and Ct (mol.L ) are the initial concentration and the concentration of feed solution measured at the time of t, respectively Vo and Vt (L) are the initial volume and the volume of feed solution measured at the time of t, respectively Results and discussion 3.1 Properties and Characterization of iron complexes Two different cations such as Fe+2 and NH4+ were found in all of various iron complexes A2S is classified as a double salt of ferrous sulfate and ammonium sulfate It form monoclinic crystals, solubility in water around 269 (g/L) About 1240 (g/L) of solubility in water and the weakly violet and octahedrical crystals were noted in A3S complex whereas A3C was appeared in yellow crystals and very soluble in water 30 Conductivity (mS/cm) 25 y = 27x R² = 20 y = 21.4x R² = A2S A3S A3C Linear (A2S) 15 y = 19x R² = 10 Linear (A3S) Linear (A3C) 0 0.2 0.4 0.6 0.8 1.2 Concentration (M) Fig.2 Conductivity of different concentrations of various iron complexes as draw solutes in FO process The solution properties of various iron complexes with different concentrations were characterized and recorded in Fig.2, which played an important role to further check whether iron complexes could act as draw solutes There is a little effect of concentrations on the pH of various iron complexes pH of different concentrations of A3S was ranged from 1.96 to 2.53, then was higher in A2S (3.79-3.88) and was 7.26-7.56 as maximum in A3C The recommended operational pH ranges of the current commercial thin film composite (TFC) FO membrane is from 2.0 to 12.0 Therefore, the FO membrane will not 83 undergo hydrolysis and structure change when it is tested in the draw solutions of the iron complexes, which can ensure the consistent FO performance As show as Figure 2, the solution conductivity was increased with increasing concentrations of various iron complexes This is in contrast with the studies of Yuntao Zhao and et al (2016), the solution conductivity of four EDTA complexes is not directly proportional to that of the increment concentration, and appears to approach plateaus or even decrease slightly after an initial increase In addition, the difference was existed in conductivity for the studied iron complexes following the order of A2S > A3C > A3S According to Ge et al (2012), the higher conductivity may lead to higher osmotic pressure The electrical conductivity in the iron complexes solution mainly derives from two sources including: the dissociation of iron ion and ligand which is affected by the property of iron ion and external conditions Therefore, the measured conductivity of ion complexes solution results from the joint effects 3.2 Effect of iron complexes on reserve salt flux and water flux in FO process The results showed that 0.1M, 0.4M and 1.0M were the most suitable concentrations of Ammonium Iron (II) Sulfate, Ammonium Iron (III) Citrate and Ammonium Iron (III) Sulfate complexes in forward osmosis process, respectively The comparing between these concentrations of these complexes was performed to select the potential draw solute for forward osmosis process The iron complexes as draw solutes were evaluated by quantifying reserve salt flux and water flux in FO tests, which was showed in Fig.3 In addition, NH4HCO3 was chosen as a benchmark for comparison with iron complexes group Results in Fig.3 shows that the experimental water flux and reserve salt flux as a function of molar concentration in FO mode where de-ionized water is employed as the feed solution We found that the water flux of A3S (11.24 LMH) was obviously higher than A2S (8.88 LMH), A3C (8.88 LMH) and the control group (NH4HCO3) (8.62 LMH) This is directly related to the fact that high water flux can generate greater osmotic driving force for water transport through the membrane Result reported that 36.0 mL of water volume was found in A3S which was obviously higher than A2S (28.4 mL), A3C (28.4 mL) and control group - AB (27.6 mL) However, the reserve salt flux was 2.62700 (GMH) as the highest in A3S solution then was A3C (1.44450 GMH) and control group (1.31415 GMH), and lowest at A2S (0.00143 GMH) This indicated that, the molecular sizes of complexes were ranged in order: A3S < A3C < AB < A2S Hence, molecular size lead to draw solutes permeated back to feed solution through FO membrane, which might be affected to the next stages of fresh water production Both water flux and water volume of both A2S and A3C were higher than AB In the other hand, the reserve salt flux of A2S was obviously lower than A3C and AB According to Kiriukhin and Collins (2002), the resereve fluxs of salts were 7.2 GMH in 0.6M NaCl, 18.2 GMH in 0.6M NH4HCO3, 5.6 GMH in 0.5M MgCl2 when deionized (DI) water was used as the feed solution In the studies of Hau et al (2015), the results showed that lowest reverse salt flux of 0.067 GMH was observed when 0.1 M EDTA-2Na coupled with 15 mM NP7 was used as a draw solution and deionized water was used as a feed solution in FO mode (active layer facing with the feed solution) These results were much higher in comparision with the reserve 84 flux of Ammonium Iron (II) Sulfate in this study This dimonstrated that just only a few of Ammonium Iron (II) Sulfate salts were permeated back to feed solution from draw solution through FO membrane This indicated that A2S might be the potential draw solute in FO process Reserve salt flux (GMH) 12 10 2.5 1.5 0.5 0 A2S A3S A3C Complexes Reserve salt flux (GMH) Water flux (LMH) Water flux (LMH) AB Fig.3 The comparison of reserve salt flux, water flux and water volume between iron complexes and NH4HCO3 3.3 Recovery test of iron complexes draw solution via NF membrane Table Recovery efficient of draw solution using NF-90 membrane Draw TDS input (mg/L) TDS output (mg/L) solution Removal efficiency (%) A2S 12700 1148 90.96 A3S 44600 1998 95.52 A3C 31300 2147 93.14 The draw solution is diluted after FO process, thus the recovery of draw solution is necessary and represents as one of challenges in FO process (Zhao et al., 2014) The large molecular weight and size of iron complexes can be considered to separate from water with a relatively larger pore size membrane than that of RO The recovery convenience of 85 iron complex draw solution was studied through a pressure-driven NF-90 process Table showed the variation in the total dissolved solids (TDS) permeate and removal efficiencies obtained using various draw solutions as A2S, A3S and A3C in comparison with AB at operation of bars Over than 90% of draw solutes was not permeated through NF-90 membrane, in which 90.96% and 93.14% removal efficiencies were reported in A2S and A3C draw solution, respectively; and 95.52% of A3S as maximum of removal efficiency In the previous studies of Hau et al (2014) indicated that the NF recovery (pressure of 5.5 bar) of EDTA sodium salts exhibiting high charged compounds performed well, and had a high salt rejection of 93% NF membrane was used by Ge and Chung (2013) to regenerate hydroacid complexes after FO, which had expanded configurations and charged groups According to Hau et al (2015), the recovery of 0.05M EDTA-2Na coupled with 15 mM NP7 was approximately 95%, which significantly higher than A2S and A3S draw solutions, but a little less than A3C draw solution These results demonstrated that a series of iron complex draw solutions can be easily recovered using NF-90 membrane, which plays an important role in FO process to produce fresh water using iron complexes as draw solutes substitute AB Conclusion In summary, various iron complexes were investigated as draw solutes in FO process Results showed that high water flux of these iron complexes were reported in ranged from 8.88 to 11.24 LMH which higher than AB draw solution In addition, more than 90% iron complexes draw solutions were recovered by NF-90 membrane, which plays an important role in FO process to produce fresh water substitute AB Abbreviations TDS: Total Dissolved Solids, FO: Forward Osmosis, NF: nanofiltration, RO: Reserve Osmosis, DI: 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