Egyptian Journal of Petroleum xxx (2017) xxx–xxx Contents lists available at ScienceDirect Egyptian Journal of Petroleum journal homepage: www.sciencedirect.com Full Length Article Magnetic zeolite-natural polymer composite for adsorption of chromium (VI) Amany Gaffer a,⇑, Amal A Al Kahlawy b, Delvin Aman b a b Petroleum Application Department, Egyptian Petroleum Research Institute (EPRI), Ahmed El Zomour St., Nasr City, PO Box 11727, Cairo, Egypt Petroleum Refining Department, Egyptian Petroleum Research Institute (EPRI), Ahmed El Zomour St., Nasr City, PO Box 11727, Cairo, Egypt a r t i c l e i n f o Article history: Received 21 August 2016 Revised 21 November 2016 Accepted December 2016 Available online xxxx Keywords: Magnetic zeolite Chitosan Composite Adsorption Sol-gel a b s t r a c t Magnetic zeolite-Chitosan (MZC) composite was prepared with sol-gel method by mixing magnetic/zeolite and Chitosan for enhanced removal of hexavalent chromium [Cr (VI)] from aqueous solution The morphology of the prepared adsorbent was analyzed with FTIR spectroscopy, field-emissions scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) The effects of pH, contact time, initial concentration and Sorbent dosage on the adsorption capacity were experimentally determined The concentration of the Cr ions was measured using (GBC) Ó 2017 Production and hosting by Elsevier B.V on behalf of Egyptian Petroleum Research Institute This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Introduction Water contamination with heavy metals is a serious problem because metals tend to persist and accumulate in the environment Industrial and mining wastewaters are important origins of pollution of heavy metals Heavy metals are considered to be potentially harmful and can cause physiological and neurological disorders [1–4] The use of chromate and dichromate has many industrial applications such as in textile, electroplating, leather tanning, cement preservations, paints, and pigment sand metallurgy industries [5] Hexavalent chromium, Cr (VI) as an example of heavy metal often exists in the effluent soft he electroplating, tanning, mining, and fertilizer industries and acts as a carcinogen, mutagen, and teratogen in biological systems [6–9] Chromium consists of two stable oxidation states such as trivalent state Cr (III) and hexavalent state Cr (VI) in natural aqueous medium It is well known that, Cr (III) is main material of living organisms, whereas, Cr (VI) is more poisonous, carcinogenic and mutagenic, is considered as a dangerous pollutant due to high water-solubility and toxicity [10–12] Different techniques have been applied to remove Cr (VI) from the industrial wastewater, such as chemical precipitation, ion Peer review under responsibility of Egyptian Petroleum Research Institute ⇑ Corresponding author E-mail address: amany_jaffer@hotmail.com (A Gaffer) exchange, reduction, electrochemical precipitation, solvent extraction, membrane separation, cementation, electrodialysis and adsorption [13] Adsorption technique using biopolymers is one of the most recommended processes, due to economic and technical advantages [14–21] The major benefits of biosorption over conventional treatment methods include: Low price, high effectiveness, minimization of chemical and/or biological mud, rebuilding of biosorbent and possibility of metal recovery Natural zeolites have been used as cationic exchange materials for the treatment of heavy metals and other contaminants due to their excellent properties as adsorbents They also have the advantages of being very abundant in nature and possessing high chemical stability Among many biosorbents, Chitosan can be a superior biosorbent for metals because its amine (–NH2) and hydroxyl (–OH) groups may act as coordination sites to form complexes with various heavy metal ions [22–25] In recent studies Chitosan has been used for removing cationic and anionic metals such as copper [26] mercury and lead [27,28] It integrates with metal ions by three forms: ion exchange, adsorption and chelation Both natural zeolite and Chitosan are adsorption materials In adsorption, bulk materials suffer from enormous mass transfer resistance due to large surface areas and large diffusion lengths To overcome these limiting factors in adsorption, adsorption media could be designed to have some nano-features in order to enlarge http://dx.doi.org/10.1016/j.ejpe.2016.12.001 1110-0621/Ó 2017 Production and hosting by Elsevier B.V on behalf of Egyptian Petroleum Research Institute This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Please cite this article in press as: A Gaffer et al., Magnetic zeolite-natural polymer composite for adsorption of chromium (VI), Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2016.12.001 A Gaffer et al / Egyptian Journal of Petroleum xxx (2017) xxx–xxx mass transport kinetics by providing contaminants with rapid access to high surface area and by encourage internal mass transport [29,30] One way of achieving this is by developing nano-composites in which nanoparticles are embedded in bulk materials This study explores the use of magnetic natural zeolite-Chitosan composite as a strong adsorption media for hexavalent chromium removal from water The main objective of the present work was to use the biosorbents for water purification, determining the effects of several variables, including solution pH, adsorbent dose, initial concentrations and contact time It is shown that the material exhibit an enhanced capacity for hexavalent chromium Materials and methods 2.1 Materials Ammonium Y zeolite was obtained in powder form Aldrich FeCl36H2O, FeCl24H2O from Sigma-Aldrich and Na2So3for magnetic zeolite preparation A stock solution of Cr (VI) was prepared by dissolving a known amount of potassium dichromate (K2Cr2O7) with deionized water Hydrochloric acid (HCl), acetone and ethanol were also used into adjust the pH of the solution and for analysis of Cr (VI), respectively Chitosan (CH) M.W (Molecular weight 100,000–300,000) was purchased from the pharmacy as tablets which were crushed by a miller Scheme The general procedure for the synthesis of magnetic zeolite-Chitosan (MZC) composite Fig Structure of Chitosan 2.2 Methods 2.2.1 Synthesis of magnetic zeolite (MZ) Magnetic particles were prepared through co-precipitation of Fe3+ and Fe2+ with Na2So3 (molar ratio 2:1) Zeolite powder mg was added to the magnetic particles and the mixture was stirred and heated up to 80 °C under N2 atmosphere for h The solution was continuously stirred and cooled down to room temperature The obtained magnetic zeolite powder was washed repeatedly with deionized water until the neutral pH was obtained Finally, obtained magnetic powder was dried under vacuum for 12 h 2.2.2 Synthesis of the magnetic zeolite-Chitosan (MZC) composite Chitosan powder (0.5) g was dissolved by stirring in 50 ml of glacial acetic acid solution A known amount of magnetic zeolite (0.5–4) g was dispersed in (80) ml deionized water and ultrasonicated for 20 After h of stirring the mixture was filtrate and the residue was washed with water and acetone The composite was then dried at 80 °C for h The general procedure for the synthesis of magnetic zeolite-Chitosan (MZC) composite is represented in Scheme the C-2, C-3 and C-6 positions, respectively, as shown in Fig 1, making it suitable for interact easily with the Cr (VI) ions The removal efficiency of Cr (IV) was determined by the following equation %Removal ¼ ½ðCo À Ce Þ=Co  100 ð1Þ where Co and Ce are the initial and the equilibrium concentration (mg/L) of Cr (VI), respectively Fig Shows X-ray diffraction patterns of crystalline structure of MZ-C nanocomposite From the Fig We can observe that iron oxide cubic structure and six peaks in 2h of 30.1, 35.5, 43.2, 53.5, 57.0 and 62.8, which were related to their corresponding indices (2 0), (3 1), (4 0), (4 2), (5 1) and (4 0), respectively Fig The weaker diffraction lines of MZ-C compared with Fe3O4 nanoparticles indicate that the 2.2.3 Characterization The morphology of the magnetic zeolite-Chitosan was characterized by FTIR spectroscopy and scanning electron microscopy (SEM) (Hitachi S-4200) using an accelerating voltage of kV X-ray diffraction Analysis (XRD) was carried out using Shimadzu XD-diffractometer with high intensity Cu K with 2h range between 4° and 80° The concentration of Cr ions were measured using an atomic absorption spectrometer (GBC) Avanta Results and discussion Chitosan has three types of reactive functional groups, an amino group as well as both primary and secondary hydroxyl groups at Fig XRD pattern of MZ-C Please cite this article in press as: A Gaffer et al., Magnetic zeolite-natural polymer composite for adsorption of chromium (VI), Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2016.12.001 A Gaffer et al / Egyptian Journal of Petroleum xxx (2017) xxx–xxx Fe3O4 nanoparticles were covered by amorphous Chitosan polymer Chitosan did not destroy the crystal structure of iron oxide NPs Moreover, a very weak broadband at 2h = 12°–20° appeared in the MZ-C, which could be related to the amorphous Chitosan formed around the MZ Fig The average crystal size of pure Fe3O4 and Chitosan-coated Fe3O4 nanoparticles are about 400– 700 nm, respectively Fig Show FTIR spectroscopy of Fe3O4, zeolite, MZ, Chitosan (C), MZ-C (composite) The strong absorption peak at $583 cmÀ1 is the characteristic band of the Fe–O stretching vibration of Fe3O4 nanoparticles The Fe–O stretching vibration band of the bulk magnetite is usually at $570 cmÀ1, and the band shifts to high wave numbers because of the finite size of nanoparticles IR spectra of zeolite show strong zeolite bands in the region 450–1200 cmÀ1 The strong band in the region 1000–1100 cmÀ1 can be attributed to the asymmetric stretching vibration of (Si/Al) O4 units For MZ sample the band of (Fe–O) observed at 445 cmÀ1 In Chitosan sample there are three characteristic absorption bands, one of them was very strong and appeared at about 3306 cmÀ1 this for stretching, vibration bands of (N–H and OH), the second strong one appeared at about 1593.54 cmÀ1 that may assign for (–CONH–) and the third band at 1054.90 cmÀ1 for (C–O–C) When the Chitosan was incorporated into the magnetic zeolite (MZ) many characteristic peaks in the FT-IR become very weak because of the strong interaction between Chitosan and (MZ) The FT-IR spectra results reveal that Chitosan is successfully coordinate with magnetic zeolite The surface morphology of the adsorption material was evaluated using field-emission scanning electron microscopy (FE-SEM) Fig shows the SEM images of MZ-C It can be seen that the magnetic zeolite has been covered by Chitosan and has a cauliflower-like structure in Fig MZ has been reported to act as growth centers for Chitosan which help in making compact structure for MZ-C composite Fig SEM images MZ-C Fig Effect of pH on Cr (VI) removal Effect of pH on Cr (VI) removal The effect of pH is an important operation in the adsorption process because it affects the solubility of metal ions, surface charge of adsorbent and also the degree of ionization and speciation of adsorbate during the reaction The pH effects were done at 2, 4, 6, 12 pH at room temperature As shown in Fig There is an obvious increase in removal efficiency when the acidity of the solution increases, i.e., from pH 12 to pH and the maximum removal occur at pH This is may be due to Hexavalent chromium exists in aqueous solution in the form of oxyanions such as HCrOÀ 4, 2À À Cr2O2À and CrO4 and as pH increase the monovalent form HCrO4 2À (dominated form) is converted to the divalent form CrO4 The increase in removal at low pH is due to the strong attraction between predominant oxyanions HCrOÀ and the positively charged surface of the adsorbent As the pH is increased more OHÀ ions are present in the solution and compete with chromate ions resulting in the reduction of Cr (VI) removal Fig FTIR spectroscopy of Fe3O4, Zeolite, MZ, Chitosan, MZ-C Please cite this article in press as: A Gaffer et al., Magnetic zeolite-natural polymer composite for adsorption of chromium (VI), Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2016.12.001 A Gaffer et al / Egyptian Journal of Petroleum xxx (2017) xxx–xxx the adsorbent dosage increased, the numbers of the active sites increased which were available for Cr ions to interact with The results therefore suggest that MZ-C is highly efficient in Cr (VI) removal as only a small quantity is required to achieve excellent performance and the optimum Sorbent dosage was at 0.1 g/L Effect of initial concentration The effect of initial concentrations of Cr (VI) was studied from (100 to 200) mg/L From the Fig It observed that when the initial concentration increases from (100 to 200 mg/L) the removal capacity increases too This is due to high driving force done by the large concentration tendency Fig Effect of Contact Time (h) Conclusion MZ-C was successfully synthesized, characterized and used as an adsorbent for the removal of Cr (VI) from aqueous solution The results show that removal efficiency is dependent on pH, initial concentration, adsorbent dosage and contact time The removal efficiency of 98% was obtained when the pH was and the initial Cr (VI) concentration was 200 mg/L This work confirms that the MZ-C is an effective adsorbent for the removal of Cr (VI) in aqueous solution However, further studies need to be done with industrial waste water to obtain real performance data References Fig Effect of adsorbent dosage Fig Effect of initial concentration of Cr (VI) Cr (VI) exists as hydrogen chromate anions (HCrOÀ ) between pH 2.0 and pH 6.5, and it exists as chromate ions (CrO2À ) at pH according to the following 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Baker, Chem Eng J 187 (2012) 193– 202 The results from the Fig Show that the removal efficiency of Cr (VI) was increased from 68% at 0.05 g to 98% in 0.1–0.25 g As Please cite this article in press as: A Gaffer et al., Magnetic zeolite-natural polymer composite for adsorption of chromium (VI), Egypt J Petrol (2017), http://dx.doi.org/10.1016/j.ejpe.2016.12.001