PREPARATION AND APPLICATION OF GLUTARALDEHYDE CROSS-LINKED CHITOSAN COATED BENTONITE CLAY CAPSULES: CHROMIUM(VI) REMOVAL FROM AQUEOUS SOLUTION
New sources in literature have explained that more efficient biosorbents can be developed from natural adsorbents. One of the methods to make these natural adsorbents more efficient is preparation of composites. Hydroxyl (-OH) and amino (-NH2) groups within the structure of chitosan leads adsorbents to have a binding potential with heavy metals. In this study, a composite adsorbent made of chitosan and bentonite clay was prepared. Bentonite clay and chitosan-coated Bentonite clay composite capsules (BC) were characterized in terms of FTIR and SEM analysis. (BC) composite adsorbent was used for the adsorption of Cr(VI) ions from aqueous solution. The effects of some parameters such as pH, adsorbent dosage, adsorbate concentration, temperature and contact time on the adsorption of Cr(VI) on BC were investigated. In order to evaluate the experimental data, Langmuir, Freundlich, Scatchard and Dubinin-Radushkevich (D-R) adsorption isotherm models were used for the analysis of adsorption equilibrium. The adsorption process was well fitted to Scatchard adsorption isotherm. While bentonite clay had 11,076 mg/g maximum adsorption capacity, BC composite had 106.444 mg/g maximum adsorption capacity for the removal of Cr(VI) ions (25 °C, pH 2, contact time 60 minutes). It was concluded that chitosan-bentonite composite adsorbent can be effectively used for the removal of Cr(VI).