Synthesis of Sepiolite-Chitosan Composites and Investigation of Cr(VI) Adsorption from Aqueous Solution by Using This Composite

Many natural or commercial adsorbents have been commonly used for the removal of dues, heavy metals, and other pollutants from the environment. Due to low-cost and abundance of natural adsorbents, they are mostly preferred. Moreover, new sources have indicated that more efficient biosorbents from natural adsorbents. One of the ways to make these natural adsorbents more efficient is preparation of composites. The hydroxyl (-OH) and amino (-NH2) groups present in the structure of chitosan provide a binding capacity for the adsorbent to remove heavy metals. Clays, on the other hand, are usually used in adsorption processes and negativities affecting hydrodynamic properties such as aggregation and coagulation are encountered in practice. These negativities can be removed by using composites prepared from clays with chitosan polymer. In this study, a composite adsorbent was prepared from sepiolite clay and chitosan (SK) and FTIR analysis of composite beads was carried out. Then SK composite was used for the removal of Cr (VI) ions from aqueous solutions. The effects of parameters such as pH, adsorbent amount, adsorbate concentration and contact time were investigated for Cr(VI) adsorption. Scatchard and Dubinin-Radushkevich (D-R) adsorption isotherm models were used for the analysis of adsorption equilibrium. For adsorption process, Scatchard adsorption was well fitted to the data of adsorption. It was determined that sepiolite and SK composite removed Cr(VI) ions respectively 3.11 and 61.048 mg/g with maximum adsorption capacity (25 ◦ C, pH 2, contact time 60 minutes, 0.04 g adsorbent amount ). It was concluded that SK composite can be effectively used for Cr(VI) removal from aqueous solutions.