Dual modifications of chitosan with PLK for amputation of cyanide ions: Equilibrium studies and optimization using RSM.

The aim of the study is to characterize and hierarchically modify chitosan using partially lateritized khondalite (PLK) rock. PLK is a metamorphic rock rich in mineral oxides and is not commercialized thus, treated as a mining reject. Chitosan was sequentially altered to Chitosan-PLK (Ch-PLK) and Chitosan-PLK-Epichlorohydrin (Ch-PLK-ECH) and both the materials were characterized by FT-IR, SEM, EDX, XRD, XRF and BET surface area analysis. The adsorbents were used for removal of cyanide ions from aqueous solution using batch adsorption experiments. The experiments were performed varying operational parameters and were optimized using RSM. The conditions optimized by RSM were carried out, more than 90 % of CN adsorption was observed. The isotherm and kinetics studies have shown that the adsorption process fitted well with Langmuir isotherm model and pseudo second order kinetics. Using Langmuir isotherm, the maximum adsorption capacities of Ch-PLK and Ch-PLK-ECH towards cyanide ions at 30 °C were found to be 23.98 mg g and 65.27 mg g respectively. Thermodynamic studies described that adsorption process was spontaneous, enthalpy-driven over entire temperature range. Column studies established that the adsorbents may be applicable to large volume of samples. The adsorbents were tested for regeneration for 5 adsorption-desorption cycles suggesting reusability of the materials.