Evaluation of the biosorption potential of a novel Caryota urens inflorescence waste biomass for the removal of hexavalent chromium from aqueous solutions

The present study was undertaken in order to evaluate the feasibility of a novel biosorbent Caryota urens inflorescence waste biomass (CUIWB) for the removal of hexavalent chromium from aqueous solutions. The biosorbent was characterized by SEM, FT-IR spectral and EDS analysis. Biosorption studies were carried out as a function of pH, initial Cr(VI) concentration, biosorbent size, biosorbent dosage, agitation speed and temperature. It was found that the biosorption capacity of CUIWB depends on solution pH, maximum biosorption capacity for Cr(VI) was observed at pH 2. The isotherm models like Langmuir, Freundlich, Dubinin-Radushkevich, Elovich, Redlich-Peterson, Sips, Koble-Corrigan were used to analyze the equilibrium data. Langmuir and Redlich-Peterson model better fitted the equilibrium data. The biosorption capacity obtained using Langmuir isotherms for Cr(VI) biosorption was 100 mg/g. Kinetic study was performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models, but higher degree of coefficient of determination was obtained for the pseudo-second-order kinetic model. Different thermodynamic parameters, viz., ΔG°, ΔH° and ΔS° have also been evaluated and it has been found that the biosorption was spontaneous at low Cr(VI) concentration (100 and 200 mg/L), endothermic and increased randomness in nature, respectively. Desorption study was carried out with 0.1 M NaOH solutions. Investigations carried out proved that CUIWB is a good potential biosorbent for the treatment of hexavalent chromium in aqueous media.