Experimentation on raw and phosphoric acid activated Eucalyptuscamadulensis seeds as novel biosorbents for hexavalent chromium removal from simulated and electroplating effluents

Abstract Efficacy of Eucalyptus camaldulensis seeds in raw (ECS) and phosphoric acid activated form (PECS) in the remediation of Cr(VI) from simulated and electroplating waste has been checked in this study. Structural and physico-chemical characterization of the biosorbents have been elucidated using CHNS, Mercury intrusion porosimetry, FTIR and SEM-EDAX analyses. Batch parameters like dose of biosorbent, pH, contact time, speed of contact, temperature were optimized for a maximum removal of 91.44% for ECS and 98.27% for PECS. Monolayer adsorption capacity for ECS and PECs were found to be 35.3 ± 4.84 mg/g and 51.93 ± 8.11mg/g respectively, elucidated from the nonlinear isotherm analysis. Freundlich Model fitted well for both the biosorbents in removing Cr(VI) at optimum conditions. Interaction of Cr(VI) with ECS and PCES was explained more suitably by kinetics. Pseudo second order model fitting for ECS and PECS revealed that the process followed multilayered chemisorption. Thermodynamic studies confirmed the adsorption of Cr(VI) by ECS and PECS are energetically favorable, stable and exothermic. Continuous column operations for maximum removal of Cr(VI) were optimized for Column bed-height, Initial Cr(VI) concentration and Initial flow rate. Column performances were checked with Adams-Bohart, Thomas, Yoon-Nelson and Bed Depth Service Time (BDST) models. Efficacy of PECS in removing Cr(VI) from real effluent was checked using electroplating effluent containing 190 mg/L of Cr(VI) and resulted with 45.35% removal. Thorough experimental findings showed that PECS is a feasible biosorbent that can remediate Cr(VI) from aqueous solutions effectively.