Removal of chromium (VI) from water using adsorbent derived from spent coffee grounds

An acid-treated adsorbent derived from spent coffee grounds is investigated for its adsorption toward chromium (VI) ions from polluted water by optimizing various physicochemical parameters such as pH, time of equilibration, initial concentration of Cr(VI), adsorbent dosage, temperature and interfering co-ions. 91.0% of removal is observed at optimum conditions, and the adsorption capacity is found to be as high as 22.75 mg/g. Adopting FTIR, EDX, XRD and SEM methods, the surface morphological studies are made. The nature of adsorption is analyzed using various adsorption isotherms, and it was found that Freundlich model describes well with R 2 : 0.9985 and R L : 0.0108, indicating the heterogeneous surface and favorable multilayer of adsorption. The kinetics of adsorption follows pseudo-second-order with R 2 : 0.9998. Further, thermodynamics studies reveal the endothermic nature of adsorption process. Even after five regenerations, the % removal has not come down below 81.0%. The methodology is successfully applied for the removal of chromium (VI) from polluted waters.