Optimization of Hexavalent Chromium Removal from Wastewater Using Activated Carbon Derived from Liming Pelt Trimming and Tannin: A Response Surface Methodology Approach

Abstract

In leather industries, chromium compound is used in tanning and around 60–70% of the applied chromium is consumed by the leather fiber and the rest of them are being discharged as a mixed toxic effluent. This effluent is a major source of chromium contamination and generates significant amounts of toxic hexavalent chromium (Cr(VI)) in wastewater. In this study, activated carbon derived from liming pelt trimmings, a byproduct of the leather industry, was utilized for the removal of Cr(VI) from aqueous solutions. The process was optimized using Response Surface Methodology (RSM) with Central Composite Design (CCD), achieving a remarkable 99% Cr(VI) removal efficiency under optimal conditions (initial concentration, 118.26 ppm; pH, 2.11; adsorbent dosage, 14.39 g/L; and time, 5.44 h). Adsorption kinetics followed a pseudo-second-order model with an R2 of 0.9889. Assessment and evaluation of different thermodynamic parameters such as ΔGo (−5.18 kJ/mol), ΔHo (−90.22 kJ/mol), and ΔSo (−0.29 kJ/mol) revealed that the adsorption of chromium species on activated carbon was exothermic and spontaneous in nature. The adsorption capacity of the activated carbon composite material from leather trimming wastes was recorded as 79.58 mg/g, exceeding that of other natural adsorbents. The results demonstrated that the synthesized activated carbon was an effective and sustainable adsorbent, offering a promising solution for the removal of Cr(VI) from industrial wastewater. This novel approach not only helps mitigate the environmental impact of leather industry effluents but also turns waste materials into a valuable resource for pollution control.