Cr(VI) removal from aqueous solutions using low-cost pumpkin peel activated carbon

Hexavalent chromium (Cr(VI)) poses a serious threat to human health, ecosystems and environmental balance due to its high toxicity. In this study, activated carbon (AC/PP) obtained from pumpkin peels (PP) was used for Cr(VI) adsorption. Cr(VI) adsorption was carried out in the range of pH (2-5), temperature (303, 318 and 333 K) and Cr(VI) (10-150 mg/L) concentration. Characterization analyses showed that the AC/PP adsorbent had a porous structure with high surface area (961 m²/g). According to FTIR results, it was evaluated that Cr(VI) adsorption did not cause a significant change in the structure. The Langmuir and Freundlich isotherm models were in good agreement with the experimental data. This shows that the AC/PP adsorption of Cr(VI) occurred on monolayer and multilayer surfaces. The adsorption process was expressed by pseudo-second-order kinetic model. Experimental results showed that the highest removal capacity obtained was 88.70 mg/g. Thermodynamic analysis showed that the adsorption of Cr(VI) onto AC/PP is an endothermic process and occurs through physical adsorption. Reuse experiments were repeated 5 times and 70 % removal was achieved in the 5th use. This study showed that AC/PP can be used in the removal of Cr(VI) ions in wastewater.