Optimization of hexavalent chromium removal from aqueous solutions using Eichhornia crassipes-derived adsorbents through a response surface methodology

Abstract

Heavy metal contamination, particularly hexavalent chromium (Cr(VI)), in water bodies poses severe environmental and health risks. In recent years, using natural adsorbents for removing heavy metals has gained intensive interest thanks to their eco-friendliness and cost-effectiveness. In this work, lignocellulosic biomass materials were modified and employed as adsorbents to remove Cr(VI) from contaminated water. Adsorbent materials derived from Eichhornia crassipes showed the significance of removing Cr (VI) from the aqueous solution after being treated by H₂SO₄ acid 1.5% w/v at 45^oC for 30 h. After localising the upper and lower limits of each factor, design under the response surface models (RSM) using the Box–Behnken Design (BBD) method was used to optimise enhancement of the removal of Cr(VI). The strategy showcased the ability to construct a second-degree polynomial model that is highly valid (R2˃0.9805) and includes statistically significant interactions (P < 0.05). The findings indicated that the highest capacity for adsorbing Cr(VI) was 41.53 mg/g, which was attained by using 15 g/L of adsorbent, maintaining a pH of 3, starting with a Cr(VI) concentration of 130 mg/L, and allowing a contact duration of 80 minutes.