Enhanced Removal of Hexavalent Chromium From Aqueous Solutions Using Locally Activated Saudi Bentonite Clay

Heavy metal contamination, particularly from chromium, poses significant health risks and environmental challenges due to its prevalence in industrial effluents. This study investigates the effectiveness of activated bentonite clay sourced from Saudi Arabian deposits for the removal of hexavalent chromium (Cr(VI)) in aqueous environments. We focus on optimizing removal efficiency based on key physicochemical parameters, including contact time, adsorbent dosage, and solution pH. Batch adsorption experiments were conducted using a prepared stock solution of chromium at a concentration of 1000 mg/L, diluted to prepare standard Cr(VI) solutions ranging from 20 to 100 mg/L. Results revealed rapid uptake of chromium ions by Saudi‐activated bentonite, achieving equilibrium within 30 min. However, higher initial chromium concentrations led to a decline in removal efficiency due to saturation of active sites on the bentonite surface. Additionally, the study demonstrated pH‐dependent adsorption behavior, with decreasing pH enhancing chromium removal. Equilibrium data fitted well with both the Langmuir and Freundlich isotherm models with maximum adsorption capacity q max ≈ 156 mg/g, while kinetic studies indicated that the adsorption process adhered to a pseudosecond‐order model with kinetic constant in order of hundredths.