Removal of hexavalent chromium from industrial wastewater using modified imperata cylindrica biosorbent and method validation

Hexavalent chromium ions are recognized for their extreme toxicity and environmental impact. Industrial effluents frequently contribute substantial amounts of these ions to ecosystems, causing a significant threat to environmental and human health. To address this issue, this study investigates the conversion of abundant parasitic plants, specifically Imperata cylindrica , into an efficient and cost-effective biosorbent for chromium ion removal. The adsorption performance of the biosorbent was enhanced through chemical modification using phosphoric acid and sodium hydroxide as acid and base treatments, respectively. Results demonstrated that acid-treated biosorbent achieved a remarkable chromium ion removal efficiency of 87.2% under optimal conditions. The optimal conditions were identified as pH 2, a contact time of 20 h, and a biosorbent dosage of 0.1 g. The untreated and base-treated biosorbents showed significantly lower efficiencies, with removal rates of 10.4% and 67.7%, respectively. The kinetic analysis confirmed that the adsorption process followed a quasi-secondary model, as evidenced by a strong agreement between experimental and calculated maximum adsorption capacity values (with a difference of 0.7121 for the untreated sample). The Freundlich isotherm model provided an excellent fit to the adsorption data, with correlation coefficients exceeding 0.96 for all biosorbent types. These findings highlight that acid treatment significantly enhances biosorption properties, making the treated biosorbent an effective and economical solution for chromium ion removal from contaminated water sources. Additionally, this study optimized the 1,5-diphenylcarbazide method using ultraviolet-visible (UV-Vis) spectroscopy for efficient and cost-effective chromium ion concentration measurement. For validation, results were compared with inductively coupled plasma mass spectrometry (ICP-MS), showing a strong correlation (R 2 > 0.93) and excellent agreement between the two methods. This confirmed that UV-Vis spectroscopy is a reliable and accurate technique for assessing chromium ion concentrations, offering a simplified and cost-effective alternative to ICP-MS analysis.