Abstract: This study investigates the eco-friendly and cost-effective adsorption of hexavalent chromium (Cr⁶⁺) from industrial wastewater of Firozabad using chemically modified orange peel as a biosorbent. Given the hazardous nature of Cr⁶⁺ and its prevalence in the effluents from Firozabad’s glass industry, this work offers a sustainable solution by utilizing agricultural waste. The orange peels were collected, washed, dried, ground, and chemically treated to enhance their functional groups for improved adsorption. The biosorbent was characterized using FTIR and SEM to confirm the presence of active sites and surface morphology. Batch adsorption experiments were conducted to evaluate the effect of parameters such as pH, contact time, initial metal concentration, and biosorbent dose. The results indicated optimal Cr⁶⁺ removal (>90%) at pH 2, a biosorbent dose of 2.5 g/L, and contact time of 90 minutes. Kinetic studies revealed that the process followed pseudo-second-order kinetics, while equilibrium data best fit the Langmuir isotherm model, indicating monolayer adsorption. Thermodynamic analysis confirmed the exothermic and spontaneous nature of the process. The biosorbent was also tested on real wastewater samples, achieving 70–88% removal efficiency despite the presence of competing ions. Compared to other agricultural wastes, the modified orange peel exhibited superior adsorption capacity (q_max = 8 mg/g), underscoring its potential as an efficient and sustainable material for heavy metal remediation in wastewater.

Keywords: Chromium (Cr⁶⁺), biosorption, orange peel, industrial wastewater, low-cost adsorbent, Firozabad, eco-friendly remediation

| DOI: 10.17148/IARJSET.2025.12715