Green synthesis of gelatin-graphene oxide hydrogel from tannery byproducts: A sustainable strategy for chromium remediation from tannery wastewater

Leather tannery industry produces two main types of wastes - chromium contaminated wastewater, and large amount of organic solid wastes like raw hide trimmings. Both are problematic in terms of their environmental and health risks and require sustainable management strategies. This study addresses this challenge by proposing a biodegradable Gelatin-Graphene Oxide (Gel-GO) hydrogel for effective Cr removal from real tannery wastewater. Gelatin was obtained by thermal-acidic hydrolysis of raw hide trimming and GO was prepared by modified Hummer’s method. The hydrogels with different GO content (0 - 4 wt%) were covalently crosslinked with glutaraldehyde and characterized by FT-IR, XRD, UV-Vis, SEM and GC-MS analysis, revealing a highly porous structure with well-integrated GO. Based on the results of the batch adsorption experiments, the optimum parameters were found to be 2.5 wt% of GO, a pH of 4, adsorbent dosage of 3 g/L and 18 min contact time. Adsorption behavior followed the pseudo-second-order kinetic model (R 2 = 0.9982) and Langmuir isotherm model (R 2 = 0.9994), indicating chemisorption on a homogeneous surface. The Gel-GO hydrogel exhibited a high maximum adsorption capacity of 622.68 mg/g, surpassing many comparable adsorbents reported in the literature. Treatment of real tannery wastewater reduced total chromium concentration from 1811 mg/L to 0.45 mg/L and significantly decreased COD, BOD 5 , TSS, TDS, turbidity, and electrical conductivity. The findings demonstrate that the waste-derived Gel-GO hydrogel provides an effective, biodegradable, and circular-economy-based solution for addressing chromium pollution and solid waste management challenges in the leather industry.