BIOSORPTION OF HEXAVALENT CHROMIUM FROM TANNERY WASTEWATER UTILIZING TELLA RESIDUE AND PEA SEED SHELLS

ABSTRACT The sustainable and cost-effective remediation of water pollutants to produce clean water remains a major challenge for scientists, researchers, and engineers worldwide. Among these pollutants, chromium (VI) is a highly toxic contaminant that contributes significantly to water pollution. In the present study, the adsorption performance of two low-cost, environmentally friendly, and locally available bioadsorbents tella residue (TR) and pea seed shells (PSS) was evaluated for the removal of Cr(VI) from tannery wastewater in Modjo, Ethiopia. Batch adsorption experiments were conducted to investigate the adsorption efficiency of the bioadsorbents. Key operational parameters, including pH, contact time, initial Cr(VI) concentration and adsorbent dosage, were optimized. The optimal conditions were found to be pH 2 for TR and pH 3 for PSS, contact times of 120 minutes for TR and 90 minutes for PSS, an initial Cr(VI) concentration of 10 mg/L, and an adsorbent dosage of 0.3 g.The optimized adsorbent dosages were found to be 0.3 g, with removal efficiencies of 87.02% for TR and 94.7% for PSS residues, respectively. The adsorbents were characterized using FTIR and XRD techniques. To understand the adsorption behaviour, both Langmuir and Freundlich isotherm models were applied. The adsorption data were best fitted by the Freundlich isotherm model, indicating the heterogeneous and multilayer nature of the adsorbent surfaces. Kinetic studies revealed that the pseudo-second-order model best described the adsorption of Cr(VI) onto Tella Residue, whereas the pseudo-first-order model was more suitable for Pea seed shell. Thermodynamic parameters (ΔGo, ΔHo and ΔSo) have also been calculated and found that the adsorption process as feasible, spontaneous and exothermic in nature. The positive values of the entropy change suggest that the increased randomness at solid-liquid interfaces during the adsorption. Overall, the batch adsorption results confirmed that tella residue and pea seed shells are effective and favourable bioadsorbents for the removal of Cr(VI) from tannery wastewater. Keywords: adsorption; Batchadsorption; chromium (VI); pea seed shell;tannery wastewater; tella residue