Adsorption Kinetics Study of Sawdust Biochar as a Sustainable Solution for the removal of Hexavalent Chromium in contaminated water

The hexavalent chromium Cr (VI) present in industrial effluent is considered to be a threat to the environment as it is highly toxic, carcinogenic, and also persist in aquatic ecosystems. Concurrently, improper disposal of wood sawdust contributes to environmental degradation, leading to soil and water contamination and air pollution from open burning. This study addresses both challenges by exploring the utilization of waste-derived materials Neem (Azadirachta indica) and Teak (Tectona grandis) sawdust chars as affordable, eco-friendly adsorbents for Cr (VI) removal from synthetically prepared chromium solution of concentration 2 mg/l through batch investigation. Experimental investigation was performed with char produced with and without chemical activation at different normality of KOH in comparison with commercially available Activated Carbon (AC) which are now widely used as adsorbents for a time period of 3 hours. The results have shown that Neem char demonstrated high adsorption capacity of 64% even without undergoing chemical activation, highlighting its natural efficacy and suggesting its superior potential as a biosorbent. The study involved comparing five different non-linear kinetics model to ensure the best fit on understanding the adsorption mechanism involved. Overall, it is evident that the Elovich model is found to be the best fit with R2 for all the cases being 0.949±0.032. This indicates that the adsorption proceeds primarily through chemisorption on a heterogeneous surface rather than diffusion. These findings underscore the applicability of Neem and Teak char in treating chromium-contaminated water while promoting sustainable waste management and paving a way for further research.