Efficiency analysis of eggshell and tea waste as Low cost adsorbents for Cr removal from wastewater sample

Abstract

This study aims to assess the efficiency of two agricultural wastes as adsorbents to remove Chromium (Cr) from a wastewater sample. Chromium-containing wastewater was treated with calcined and non-calcined eggshell and biochar tea waste with the adsorption method, and the effect of contact time, pH, and adsorbent dosage were investigated to examine the efficiency. The results indicate that 120 min is sufficient for the biochar tea waste and the non-calcined eggshell to reach adsorption equilibrium, where the calcined eggshell was reached equilibrium at 30 min. The optimal pH of all adsorbents was found to be 5, which indicates the interference of H+ ions on removing metal ions at low pH. Pseudo-first order and pseudo-second-order kinetic models were studied to assess the kinetic adsorption mechanism. Results also reveal that an increasing amount of adsorbent dose improves the removal efficiency of the adsorbent. The removal rates of using 2.0 g of non-calcined eggshell, 1.5 g of calcined eggshell and 2.5 g of biochar tea waste were found to be 70.70%, 100%, and 68.2%, respectively. The results show that the adsorption can be more appropriately described by the pseudo-second-order kinetic model for the adsorption of chromium ions from the wastewater. The findings of this study suggest that using these adsorbents, industrial wastewater can be treated in a more cost-effective and simple way than other existing methods.