Waste Tea Leaves as an Adsorbent for the Removal of Heavy Metal Ions from Aqueous Solutions: Quantitative Estimation using Spectrophotometry and Titrimetry

Abstract

The rapid increase in industrialization and globalization in the last few decades has led to increased disposal of heavy metals in the environment leading to severe water and soil contamination. Among all known pollutants, heavy metals are especially notorious due to their high toxicity, persistent and bioaccumulative nature. Heavy metal toxicity is a major threat and therefore its removal and remediation require special attention to protect human, animal and plant health and to restore soil and water quality. Waste tea leaves (Camellia sinensis) are low-cost adsorbents and their use for the removal of heavy metal ions is likely to address the problems of waste management and heavy metal ion toxicity. In the present study, we have tested the efficacy of waste tea leaves for the quantitative removal of heavy metal ions like Ni(II) and Pb(II) from their aqueous test solutions using spectrophotometric and titrimetric methods respectively. With 5 g tea leaves in the Ni(II) solution, the removal percentage of the ion was found to be 85.56%. From a Pb(II) containing test solution, 286 ppm of the ion was adsorbed by the same amount of tea leaves. The amount of adsorbent dose was found to be directly related to the removal percentage of the metal ion. However, after reaching a threshold, increasing the adsorbent dose has only a negligible effect on adsorption. The adsorption was found to be primarily physisorption and follows Freundlich's adsorption isotherm. The zero-cost and easy availability of waste tea leaves make it a substrate of interest that can be used for the cost-effective removal of heavy metal ions from water and soil.