Removal of lead ions from aqueous solution using potassium hydroxide modified natural adsorbents

Abstract

As time progresses, a combination of human activities and natural occurrences releases contaminants, specifically heavy metals. These contaminants enter into water bodies, posing a threat to aquatic ecosystems and emphasizing the importance of implementing effective measures for pollution control and water quality preservation. This makes it necessary to treat water to reduce the negative impacts of toxic heavy metals in water and supply pure water for domestic and environmental use. Thus, the increased release of heavy metals like lead into the environment due to rapid industrialization has raised severe global concerns. This study aims to remove lead ions from water using a low-cost bio adsorbent. The present study examined the utilization of groundnut shells, tamarind pod shells, rubber seed shells, and pistachio shells as lead adsorbents. The adsorption efficiency is examined in relation to adsorbent dose, pH, contact time, and initial concentration, and the most efficient adsorption parameters are identified. In addition, adsorption mechanism, thermodynamics parameters and kinetic modeling are carried out to clarify the mechanism of adsorption. Isometric models, namely, Langmuir and Freundlich, are used to characterize the adsorption process, with better correlation to the Langmuir model. Kinetic observations indicated that adsorption in similar manner with transition of pseudo-second-order model and thermodynamic analysis confirmed the nature of spontaneous exothermic and spontaneous endothermic adsorption reaction. The pistachio shell emerged as the most effective of the four examined adsorbents, displaying the highest adsorption capacity of 88.9% at an adsorbent dosage of 1.2 g/L. This result underscores the superior performance of pistachio shells, positioning it as the optimal choice among the tested adsorbents.