Characterization of Eichhornia crassipes bio-adsorbent activated by H3PO4 for the removal of lead ion (Pb2+) from wastewater of battery industry

Abstract

Lead ion (Pb²⁺) contamination from battery industry wastewater affects significant environmental and health risks. This study explored the use of H₃PO₄-activated water hyacinth (WH) bio-adsorbent as an effective solution for removing Pb²⁺. The WH bio-adsorbent was prepared by activating dried water hyacinth stems with 1.2 M H₃PO₄, enhancing adsorption properties. SEM-EDX analysis revealed significant morphological changes, with increased porosity and oxygen-containing functional groups (O-H, C-O-P), which improved adsorption capacity. Adsorption kinetics followed a pseudo-second-order model (R² = 0.99981), indicating that chemisorption dominated the Pb²⁺ removal process. Adsorption isotherms firmly fit the Langmuir model (R² = 0.96), confirming monolayer adsorption on a homogeneous surface. The effect of pH was also investigated, with maximum adsorption efficiency (96.928%) observed at pH 7. FTIR analysis showed changes in functional groups before and after adsorption, confirming the ion exchange mechanism between Pb²⁺ and the activated bio-adsorbent. The findings suggest that H₃PO₄ activation increases the surface area and raises the chemical activity of WH, providing new insights into the dual mechanism of physical and chemical modifications for lead removal. This study addresses a critical gap in optimizing adsorbents for heavy metal removal, demonstrating the potential of H₃PO₄-activated WH for industrial wastewater treatment.