Microstructure and adsorption studies on the simultaneous removal of Cu2+, Ni2+, and Zn2+ from simulated wastewater using magnetically functionalized Philippine natural zeolite composite

This study reports the microstructural characteristics and adsorption properties for heavy metal ions of the surface-modified Philippine natural zeolite (MPNZ) and magnetically functionalized Philippine natural zeolite (PNZM) composite. SEM analysis confirmed the presence of magnetite particles dispersed on PNZM, making its surface rougher and irregular while retaining its porous structure. X-ray diffractogram revealed distinct peaks corresponding to the spinel crystalline structure of magnetite and the aluminosilicate structure of the zeolite framework, suggesting a well-integrated composite material. BET analysis showed an increase in the surface area of MPNZ from 33.876 m²/g to 45.052 m²/g after adding magnetite. EDS characterization verified the strong presence of Fe⁺ ions in the PNZM structure, enhancing its cation-exchange capacity (CEC). The Si/Al ratio of MPNZ decreased from 3.75 to 3.37, indicating a more negative charge, supported by zeta potential results that showed surface charges of (-)12.200 for MPNZ to (-) 20.854 mV for PNZM. In single ion solutions, PNZM obtained a removal uptake of 98.85 %, 99.99 % and 99.48 % for Ni²⁺, Cu²⁺and Zn²⁺ respectively, which are higher than MPNZ. In mixed-ion solutions, PNZM also showed improved adsorption with removal rates of 91.17 % for Ni²⁺ and 97.90 % for Cu²⁺, although Zn²⁺ uptake decreased to 97.98 % compared to the 99.99 % of MPNZ. Overall, incorporating magnetite has functionalized the ability of PNZM for sustainable water treatment by removing heavy metal ions through the synergistic mechanism of ion-exchange and Coulombic electrostatic interactions.