Modified Silica Particles Coated with Cu-Al Layered Double Hydroxide for Phosphate and Arsenate Removal in Water Treatment.

Environmental pollution remains one of the most pressing challenges facing modern society, with the removal of toxic substances from water sources being of particular concern. In this study, a composite material was synthesized by combining Cu-Al layered double hydroxides (CuAl-LDHs) with modified silica particles, aiming to develop an efficient and environmentally friendly adsorbent for the removal of phosphate and arsenate ions from water. CuAl-LDH, with a Cu/Al molar ratio of 2:1, was synthesized using the co-precipitation method in the presence of modified silica maintaining an LDH/SiO mass ratio of 2:1. The silica particles were functionalized with 3-glycidyloxypropyltrimethoxysilane (GLYMO) followed by modification with polyethyleneimine (PEI) to enhance their adsorption properties. X-ray diffraction (XRD) confirmed the successful deposition of CuAl-LDH on the silica surface, while scanning electron microscopy (SEM) revealed the porous structure of the silica and the uniform deposition of LDH. Adsorption experiments were performed to evaluate the removal efficiency of phosphate and arsenate ions under varying conditions. Equilibrium adsorption capacities, based on the Langmuir isotherm model, were determined to be 44.6 mg·g for phosphate (PO) and 32.3 mg·g for arsenate (As(V)) at 25 °C. The sorption behavior was better described by the Freundlich isotherm model, which yielded K values of 15.4 L·mg for phosphate and 13.9 L·mg for arsenate. Both batch and kinetic experiments confirmed the high adsorption efficiency of the composite, demonstrating its potential as a promising material for water treatment applications.