Synthesis of calcium and iron oxide/hydroxide bifunctional materials for treating phosphate and hardness in water

This article focuses on synthesizing dual-functional adsorption-ion exchange material (Fe-Ca/225H) by precipitation method on 225H cation exchange resin for the treatment of phosphate and hardness in water. Materials were analyzed through methods such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction studies (XRD), and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). For the phosphate adsorption, suitable conditions were experimentally found to include reaction time (48 h), pH (6.5), adsorbent dosage (10 g/L), and HCO₃⁻ ions as the most impact ion on the phosphate adsorption. When calcium and magnesium were present in a solution containing phosphate, the phosphate adsorption capacity increased by 1.24 times. This was due to the combination of calcium and magnesium with phosphate on the surface of the material, which improves the adsorption efficiency. Besides, when compared with materials containing only iron (Fe/225H), the adsorption capacity of Ca-Fe/225H materials is still higher in both synthetic wastewater and domestic wastewater. The durability of the material after 10 regenerations was still over 80% effective. The material is effective in simultaneously treating both phosphate and hardness in the solution, with a much higher hardness treatment efficiency than amphoteric resin on the market (MB6SR).