Advanced natural hydrated iron-alum oxides cation exchange resin for simultaneous phosphate and hardness removal
Le Ba Tran, Trung Thanh Nguyen, Surapol Padungthon, Tri Thich Le, Quynh Anh Nguyen Thi, Nguyễn Nhật Huy
Abstract
Abstract In this study, a hydrated iron-alum oxides-contained cation exchange resin (HIAO/225H) was synthesized for the first time from natural alum-ferric water of acid sulfate soil to improve the water quality. The HIAO/225H material was then characterized by FTIR, XRD, SEM, and EDX-mapping techniques and applied for phosphate and hardness removal tests. The phosphate removal by the HIAO/225H material reached equilibrium after 50 h with the highest adsorption capacity of 2.075 mg P g −1 (e.g., 69.16 mg P g −1 Fe) at pH 6, which was 1.12, 11.15, and 2.11 times higher than by hydrated ferric oxide/225H material, anion exchange resin (Akualite A420), and amphoteric ion exchange resin (MB6SR), respectively, under the same experimental conditions. The reason for the higher phosphate adsorption efficiency of HIAO/225H than the hydrated ferric oxide/225H material may be that HIAO contains Ca, Mg, and Al elements, leading to an easy formation of FeOOH on the surface. Particularly, HIAO/225H material was also effective for both hardness and phosphate removal with an adsorption capacity of 15.6 mg Ca g −1 , 9.4 mg Mg g −1 , and 1.825 mg P g −1 , which is higher 1.2 times than the phosphate removal only. This may be due to co-precipitation to form Ca 3 (PO 4 ) 2 and Mg 3 (PO 4 ) 2 with the support of cation exchange resins. These results showed that the HIAO/225H material has a good performance in removing both phosphate and hardness, which could be applied in practical water and advanced wastewater treatment.