Adsorption mechanism of phosphate and arsenate in water by Al-doped Zr-based MOF and theoretical DFT study

Excessive phosphorus and arsenic in water bodies not only destroy ecosystems but also pose a serious threat to human health. In this study, a series of Al-doped modified metal-organic frameworks (Zr-Al-MOF) were prepared by solvothermal method, which achieved efficient removal of phosphate and arsenate in water. Due to the use of inexpensive Al salts, the material has a lower cost and is more economical. The molar ratio of metal salts, adsorption time, solution pH, initial concentration, temperature and coexisting anions were studied, and it was found that when the molar ratio of Zr: Al was 2, Zr-Al-MOF had the best adsorption performance for phosphate and arsenate, and the maximum adsorption capacity was 93.04 mg P/g and 173.83 mg As/g, respectively. It traps phosphate and arsenate at a fast reaction rate and can be recycled repeatedly. In addition, 0.15 g/L of 2Zr-Al-MOF can effectively reduce the phosphate and arsenate content in the contaminated spring water samples of Yangzonghai Lake to the standard range of drinking water, which further confirms the application potential of 2Zr-Al-MOF. By FT-IR and XPS analysis, it was found that the adsorption mechanism was ligand exchange, electrostatic attraction and hydrogen bond formation. The theoretical calculation shows that the adsorption energy is negative, which indicates that 2Zr-Al-MOF is attractive to phosphate and arsenate, and the adsorption state is stable. The results show that 2Zr-Al-MOF is an effective phosphate and arsenate adsorbent and has broad application prospects in eutrophication water treatment.