Oxygen defects of MgLa-LDH enhancing electrostatic attraction and inner-sphere complexation during phosphate adsorption from wastewater

The introduction of oxygen defects toward constructing new binding sites is a promising strategy for improving the adsorption performance of layered double hydroxide (LDH). Here, a facile and novel method for adjusting the abundance of oxygen defects by regulating the preparation pH values of MgLa-LDH was used to enhance phosphate efficient adsorption. The MgLa-LDH with high-defect-degree (ML-11) presented a larger adsorption capacity and faster mass-transfer than that of low-defect-degree LDH (ML-10). Particularly, the adsorption capacity (121.56 mg/g) and initial adsorption rate (16.25 mg/g⋅min) of ML-11 were 1.8 times and 2.6 times higher than those in ML-10 in neutral condition, respectively. Characterization results confirmed that oxygen defects played a vital role in phosphate adsorption. The promotion mechanism of oxygen defects on phosphate absorption included the enhancing electrostatic attraction via increasing surface electron density, boosting M-OH groups generated by oxygen defects, and reducing adsorption energy. Compared with ML-10, ML-11 had similar or even better resistance of coexisting anions, and regeneration performance. Furthermore, the performance of ML-11 was verified in fixed-bed column experiment with real wastewater, and the treatment bed volume of it (978.6 BV) was higher than that in ML-10 (509.7 BV). The oxygen defects method can provide a promising choice for improving the material properties of efficient phosphate removal.