Adsorption of titanium-aluminum layered hydroxides for removal of fluorine at low concentrations in water

Layered double hydroxides have good application prospects in the fields of water treatment and defluoridation. In this study, Ti-Al layered hydroxides (Ti-Al LDHs) were synthesized by the co-precipitation method at a Ti/Al molar ratio of 2/8 and a medium solution pH of 6.0. The SEM, XRD, and BET results showed that the Ti-Al LDHs showed a uniform stacking of lamellar structure and existed mainly in dispersed amorphous form, with a wide pore size and a larger specific surface area (108.34 m2/g). The results of adsorption experiments showed that the highest capacity could reach 116.2 mg/g, and the adsorption adsorption of Ti-Al LDHs on fluoride was more in line with the proposed second-order model, and the adsorption isotherm was more in line with the Langmuir model.In addition, Ti-Al LDHs can be applied in a wide pH range (4−10), have strong resistance to anionic competition, and have good regeneration performance after five adsorption-desorption cycles where the adsorption capacity is still equivalent to 73 % of the initial capacity. From the FTIR and XPS results, the adsorption process was mainly attributed to ion exchange, electrostatic attraction and surface complexation. Therefore, Ti-Al LDHs is a layered hydroxide fluoride removal adsorbent with good application prospects.