Lanthanum-modified sepiolite for real application of phosphate removal from rural sewage

Being able to cause eutrophication, a severe ecological problem that leads to the demise of aquatic animals, excessive phosphate in water bodies, has been a threat to the environment. Aiming to remove phosphate from wastewater in rural areas, adsorption is a promising method. In this study, a novel phosphate adsorbent, SEP-La, was synthesized by doping lanthanum into sepiolite. Characterization and batch adsorption experiments were performed. Lanthanum was loaded on sepiolite through hydrogen bond as forms of peroxides, and it greatly enhanced the adsorption capacity of sepiolite, reaching 135.78 mg/g. Pseudo-second-order kinetic model described the adsorption kinetics the best, indicating a chemisorption process. An endothermic yet spontaneous adsorption process was revealed by the fitting of the Langmuir isotherm model. The adsorbent exhibited great tolerance to pH change and interference ions. The remaining 67.82% of the original performance after 6 cycles of adsorption-desorption demonstrated its robust recyclability. Its real application potential was also manifested through column experiments using locally collected real wastewater and was able to treat 2072 mL of water per gram of adsorbent, which represents a significant milestone in translating theory into practice. FT-IR, XRD, and XPS were performed to prove that its mechanism involved electrostatic interaction and ligand exchange. This work provides an affordable while auspicious phosphate adsorptive material with the potential to effectively address the issue of excessive phosphate in water at a low cost.