Synthesis of Lanthanum-Modified Attapulgite and Its Phosphorus-Fixing Mechanism for Urban Eutrophic Lake

Metal-salt-modified clay minerals are widely used for endogenous phosphorus control in eutrophic lakes because of its high efficiency of P adsorption, but changes in water quality due to material dosing limit their practical remediation performance. In this study, lanthanum was embedded in thermally-treated calcium-rich attapulgite (TCAP) to strengthen its P uptake ability, and a novel and efficient phosphorus fixation material lanthanum-modified attapulgite (La-TCAP) was synthesized. Batch adsorption experiment indicated that the maximum P sorption capacity of La-TCAP can reach as high as 9.777 mg P/g, which was more than twice that of TCAP. The P removal rate of La-TCAP was maintained between 55.62% and 68% at 4-10 pH. La-TCAP exhibits strong resistance to interfering ions including SO42-, NO3-, Cl-, and HCO3- during phosphorus adsorption. The characterization analysis of La-TCAP showed that the adsorption of phosphate on La-TCAP was mainly based on the surface complexation reaction. Sediment P immobilization studies demonstrated that the coverage of La-TCAP contributed the P recession of 30% to 58.8% in overlying water during the aerobic and anaerobic incubation. Meanwhile, other water quality indicators in the overlying water had hardly changed. The content of Mobile-P in the surface sediments (0-4 cm) was drastically reduced, while the content of Al-P and Ca-P was greatly increased. The results of this study suggest that La-TCAP is a promising P immobilization material for sediment P control in urban eutrophic lake.

Automated summary

In this study, a novel and efficient phosphorus fixation material, lanthanum-modified attapulgite (La-TCAP), was synthesized by embedding lanthanum in thermally-treated calcium-rich attapulgite. The results showed that La-TCAP has a high P sorption capacity and strong resistance to interfering ions. It can effectively immobilize sediment P and improve the water quality of urban eutrophic lakes.