Combining lanthanum-modified bentonite and calcium peroxide to enhance phosphorus removal from lake sediments

Lanthanum-modified bentonite (LMB) and calcium peroxide (CP) are known for their effective removal phosphorus (P) capacities. The present study aims to investigate the effects of the combined use of LMB and CP（LMB + CP）on the sediment P, dissolved organic matter (DOM) and iron (Fe) concentrations through a 90-day incubation experiment. The combined treatment showed strong removal effects on sediment P and DOM. Indeed, the SRP and DOM concentrations in the 0-10 cm sediment layer decreased following the combined application of LMB and CP by 40.67 and 28.95%, respectively, compared to those of the control group (CK). In contrast, the HCl-P in the 0-5 cm sediment layer increased following the combined treatment by 13.28%. In addition, compared with the single application of LMB, the LMB + CP treatment significantly reduced the soluble Fe (Ⅱ) in the sediment pore water and promoted the oxidation of Fe. Therefore, LMB + CP can enhance the removal of internal P from sediments. The DOM removal and Fe oxidation in sediment pore waters are beneficial for enhancing the adsorption of P by LMB. On the other hand, the single and combined applications of LMB and CP increased the richness of the sediment microbial communities while exhibiting slight effects on their diversity. According to the results of this study, the combined use of LMB and oxidizing materials represents a novel method for treating lakes with high internal phosphorus and DOM loads in sediments.