Effects of modified sediments from a eutrophic lake in removing phosphorus and inhibiting phosphatase activity

Phosphorus is one of the main limiting and strong influencing factors of eutrophication, and phosphorus controlling in lake is of great significance for eutrophication. To do this, sediment materials were taken from Dianchi Lake, a typically eutrophic lake, and modified by hexadecyltrimethylammonium bromide (CTAB) and ZnSO₄ to remove phosphorus and inhibit alkaline phosphatase activity (APA). Results indicated that phosphorus removal efficiencies of sediments modified by CTAB (S-CTAB), ZnSO₄ (S-Zn), and oxidized sediments (OS) were higher than that of the raw sediment (RS). Ability to absorb phosphorus varied, following the order S-Zn>S-CTAB>OS>RS. Sorption was influenced by ionic strength, with the former decreasing with the increase of the latter. Freundlich model well described the sorption isotherm, with an R² ranging from 0.9168 to 0.9958. Furthermore, compared with the raw sediments, the maximum phosphorus sorption capacities of S-Zn and S-CTAB increased by 12.2% and 124.5%, respectively. Results of desorption studies suggest that the desorption rate of S-Zn was from 3.88 to 13.76%, lower than that of other sediment materials. APA was inhibited by S-CTAB and S-Zn at the same time, with inhibition rates from 29.6% and 61.0% when the concentrations of S-CTAB and S-Zn were 10 nmol L^-1 and 0.2 nmol L^-1, respectively. This study provides new insights into phosphorus removal and phosphatase activity inhibition in water treatment.