Ca/Fe-layered double hydroxide–zeolite composites for the control of phosphorus pollution in sediments: Performance, mechanisms, and microbial community response

Despite the strict management of eutrophic waters globally, the release of phosphorus (P) from sediments maintains the eutrophic state of water bodies and poses a serious challenge to their management. Ca/Fe–LDH was synthesized with natural zeolite (NZ) by using a co-precipitation method (denoted as CFL-Z) to solve this problem. Results showed that Ca/Fe–LDH was successfully loaded onto the surface and inside the pores of NZ. The maximum P adsorption capacity value of CFL-Z was 46.7 mg/g under the mechanisms of electrostatic attraction, ligand exchange, and ion exchange. In incubation experiments, the addition of 6 % CFL-Z into P-contaminated sediments reduced P concentrations in overlying and interstitial water to 0.013 (97.3 % reduction) and 0.358 (82.1 % reduction) mg/L, respectively. In addition, unstable P forms (NH 4 Cl-P and BD-P) in sediments were converted into stable P forms (HCl-P and Res-P, respectively). Subsequent long-term anoxic experiments showed that CFL-Z capping sediments exhibited better inhibition of sediment P release compared with CFL-Z amendment sediments and was efficient and stable. Microbial community analysis showed that CFL-Z amendment and capping reshaped the microbial community structure, and different functional bacteria influenced the stability of sediment P. This work showed that CFL-Z overlays were considered to have potential applications in sediment P fixation, providing a new way to improve the P-binding capacity of natural mineral-like materials and resolve P-contaminated sediments.