Liu Ying, He Liwenze, Chen Yu, Tang Jingxiang, Li Haiquan, Liu Yanxia
Faculty of Environmental Science and Engineering, Southwest Jiaotong University, Chengdu, People's Republic of China.
Department of Civil Engineering, Chengdu Technological University, Yibin, People's Republic of China.
Environ Technol. 2025 Aug;46(19):3959-3972. doi: 10.1080/09593330.2025.2482969. Epub 2025 Mar 27.
Sediment is a critical component of aquatic ecosystems, that acts as a natural sink for diverse pollutants such as heavy metals and phosphorus (P). However, the current research on sediment remediation has predominantly focused on single contaminants. In this study, a novel composite material, calcium peroxide/lanthanum-loaded hydrochar (CaO-LaHyd), was synthesised through the hydrothermal carbonisation of water purification sludge, followed by the sequential loading of lanthanum ions and nano-calcium peroxide. The adsorption capacities of CaO-LaHyd for P and Pb were evaluated via adsorption experiments, and their passivation mechanisms were investigated through sediment capping simulations. Materials were characterised using scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and energy-dispersive spectroscopy. Results indicated that CaO-LaHyd exhibited maximum adsorption capacities of 66.05 mg·g⁻¹ for P and 230.41 mg·g⁻¹ for Pb. In the simulated capping experiments, the addition of 5% CaO-LaHyd significantly reduced the phosphate concentrations in the overlying water. The slow release of oxygen from calcium peroxide improves sediment redox conditions, suppresses endogenous P release, and decreases interstitial P levels. Speciation analysis revealed that CaO-LaHyd promoted the endogenous P transformation into stable forms while reducing the bioavailable P fractions. Concurrently, it enhanced Pb passivation, thereby mitigating Pb leaching risks from the sediment.
