Phosphate Removal by Ca-Modified Magnetic Sludge Biochar Prepared by a One-Step Hydrothermal Method
Xu Liu, Yushan Li, Hao Zhou, Jing Guo, Yonghou Xiao, Cong Liu, Boxing An, Zhengqi Liang
Abstract
The problem of phosphorus pollution and its resource utilization has been a source of general concern. The preparation of green, renewable, and non-secondary pollution adsorbents has become a research direction. In this paper, a one-step hydrothermal preparation method of Ca-modified magnetic sludge biochar (Ca-MSBC) is used for enhancing phosphate removal. The results show that the adsorption rate of phosphate by Ca-MSBC is mainly controlled by chemisorption but is also related to physical adsorption and an internal diffusion mechanism. The maximum phosphorus adsorption capacity of Ca-MSBC was 89.25 mg g−1 at 343 K (initial phosphate concentration 500 mg L−1). After nine cycles of adsorption experiments, the adsorption capacity of 70.16 mg g−1 was still high. In addition, coexisting ions Cl−, NO3−, SO42−, and CO32− have no significant effect on the adsorption properties of phosphate. XRD, FT-IR, VSM, XPS, and N2 adsorption/desorption isotherms showed that the mechanism of phosphate removal from water by Ca-MSBC was mainly the chemical precipitation reaction of phosphate and calcium. The results of this study indicate that Ca-MSBC has potential application and environmental value as a solid waste recycling material for environmental remediation.