The Phosphorus Adsorption and Recovery of Mg/Fe-LDHs Mulberry Rod Biochar Composite

Mg/Fe layered bimetallic oxide mulberry rod biochar composites (MFBCs) were prepared from mulberry rods and characterized using electron microscopy scanning (SEM), X-ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). We investigated the adsorption properties of MFBCs for phosphorus, which was recovered via crystallization using calcium chloride as a precipitant. According to the findings, the MFBC is a layered bimetallic oxide with a specific surface area of 70.93 m²·g⁻¹. Its point of zero charge values, or pHzpc, was 7.66. The removal of phosphorus usingMFBCs gradually decreased with increasing pH, and the optimum pH for phosphorus removal was 4.0. The maximum phosphorus adsorption by MFBCs at 298 K was 29.682 mg·g⁻¹ for MFBCs. The adsorption process of phosphorus onto MFBCs is a heat absorption process, and the adsorption isothermal data of phosphorus onto MFBCs fit with the Langmuir adsorption isothermal model. Phosphorus recovery is achieved when calcium chloride is added to the phosphate-enriched desorption solution at a Ca/P molar ratio of 2.2. The phosphorus product obtained from this process is very pure hydroxyphospapatite. The recovery rate of phosphorus in the desorption solution is 99.64%.