Corn stover waste preparation cerium-modified biochar for phosphate removal from pig farm wastewater: Adsorption performance and mechanism

The high phosphorus content in livestock and poultry wastewater is a significant factor contributing to water eutrophication. It is imperative to seek an economically efficient method for phosphate recovery. This study employed cerium-modified biochar to recover phosphate from pig farm wastewater. An investigation was conducted to examine the adsorption performance and removal mechanism of phosphate. Among the different samples, 0.1CeB-500℃ was selected for subsequent experiments. It exhibited a phosphate adsorption capacity of 9.58 mg/g and a removal efficiency of 95.75 %. The results showed that the phosphate adsorption process followed not only the pseudo-second-order kinetic model, but also the Langmuir isotherm model. It suggested that the adsorption of phosphate onto the biochar occurred in a monolayer chemical manner, with a maximum adsorption capacity of 10.86 mg/g. Phosphate adsorption was minimally affected within the pH range of 2–9, with Cl^- having negligible impact, NO₃^- slightly inhibiting, and HCO₃^- and CO₃^2- significantly hindering phosphate adsorption. A series of characterization results indicated that phosphate removal occurred through surface precipitation forming CePO₄, ligand exchange between carbonate and phosphate, inner-sphere complexation, and electrostatic attraction. The phosphate removal efficiency from pig farm wastewater was 43.25 %, demonstrating promising potential for practical application.