Phosphorus capturing from biogas slurry using different adsorbents: adsorption and mechanism

The recovery and utilization of phosphorus elements from biogas slurry can effectively prevent secondary pollution caused by biogas slurry application in farmland and eutrophication of water bodies. This study systematically evaluated the adsorption efficiency of soluble P from biogas slurry using biochars (corn straw biochar (CSB), cherry wood biochar (CWB), and cattle manure biochar (CMB)) and biomass power plant residues ash (BPP-ash) and slag (BPP-slag). Physicochemical characterization revealed that BPP-slag exhibited the highest soluble P removal efficiency (92.17%) at 30 g L^-1 dosage, attributed to its high metal oxide content (e.g., Ca²⁺, Mg²⁺). Kinetic and isotherm analyses indicated that adsorption followed pseudo-second-order kinetics (<i>R</i>² > 0.96) and Freundlich models (<i>R</i>² > 0.98), suggesting chemisorption-dominated multilayer adsorption. Mineral precipitation (contributing >70% to total adsorption) was identified as the primary mechanism via XRD and quantitative analysis. This work highlights the potential of biomass power plant residues as cost-effective adsorbents for P capturing, offering a sustainable strategy for waste valorization.