Treatment of Pb(II) pollution in livestock wastewater by MgFe2O4 modified manure-biochar derived from livestock itself: Special role of endogenous dissolved organic matter and P species

• MgFe 2 O 4 modification improved Pb(II) adsorption capacity of MFSCs. • More polysaccharides were obtained in the EDOM derived from MFSC2. • Polysaccharides could be complexed with Pb(II) and deposited on MFSC2 surface. • MgFe 2 O 4 modification stimulated the activity of P species for Pb(II) removal. • Chemical precipitation of Pb 5 (PO 4 ) 3 OH was the major pathway for Pb(II) removal. In this work, swine manure biochar (SC) and its MgFe 2 O 4 modified product (MFSC) were fabricated by hydrothermal method to remove Pb(II) pollution from livestock wastewater. The physicochemical properties of materials were analyzed by BET, XRD, SEM and VSM. The MFSC showed abundant pore structure, high MgFe 2 O 4 dispersion and superior magnetization, which improved its application prospect and the capacity of pollutant removal. The results of adsorption experiments showed that MFSC has much higher Pb(II) adsorption efficiency (242.723 mg/g) than SC (42.158 mg/g), and chemical adsorption was the main removal pathway of Pb(II). The modification of MgFe 2 O 4 changed the character of endogenous dissolved organic matter (EDOM) of MFSCs, producing more polysaccharides that could be complexed with Pb(II), further influencing the adsorption process. In addition, the addition of MgFe 2 O 4 stimulated the activity of P for Pb(II) removal via converting organic P into inorganic P, as well increasing the percentage of Fe/Al mineral adsorbed P. The chemical precipitation of hydroxylpyromorphite (Pb 5 (PO 4 ) 3 OH) was identified as the major pathway for Pb(II) adsorption. In conclusion, MFSC has the potential to be a novel composite for the treatment of heavy metals in livestock wastewater, and this study could be of great significance to achieve the sustainable development of the livestock industry.