Capture and Release of Orthophosphate by Fe-Modified Biochars: Mechanisms and Environmental Applications

Biochars have been suggested to P capture potential from effluent streams and recycle the captured agricultural soils. However, most biochars low sorption capacity. The objective of this study was engineer biochar for enhanced affinity. Biochar produced corn stover biomass pre-treated with FeSO4 (ISIB) using autothermal (air-blown) pyrolysis at 500 °C. Point zero charge (pHZPC) shifted 8.48 4.31, indicating that Fe treatment increased dominance acid functional groups. Batch equilibration isotherm showed ISIB had 11–12 times more capacity (3763 versus 46,300 mg kg–1 6704 48,821 non-oxidized oxidized conditions, respectively), while desorption rate ?1/3 relative control biochar. A column leaching also shows effective removing simulated effluent. XRD (X-ray diffraction) SEM-EDS (scanning electron microscopy–energy-dispersive X-ray spectrometry) analyses predominately through inner-sphere surface complexation followed by precipitation is preferentially sorbed hematite (?-Fe2O3) magnetite (FeIII2O3 + FeIIO) or maghemite (?-Fe2O3). This demonstrates can be pyrolyzing FeSO4, resulting adsorption recycling P. When loaded P, potentially used as a slow-release fertilizer.