Boosting synergistic recovery of ammonia nitrogen and phosphate from phosphorus chemical wastewater by co-pyrolyzing the biomass and magnesite

Abstract

In this study, biomass was co-pyrolyzed with the low-cost magnesite to prepare nano-MgO loaded biochar (n-MgO/biochar) composites for the simultaneous recovery of NH4+-N and PO43--P consisting in wastewater. It was found from the outcomes that the addition of biomass effectively reduced the pyrolysis temperature of magnesite, and the dispersion of biochar promoted the reactive activation of nano-scale MgO. The nano-MgO could provide Mg2+ and OH− simultaneously for the efficient recovery of NH4+-N and PO43--P. At a pH of approximately 9 and an N/P/Mg molar ratio of 1:2:1.5, the NH4+-N and PO43--P in the experimental wastewater were recovered by 93.7 % and 84.8 %, respectively. Mechanism analysis revealed that chemical adsorption, with the main product being MgNH4PO4·6H2O, predominantly controlled the recovery process. Furthermore, n-MgO/biochar demonstrated a successful recovery of NH4+-N and PO43--P consisting in the complex phosphogypsum leachate. What’s more, NaH2PO4, n-MgO/biochar/P, and raw phosphogypsum leachate could all serve as effective phosphorus sources for recovering NH4+-N consisting in nitrogenous wastewater with phosphorus deficiency. Conclusively, this study provides an alternative method for the simultaneous recovery of NH4+-N and PO43--P consisting in the wastewater.