Preparation and characterization of MgO hybrid biochar and its mechanism for high efficient recovery of phosphorus from aqueous media

Conversion of organic waste into engineered metal-biochar composite is an effective way of enhancing biochar’s efficiency for adsorptive capture of phosphorus(P)from aqueous media.Thus,various strategies have been created for the production of metal-biochar composites;however,the complex preparation steps,high-cost metal salt reagent application,or extreme process equipment requirements involved in those strategies limited the large-scale production of metal-biochar composites.In this study,a novel biochar composite rich in magnesium oxides(MFBC)was directly produced through co-pyrolysis of magnesite with food waste;the product,MFBC was used to adsorptively capture P from solution and bio-liquid wastewater.The results showed that compared to the pristine food waste biochar,MFBC was a uniformly hybrid MgO biochar composite with a P capture capacity of 523.91 mg/g.The capture of P by MFBC was fitted using the Langmuir and pseudo-first-order kinetic models.The P adsorptive capture was controlled by MgHPO4 formation and electrostatic attraction,which was affected by the coexisting F−and CO_(3)^(2−)ions.MFBC could recover more than 98%of P from the solution and bio-liquid wastewater.Although the P-adsorbed MFBC showed very limited reusability but it can be substituted for phosphate fertiliser in agricultural practices.This study provided an innovative technology for preparing MgO-biochar composite against P recovery from aqueous media,and also highlighted high-value-added approaches for resource utilization of bio-liquid wastewater and food waste.