Removal of phosphorus from wastewater by magnetic lanthanum- modified magnesium iron hydroxide/biochar
摘要
Biochar(BC) has been widely studied for phosphorus removal from wastewater due to its rich pore structure and surface functional groups, but its poor adsorption capacity and lack of selectivity still need to be improved. Magnetic lanthanum-modified magnesium iron hydroxide/biochar composite adsorbent(La-MgFe-LDH/BCm@Fe3O4) was prepared by co-precipitation of ferroferric oxide(Fe3O4) and lanthanum-modified magnesium iron hydroxide(La-MgFe-LDH) on corn stalk biochar(BCm) in turn. The phosphorus removal performance was investigated by static phosphate adsorption experiment and actual wastewater phosphorus removal experiment. The results showed that La-MgFe-LDH/BCm@Fe3O4 had a high adsorption capacity for phosphate(48.75 mg/g, calculated as P), extremely fast phosphorus removal rate(reaching adsorption equilibrium in 60 minutes), excellent pH(3-11) adaptability and resistance to disturbance. Furthermore, La-MgFe-LDH/BCm@Fe3O4 also had good removal effect on total phosphorus in domestic sewage and secondary sedimentation tank effluent. The main mechanism of phosphorus removal was the anion exchange between carbonate and phosphate and the surface complexation between metal ions in composite adsorbent and phosphate. La-MgFe-LDH/BCm@Fe3O4 had the prospect of phosphorus removal from actual wastewater.