Construction of iron-manganese modified mulberry branch biochar and the adsorption of aqueous phosphorus

The water eutrophication caused by the discharge of phosphorus-containing wastewater brings a lot of harm to the water environment and ecology, and the adsorption method can effectively alleviate the pollution. A composite material was prepared by using waste mulberry as raw materials, magnetic biochar as carrier and loaded with iron-manganese oxide. The adsorption and phosphorus removal and recycling properties were studied and the characterization of the composite material was studied by XRD, FTIR, SEM, BET, and VSM. The results showed that the composite adsorbent had Fe-Mn composite oxide structure and good magnetism. The adsorption and removal of phosphorus were mainly through the adsorption of phosphate to metal active sites and the coordination exchange with surface hydroxyl groups. When the temperature was 25 ℃, the dosage of adsorbent was 0.20 g, the adsorption time was 260 min, the mass concentration of phosphorus in wastewater was 7.5 mg/L, and the solution pH was 6, the adsorption rate of phosphorus on the composite material reached 98.08%, and the mass concentration of residual phosphorus was 0.14 mg/L, which met the Class A standard of Pollutant Discharge Standard of Urban Sewage Treatment Plant (GB 18918-2002). The co-existing ions Cl- and NO3- had less interference on the adsorption of phosphate, while CO32- had more influence. After magnetic recovery and pickling regeneration for 5 times, the adsorption rate of phosphorus was kept above 67%. The adsorption process conformed more to the pseudo-second-order kinetic and the Langmuir isotherm models, and the reaction was a spontaneous and exothermic process. The preparation of iron-manganese modified mulberry branch biochar composite provided an effective solution for the purification of phosphorus-containing wastewater.