Remediation of Cu(II) and its adsorption mechanism in aqueous system by novel magnetic biochar derived from co-pyrolysis of sewage sludge and biomass

The novel magnetic biochar (MBC), derived from co-pyrolysis of sewage sludge and biomass loading nanosized iron oxide particles, was used as an environmentally friendly adsorbent. The loading of magnetic particles was in favor of increasing the adsorption capacity and separation from aqueous system for biochar (BC). The physical/chemical characteristics of MBC were revealed by elemental analysis, VSM, SEM-EDS, XRD, FTIR, zeta potential, and batch adsorption-desorption experiments. The nanosized γ-Fe 2 O 3 particles grown on the surface of biochar showed ferromagnetic property. For the remediation of Cu(II) contamination, MBC-5 showed remarkable adsorption capacity of 67.68 mg/g, and presented a wide pH range of 3.0–6.0. The Langmuir isothermal and pseudo-second-order model could describe adsorption process well. The adsorption mechanism of Cu(II) involved physical adsorption, ion exchange, and electrostatic surface complexation on the surface of MBCs. In the desorption experiments, MBC-5 holds the adsorption efficiency of 81.09% after fifth recycle still, which illustrated a remarkable performance of cyclic utilization by the solid waste of sewage sludge and biomass. Graphical abstract