Fabrication of sewage sludge-derived magnetic nanocomposites as heterogeneous catalyst for persulfate activation of Orange G degradation

An increasing amount of sewage sludge is produced by wastewater treatment plants worldwide. Therefore, the disposal of sewage sludge is one of the vital environmental issues currently. In the present work, we developed an alternative strategy of converting sewage sludge into porous activated carbon (SAC), and then synthesized a magnetically separable MnFe 2 O 4 -SAC heterogeneous catalyst through an environmentally friendly method. Several characterization techniques such as XRD, FTIR, SEM and XPS indicated the evidence of MnFe 2 O 4 nanoparticles successfully sticking to surface of porous SAC. The MnFe 2 O 4 -SAC composites exhibited stable and excellent catalytic activity in activating persulfate (PS) for the degradation of Orange G (OG) throughout the wide pH range of 3–9, and could be recycled by a magnet without any loss. The activation energy was calculated to be 14.94   kJ mol −1 , indicating that the OG degradation in MnFe 2 O 4 -SAC/PS process required moderate activation energy. The results of heavy metals leaching experiments revealed an excellent stability of the MnFe 2 O 4 -SAC catalyst. Possible reaction mechanism in MnFe 2 O 4 -SAC/PS system was also discussed in detail.