A novel fluidized electrode electrolysis system activated ferrate (VI) oxidation promoting sludge solubilization: Performance and mechanism

Abstract

Energy and resource recovery is a viable and sustainable solution for sludge treatment and disposal, while sludge solubilization is one of the most critical issues hindering sludge conversion to valuable products. Although ferrate (VI) was considered a green sludge pretreatment approach, the poor stability of ferrate (VI) hindered the effective utilization of its oxidative potential. This study demonstrated that an innovative electrochemical system with granular activated carbon (GAC) as the fluidized electrode activated potassium ferrate (PF) oxidation could effectively catalyze the destruction of sludge structure, thereby promoting the release of organic matter and improving sludge solubilization. The results showed that the electro- granular activated carbon- potassium ferrate (E-GAC-PF) process achieved a sludge solubilization of 30.9 % within 15 min, resulting in a reduction in sludge volume by 33.9 %. In comparison, the sludge solubilization rate under PF oxidation alone was 11.5 %, with corresponding in sludge volume reduction of 13.0 %. The radical scavenging experiment and probe compound (sulfoxide) oxidation experiment revealed that the E-GAC-PF system was responsible for the production of a higher quantity of Fe (V) and Fe (IV), which significantly contributed to the sludge decomposition. Additionally, XPS and XRD analysis discovered that Fe3O4 was present as a byproduct, which opened up a new route for iron recycling during the pretreatment. Hence, E-GAC-PF system held promise as a pioneering and efficient alternative for catalytically activating PF, thereby facilitating environmentally friendly and highly efficient pretreatment of sludge.