Dyeing sludge carbons activated by alkali-etching for outperformed 4-chlorophenol degradation in electro-Fenton process

Abstract

Developing outperformed and cost-effective heterogenous electro-Fenton catalysts will be necessary for halogen-containing compounds removal. In this contribution, dyeing based sludge carbons are activated via alkali etching to achieve extremely high removal of 4-Chlorophenols (4-CPs) in electro-Fenton process, fabricating robust and inexpensive catalysts via solid waste resources. The sludge carbons are initially activated by KOH etching and the corresponding structural and morphological features are characterized by pXRD, Raman, FT-IR, BET, and SEM. Further mechanism investigation is conducted via Rotating Ring-disc Electrode (RRDE) and EPR by confirming in-situ oxygen reduction pathway and the type of free radicals. The outcomes of this contribution suggest that the increment of alkali activation level facilitates oxygen reduction towards two-electrons transfer pathway with extremely high H2O2 yield (81.32 %). Meanwhile, the removal rate and mineralization efficiency of 4-CP achieves 100 % and 62.14 %, respectively after reaction time with 150 min. Additionally, the high activated sludge carbons showcase extraordinary stability: H2O2 yield and 4-chlorophenol removal present no obvious decay even enduring five cycles. Thus, alkali-etched dyeing sludge carbons not only provide outperformed, economic, and robust heterogenous electro-Fenton catalysts to remove halogen-containing compounds, but also benefit for solid waste reutilization.