Dye wastewater treatment through adsorption-photocatalysis using electroplating sludge-derived NiFe2O4@C catalyst

Abstract

Electroplating sludge (ES) is classified as HW46 hazardous waste, and its high-value utilization offers superior economic and environmental benefits compared to traditional methods such as thermal treatment, solidification, and landfill. This paper exploits ES's inherent properties while preserving its carbon structure, and a NiFe2O4@C heterojunction catalyst with high adsorption and excellent photocatalytic capabilities is innovatively developed through a novel “one-step” approach. This catalyst is used to activate peroxymonosulfate (PMS) for the degradation of rhodamine B (RhB). Characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the Brunner-Emmet-Teller (BET) method, confirm that the NiFe2O4@C prepared under low-oxygen concentration exhibits a remarkably larger surface area and heterogeneous structure. In dark adsorption experiments lasting 60 min, the NiFe2O4@C achieves an adsorption capacity (Qe) of 295.65 mg/kg. During the subsequent 120-minute photoreaction stage, RhB removal efficiency reaches 96.98 %. Quenching experiments reveal that several active radicals (SO4−, ∙OH, and O2−) play a predominant role in RhB degradation, while nonradicals (1O2 and charge transfer) and high-valent metals also contribute to RhB removal. Density functional theory (DFT) calculations predict RhB molecular sites susceptible to attacks by reactive species. The identification of intermediates using liquid chromatography-mass spectrometry (LC-MS), combined with these theoretical insights, confirmed the main degradation pathways of RhB.