CuS/Nitrogen-biomass derived carbon composites for heterogeneous Fenton-like degradation of dyes: C-, N- and S-mediated electron transfer mechanism for redox cycling of Cu(I)/Cu (II) couple

Wastewater treatment is a critical environmental issue, and Fenton-like catalysts have emerged as effective solutions for degrading persistent organic pollutants. One promising group of catalysts introduced for hydrogen peroxide activation in Fenton and Fenton-like reactions are transition metal sulfides. However, their applications are limited due to the insufficient number of active sites on the surfaces of these catalysts. CuS functions as a photo-Fenton catalyst only in the presence of light. Therefore, making the catalyst to retain its catalytic ability even in the absence of light is a fundamental objective of the present study. The anchoring of the CuS matrix to carbonaceous materials enhances active site exposure and catalyst stability. In this study, a CuS/nitrogen-biomass-derived carbon (CuS/N-BMC) nanocomposite catalyst was synthesized to enhance catalytic activity and stability. The composite showed high degradation efficiency of methylene blue (MB) without light irradiation, achieving 93% degradation within 60 min at pH 4.1 with a rate constant of 0.0367 min-1. It demonstrated its efficiency in degrading mixed dyes. The catalyst demonstrated effectiveness over a wide pH range (3.3-8.6) showcasing its potential in waste water treatment. The mechanism involved H2O2 activation, electron donation by the active functional groups, i.e., sp2C = C/C-C present in the carbon, pyridinic-N of nitrogen, and reduced state of S-species and regeneration of Cu+ species. The CuS/N-BMC composite demonstrated excellent stability and could be reused for five cycles, retaining 83% degradation efficiency. This study contributes to the development of efficient catalysts for environmental applications.