Chemically deposited thin CuS films for photocatalytic degradation of methyl green in UV-assisted persulfate

Abstract Copper sulfide (CuS) thin films were deposited onto glass substrates using chemical bath deposition with copper chloride and thiourea as precursors. Deposition times varied from 2 hours to 3 hours 30 minutes. Characterization was performed using Rutherford backscattering spectrometry (RBS), atomic force microscopy, x-ray diffractometry (XRD), and UV–Vis spectroscopy. RBS confirmed a stoichiometric composition (50% Cu, 50% S) and film thicknesses increasing from 50 to 75 nm with deposition time. XRD analysis identified the CuS covellite phase. The energy band gap increases from (2.24±0.1) to (2.40±0.1)eV with deposition time. The photocatalytic activity of thin films was evaluated using a UV-assisted persulfate (PS) activation process for methyl green (MG) degradation. Experiments with varying MG concentrations showed a high degradation efficiency (95.48±4.62)% at 20 mg/L MG, pH 3, PS concentration of 80 mg/L, and 3 hours 30 minutes deposition time. Kinetic analysis revealed a high pseudo-first-order rate constant (5.51×10−2±1.57×10−4)min−1 and a short half-life (12.56±4.41×10−5)min. The system showed excellent stability over five reuse cycles. This research highlights the sodium PS effectiveness in enhancing CuS photocatalytic activity for MG wastewater treatment, offering a promising approach for environmental remediation. GRAPHICAL ABSTRACT