The dissolution of CuS particles with Fe3+ in acidic sulfate solutions was investigated in an oxygen-free environment. CuS particles, used in this study, were obtained from H2S removal operations from biogas with an acidic CuSO4 solution in a Vitrisol pilot absorber. The CuS particles were porous with an average diameter of 5.8 X 10(-6) m. Zero orders of reaction for both Fe3+ and H2SO4 were determined. Full conversion of CuS could be obtained independent of temperature. The activation energy was determined to be E-A = 22.0 kJ/mol. It seems plausible that the CuS dissolution reaction was affected by diffusion.