Mineralogical and leaching characteristics of sulfur concentrate and hot filter residue from zinc–oxygen-pressure leaching

Abstract

The mineralogical properties and environmental impact of sulfur concentrate and hot filter residue produced from the zinc–oxygen-pressure leaching were studied through a series of characterization, including X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP–OES), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDS), particle size distribution (PSD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetry and differential thermal analysis (TG–DTA). Furthermore, short-term environmental activity was assessed using the toxic leaching procedure (TCLP). The results indicated that the sulfur concentrate exhibited a coarser particle size compared with the hot filter residue, primarily appearing as spindle-shaped element sulfur (S⁰). The hot filter residue contained spindle-shaped S⁰ and rod gypsum, alongside phases of sphalerite, pyrite, and copper–silver-containing phases encapsulated by S⁰, recovering valuable metals first requires the removal of S⁰. The surfaces of both sulfur concentrate and hot filter residue were composed of S, ZnS, Al-O, PbSO₄, and SiO₂. They exhibited thermal instability and some degree of water absorption, with vigorous burning observed at temperatures ranging from 200 °C to 380 °C. The leachates from these materials exhibited increased concentrations of elements such as zinc, lead, and cadmium surpassing permissible limits, highlighting the importance of their safe disposal for the stable production of zinc–oxygen-pressure systems.