A previously pyrometallurgical process, developed to obtain a Pb-Ag alloy and a slag rich in sulfur from the recycling of a mixture of industrial wastes of jarosite and lead paste, was thermodynamically assessed at 1200 °C. The industrial jarosite sourced from a Mexican zinc hydrometallurgical plant corresponded to an ammonium jarosite with a measurable silver content. The specific heat capacity (Cp) of the ammonium jarosite was obtained from TGA and DSC measurements, as well as the thermodynamic functions of enthalpy, entropy, and Gibbs free energy. The Cp was successfully modeled using polynomial regression, with a second-degree polynomial employed to describe the low-temperature behavior. The thermodynamic data generated were input into the thermodynamic software FactSage 8.2 for modeling of the lead paste–ammonium jarosite-Na₂CO₃-SiC system and represented by stability phase diagrams. The thermodynamic assessment of the pyrometallurgical process predicted compounds formed at high temperatures, showing that a Pb-Ag alloy and a slag rich in Na, S, and Fe (NaFeS₂ and NaFeO₂) were obtained. The compounds formed evidence of the effective sulfur retention in the slag, which is crucial for mitigating SO₂ emissions during high-temperature treatments. The experimental compounds, after solidification, were determined by X-ray diffraction measurements to be Na₂Fe(SO₄)₂ and Na₂(SO₄), which reasonably match the thermodynamic assessment. The heat capacity of the ammonium jarosite provides essential thermodynamic insights into the compositional complexities of industrial waste, which are particularly relevant for thermodynamic modeling and process optimization in pyrometallurgical systems aimed at metal recovery and residue valorization.

A silver-rich lead alloy was obtained through the recycling of two metallurgical wastes: these are lead paste obtained from spent lead–acid batteries and a jarosite residue obtained from the hydrometallurgical production of zinc. Mixtures of both wastes were pyrometallurgically treated with sodium carbonate in a silicon carbide crucible at 1200 °C. The alloy and slag produced were analyzed by atomic absorption spectrometry, X-ray diffraction, and scanning electron microscopy with energy-dispersive spectra. High silver recovery was obtained in a Pb-Ag alloy for a mixture ratio of 30% Na₂CO₃–40% lead paste–30% jarosite, reaching a silver grade of 126 ppm. The slags produced for the highest jarosite content allow the compound formation of Na₂(SO₄) and Na₂Fe(SO₄)₂, which have high sulfur-fixing, avoiding SO₂ release and contributing to the minimization of atmospheric pollution. The novel pyrometallurgical route addresses not only the valorization of precious metals such as silver and lead but also the reduction in accumulated industrial waste.

During the roasting, leaching, and electrodeposition of zinc ores, lead–silver residues are produced. These residues contain valuable metals (Pb, Zn, and Ag) and toxic metals (Cd and As). In this study, a pyrometallurgical process is proposed for treating Pb-Ag residues, consisting of drying, roasting, and reduction steps to recover valuable metals, such as silver in a metallic Pb phase, while converting the waste into an environmentally friendly slag. First, the Pb-Ag residue is dried at 100 °C, then roasted at 700 °C, and finally reduced at a high temperature, with Na₂CO₃ as a flux and CaSi as a reducing agent, rather than carbon-based reducing agents (carbon or carbon monoxide), to minimize greenhouse gas production. The effects of the reduction temperature and the mass of the reducing agent were investigated on a laboratory scale. The metallic phase and slag obtained in the reduction step were characterized by their chemical composition and mineralogy via chemical analysis, X-ray diffraction, and SEM-EDS. The results showed that silver and lead formed a metallic phase, and that silver content decreased from 1700 ppm in the Pb-Ag residue to 32 ppm in the final slag at 1300 °C. The Pb-Ag residue and final slag were leached with an aqueous acetic acid solution to evaluate their chemical stability.

Industrial jarosite residues from zinc hydrometallurgy are both an environmental liability and a secondary resource for valuable metal recovery (Zn, Pb, Ag). The mineralogical evolution of an ammonium-jarosite residue during oxidizing roasting was evaluated, comparing (i) pure residue and (ii) a flux-assisted/reducing formulation (45 wt% jarosite + 40 wt% Na₂CO₃ + 15 wt% SiC). Thermogravimetric analysis shows decomposition events related to dehydration, dehydroxylation, and sulfate breakdown with an overall mass loss of ~49%. X-ray diffraction measurements to temperature in the range from 600 to 1400 °C evidence the pathway of spinel formation: jarosite → hematite + ZnO → ZnFe₂O₄ (spinel) for pure jarosite roasting, which immobilizes Zn. In contrast, the addition of Na₂CO₃ and SiC to jarosite suppresses ZnFe₂O₄, fixes sulfur predominantly as Na₂SO₄ and CaSO₄, while iron is contained in oxide and sulfate compounds. SEM/EDS reveals a locally Pb-rich droplet domain at elevated temperatures, indicating partial metal liberation under optimized redox conditions.

Jarosite-type residues generated during zinc hydrometallurgical processing represent a significant environmental liability and a latent source of valuable metals (Zn, Pb, Ag). In this study, the thermal decomposition and mineralogical evolution of an industrial ammonium jarosite residue were investigated to 600–1400 °C. The behavior of the as-received residue was compared against a designed flux-assisted formulation comprising 45 wt% jarosite, 40 wt% Na₂CO₃, and 15 wt% SiC. The conventional roasting of pure jarosite forms refractory zinc ferrite (ZnFe₂O₄) and releases SO₂ above 800 °C, while the flux-assisted route stabilized the sulfur as Na₂SO₄ and CaSO₄, decreasing toxic gas emissions. Concurrently, the reducing effect of the SiC significantly inhibited bulk zinc ferrite formation up to 1200 °C and favored the partial reduction of iron to magnetite (Fe₃O₄). Thermodynamic assessment using FactSage reasonably matches experimental results by X-ray diffraction and SEM-EDS measurements. The thermodynamic evaluation predicts the formation of elemental silver available for subsequent pickup by a collector metal and a liquid slag phase at approximately 1000 °C for the flux-assisted jarosite samples. The ammonium jarosite flux-assisted roasting strategy enhances the potential for metal recovery while increasing environmental sulfur fixation in the slag, aligning with sustainable circular economy principles in non-ferrous metallurgy.

Yttrium oxide (Y₂O₃) is a phosphor material, since as an inorganic solid compound that can absorb energy and transfer it to a luminescent center and subsequently emit it as light when the excitation source is removed. The emitted color intensity and decay time of the emission of the phosphor depend strongly on the structure of the host material and the choice of the emission center. The aim of this research is to determine the decay times at different molar concentrations of europium doping ion into yttrium oxide matrix. The experimental methodology involved synthesizing yttrium oxide via the sol-gel method doping at concentrations ranging from 0 to 5 mol % of Eu³⁺. Upon exposing the experimental matrix to an excitation source of l = 254 nm, different intensities of red emissions were obtained. These emissions were characterized by emission spectroscopy and luminescent decay times were determined. Based on the results, europium-doped yttrium oxide powder with a cubic structure and decay times ranging from 1632 to 1857 µs is a promising phosphor for applications in fields such as optics and/or biomedicine.