This work focuses on the recovery of lead and silver from jarosite waste by a three-stage process: drying, roasting and reduction at 100 °C, 700 °C and 1400 °C, respectively. A flux mixture with 48 mass% CaO and 52% SiO₂ was used for the reduction stage. A gas consisting of 70 vol% CO and 30 vol% CO₂ was used as a reducing agent. To select the temperatures and the amount of flux and reducing agent, a characterization of the jarosite waste was carried out using thermogravimetry and high-temperature X-ray diffraction, as well as a thermodynamic study of the effects of the process parameters. The lead-rich metallic and slag phases were characterized by chemical analysis, SEM-EDS and XRD. In addition, the jarosite residue and the final slag were leached with an aqueous acetic acid solution to estimate their chemical stability. The results show a recovery of over 95% of the lead and silver and the formation of an environmentally friendly residual slag.

Terminals obtained from spent lead-acid batteries in Mexico contain around 2 wt% Sb. The terminals were melted in an electric furnace and then oxygen was injected at 750 ?C with a gas flow rate of 2 L/min to produce high purity Sb2O3. The antimony trioxide obtained was treated with a mixture of Na2CO3-SiC at 1000 ?C to obtain metallic antimony. The antimony trioxide was reduced by C present in reagents while silicon and sodium formed a slag phase. The amounts of Sb2O3 and SiC were held constant while the Na2CO3 was evaluated in the range from 30 to 42 wt%. The produced antimony and slag were characterized by the X-ray diffraction and SEM-EDS techniques. The addition of 34 wt% Na2CO3 led to the recovery of antimony up to 90.16 wt% (99.57 wt% purity) and the lowest antimony losses in the slag (2 wt%). In addition, the compounds Na2SiO3 and Na2Si2O5 formed in the slag indicated a more stable slag. Na2CO3 contents higher than 38 wt% decreased the antimony recovery since Na2Sb4O7 compound was promoted in the slag. The oxidation and reduction process was modeled in FactSage 7.3 software for a better understanding of the Na2CO3 and SiC additions on the antimony recovery rates and compounds formed in the slag.

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.

High silicon and molybdenum (SiMo) ductile irons present a metallic matrix composed principally of ferrite with little volume fraction of pearlite and carbides. In this work, two SiMo ductile irons with similar levels of silicon, 0.3% Mo (DI-0.3Mo) and 0.6% Mo with 0.8% Co (DI-0.6Mo-0.8Co), were evaluated to determine the effect of molybdenum and cobalt on the microstructure, hardness, and wear performance at room temperature. The microstructural characterization of the ductile irons was performed using light microscopy and SEM-EDS. At the same time, mechanical characterization was carried out using Rockwell C hardness, and wear was evaluated using reciprocating ball-on-flat sliding wear tests. The result showed that DI-0.6Mo-0.8Co obtained the higher nodule count (247 nod/mm²), nodularity (86.69%), volume fraction of ferrite (78.15%), and molybdenum carbides (2.1%), while DI-0.3Mo presented a higher volume fraction of pearlite (12.8%) and free graphite (13.88%). The higher value of Rockwell C hardness with 21.29 HRC was obtained in DI-0.6Mo-0.8Co due to a higher amount of molybdenum carbides. The wear resistance shows that the DI-0.6Mo-0.8Co sample presented the highest wear resistance due to an adequate balance between a ferritic matrix reinforced by the molybdenum and cobalt addition and a high carbide content.