RESUMEN

Spent hydrogenation catalysts (HDCs) contain many Mo, V, Co, Ni, and Al2O3 carriers, which are valuable secondary resources. However, improper disposal can also lead to environmental pollution risks. In the past decade, research reviews on the recovery of valuable metals from spent HDCs have been somewhat reported, mainly summarizing basic technical processes. Based on previous work, this article reviews the emerging recycling technologies of spent HDCs in recent years. The research trend of furnace optimization in the pyrometallurgical process was innovatively proposed, and the importance of developing new mild leaching agents for the high-quality recycling of Al2O3 carriers in the hydrometallurgical process was clarified.

RESUMEN

High-chloride leachate is a solution rich in precious metals that is produced in chloride hydrometallurgy. It has high levels of both rare and precious metals and hazardous chloride ions, and resource recovery from this solution and its safe disposal have become key objectives in the field of hydrometallurgy. In this study, a sustainable process involving "ultrasound-assisted precipitation-Pb powder cementation" was proposed for the stepwise separation and high-value utilization of Bi, Au and Ag obtained from high-chloride leachate. Targeted separation and conversion of Bi were achieved by precipitation-re-acid hydrolysis-ultrasonication-assisted coprecipitation-centrifugal purification. Under the optimal process conditions, the removal rate of Bi reached 99.52%, while the loss rates of Au and Ag were only 4.63% and 8.72%, respectively. Single-factor experiments of Au and Ag cementation by Pb powder showed that the recovery rates of precious metals could be improved by increasing the temperature, raising the solution pH, and applying mechanical force and ultrasonication. A possible reaction mechanism for Au and Ag cementation with Pb powder was proposed based on macroscopic kinetic analysis and microscopic mineral characterization. This work provides technical support and a theoretical basis for the separation and enrichment of rare and precious metals in chloride hydrometallurgy.

RESUMEN

Due to containing abundant FeOx and trace heavy metals (Pb, As, Cr, Cd, etc.), the disposal of lead/zinc smelting slag (LSS-ZSS) with ultra-high historical reserves has attracted increased attention. Using LSS-ZSS to prepare glass-ceramics is a good method to solve the problem of LSS-ZSS accumulation and realize heavy metal solidification, whereas there are some technical challenges that are difficult to deal with. A large amount of FeOx component in LSS-ZSS would not only lead to melt overflow, but also cause early crystallization of basic glass. In this work, through the directional modification of LSS-ZSS and the subsequent crystallization kinetics regulation, we successfully prepare high performance glass-ceramics with andradite and hematite as the main crystal phases. In addition, by means of SEM, PXRD, FTIR spectra and XPS, the morphology/phase transformation, fine structure and valence variations of iron components in LSS-ZSS at different temperature zones are systematically studied. The maximum shrinkage rate of resultant basic glasses is 27 %, and the maximum flexural strength and compressive strength of glass-ceramics are 128 MPa and 890 MPa, respectively. This work would not only benefit to solve the problem of resource utilization of harmful LSS-ZSS, but also provide a possible reference for the utilization of iron-rich waste slag in magnetic properties related fields.

RESUMEN

This study developed an efficient and sustainable hydrometallurgical process for the enrichment of gold and silver and the stepwise separation of copper, zinc, and lead from sulfated roasted sand of waste printed circuit board smelting ash. Selective separation of copper and zinc was achieved by water leaching, and silver dispersion was reduced by controlling the amount of NaCl added during the leaching process. The results of the water leaching showed that the copper and zinc leaching rates were 99.85% and 99.47%, respectively, whereas the loss rate of silver was 2.1% with optimal leaching parameters. The high-chloride-complex method was used to study the efficient conversion and separation of lead from the leached residue, and the leaching kinetics and conversion mechanism of lead were discussed. The results showed that under the optimal conditions, the leaching rate of lead was 99.79%. Leaching kinetics analysis showed that lead leaching in the high - chlorine system was controlled by a chemical reaction; the apparent activation energy was 53.63 kJ/mol. After the leaching of copper, zinc, and lead, 1.66% Ag and 213 g/t Au were enriched in the leached residue; and the precious metal enrichment goal was reached. The chlorinated leachate showed good recycling performance, and a lead leaching rate of 97.93% was obtained after three circulations. After cooling, crystallization, and purification, lead chloride with a purity of 99.89% and high economic and industrial value was obtained from the lead-rich leachate. This process has favorable and sustainable industrial application prospects.

Asunto(s)

RESUMEN

The waste printed circuit board smelting ash (WPCB-SA) produced in the waste printed circuit board smelting process is a hazardous material that not only contains valuable metals, but also contains a large amount of toxic and harmful inorganic bromides. The utilization of metals has received considerable attention in previous studies, but the recovery of hazardous bromides requires further study. In this article, a new idea of converting inorganic bromine in WPCB-SA by traditional sulfated roasting is proposed. Debromination kinetics under simulated experimental conditions are discussed, and kinetic equations are established. The kinetic results show that during low-temperature sulfated roasting, the conversion of Br in CuBr and PbBr2 conforms to the chemical reaction diffusion model and diffusion control the product layer model, respectively. A possible reaction mechanism is also proposed. Our research shows that the conversion of Br in CuBr is divided into three processes: covalent bond decomposition, hydrogen ion form acid, copper ion form salt, and HBr oxidation conversion, whereas the conversion of Br in PbBr2 is divided into two processes: sulfuric acid ionization, lead ion form salt and HBr oxidation conversion. This work provides the theoretical basis for the improvement and application of inorganic bromide recovery technology in WPCB-SA.

RESUMEN

Waste electrical and electronic equipment (WEEE) has been one of the fastest growing waste streams worldwide. Effective and efficient management and treatment of WEEE has become a global problem. As one of the world's largest electronic products manufacturing and consumption countries, China plays a key role in the material life cycle of electrical and electronic equipment. Over the past 20 years, China has made a great effort to improve WEEE recycling. Centered on the legal, recycling and technical systems, this paper reviews the progresses of WEEE recycling in China. An integrated recycling system is proposed to realize WEEE high recycling rate for future WEEE recycling.

Asunto(s)

RESUMEN

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.