High-efficiency recycling of Mo and Ni from spent HDS catalysts: Enhanced oxidation with O2-rich roasting and selective separation with organic acid leaching- complexation extraction

One-step high-efficiency recovery of high-purity MoO3 from spent hydrodesulfurization catalyst by water-vapor enhanced sublimation process

Spent hydrodesulfurization (HDS) catalysts were considered as a vital secondary resource for precious metals like Mo. The current pyrometallurgy and hydrometallurgy usually exhibits the characteristic of remarkable high energy consumption and high secondary pollutions. This study proposes an innovative technique to recycling MoO3 from spent HDS catalyst by sublimation process at high temperature, which has notable advantages of zero wastewater-generation and zero chemical reagent consumption. Notably, MoO3 recovery efficiency was improved remarkably with the introduction of water-vapor. About 99.33 % of MoO3 was recovered by heating spent HDS catalyst at 1100℃ for 2.5 h in water-vapor atmosphere with partial pressure of 101.33 kPa. The yielded MoO3 was tested with the purity of 99.94 % and exhibited the appearance of thin strips. Furthermore, the sublimation kinetic of MoO3 in air was adhered to a desorption model, while agreed with a non-desorption model in water-vapor atmosphere. Density Functional Theory (DFT) calculations revealed that -OH obtained by the dissociation of H2O molecules preferably combined with MoO3 and formed the volatile MoO3-OH, which was responsible for enhancing MoO3 sublimation efficiency significantly in water-vapor atmosphere. Economic analysis suggested that the direct cost of this method was 345 $/t, accounting for around 50 % compared to current roasting-leaching-purification methods. Overall, MoO3 sublimation enhanced by water-vapor atmosphere can be considered as a high-efficient and environmental-friendly approach for Mo recovery from spent catalysts.

Recovery of valuable metals from spent hydrodesulfurization (HDS) catalysts: A comprehensive research review and specific industrial cases

Spent hydrodesulfurization (HDS) catalysts, produced in the petroleum refining process, are usually classified in hazardous solid waste. Recovery of valuable metals from spent HDS catalyst not only reduce substantially environmental risk but is an important way to alleviate global resource shortages for high-valuable metals. This study reviews numerous references regarding to recovery valuable metals from spent HDS catalyst in last decades, and divided current methods into three processes: pretreatment, oxidation-leaching, and separation-purification processes. Roasting and solvent washing usually emerge as primary methods in the pretreatment process, and effectively eliminate the surface oily substances and sulfur. Sodium salt roasting-leaching are considered as higher efficient among all leaching methods. The application of organic acid in the leaching can separate valuable metals selectively and simplify subsequent purification steps. In separation-purification processes, solvent extraction is still a standout method to isolate challenging metals such as Mo, W and V. However, the burgeoning field of ion imprinting technology exhibits the promising potential. Additionally, Random Forest and XGBoost model are used to analyze reported methods to recovery Mo and Ni and predict the key factor to regulate recovery efficiency. The results show that Mo recovery process is depended on the spent HDS characteristics and solid-liquid ratio in leaching process, while Ni recovery processes is depended on the roasting time and roasting temperature. Finally, serval specific industrial cases on recycling valuable metals from spent HDS were given, and found that sodium salt roasting-water leaching process was still frequent used in practical application due to its characteristics of high efficiency and low cost.

Acid-free process for selective and efficient recovery of molybdenum from spent hydrodesulfurization catalysts

The spent hydrodesulfurization catalyst represents a significant hazardous solid waste due to its heavy metal content, necessitating stringent treatment protocols. Current commercial treatment methodologies predominantly employ substantial quantities of hydrochloric and sulfuric acids, resulting in severe secondary pollution, including challenging wastewater treatment and excessive sulfur and carbon emissions. This study introduces an innovative acid-free process for the treatment of spent catalysts, encompassing mineral phase reconstruction, acid-free water leaching, and solvent extraction. This novel approach achieves efficient separation and recovery of molybdenum, with a molybdenum-aluminum separation coefficient of 19,258.26 and a molybdenum recovery rate of 98.95%. The purity of the molybdenum product attained through single-stage extraction is 93.83%, which increases to 99.7% with three-stage extraction. Life cycle assessment indicates that this process reduces CO2 emissions by 42.4% and SO2 emissions by 73.7% compared to traditional methods. From the perspectives of environmental protection, energy conservation, and carbon reduction, this advanced process holds substantial industrial applicability.

Recovery technology of spent hydrogenation catalysts -A review

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.

A hybrid thermal-biological recycling route for efficient extraction of metals and metalloids from end-of-life liquid crystal displays (LCDs)

Waste liquid crystal displays (LCDs) are one of the most substantial and rapidly growing e-waste streams that contain a notable amount of critical, precious, and toxic elements. This study presented a novel thermal-biological hybrid method for resource recovery from waste LCDs. Through the design of a multistage thermal treatment process with the addition of optimized 20 wt% B2O3 to waste, the LCD's glass structure was separated into two interconnected phases, resulting in the transfer of metals from the LCD's glass phase to the B2O3 phase that can solubilize in the acid solution. Following the thermal treatment step, the biometabolites of Aspergillus niger were used for bioleaching of In, Sr, Al, and As from the obtained thermally treated product. The optimal bioleaching parameters were a pulp density of 10 g/L, temperature of 70 °C, and leaching time of 2 days, which led to the highest extraction of 82.6% Al, 70.8% As, 64.5% In, and 36.2% Sr from thermally treated LCD waste, representing a multifold increase in Al, As, and Sr extraction levels compared to untreated waste. This study demonstrated that the proposed hybrid method could successfully overcome waste complexities and ensure effective element extraction from discarded LCDs.