Mechanochemical processing of molybdenum and vanadium sulfides for metal recovery from spent catalysts wastes

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

Spent petroleum refining catalyst is regarded as the important secondary resource for valuable metals. However, common recycling strategies, including soda roasting, acid and alkaline solutions leaching and chemically precipitation, produced large quantities of high salinity wastewater. This study proposed an efficient method to recovery of Mo and Ni from the spent hydrodesulfurization (HDS) catalyst via O2-rich roasting and organic acid leaching with the advantage of less salinity wastewater production. The transformation of Mo(IV) into soluble Mo(VI) was enhanced by O2-rich atmosphere roasting, and 98.64% of Mo(IV) was oxidized at 650 ℃ for 2 h in atmosphere containing 30% of O2. The oxidation process of Mo(IV) was agreed with the shrinkage pore model, and regulated by surface reaction and internal diffusion. 97.97% of Mo(VI) was leached from roasted product by oxalic acid, separated with complexation extraction agent of Ala-TBP and recovered as (NH4)8Mo10O34 and (NH4)2Mo3O10 by evaporative crystallization. Ni was leached out from spent catalyst with 1 mol/L acetic acid, and precipitated as NiC2O4 with oxalic acid. 95.92% of Mo and 96.77% of Ni were recovered from spent HDS catalyst with this recycling route. This study provided a high-efficient and eco-friendly method to recovery of valuable metals from spent catalyst.

Industrial-Scale Technology for Molybdic Acid Production from Waste Petrochemical Catalysts

The article describes the technology of molybdic acid recovery from spent petrochemical catalysts (HDS) developed and implemented in industrial activity. HDS catalysts contain molybdenum in the form of MoO3 and are used for the hydrodesulfurization of petroleum products. After deactivation, due to the impurities content in the form of sulfur, carbon and heavy metals, they constitute hazardous waste and, at the same time, a valuable source of the Mo element, recognized as a critical raw material. The presented technology allows the recovery of molybdic acid with a yield of min. 81%, and the product contains min. 95% H2MoO4. The technology consisted of oxidizing roasting of the spent catalyst, then leaching molybdenum trioxide with aqueous NaOH to produce water-soluble sodium molybdate (Na2MoO4), and finally precipitation of molybdenum using aqueous HCl, as molybdic acid (H2MoO4). Industrial-scale testing proved that the technology could recover Mo from the catalyst and convert it into marketable molybdic acid. This proves that the technology can be effectively used to preserve molybdenum.

Effect of pulp density on the bioleaching of metals from petroleum refinery spent catalyst

Bioleaching is one of the well-known methods of metal recovery with Environmental benefits. This process has been extensively used for combating improper waste management issues along with metal reclamation. The aim of this study is to bioleach spent petroleum refinery catalyst at variant pulp densities (PD) (5, 10 and 15%) using microorganisms in acidic pH (1.5-1.6) and mesophilic temperature (30-35 °C). The study includes leaching yields of metals like nickel, molybdenum, copper and aluminum. The three bioleaching experiments with different pulp densities yielded a maximum of more than 90% nickel, 73% copper, 87% molybdenum and 24% aluminum. The results are validated 5, 10, and 15% pulp density and the result is validated with pH, Redox potential, microbial population, sulphate concentration and ferrous iron, concentration. The time saving due to faster nickel dissolution using iron and sulphur oxidizing microorganisms would be economical for the bioleaching process.

An Experimental Study for the Remediation of Industrial Waste Water Using a Combination of Low Cost Mineral Raw Materials

This paper investigates an alternative use of sterile aggregate materials which may arise from various construction applications in conjunction with other low-cost mineral raw materials to remediate the acid mine drainage phenomenon. This study is based on the combination of unprocessed mineral raw materials, as well as on the basic concept of the cyclic economy where the conversion of a waste into a raw material for another application can be achieved. In this study, in order to examine the remediation, in lab scale, of the drainage waste water of Agios Philippos mine, an experimental electrically continuous flow-driven forced device was constructed, enriching the research gap relative to this type of remediation approach. Through this experimental device, the use of certain mixes of mineral raw materials (serpentinite, andesite, magnesite, peat, and biochar) was studied. Our results focus on the impact of the studied mineral raw materials and especially on their synergy on the water purification potential under continuous water flow operation. Using the new 7-day experimental electrically continuous flow-driven forced device with certain mixes of mineral raw materials, the increase of pH values from 3.00 to 6.82 was achieved. Moreover, with use of the experimental device, the removal of toxic load was achieved, and more specifically the concentration of Fe was decreased from 6149 to 1300 ppb, Cu from 8847 to 35 ppb, and Zn from 285,458 to 50,000 ppb.

Ultrasound-assisted oil removal of γ-Al2O3-based spent hydrodesulfurization catalyst and microwave roasting recovery of metal Mo

Currently, roasting-leaching is the main treatment process of spent hydrodesulfurization (HDS) catalyst, but it will produce impurities, such as nickel molybdate and cobalt molybdate (NiMoO₄ or CoMoO₄), which is adverse to recover valuable metals. In this paper, a combined ultrasonic-microwave method was developed to remove oil and recover molybdenum (Mo) from the spent HDS catalyst. Firstly, ethanol was used to extract the surface oil of the spent MoNiCo/Al₂O₃ catalyst with ultrasonic assistance. Effects of temperature, ultrasonic time, liquid-solid ratio and ultrasonic power on the oil removal rate were investigated systematically and the process conditions were optimized using response surface methodology (RSM). The results showed that the oil removal rate was over 99% under the optimum conditions of temperature 55 °C, ultrasonic time 2 h, liquid to solid ratio 5:1, and ultrasonic power 600 W. After oil removal, the sample was roasted in microwave field at 500 °C for 15 min. The generation of toxic gas could be effectively avoided and no hardest-to-recycle impurity CoMoO₄ was found. At last, the roasted sample was subjected to ultrasonic leaching with sodium carbonate (Na₂CO₃) solution for recovering Mo. Extraction of Mo of the deoiled sample after microwave roasting reached 94.3%, which is about 7% higher than that of oily sample. Moreover, microwave roasting method resulted in a much higher Mo extraction than traditional method for both the oily and deoiled spent catalyst. It was concluded that the ultrasonic-microwave assisted method could remarkably improve the recovery of Mo and greatly shorten the processing time.

Oil removal from spent HDT catalyst by an aqueous method with assistance of ultrasound

Deoiling enjoys great significance in recycling and landfill of spent hydrotreating (HDT) catalyst. In this study, a novel approach for oil removal from spent HDT catalyst with assistance of ultrasound was developed. The effects of variables on oil removal were investigated by response surface methodology and central composite design method. The oil removal efficiency reaches 96.03 ± 0.82% under the optimum conditions of liquid-solid ratio 16.00 ml·g^-1, 75 °C, sodium hydroxide dosage 3.88 wt%, and 40 kHz ultrasonic irradiation for 3.25 h. Under the optimum conditions, the contact angle of spent catalyst is 98.7° before oil removal, and then reduces to 57.2° after deoiling with the help of ultrasound, but turns to 72° after deoiling in the absence of ultrasound, which further verifies that the oil removal efficiency can be improved by ultrasound. Compared to traditional extraction or hydrothermal methods for removing oil from spent catalyst, the proposed approach introduced ultrasonic force field to enhance oil removal efficiency without adding organic solvent or surfactant.