Bioleaching kinetics and multivariate analysis of spent petroleum catalyst dissolution using two acidophiles

Vanadium extraction from steel slag: Generation, recycling and management

The metal vanadium has superior physical and chemical properties and has a wide range of applications in many fields of modern industry. The increasing demand for vanadium worldwide has led to the need to guarantee sustainable vanadium production. The smelting process of vanadium and titanium magnetite produces vanadium-bearing steel slag, a key material for vanadium extraction. Herein, vanadium production, consumption, and steel slag properties are discussed. A detailed review of methods for extracting vanadium from vanadium-bearing steel slag is presented, including the most commonly used roasting and leaching method, and direct leaching, bioleaching and enhanced leaching methods are also described. Finally, the rules and regulations of steel slag management are introduced. In general, it is necessary to further develop environmentally friendly vanadium extraction methods and technologies from vanadium containing solid wastes. This study provides research directions for the technology of vanadium extraction from steel slag.

Bioleaching of the α-alumina layer of spent three-way catalysts as a pretreatment for the recovery of platinum group metals

Acid bioleaching of Al by Acidithiobacillus thiooxidans has been explored as an environmentally friendly pretreatment to facilitate the extraction of platinum group metals from spent three-way catalysts (TWC). Biogenic sulfur obtained from desulfurization bioreactors improved the production of acid by A. thiooxidans compared to commercially available elemental sulfur. The lixiviation abilities of bacteria-free biogenic acid and biogenic acid with exponential or stationary phase bacteria were compared against a control batch produced by commercial H2SO4. The maximum Al leaching percentage (54.5%) was achieved using biogenic acids with stationary-phase bacteria at a TWC pulp density of 5% w/v whereas bacteria-free biogenic acid (23.4%), biogenic acid with exponential phase bacteria (21.7%) and commercial H2SO4 (24.7%) showed lower leaching abilities. The effect of different pulp densities of ground TWC (5, 30, and 60% w/v) on Al leaching and bacterial growth was determined. While greater Al leaching yields were obtained at lower TWC pulp density solutions (54.5% at 5% w/v and 2.5% at 60% w/v), higher pulp densities enhanced microbial growth (2.3 × 109 cells/mL at 5% w/v and 9.5 × 1010 cells/mL at 60% w/v). The dissolution of the metal from the solid into the liquid phase triggered the production of biological polymeric substances that were able to absorb traces of both Al (up to 24.80% at 5% w/v) and Pt (up to 0.40% at 60% w/v).

Vanadium in the Environment: Biogeochemistry and Bioremediation

Vanadium(V) is a highly toxic multivalent, redox-sensitive element. It is widely distributed in the environment and employed in various industrial applications. Interactions between V and (micro)organisms have recently garnered considerable attention. This Review discusses the biogeochemical cycling of V and its corresponding bioremediation strategies. Anthropogenic activities have resulted in elevated environmental V concentrations compared to natural emissions. The global distributions of V in the atmosphere, soils, water bodies, and sediments are outlined here, with notable prevalence in Europe. Soluble V(V) predominantly exists in the environment and exhibits high mobility and chemical reactivity. The transport of V within environmental media and across food chains is also discussed. Microbially mediated V transformation is evaluated to shed light on the primary mechanisms underlying microbial V(V) reduction, namely electron transfer and enzymatic catalysis. Additionally, this Review highlights bioremediation strategies by exploring their geochemical influences and technical implementation methods. The identified knowledge gaps include the particulate speciation of V and its associated environmental behaviors as well as the biogeochemical processes of V in marine environments. Finally, challenges for future research are reported, including the screening of V hyperaccumulators and V(V)-reducing microbes and field tests for bioremediation approaches.

Bioleaching performance of vanadium-bearing smelting ash by Acidithiobacillus ferrooxidans for vanadium recovery

The bioleaching process is widely used in the treatment of ores or solid wastes, but little is known about its application in the treatment of vanadium-bearing smelting ash. This study investigated bioleaching of smelting ash with Acidithiobacillus ferrooxidans. The vanadium-bearing smelting ash was first treated with 0.1 M acetate buffer and then leached in the culture of Acidithiobacillus ferrooxidans. Comparison between one-step and two-step leaching process indicated that microbial metabolites could contribute to the bioleaching. The Acidithiobacillus ferrooxidans demonstrated a high vanadium leaching potential, solubilizing 41.9% of vanadium from the smelting ash. The optimal leaching condition was determined, which was 1% pulp density, 10% inoculum volume, an initial pH of 1.8, and 3 Fe²⁺g/L. The compositional analysis showed that the fraction of reducible, oxidizable, and acid-soluble was transferred into the leaching liquor. Therefore, as the alternative to the chemical/physical process, an efficient bioleaching process was proposed to enhance the recovery of vanadium from the vanadium-bearing smelting ash.

Heterotrophic Bioleaching of Vanadium from Low-Grade Stone Coal by Aerobic Microbial Consortium

Bioleaching is a viable method that assists in increasing the vanadium output in an economical and environmentally friendly manner. Most bioleaching is conducted by pure cultures under autotrophic conditions, which frequently require strong acidity and produce acid wastewater. However, little is known about heterotrophic bioleaching of vanadium by mixed culture. This study investigated the bioleaching of vanadium from low-grade stone coal by heterotrophic microbial consortium. According to the results, vanadium was efficiently extracted by the employed culture, with the vanadium recovery percentage in the biosystem being 7.24 times greater than that in the control group without inoculum. The average vanadium leaching concentration reached 680.7 μg/L in the first three cycles. The kinetic equation indicated that the main leaching process of vanadium was modulated by a diffusion process. Scanning electron microscopy revealed traces of bacterial erosion with fluffy structures on the surface of the treated stone coal. X-ray photoelectron spectroscopy confirmed the reduction of the vanadium content in the stone coal after leaching. Analysis of high-throughput 16S rRNA gene sequencing revealed that the metal-oxidizing bacteria, Acidovorax and Delftia, and the heterotrophic-metal-resistant Pseudomonas, were significantly enriched in the bioleaching system. Our findings advance the understanding of bioleaching by aerobic heterotrophic microbial consortium and offer a promising technique for vanadium extraction from low-grade stone coals.

Enhanced metal bioleaching mechanisms of extracellular polymeric substance for obsolete LiNixCoyMn1-x-yO2 at high pulp density

Harmful chemicals present in electric vehicle Li-ion batteries (EV LIBs) can limit the pulp density of bioleaching processes using Acidithiobacillus sp. to 1.0% (w/v) or lower. The strong enhancing mechanisms of extracellular polymeric substances (EPS) on the bioleaching of metals from spent EV LIBs at high pulp density (4% w/v) were studied using bio-chemical, spectroscopic, surface structure imaging and bioleaching kinetic methods. Results demonstrated that the added EPS significantly improved bioleaching efficiency of Ni, Co and Mn improved by 42%, 40% and 44%, respectively. EPS addition boosted the growth of cells under adverse conditions to produce more biogenic H⁺ while Fe³⁺ and Fe²⁺ were adsorbed by the biopolymer. This increased Li extraction by acid dissolution and concentrated the Fe³⁺/Fe²⁺ cycle via non-contact mechanisms for the subsequent contact bioleaching of Ni, CO and Mn at the EV LIB-bacteria interface. During the leaching process, added EPS improved adhesion of the bacterial cells to the EV LIBs, and the resultant strong interfacial reactions promoted bioleaching of the target metals. Hence, a combination of non-contact and contact mechanisms initiated by the addition of EPS enhanced the bioleaching of spent EV LIBs at high pulp density.

Accessing Metals from Low-Grade Ores and the Environmental Impact Considerations: A Review of the Perspectives of Conventional versus Bioleaching Strategies

Mining has advanced primarily through the use of two strategies: pyrometallurgy and hydrometallurgy. Both have been used successfully to extract valuable metals from ore deposits. These strategies, without a doubt, harm the environment. Furthermore, due to decades of excessive mining, there has been a global decline in high-grade ores. This has resulted in a decrease in valuable metal supply, which has prompted a reconsideration of these traditional strategies, as the industry faces the current challenge of accessing the highly sought-after valuable metals from low-grade ores. This review outlines these challenges in detail, provides insights into metal recovery issues, and describes technological advances being made to address the issues associated with dealing with low-grade metals. It also discusses the pragmatic paradigm shift that necessitates the use of biotechnological solutions provided by bioleaching, particularly its environmental friendliness. However, it goes on to criticize the shortcomings of bioleaching while highlighting the potential solutions provided by a bespoke approach that integrates research applications from omics technologies and their applications in the adaptation of bioleaching microorganisms and their interaction with the harsh environments associated with metal ore degradation.

Sequential-Anaerobic and Sequential-Aerobic Bioleaching of Metals (Ni, Mo, Al and V) from Spent Petroleum Catalyst in Stirred Tank Batch Reactor: A Comparative Study

Spent petroleum catalyst as a repository of several toxic metals is recommended for metal removal before safe disposal. To evaluate an effective biotechnological approach for metal removal, a comparative study between sequential-aerobic and sequential-anaerobic bioleaching processes was conducted for the removal of metals from crushed-acetone-pretreated spent petroleum catalyst. The SEM-EDX and XPS analysis confirmed the presence of Ni, Al, Mo and V in their oxidic and sulphidic forms in spent catalyst. The bioleaching experiments were performed in stirred tank batch reactors (2.5 L), temperature 30 °C, pH 1.4 and stirring speed 250 rpm for the period of 160 h. Sulfuric acid acted as lechant for both sequential-aerobic (Acidithiobacillus ferrooxidans oxidised sulfur to sulfuric acid aerobically) and sequential-anaerobic (Acidithiobacillus ferrooxidans oxidised sulphur to sulfuric acid coupled with the ferric reduction to ferrous anaerobically) bioleaching studies. The higher Ni and V extractions compared to Al and Mo for all the studies were due to increased solubility of Ni and V, and supported by XPS which showed marginal signs of Ni and V peaks in leach residues compared to feed spent catalyst. At the end (320 h), sequential-aerobic bioleaching was resulted to 99% Ni, 65% Al, 90% Mo and 99% V extraction quite more effective than sequential-anaerobic bioleaching (88% Ni, 28% Al, 33% Mo and 77% V) and sequential-control leaching (94% Ni, 20% Al, 40% Mo and 57% V). Although anaerobic bioleaching a possible approach, aerobic condition was found to be more suitable for sulfuric acid generation by A. ferrooxidans and high yield. So aerobic bioleaching is recommended to be favourable approach compared to anaerobic counterpart for future study and extrapolation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12088-021-00978-8.

Bioleaching of vanadium by Acidithiobacillus ferrooxidans from vanadium-bearing resources: Performance and mechanisms

Bioleaching is promising to meet the demand of strategic vanadium both economically and environmentally. Whereas the combination of bioleaching with traditional techniques is of great interest, little is known on bioleaching of vanadium from abundant vanadium-bearing resources utilized/produced in existing processes. This study investigated the bioleaching of vanadium from vanadium-titanium magnetite, steel slag, and clinker, which are common raw mineral and intermediates used in conventional vanadium extraction process. Clinker had greater leachability by Acidithiobacillus ferrooxidans, compared to vanadium-titanium magnetite and steel slag. Pulp density, inoculum volume, initial pH and initial Fe²⁺ concentration had influencing effects on this bioleaching process. Under optimal condition with 3% pulp density, 10% inoculum volume, initial pH at 1.8, and 3 g/L initial Fe²⁺ concentration, the bioleaching of clinker achieved the maximum vanadium leaching efficiency of 59.0%. Both X-ray fluorescence and energy dispersive spectroscopy analysis confirmed the reduction of vanadium content in the solid residues after leaching. The results of Community Bureau of Reference sequential extraction suggested that vanadium in acid-soluble and oxidizable phase was more easily leachable. This study is helpful to develop sustainable and practical techniques for vanadium extraction from abundant raw materials and step forward in combining bioleaching with traditional process.

Bioleaching of critical metals from waste OLED touch screens using adapted acidophilic bacteria

The mobile phone is a fast-growing E-waste stream that includes hazardous substances and valuable metals. Smartphone touch screens (SPTS) contain a considerable amount of critical metals, such as indium and strontium that can be recovered from end of life devices as a secondary resource. Bioleaching is an emerging and environmentally friendly method for metal recovery from electronic waste. In the present study, bioleaching was assessed for the extraction of indium and strontium from organic light emitting diode type smartphone touch screens. A statistical approach based on the response surface methodology was successfully applied. The effects of influential variables: pH, ferrous sulfate, elemental sulfur, and solid content and their interactions on indium and strontium recovery using adapted Acidithiobacillus ferrooxidans were evaluated. Under optimum conditions (ferrous sulfate: 13.0 g/L; solid content; 3.0 g/L; elemental sulfur: 5.6 g/L; and initial pH of 1.1), a complete indium extraction was observed, with a concentration in solution of about 200 mg/L indium. As concerns strontium, a 5% extraction efficiency was observed, which, even if quite low, resulted in a relatively high strontium concentration in solution, around 3000 mg/L, due to its high content in the solid (2%). This work opens new perspectives in the application of clean technologies for the extraction of valuable metals, such as indium and strontium from smartphone screens.

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.

Enfoques microbiológicos para el tratamiento de catalizadores agotados

Los catalizadores, homogéneos o heterogéneos, son ampliamente utilizados para una gran variedad de procesos industriales, con el fin de producir combustibles limpios y muchos otros productos valiosos, siendo los catalizadores agotados provenientes del hidroprocesamiento los mayores residuos sólidos de la industria de la refinería y la contribución principal a la generación de catalizadores agotados. Debido a su naturaleza peligrosa, el tratamiento y la recuperación de metales de este tipo de residuos han ganado cada vez más importancia, debido al agotamiento de los recursos naturales y a la contaminación ambiental. Aunque ya existen técnicas disponibles para estos fines, éstas generan grandes volúmenes de desechos potencialmente peligrosos y producen emisiones de gases nocivos. Por lo tanto, las técnicas biotecnológicas pueden representar una alternativa promisoria para el biotratamiento y la recuperación de metales contenidos en los catalizadores agotados. Con este fin, se han analizado diversos microorganismos, que comprenden bacterias, arqueobacterias y hongos, capacitados para facilitar la eliminación de losmetales contenidos en estoscatalizadores. En estarevisión se presenta un amplio escenario sobre los avances con respecto al manejo de los catalizadores agotados y su tratamiento tradicional, seguido de una descripción detallada sobre los enfoques microbiológicos reportados hasta la actualidad.

Evaluation of molybdenum recovery from sulfur removed spent catalyst using leaching and solvent extraction

In this article a new spent catalyst sample preparation method was implemented for the purpose of molybdenum leaching in a single step. Further molybdenum and vanadium in the leach liquor were separated and their concentrations were enriched using the solvent extraction and stripping techniques. The impervious sulfur (S⁰) layer of the spent catalyst sample was removed using carbon disulfide (CS₂). The advantages of S⁰removal were evaluated by conducting different sets of the Mo leaching experiments and they were further examined by varying different conditions such as three lixiviants, hydrogen peroxide (H₂O₂) addition, and three leaching parameters. The leaching rate increased in an order, e.g. acetone washed < acetone-CS₂ washed < acetone washed-H₂O₂ < acetone-CS₂ washed-H₂O₂, for the experimental concentration range of different lixiviants with the maximum of 94.8%(w/w) Mo dissolution in a single step. Optimization of the pulp density was important as the interaction of lixiviant molecules with multiple reacting solid particles decreased the driving force of the chemical reactions. The solvent extraction followed by the stripping technique was found to be excellent as the concentration of vanadium and molybdenum enriched from 0.55 to 1.9 M and 0.0448 to 1.08 M, respectively.

Environmentally friendly recovery of valuable metals from spent coin cells through two-step bioleaching using Acidithiobacillus thiooxidans

The technology for recycling the spent coin cells is pressing needed due to a large amount of generated spent coin cells. However, there is little information about the recycling technology of spent coin cells. In this work, a two-step bioleaching method for recovery of metals from spent coin cells by Acidithiobacillus thiooxidans is performed for the first time. In this regard, the growth characteristics of A. thiooxidans was investigated in pure culture and during the two-step bioleaching approach. The highest recovery of Li, Co and Mn was achieved at a pulp density of 30 g L^-1, in values of 99%, 60%, and 20%, respectively. The structural analyzes confirmed the progress of bioleaching process. In addition, the kinetics models showed that the chemical reaction was the rate-controlling step of the two-step bioleaching of spent coin cells. The comparative results between bioleaching and chemical leaching showed that Acidithiobacillus thiooxidans can enhance the leaching of metals. Toxicity characteristic leaching procedure of the spent coin cells powder demonstrated that the bioleached residue met the environmental limitations for safe disposal. In fact, bioleaching is an effective and promising route to reduce the environmental hazard of spent coin cells.

Chemical and petrochemical industry

The potential sources of various metals in chemical and petrochemical processes are discussed. Special emphasis is put on the catalysts used in the industry. Their main applications, compositions, especially metal contents are presented both for fresh and spent ones. The focus is on the main types of metals used in catalysts: the platinum-group metals, the rare-earth elements, and the variety of transition metals. The analysis suggested that chemical and petrochemical sectors can be considered as the secondary source of metals. Because the utilization of spent refinery catalysts for metal recovery is potentially viable, different methods were applied. The conventional approaches used in metal reclamation as hydrometallurgy and pyrometallurgy, as well as new methods include bioleaching, were described. Some industrial solutions for metal recovery from spent solution were also presented.

Sequential biological process for molybdenum extraction from hydrodesulphurization spent catalyst

Spent catalyst bioleaching with Acidithiobacillus ferrooxidans has been widely studied and low Mo leaching has often been reported. This work describes an enhanced extraction of Mo via a two stage sequential process for the bioleaching of hydrodesulphurization spent catalyst containing Molybdenum, Nickel and, Aluminium. In the first stage, two-step bioleaching was performed using Acidithiobacillus ferrooxidans, and achieved 89.4% Ni, 20.9% Mo and 12.7% Al extraction in 15 days. To increase Mo extraction, the bioleached catalyst was subjected to a second stage bioleaching using Escherichia coli, during which 99% of the remaining Mo was extracted in 25 days. This sequential bioleaching strategy selectively extracted Ni in the first stage and Mo in the second stage, and is a more environmentally friendly alternative to sequential chemical leaching with alkaline reagents for improved Mo extraction. Kinetic modelling to establish the rate determining step in both stages of bioleaching showed that in the first stage, Mo extraction was chemical reaction controlled whereas in the subsequent stage, product layer diffusion model provided the best fit.

Bioleaching of hazardous waste

Landfill represents the least environmentally-friendly method of waste disposal because of possible pollution to the environment. Dangerous wastes pose the greatest problems and are often disposed of by combustion. This process reduces their volume but entails the formation of new types of dangerous waste. The present study focuses on the possibilities of the removal of the hazardous properties of waste originating from hazardous waste incinerators (three types of bottom ash and charcoal from flue gas cleaning) by bioleaching. Toxic pollutants originating from waste could be removed by bioleaching with Acidithiobacillus ferrooxidans. The effectiveness of bioleaching was evaluated on the basis of the pollutant content in the aqueous leachates. For studying the relation between the efficiency of bioleaching and the binding of pollutants in the waste, Tessier’s sequential extraction was used. A comparison of bioleaching efficiency and the results of sequential extraction shows that bioleaching can be used to remove elements which are in an exchangeable form or are bound to carbonates, meaning that they are bound in bio-available forms. Bacterial activity was also shown to change the bonds of pollutants in wastes, leading to increased solubility of the pollutant.

An environmentally friendly process for the recovery of valuable metals from spent refinery catalysts

The present study dealt with the whole valorization process of exhaust refinery catalysts, including metal extraction by ferric iron leaching and metal recovery by precipitation with sodium hydroxide. In the leaching operation the effects on metal recovery of the concentration and kind of acid, the concentration of catalyst and iron (III) were determined. The best operating conditions were 0.05 mol L(-1) sulfuric acid, 40 g L(-1) iron (III), 10% catalyst concentration; almost complete extraction of nickel and vanadium, and 50%extraction efficiency of aluminium and less than 20% for molybdenum. Sequential precipitation on the leach liquor showed that it was not possible to separate metals through such an approach and a recovery operation by means of a single-stage precipitation at pH 6.5 would simplify the procedures and give a product with an average content of iron (68%), aluminium (13%), vanadium (11%), nickel (6%) and molybdenum (1%) which would be potentially of interest in the iron alloy market. The environmental sustainability of the process was also assessed by means of life cycle assessment and yielded an estimate that the highest impact was in the category of global warming potential with 0.42 kg carbon dioxide per kg recovered metal.