Due to the great importance of industrial recycling of electrical and electronic waste that currently exists, today we will talk about the eco-innovative process that is being developed to reuse electronic waste generated by humans: biohydrometallurgy.
Find out what it is about in this post!
What is biohydrometallurgy?
Biohydrometallurgy is a process that is within the framework of hydrometallurgical processes, that is, processes that allow to leach or dissolve metals from a complex matrix through the use of chemical reagents.
Chemical reagents are normally needed for a metal leaching process to take place, however, in this case, these reagents are provided by biological elements, specifically, by living organisms such as fungi or bacteria. All this implies that biohydrometallurgy is a promising process within the reuse and recycling of electronic and electrical waste as an option with very low environmental impact.
The foundation of biohydrometallurgy is to use the resulting by-products produced by microorganisms in their vital processes as reagents in metal recovery processes. In this way, microorganisms play a leading role in the oxidation and leaching processes of metals.
At present, there are different lines of research initiated to develop processes for the recovery of metals from electronic waste. The common objective is clear: to make biohydrometallurgy as close and efficient an option as pyrometallurgy and hydrometallurgy processes are today.
One of the great motivations that drive the development of biohydrometallurgy is to reduce costs, both in terms of resources and reagents, neutralizers, special equipment and energy, since the reaction conditions are not as drastic as in other metallurgical processes.
Finally, another of the objectives that arise with this technology is to discover the route of use of the by-products that can be generated, focusing on them as raw material recovery or energy generation by applying the circular economy model.
What is biohydrometallurgy for in the company?
Biohydrometallurgy aims to recover valuable materials from discarded materials. The most promising use of biohydrometallurgy could be defined as the extraction of valuable metals from the matrix of waste products. At the same time, this recovery process would lead to the reuse and recycling of these wastes, which implies savings regarding the energy cost and material cost of any industrial process.
In this video you can see how a biohydrometallurgical process works!
Main differences of biohydrometallurgy with pyrometallurgy and conventional hydrometallurgy.
Pyrometallurgy, hydrometallurgy and biohydrometallurgy are three variants of what is known as metallurgy processes. Metallurgy encompasses the techniques used for the extraction and refinement of metals.
The difference between the different variants of metallurgy lies in the mechanism used to extract the metals.
- In pyrometallurgy, the extraction medium is heat. High temperatures around 1000ºC are used, so the extraction reactions are very fast. Furthermore, this methodology favors the refinement of large quantities of material, with complex heterogeneous mixtures. However, the performance of these extractions is very limited, which usually implies the repetition of the extraction steps, and, therefore, a very high energy cost. Another of the important disadvantages of pyrometallurgy is the high amount of pollutant emissions that are produced, among which are mostly carbon dioxide and sulfides.
- In hydrometallurgical processes, the means of extraction is the use of redox chemical reactions in aqueous or organic liquid solution. In this methodology, metals previously undergo leaching processes, that is, they have been oxidized from their matrices and are transformed into soluble salts. Low temperatures and high pressures are used, reaching values of up to 5000 pascals. The great advantage of this technique is its flexibility, since there are a large number of reactions to separate metals once they are dissolved in the form of salts. Compared to pyrometallurgy, hydrometallurgy reactions are slow kinetic and yields are limited, as the reactions are highly sensitive to variations in environmental conditions. It should be noted that the generation of waste persists in this methodology, since waste is generated in the form of wastewater and solids, and the energy costs necessary for the leaching reactions to take place are high.
- Regarding biohydrometallurgy, the principles of the process are very similar to hydrometallurgical processes: metals are leached, forming salts, facilitating their separation. The main difference is that the reagents used are produced by microorganisms, as a result of by-products of their metabolic reactions. In this way, the cost of this methodology is reduced, reducing the sensitivity of the processes, since it is determined by the conditions that favor the growth and development of microorganisms. In addition, the production of toxic gas emissions and wastewater more reduced and controlled. However, the main limitation of biohydrometallurgy processes is that reaction kinetics are very slow, and once they have started, they cannot be stopped.
Types of biohydrometallurgy processes and examples of applications.
Biohydrometallurgy is based on the theoretical principle of metal leaching: a process by which a selective dissolution of a material occurs against a matrix of a different nature. Leaching methods allow the selective extraction of metals in complex matrices through the use of specific solvents, depending on the type of matrix and the concentration, distribution and size of the metal to be extracted. In the case of biohydrometallurgy, two variants can be distinguished:
- Direct biohydrometallurgy: microorganisms participate in the process of separating metals from their matrix, through enzymatic reactions.
- Indirect biohydrometallurgy: microorganisms intervene only in the metal leaching process once they have been separated from their matrix.
The main application of biohydrometallurgy is the extraction and recovery of metals found in complex matrices. From an industrial point of view, this framework opens up a wide range of utilities for us, from the recovery of valuable metals in mining to the decontamination of soils and wastewater. Some of the applications that are being studied extensively are:
- Extraction of valuable metals such as copper and arsenium in mining with chemo-lithoautotrophic bacteria.
- Decontamination of soils and waters, and recovery of metals from them, by fungi.
- Extraction of precious metals from electrical and electronic waste through the use of cyanogenic bacteria.
Advantages and disadvantages of biohydrometallurgy
As we have discussed throughout the blog, biohydrometallurgy has appeared on the scene as a promising option for the recovery of metals from waste materials with very low environmental impact. However, this technology is still in an early age that needs to mature, so it presents lights and shadows. Next, we will look at the main current advantages and disadvantages of biohydrometallurgy.
The main advantages of biohydrometallurgy are:
- Low environmental impact, reducing waste and toxic emissions
- Reduction of energy cost and raw materials
- Lower risk of toxicity due to the use of chemical reagents
- Selective extraction of metals that are very expensive for other metallurgical techniques such as pyrometallurgy or hydrometallurgy
The main disadvantages of biohydrometallurgy are:
- Lack of knowledge about the efficiency and maintenance of large-scale biohydrometallurgical processes
- High risk of toxicity from biological elements
- High specificity of the process, being the optimum performance for few metals in the same process
- Very slow reaction kinetics
Therefore, biohydrometallurgy has become one of the main lines of current research, whose expectations are very promising.
What did you think of this type of recycling? Do you see applicability in your process? Contact us or call us at 876715051!
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