INTRODUCTION
The usage of metallic elements for the building of new infrastructure and projects has grown massively in this Era. Metals are utilized in practically every facet of life. The growing utilization of metals impose a great stress on the environment. The industrial and manufacturing processing of metals generally leads in the release of several metals to the environment creating pollution. Implementing proper disposal procedures is the only method of reducing this source of waste. However, owing to the increased complexity of metallic goods and the low concentration of certain core components, existing recycling rate is considerably low, prohibiting a cost effective metal recovery. Bio-recycling methods may be relied on to deal with these problems. Biological techniques can increase metal recovery from technological waste products, industrial waste, etc. Many microorganisms, such as bacteria and others, have evolved mechanisms that impact the biogeochemical cycles of elements. These several methods can aid in the bio-recycling of metals. Bioleaching, Biosorption and Bioflotation, and Bioprecipitation are examples of these processes. [1]
BIOLEACHING
It is the utilization of microbes to extract metals from low-quality ores. During the separation of higher-grade ores, massive volumes of low-grade ores are created and disposed of in waste heaps. Chemical processing of metals from such ores is not cost-effective. There are a lot of low-grade ores, notably copper ores, that can be efficiently treated via bioleaching. Direct and indirect bioleaching are 2 techniques for completing the process. [2]
BIOSORPTION
It's a method for removing heavy metals that uses biological materials as adsorbents, and it's been examined by a group of studies as an alternative to the traditional techniques. Biosorption for metal removal is seen to be an appealing method due to its low cost, high efficiency, and specificity, absence of chemical or sludge development, lack of extra nutritional needs, biosorbent regeneration, and eco-friendliness.
This technique has finally gotten a lot of interest in research and industry. As a result, biosorption is a relatively new technique in which various forms of biomass are utilized as biosorbents to clean polluted water bodies. Heavy metals have been recovered from metal-contaminated environments using microorganisms such as algae, fungus, yeast, mold, and bacteria. The absorption, adsorption, ion exchange, surface complexation, and precipitation processes are all dependent on the affinity of the organism or biological substance (sorbent) to the metal (sorbate). [3]
BIOFLOATATION
Flotation has been used in the mining industry for over 150 expanding the copper concentration of unrefined ores from 1% to 30%. The finely crushed ore is washed with water during flotation. Chemicals make mineral particles differently wettable, allowing valuable compounds to be removed while useless particles are left behind. Bioflotation simply substitutes bioactive molecules for chemicals. The most recent research shows that Microbial Cells or EPS may be used to separate minerals.
Another benefit is that bioactive chemicals naturally decay in the environment. [4]
BIOPRECIPITATION
Microorganisms, especially bacteria, are being used in bioprecipitation. During bioprecipitation, the generated metabolites react with metals in the wastewater to form metal precipitates, transforming the metals from their aqueous to solid state. Bioprecipitation would be used in both poor and developed nations; however, depending on the company's spending on infrastructure, the cost-benefit of reusing or selling the recovered metals may fluctuate.
Furthermore, the costs of secondary metals in the global metal market are controlled by the separation and purification processes. Future aspect of this study should focus on cost-benefit analysis of the bioprocess, process integration for resource recovery, the construction of phenomenological models to understand the bioprecipitation mechanism, and research into the enzymatic pathways involved.
Surface attachment, mineral dissolution, transformation, and metal complexation are examples of biological characteristics of organisms, bio-compounds, and biomolecules that interact with minerals, materials, metals, or metal ions. Furthermore, current genetic techniques, such as synthetic biology, allow for the intellectual creation of novel molecules. Only a few of these innovations have been commercialized thus far. [5]
High costs compared to traditional methods and limited element selectivity are
two major problems. Interdisciplinary approaches, the combination of various technologies, the use of contemporary genetic procedures, and the study of existent yet untouched natural resources will all drive innovation in these sectors.
REFERENCES
1.KatrinPollmanna,SabineKutschkea,SabineMatysa,JohannesRaffb,GregorHlawacekc,Franziska L.Lederera, Bio-recycling of metals: Recycling of technical products using biological applications, Elsevier, 1048-1062, 2018
2. Dashmeet, Bioleaching: Introduction, Methods, Application, Copper, Microorganisms, and Processes, Bio Technology,
3. Simranjeet Singh, Joginder Singh, Biosorbents for heavy metal removal from industrial effluents, Bioremediation for Environmental Sustainability, 219-233, 2021
4. EdySanwania,SitiKhodijahChaerunab,RiriaZendyMirahatia,TriWahyuningsiha, Bioflotation: Bacteria-Mineral Interaction for Eco-friendly and Sustainable Mineral Processing, Elsevier, 666-672, 2016
5. Suthee Janyasuthi Wong, Eldon R Rene, Bioprecipitation-A Promising Technique for Heavy Metal Removal and Recovery from Contaminated Wastewater Streams, Medcrave, 2017
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