Toward a sustainable and enhanced iron ore recovery: Biobeneficiation review

Iron ore is essential in steelmaking but high-grade ores have diminished, making it necessary to turn to low-grade ores, which need further beneficiation to upgrade the iron content. Biobeneficiation techniques such as bioleaching, bioflotation and bioflocculation have proven successful in iron ore processing. Consequently, these methods have emerged as sustainable alternatives to conventional beneficiation. The biobeneficiation processes occur in mild conditions using bioreagents and biosurfactants derived from microbes, and offer a reduction of chemicals used in processing. This potentially offers methods that are relatively energy efficient, cost effective and environmentally friendly while tackling the constraints of dwindling high-grade iron ore resources. Introduction The demand for iron ore has increased substantially as modern societies continue to fulfill their development goals. Due to the extensive exploitation of high-grade reserves, viable iron ore deposits are diminishing rapidly. Traditional beneficiation of low-grade iron ores is also challenging because of the complexity of their mineralogy. Therefore, developing sustainable, efficient and enhanced iron recovery processes for low-grade ores is urgently needed. Iron ore beneficiation Iron ore extraction involves processes ranging from exploration to processing while utilizing traditional methods like gravity separation as well as innovative techniques like bioleaching to enhance mineral recovery and minimize environmental impact. Traditional iron ore beneficiation techniques are generally physical, requiring high energy, grinding, dewatering and filtration capacity. Rising costs, environmental concerns and increasing regulations threaten the long-term viability of these traditional processes. In this context, biobeneficiation methods represent new opportunities as viable and sustainable alternatives to conventional iron ore processing by utilizing microorganisms and/or derived microbial products to extract desired minerals from ores sustainably. This minimizes the need for energy, water and chemicals while reducing waste generation. The processes include bioleaching, bioflotation and bioflocculation. Bioleaching harnesses iron-oxidizing bacteria like Leptospirillum ferrooxidans, Leptospirillum ferriphilum, Acidithiobacillus ferrooxidans or Sulfolobus thermosulfidooxidans cultured in bioreactors to solubilize metals via metabolite. During bioleaching, the iron ore is attacked by microorganisms directly or indirectly, as shown in Fig. 1, removing the gangue minerals and leaving the iron behind. In mineral bioflotation, microbes or microorganisms and their derived microbial products are used as frothers, collectors or depressors, or acting in combination for froth flotation. These microbes and their metabolite derivates have been extensively studied and used to selectively remove gangue minerals from ores to form concentrates for metallurgical and industrial applications. The activities and optimized conditions for the action of some of these microbes are summarized in Table 1. Their uses have resulted in significant advancements in the mineral beneficiation industry. Bioflocculation, on the other hand, utilizes microbes to aggregate fine gangue mineral particles for removal from ore slurries, thereby increasing the iron content of the concentrate. The mechanism of action of these bioflocculants involves the binding and bridging of fine ore particles by biopolymers with high molecular weight and, therefore, the formation of flocs that settle out fast. Microbes used in flocculation include stains from Bacillus, Aspergillus and Chlorella species, which are summarized in Table 2. Conclusions Biobeneficiation presents a long-term, environmentally friendly and sustainable alternative to traditional iron ore processing methods. Bioleaching, bioflotation and bioflocculation have proved effective in increasing iron ore content in off-grade iron ores through the activity of microbes. Further research needs to be done to optimize these intricate processes and scale up laboratory studies to pilot studies and then to industrial applications. Biobeneficiation holds high potential in the processing of iron ore in an environmentally friendly way, minimizing use of water, energy and toxic chemicals. With continued research, development and integration into mineral-processing operations, biobeneficiation is promising for sustainable iron ore recovery. References A list of all references is available in the full paper.

Toward a sustainable and enhanced iron ore recovery: Biobeneficiation review

Authored by: Francis Gitau, Oladunni Oyelola Alabi, Fatai Olufemi Aramide, Talabi Henry Kayode and Mary Nelima Ondiaka

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