Mineral resources have been counted as public assets with economic benefit since time immemor-ial. Due to the rising issue of decreasing mineral deposits, recovery of metals from several waste residues has become progressively more essential. Novel and efficient recycling processes have been on the rise globally. Manganese (Mn) as the fourth most industrially applicable metal generates an extensive quantity of metallic waste which not only leads to loss of precious metal but also results in environmental toxicity. Globally, around 7 million tons of high-grade ores are produced , whereas 8 million tons of Mn alloys are produced yearly. Therefore, it is of greater significance to recover and recycle Mn from various waste residues. Various physical and biological techniques have been developed for recycling Mn from waste residues. Traditional Mn extraction processes are costly and labor intensive in nature, on the contrary, bioleaching techniques using diverse microorganism's, form the basis of an efficient, eco-friendly, and economically sustainable process of metal recovery. The quick progress in current methodologies to counteract the fast consumption of innate mineral resources involves the proper utilization of unused waste residues containing industrially important metals like Mn. This review focuses to enumerate diverse features of Mn recovery, efficient methodologies, bioleaching of Mn, merits of Mn bioleaching, and applications of recycled Mn along with the futuristic applications. Manganese recovery by means of biol-eaching will play a major role in changing the present situation where innate assets are quickly diminishing and substitute for metal recovery methodologies are the demand of this time. ARTICLE HISTORY
Manganese recoveries from low-grade ores using organic acids as reducing agents were investigated in the present work. The acid leaching potential of both oxalic acid and citric acid were estimated. Manganese leaching amount were measured by using standard manganese curve and estimated by titration method. Effects of various acid concentrations on leaching efficiency were studied. The observed result suggested prominent manganese recovery of 66% by oxalic acid at 2 M concentration whereas citric acid had less effect on leaching showing leaching percentage upto 40% in 6 days. Acid leaching of manganese ore with both the acids gave a comparative data stating that oxalic acid leached better than citric acid.
India ranks 4th in the global production of Manganese (Mn) and boasts around 160 million tonnes of Mn ore reserve. It has been reported that the export of ferro alloys from India has increased from 0.42 million tonnes in 2008 to 1.08 million tonnes in 2013. This necessitates the development of novel techniques for Mn extraction from low grade ores. In the present investigation low grade Mn ore samples from different Mn mining sites of Odisha were collected for isolation and screening of indigenous bacterial strains for investigating their Mn solubilizing efficiencies. The isolated bacterial colonies were studied for their Mn resistant ability on MnO2 supplemented plates with concentration ranging from 100mM to 500mM. Variation in pH due to bio generated acid production and their Mn bioleaching efficiency was investigated for 20 days. A total of 22 bacterial colonies were initially isolated out of which only 8 bacteria colonies were able to grow in 100mM MnO2 supplemented plates. When the MnO2 concentration in the plates was raised five folds, i.e, to 500mM, 2 colonies were able to survive, which implied their Mn resistant nature. A considerable alteration of pH was observed due to organic acid production and utilisation during bioleaching throughout the period of solubilisation study. From the total 22 isolated bacterial strains only 2 isolates were able to grow on 500mM concentration. The alteration in pH during the solubilisation study implied the biogeneration of organic acids and indicated a high Mn solubilizing capacity of the isolated bacterial strains.
Abstract: Manganese ore is considered as a crucial industrial element and is consumed both metallurgically and non-metallurgically. World Steel Association reported that the driving factor in ore industry is Mn whose production of steel competence has increased from 47.91 million tons (2000-01) to 88.40 million tons (2011-12). Due to rise in the consumption of steel over years, the demand for manganese has augmented extensively. Bioleaching is the application to recover manganese from low grade ore using Mn oxidizing and solubilizing fungal strains. This investigation involves isolation of fungus from low grade Mn ore, collected from Sanindipur Mn mines of Barbil in Orissa, India. Fungal colonies were cultured in Mn supplemented plates containing 0.5gm/L MnO2. Further screening procedure was carried out by increasing the concentration of MnO2 from 0.5-2.5gm/L to select potential Mn resistant and solubilising fungal strains. In the initial isolation experimentation 10 fungal species were isolated with Mn concentration 0.5gm/L within 48 hours of incubation. Further increasing the concentration, upto 2.5gm/L only 4 fungal species were able to grow and were selected as potential Mn resistant microorganism. With increased concentration of Mn, solubilization of manganese oxides is observed with white colour zone formation. These selected fungal colonies showing maximum efficiency for manganese solubilization were processed for 16S rRNA sequencing for identification. Hence potential fungal colonies were isolated from elevated low grade Mn ore showing maximum capability of utilizing and oxidizing Mn.
A comprehensive study on fungus assisted bioleaching of manganese (Mn) was carried out to demonstrate Mn solubilization of collected low grade ore from mining deposits of Sanindipur, Odisha, India. A native fungal strain MSF 5 was isolated and identified as Aspergillus sp. by Inter Transcribed Spacer (ITS) sequencing. The identified strain revealed an elevated tolerance ability to Mn under varying optimizing conditions like initial pH (2, 3, 4, 5, 6, 7), carbon sources (dextrose, sucrose, fructose and glucose) and pulp density (2%, 3%, 4%, 5% and 6%). Bioleaching studies carried out under optimized conditions of 2% pulp density of Mn ore at pH 6, temperature 37 °C and carbon dosage (dextrose) resulted with 79% Mn recovery from the ore sample within 20 days. SEM-EDX characterization of the ore sample and leach residue was carried out and the micrographs demonstrated porous and coagulated precipitates scattered across the matrix. The corresponding approach of FTIR analysis regulating the Mn oxide formation shows a distinctive peak of mycelium cells with and without treated Mn, resulting with generalized vibrations like MnOx stretching and CH2 stretch. Thus, our investigation endeavors’ the considerate possible mechanism involved in fungal surface cells onto Mn ore illustrating an alteration in cellular Mn interaction.
The present investigation reports the isolation, molecular identification and screening of Mn solubilizing fungal strains from low grade Mn mine tailings. Six morphologically distinct Mn solubilizing fungal strains were isolated on MnO2 supplemented agar plates with Mn concentration of 0.1 % (w/v).The biochemical characterization of the isolated fungal strains was carried out. The molecular identification by Internal Transcribed Spacer (ITS) sequencing identified the strains as Aspergillus terreus, Aspergillus oryzae, Penicillium species, Penicillium species, Penicillium dalea, and Penicillium species with GenBank accession numbers KP309809, KP309810, KP309811, KP309812, KP309813 and KP309814 respectively. The ability of the isolated fungal strains to tolerate and solubilize Mn was investigated by sub-culturing them on Mn supplemented plates with concentration ranging from 0.1-0.5% (w/v). Mn solubilizing ability of the fungal isolates is possibly due to the mycelia production of bio generated organic acids such as oxalic acid, citric acid, maleic acid and gluconic acid as revealed by ion chromatography. Our investigation signifies the role of fungi in biotransformation of insoluble Mn oxide.