Bioleaching Of Manganese Ion From Manganese-electrolyzed Slag By Microbiology

There are more and more manganese-electrolyzed slag discharged into the environment along with the fast growth of the manganese-electrolyzed industry. Because of the low pH value of the slag and with the rainfall leaching or its own leakage the plentiful of heavy metal ions contained in the slag will enter into the surface water and underground water. Even more the heavy metal ions which were entered into the surface water and the ground water will accumulate in the human body along with the food chain, and then threatens and influences the healthy of the human body. Meanwhile open-air piled up of those manganese-electrolyzed slag will destroy the ecotope environmental of the soil around the site, converted the structure of the soil, and there by influence the crops'growth. However there are also some worthy metal ions contained in the manganese- electrolyzed slag that can be recycled and reused by some certained methods. Those methods including chemical methods, physical methods and the combined chemical-physical methods, however those methods had a lot of weakness, for example: low leaching efficiency, high cost, could lead to secondary pollution and so on. Bioleaching technology is a method which can leach out the worthy metal elements from mineral ores by microorganisms'own oxidation and reduction during its vitalmovement, and let the worthy metal elements oxidized or reduced, then entered into the solution as ion form or precipitate form. Compared with chemical methods and physical methods, bioleaching method had some advantages, such as safety, economical efficiency and environmental friendly, and has become one of the most important leaching methods for leaching metal element from mineral ores. However the existing bioleaching methods just had breakthrough research development on several common metals, and used only some type of the microbiology.Recently there had some obvious developments on bioleaching of manganese ion from manganese minerals. But the main part was concentrated on bioleaching manganese from low grade manganese ores and manganese nodules in the oceans. Manganese-electrolyzed slag was an acidity slag which was abundance produced during the manganese-electrolyze industry. It can be treated as low grade manganese ores as it contained relatively high concentration of manganese element. The recently research of leach methods were remained on the chemical leaching, a few study used the combined chemical-physical methods. There still exist some microbe though the environment of the landfill were hostile, obviously those exist microbe had resistance on high concentration of manganese. Based on this suppose, we isolated some microbes from manganese-electrolyzed slag. Then we screened out two microbes which had high resistance on manganese from manganese-electrolyzed slag landfill, and then using those two microbes to conduct a study on bioleaching manganese from manganese- electrolyzed slag.Firstly, we firstly isolated and screened out two bacterial strains from manganese-electrolyzed slag to conduct a study on bioleaching of manganese from manganese-electrolyzed slag, and it had high innovation compared with the traditional chemical and combined chemical-physical leaching methods. Then we identified the two bacterial strains by the methods of growth morphology observing, micro morphology observing and molecular biology identification. After Phylogenetic Tree analysis we confirmed the name of those two bacterial strains were Fusarium sp. and Serratia sp. respectively.Following, we used those two strains Fusarium sp. and Serratia sp. conducted the bioleaching experiment, investigated some influence factors, such as pH value, solid-to-liquid ratio, temperature, rotation speed, inoculum concentrations, ferrous ion's concentrations and mercury ion concentrations, on affecting the bioleaching efficiency and compared the bioleaching efficiency of those two strains. The result showed that the optimum bioleaching conditions for bioleaching of manganese from manganese-electrolyzed slag by Fusarium sp. and Serratia sp. were as follows: for Serratia sp.: the optimum condition was the bioleaching was conduct with 2 mL inoculum of strain, pH value 6, rotation speed 150 rpm, add 10 g/L ferrousion, 10% solid-to-liquid ratio at 37 oC for 74 h, the bioleaching efficiency can reach to 76.9%. for Fusarium sp.: the optimum condition was the bioleaching was conduct with 2 mL inoculum of strain, pH value 4, rotation speed 150 rpm, add 10 g/L ferrousion, 10% solid-to-liquid ratio at 28 oC for 74 h, the bioleaching efficiency can reach to 82.5%. Mercury ion had negative effects on bioleaching process.It seems there are two mechanisms for bioleaching, i.e. direct and indirect action. In this research, we also studied the bioleaching mechanism by following methods: component analysis of lixivium, the variation of concentrations of organic acids during bioleaching process, variation of pH value during bioleaching, surface morphology alteration of manganese-electrolyzed slag before and after bioleaching, and comparation of heavy metal ions'morphology before and after bioleaching. Then we discussed and analysis the mechanism of the bioleaching with Fusarium sp. by combined the results with the variation of bioleaching efficiency during the bioleaching process. The results showed that: Fusarium sp. can directly act on the surface of the slag, and it can produce some organic acids (mainly were oxalic acid, citric acid, malic acid, succinic acid) during the bioleaching process by its own metabolize, those organic acids can cause redox, chelation and complexation chemical reaction with manganese slag, which promoted the leaching out of manganese from the slag.After studied the mechanism of the bioleaching process, we expanded the experiment to Industrial applications, and improve some factors such as organic carbon source melioration, aerating device and stiring device setting and so on, during the bioleaching process we monitoring the variation of pH value. The result showed that: glucose can take the place of sucrose as the best organic carbon source; aerating and stiring can facilitate the bioleaching efficiency during the process because it can not only supply oxygen, but also can promote the contact of manganese slag and the fungi to improve the direct and indirect reaction. The economic loss-benefit analysis result showed that compared with the chemical leaching process, the bioleaching process can save about 520 RMB/t of manganese ores. This obviously showed that the bioleaching process had not only economic benefits, but also had environmental benefits.In this research, we firstly isolated and screened out two strains of microbe which had high resistance on manganese from manganese slag, then used those two strains conduct bioleaching experiment with the slag in turn. It's the first time that using biological method to treat manganese-electrolyzed slag. The research indicates that those two strains had strong bioleaching ability on manganese leaching out from the slag. We improved the bioleaching conditions according the bioleaching mechanism to let those microbes had high industrial applying worthy. In this research, we not only provided a new microbe for bioleaching study, but also supported a more economic and more environmental protecting method for manganese-electrolyzed slag recycling. This study offers the ability to fully achieve of the application of manganese-electrolyzed slag reusing.