Study On Biochemical Process And Mechanism Of Manganese-recovering From Manganese-electrolytic Residue

At present, the output of manganese-electrolytic residue increased with the developing ofmanganese production industry. In this investigation, manganese-electrolytic residue wasdisposed with biological-chemical method, and manganese in the form of manganesecompounds was recoved after leaching. Paid equal attention to the environmental andeconomic development,this study had important sense.Bioleaching of mine has the advantage of environmental friendly process, effectiveproduce and low cast. In this study, manganese was leached84%with the action of Fusariumsp. which was domesticated. At the same time, Fe、Al etc. was leached by it, and removed byusing NaOH and HCl. Final product of purificatation was MnCl2with more than77%purity.In order to compensate the deficiencies, i.e.the difficuty to refining products in biologicalmethod and secondary pollution, high energy consumption or complex processing in chemicalmethod, the biological-chemical method was introduced in this study. Firstly, the morphologyand composition of manganese-electrolytic residue were investigated by scanning electronmicroscope（SEM） and energy dispersive spectroscopy（EDS） and X-Ray Diffractomer（XRD）in this paper. The result indicated that, appearance of manganese-electrolytic residue withoutmicrobial treatment is smooth, and it was composed of plentiful metallic or non-metallicimpurities in which the most element was manganese with the content of56.08%and ironand aluminum was about19.58%,16.74%respectively. In additon, the manganese mainly hadthe form of MnSO₄·H₂O in manganese-electrolytic residue.The mechanism of manganse bioleaching by manganese-resistant strain Fusarium sp.was investigated in this study, through analyzing the bioleaching rate and manganese-electrolytic residue’s characteristic ions with the presence of Fusarium sp. and with theaddition of organic acids. Special attention was paid to explore the relationship among theleaching rate of manganese, pH, and organic acid concentration during Fusarium sp.bioleaching process. The research results showed that some looser and more porousmanganese-electrolytic residues could be obtained with the addition of Fusarium sp. Andafter47hours, the leaching rate reached to84%which was2.30times higher than thatleached by individual organic acid even after130hours; the leaching rate of manganese andthe concentrations of organic acids increased at the first stage and then decreased, while pHwas the reversed. Additionally, the concentration of succinic acid and L-malic acid reachedtheir maximal value （11.12g/L and10.23g/L） at57and62hours respectively, yet pH reachedthe lowest （4.09） at29h. The results implied that Fusarium sp. and organic acids produced played an important role in the leaching of manganese, which led to a high-efficiency andtime-saving process. However, due to the high density of manganese-electrolytic residue andthe concurrence of the produce and consumption of organic acids together with the adsorptionand complexation, the relationship among the extraction rate for manganese ion, pH, and theconcentration of organic acid produced could not be described by simple linear and theleaching rate decreased significantly in later stage.Leached out manganese from manganese-electrolytic residue by biological method,Fusarium sp. possessed selective adsorption on manganese and this increasesed the finenessof manganese, compared with chemical leaching method. To improve purity of the manganesecompounds，the study obtained the acid manganese products （MnCl2） with a purity of77-93%by using the dissoluble of amphoteric metal in excess quantity alkaline solution and theinsoluble of Mn₂O₃in cold HCl. The purification process included two steps: the first step isthe purification process for gettingg brown Mn₂O₃solid content by removing amphotericmetal compounds such as Al; the second step is the purification process for removingnon-amphoteric metal compounds such as Fe, then getting pink MnCl2pink products byreduction of Mn₂O₃with HCl under the heating condition.Biological-chemical method to leach out manganese from manganese-electrolyticresidue included four aspects: Firstly, bio-extraction period for leaching out manganese frommanganese-electrolytic residue. Secondly, the purification process for removing amphotericmetal compounds such as Al. Thirdly, the purification process for removing non-amphotericmetal compounds such as Fe. Fourthly, the transformation of final product.Based on the investiagtion of the process and mechanism, the study had directlyreference value for the treatment and comprehensive utilization of manganese-electrolyticresidue. And it provided the theoretical basis for further study of the recovery process of themanganese ions in poor manganese ore.