The Study Of Recycling Of Iron From Acidic Metallurgical Waste Water And Its High-Value Utilization

With the rapid development of gold industry, the gold mine resources which are easily treated are becoming more and more scarcely. The biological oxidation technology for extracting gold is an efficient way of dealing with refractory gold mine, but this technology will produce a large number of acidic waste water containing Fe and As elements. The traditional methods not only make valuable elements wasted, but also exist potential secondary pollution. In view of this weakness, this paper developed an efficient method of separating arsenic and iron, and valuable element iron can also be high-value used. Olive LiFePO4is a promising cathode material of lithium-ion battery due to its relatively high energy density, low cost, environmental friendliness and safety, which is expected to become positive material of commercial lithium ion power battery. In this paper, LiFePO4/C cathode material was prepared using recycled FePO4by carbothermal reduction method and modified by metal ions doping. The main research works and results were as follows:This process used diammonium hydrogen phosphate as a precipitator, the iron was recycled from biological oxidation metallurgical wastewater through selective precipitation. In this paper, the influences of pH, ratio of phosphorus to iron and different feeding methods on arsenic-iron separation efficiency and the effects of these process conditions on electrochemical performance of LiFePO4/C were investigated; The synthesis technology of LiFePO4/C cathode material was discussed by carbothermal reduction using Li2CO3, C12H22O11and FePO4which prepared at optimal conditions as the materials, the effects of raw material pretreatment temperature on the crystal structure and morphology of FePO4were investigated, and this pretreatment temperature, calcination temperature, calcination time and excessive carbon content on the crystal structure, morphology and performance of LiFePO4/C material were also studied, the optimal conditions for synthesizing LiFePO4/C were determined by orthogonal experiment; based on orthogonal experiment, the doping effects of V2O5and Mb2O5were studied on the Fe sites and Li sites of LiFePO4/C which synthesized at optimal conditions. The crystal structure, morphology and electrochemical performance of samples were characterized using XRD, SEM, FTIR and charge-discharge test. The conclusions were as follows:(1) The following were the suitable conditions of iron selective precipitation using diammonium hydrogen phosphate as precipitator:The liquid feeding methods, pH2.5, the ratio of phosphorus to iron3.5, temperature50℃, mixing speed500r-min-1;The suitable pretreatment temperature and time of FePO4·H2O were450℃and six hours;(2) The optimal conditions of synthesizing LiFePO4/C were as follows:Excessive carbon content was3%, calcination temperature and time were700℃and ten hours; the initial discharge specific capacity of the LiFePO4/C composite material synthesized under these conditions was132.8mAh/g, the charging and discharging platform were about3.5and3.4V, cycle performances of the sample were better when discharged at0.5C and1C rate respectively, capacity retention rate was higher;(3) The electrochemical performance of LiFePO4/C was improved obviously through V doping, optimum doping content was3%, LiFe0.97V0.03PO4/C had discharge specific capacity of150.1,137.7and130.3mAh/g at0.1C,0.5C and1C rate, the sample had better rate capacity and circulation performance; the doping of V reduced electrode polarization of the material and improved the electronic conductivity and ionic conductivity effectively.With Nb as doping element, EDS spectrum showed that Nb was doped into lattice of LiFePO4/C successfully, when x=0.02, initial discharge specific capacity of the sample was improved7.2mAh/g at0.1C rate compared with the undoped sample, electrochemical performance had been improved to a certain extent.