Alkaline Sodium Glutamate System To Handle The Basic Theory And Technology Of Low-grade Zinc Oxide Ore

In this work,a new process of treating low grade zinc ores bearing high basic gangues in the alkaline solution of monosodium glutamate was proposed in accordance with the existing zinc metallurgical way. The influence of high basic gangues to effectively extract zinc could be eliminated by the technique,and the pollution problem could be avoided in the process.The basic contents and results were shown as follows:Species distribution disgrams of glutamate (Glu2")and carbonate ion(CO32-)in the solution were obtained based on the coordination chemistry theory.Thermodynamics of Zn(Ⅱ)complex equilibrium in the system of Zn(Ⅱ)-Glu2--CO32--H2O were studied by the double equilibrium theory.When the concentration of monosodium glutamate and pH value varied accordingly in ranges of 0～5mol·L-1 and 7～14,the equilibrium thermodynamic diagrams were constructed.It is indicated that total zinc concentration reaches the maxium value when the pH value is 10 under a certain monosodium glutamate concentration.The theoretical calculation results were testified by solubility experiments.The absolute average value of relative error between them is 11.39%.Meanwhile,the behavior and equilibrium law of major impurities such as Ca,Mg were studied in the leaching of zinc oxide ores in the Zn(Ⅱ)-Glu2--CO32--H2O system.The results show that the total concentration of calcium and magnesium gradually decreases when th pH value changes in ranges of 7～12,while increases when the pH value reaches above 12.The technique conditions of leaching zinc oxide ores were studied in the alkaline solution of monosodium glutamate.Two batches of zinc oxide ores were leached under the following optium conditions:the ratio of liquid to solid being 5:1,monosodium glutamate concentration of 1.5 mol·L-1,pH value of 9,leaching time for 5 h at 80℃without oxidant.The leaching yield of zinc was 64.52% and 66.60%,and the concentration of zinc in the leaching solution was 7.97g·L-1,7.90g·L-1,respectively.The leaching solution was purified to remove impurities such as Cu,Pb,Cd with zinc powder displacement. When the purification process followed the condition of 1 h at ambient temperature in the presence of 3g·L-1 zinc powder,the contents of Cu,Pb,Cd in the solution were 0.18mg·L-1,1.88mg·L-1 and 0.88mg·L-1,respectively.The technique conditions of extracting zinc were explored from purified leaching solutions.Compared with the technique of cycle leaching-purification-electrowinning,direct zinc precipitation technique could be a better one. Sodium zincophosphate was obtained by direct precipitation with phosphate from purified leaching solutions.The product prepared under optium conditions was characterized by laser particle sizer and scanning electron microscopy.The particle of sodium zincophosphate showed normal distribution,and the average particle size was 4.146μm;the sodium zincophosphate particle was spherical shape and had no porosity.