China's provinces of Hunan, Hubei, Guizhou, Guizhou, Sichuan, Guangxi, Shaanxi, Gansu and other provinces are rich in nickel- molybdenum ore resources. In the past, nickel-molybdenum ore was not used due to restrictions on mineral processing methods and technical levels. In recent years, due to the increasing market demand for nickel and molybdenum, the resources of nickel and molybdenum have become increasingly tense. The extraction of nickel and molybdenum from nickel-molybdenum ore in China has been paid more and more attention. However, previous researches on nickel-molybdenum ore were limited to the extraction of molybdenum and the leaching of nickel. The subsequent treatment process has rarely been reported, so it is necessary to study the subsequent purification process of nickel leachate. Nickel leachate generally contains impurities such as zinc , copper , iron , calcium and magnesium . Currently, in addition to the nickel-zinc leaching solution methods are zinc phosphate, zinc in addition to other D2EHPA extraction. The extraction and removal of zinc is better than zinc phosphate and is more suitable for large-scale industrial production. It has been widely used. The copper removal method applied in industry is mainly a vulcanization method, and the commonly used vulcanizing agents are sodium sulfide and hydrogen sulfide, but there are problems in accurately controlling potential and environmental pollution. Meng Yanshuang studied the extraction of copper by D2EHPA nickel electrolyte, and the extraction effect was very good. From the above discussion, both zinc and copper can be separated from the nickel leaching solution by solvent extraction. Iron, calcium and magnesium have a great influence on the extraction and impurity removal. Therefore, the industrial precipitation method is used to preliminarily treat the leachate. The solution used in this study was a complex nickel leaching solution of nickel-molybdenum ore, which was a mixed system of sulfuric acid and hydrochloric acid containing nickel, zinc, copper and a large amount of sodium ions, and iron, calcium and magnesium were previously removed by chemical precipitation. The effects of the volume concentration of the extractant, the pH of the feed solution, the extraction time and the extraction equilibrium time on the extraction and the stripping effect of the supported organic phase were investigated, and the effect of multi-stage countercurrent extraction was verified. First, the experiment (1) Experimental methods In extractant D2EHPA as sulfonated kerosene as diluent, organic phases were formulated according to a certain volume ratio, and a certain volume ratio of organic to aqueous phase (0 / A) placed in a separatory funnel, thoroughly shaken balance , static layers were separated and the organic and aqueous phases were separated; the metal ion concentration in the aqueous phase equilibrium flame atomic absorption spectrophotometer, the organic phase concentration of metal ions calculated by subtraction; concentration of metal ions in the two phases The extraction rate of each metal was calculated. The experiment was carried out at room temperature and the aqueous phase pH was adjusted with H 2 SO 4 and NaOH solution. By analyzing the influence of various factors on the extraction, the optimum process conditions for extraction and impurity removal were determined, and the multi-stage countercurrent extraction experiments were carried out under the optimal extraction conditions. (2) Instruments and reagents Instruments: pear-shaped separatory funnel, KS Kang's oscillator, PHS-25 precision pH meter, magnetic heating stirrer, volumetric flask, measuring cylinder, TAS-990 atomic absorption spectrophotometer. Reagents: D2EHPA, sulfonated kerosene, deionized water. Nickel leachate composition: c (Ni 2 + ) = 5.0 g / L, c (Cu 2 + ) = 0.29 g / L, c (Zn 2+ ) = 0.81 g / L, sulfuric acid hydrochloric acid mixed system. Second, the results and discussion (1) Effect of extraction equilibrium time on extraction The volume concentration of D2EHPA is 20%, the pH of the aqueous phase is 2.0, and the temperature is room temperature. The effect of equilibrium time on the extraction is shown in Figure 1. Figure 1 Effect of equilibrium time on the extraction rates of zinc, copper and nickel It can be seen from Fig. 1 that the extraction equilibrium can be achieved by extracting zinc and copper in about 3 minutes, the extraction rate of zinc is 88.3%, the extraction rate of copper is 11.0%, and the extraction rate of nickel is only 1.2%. It can be seen that the extraction rate of the extraction system is fast, which is advantageous for industrial applications, can improve equipment capacity and reduce operating costs. This determined the optimum extraction equilibration time to be 3 min. (2) Effect of extractant concentration on extraction The volume concentration of D2EHPA is 20%, the pH of the feed liquid is 2.0, compared with (0/A)=1:1, the equilibrium time is 3 min, the temperature is room temperature, and the effect of extractant concentration on the extraction is shown in Fig. 2. Figure 2 Effect of extractant concentration on extraction rates of zinc, copper and nickel It can be seen from Fig. 2 that with the increase of the volume concentration of D2EHPA, the extraction rate of zinc is obviously increased, the extraction rate of copper is slowly increased, and the extraction rate of nickel is not changed. When the volume concentration of D2EHPA reaches 20%, zinc is obtained. The extraction rate curve is gradually flat. The extraction rate of zinc is 89.5% at 20%, the extraction rate of copper is 17.0%, and the extraction rate of nickel is only about 1%. The optimum volume concentration of the extractant was determined to be 20% in consideration of the loss of the organic phase and nickel and other factors. (3) The effect of (O/A) on extraction The volume concentration of D2EHPA is 20%, the pH of the feed liquid is 2.0, the equilibrium time is 3 min, and the temperature is room temperature, as shown in Figure 3. Figure 3 Effect of (O/A) on the extraction rates of zinc, copper and nickel It can be seen from Fig. 3 that the extraction ratios of zinc, copper and nickel are significantly decreased as the ratio is reduced. At the same time, the larger the comparison, the greater the loss of the organic phase in the aqueous phase, and the smaller the phase, the more difficult the phase separation. Considering the loss of the organic phase and the ease of phase separation, it is determined that the optimum ratio of extraction is 1:1. (4) Effect of pH of feed solution on extraction The volume concentration of D2EHPA is 20%, compared with (O/A)=:1 equilibrium time 3 min, the temperature is room temperature, and the effect of feed pH on extraction is shown in Fig. 4. Figure 4 Effect of pH on the extraction rate of zinc, copper and nickel It can be seen from Fig. 4 that when the pH of the feed liquid is less than 2.0, the extraction rate of zinc increases remarkably with the increase of pH. After the pH reaches 2.0, the effect of the increase of pH on the extraction of zinc is no longer obvious. In the scope of this study, the extraction rate of copper has been increasing with the increase of the pH of the feed solution. However, as the pH increases, the extraction rate of nickel also increases. Excessive pH of the feed liquid leads to a large loss of nickel. Considering various factors, the optimum pH for extraction is determined to be 2.0. (5) Multi-stage countercurrent extraction It can be seen from the above experimental results that single-stage extraction is difficult to obtain a satisfactory impurity removal effect, so multi-stage countercurrent extraction is often used in the industry. However, because the single-stage extraction rate of copper is only about 11% under the optimal impurity removal process conditions, a large extraction stage is required to achieve a satisfactory extraction effect. Considering the complexity of the operation, only a lot of exploration is carried out here. Staged countercurrent extraction separates zinc. In this study, a multi-stage countercurrent extraction "matrix" simulation method was used to carry out a three-stage countercurrent extraction simulation experiment. After three stages of countercurrent extraction, the zinc concentration can be reduced to 0.01 g/L, and the zinc extraction rate is 98.9%. In actual industrial production, increasing the number of extraction stages completely separates zinc and copper from the nickel leaching solution. (6) Anti-collection The loaded organic phase obtained by the extraction experiment under the optimal conditions was subjected to a primary stripping experiment. The stripping conditions were as follows: the organic phase was 20% D2EHPA monosulfonated kerosene loaded organic phase, and the stripping agent was sulfuric acid solution. Compared with (O/A)=1:1, the stripping equilibrium time was 5 min, and the sulfuric acid concentration was 1.0 mol/ L. After standing still, the liquid was separated, and the lower stripping solution was taken. The concentrations of zinc, copper and nickel in the stripping solution were analyzed, and the stripping rate was calculated. Zinc, copper and nickel can be completely stripped to the aqueous phase, and the stripping solution is clear and transparent, and the stripping effect is good. Third, the conclusion (1) D2EHPA extracts zinc and copper to reach equilibrium at 3 min; with the increase of D2EHPA volume concentration, the extraction rate of zinc and copper increases significantly. When the volume concentration of D2EHPA reaches 20%, the extraction rate of zinc It tends to be stable; as the ratio of (O/A) decreases, the extraction rate of zinc and copper decreases significantly; as the initial pH of the feed increases, the extraction rate of zinc and copper increases significantly, when the initial of the liquid When the pH reaches 2.0, the extraction rates of zinc and copper tend to be stable. (2) The optimal extraction conditions are as follows: the extraction time is 3 min, the volume concentration of D2EHPA is 20%, and the initial pH of the feed solution is 2.0 compared to 1:1. The supported organic phase was back extracted with 1.0 mol/L of H 2 SO 4 . (3) Under the optimal extraction conditions, the “matrix†simulation experiment of 3-stage countercurrent extraction can reduce the concentration of zinc in the aqueous phase to 0.01g/L, the extraction rate of zinc can reach 98.9%, and the loss of nickel is better. small.
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Study on Extraction and Purification of Complex Nickel Leachate
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