In the electrolytic production of manganese metal, manganese affects the quality of the raw material contained nickel cobalt manganese large, the production process must be removed EMM harmful elements. On the other hand, with the development of the stainless steel and battery industries, the demand for nickel and cobalt is increasing. Since 2000, the price of nickel and cobalt has climbed all the way. The price of nickel once exceeded 180,000 yuan/t, and the price of cobalt was above 500,000 yuan/t. The price of cobalt and nickel declined in 2005, but after the year 2006, the global stainless steel market began to warm up. Stainless steel mills in Europe, the United States and Asia have raised the ex-factory price of stainless steel products, causing nickel prices to rise again and remain high. According to the data of the Stainless Steel Branch of China Special Steel Association, due to the expansion and construction of China's Taigang, Baosteel, Jiugang and Zhangjiagang stainless steel smelting projects, it is estimated that China's stainless steel crude steel output will increase by 1.5 million tons in 2007, so the domestic demand for nickel is also Will increase.
China's total manganese resources accounted for the first four of the world, but 93% of the reserves of iron and steel industry could not be applied directly to the low-grade manganese ore. With the rapid increase in the demand for manganese ore resources in the development of the iron and steel industry, manganese ore needs to be imported in large quantities. Since 2004, the import volume has exceeded 4 million tons. In order to make full use of China's low-grade manganese ore resources, China's efforts to develop electrolytic manganese industry, China's electrolytic manganese production capacity reached 1 million tons in 2006, and began to use low-grade manganese oxide to produce electrolytic manganese. Most of the manganese oxide ore is accompanied by cobalt and nickel, and some even have a content of more than 0.1%. Therefore, the recovery of cobalt and nickel from low-grade manganese ore can not only slow down the situation of China's nickel-cobalt products, but also facilitate the comprehensive utilization of resources.
At present, there are many methods for recovering nickel and cobalt, mainly in the wet method, but the recovery of cobalt and nickel from low-grade manganese oxide ore has not been reported. In this study, the low-grade manganese oxide ore in a certain area of ​​Guangxi was used to enrich the nickel-cobalt by roasting-leaching-sulfide precipitation method, and good results were obtained. This method is simple, fast, and low in cost, and is suitable for industrial production.
First, test the ore sample
The ore sample used in the test was a low-grade manganese oxide ore in a certain area of ​​Guangxi. The analysis results of the main chemical components in the ore samples are shown in Table 1. It can be seen that the nickel content is 3 ‰ and the cobalt content is 0.8 ‰.
Table 1 Analysis results of main chemical components of ore samples %
Second, the test method
First, the method of reduction roasting is used to reduce manganese oxide ore (mainly in the form of MnO 2 ) to MnO, and then to concentrate H 2 SO 4 in acid to mineral mass ratio = 0.55, leaching temperature is 60 ° C, and liquid to solid ratio is 5:1. The mixture was leached for 1 hour, and the filtrate obtained by filtration was used as a raw material liquid for the test.
The pH of the raw material liquid was adjusted with calcium oxide, and Na 2 S, BaS and MnS were respectively added, and Ni and Co were formed into a sulfide precipitate to obtain enrichment. The precipitation rate was calculated by analyzing the Ni and Co contents of the raw material liquid and the precipitated filtrate.
The MnS precipitating agent is obtained by reacting manganese sulfate with sodium sulfide, filtering the reaction precipitate, washing and drying.
Deionized water was used during the test. Calcium oxide, Na 2 S, and BaS are all chemically pure. The Ni and Co contents of the raw material liquid and the precipitated filtrate were analyzed by spectrophotometry.
Third, the test results and discussion
Nickel-cobalt can be formed by the formation of hydroxide precipitates in a certain pH range. Therefore, before investigating the precipitation of nickel-cobalt with sulfide, the effect of pH on the loss of nickel-cobalt hydroxide was first investigated, and then the different sulfide precipitants (Na 2 S, BaS and MnS) were used to precipitate the manganese ore leaching solution. Nickel-cobalt, compare the precipitation effect of each precipitant, and then determine the appropriate precipitant.
(1) Effect of pH on the loss of nickel-cobalt hydroxide formation
The raw material liquid obtained by oxidizing manganese ore by reduction roasting-sulfuric acid is adjusted to different pH values, and the residual nickel and cobalt contents in the raw material liquid are measured to determine the loss of nickel and cobalt at each pH value. The test results are shown in Figure 1.
Fig.1 Effect of pH on the loss of Ni and Co
â– -Ni; â—‹-Co
It can be seen from Fig. 1 that the loss amounts of Ni and Co are different at different pH values. The higher the pH, the greater the loss of nickel and cobalt, and the loss of cobalt is more pronounced. At the same time, the test also found that at a pH higher than 4, manganese in the raw material liquid also formed a loss. This is mainly because nickel, cobalt and manganese precipitate Ni(OH) 2 , Co(OH) 2 and Mn(OH) 2 under alkaline conditions. Therefore, before recovering nickel and cobalt with sulfide, the pH should be adjusted to a range of 2 or less to reduce the loss of cobalt, nickel and manganese.
(2) Selection of sulfide precipitants
1. The precipitation effect of Na 2 S on nickel and cobalt
The raw material liquid was adjusted to a different pH with calcium oxide, and then cobalt Na was precipitated by adding a Na 2 S solution (the molar amount of Na 2 S added was equal to the total molar amount of cobalt nickel). The mixture was stirred for 1 hour, filtered, and the nickel-cobalt content in the filtrate was measured to calculate the precipitation rate of nickel-cobalt, and the test results shown in Fig. 2 were obtained.
Figure 2 Precipitation rate of Na, Co to Na 2 S at different pH values
â– -Ni; â—‹-Co
It can be seen from the results of Fig. 2 that when nickel-cobalt is precipitated by Na 2 S, the precipitation rate of nickel-cobalt has a considerable relationship with the pH value of the raw material liquid, and the precipitation effect of nickel-cobalt is very poor when the acidity is strong. In the range of pH=1~3, the precipitation rate of cobalt nickel increases remarkably with the increase of pH value; when pH≥4, the cobalt nickel in the raw material liquid almost completely precipitates. Therefore, when precipitating nickel and cobalt with Na 2 S as a precipitating agent, it is preferred to control the pH between 3 and 4. However, the test results of 3.1 have shown that when the pH is higher than 3, the loss rate of cobalt is higher than 30%, and the loss rate of nickel is higher than 20%. In addition, Na2S introduces sodium ions into the solution, which is disadvantageous for the utilization of the manganese raw material liquid. Therefore, it is not suitable to recover cobalt nickel using Na 2 S as a precipitant.
2. Precipitation effect of BaS on nickel and cobalt
The raw material liquid was adjusted to a different pH with calcium oxide, and then BaS solid precipitated cobalt nickel (the molar amount of BaS in force was equal to the total molar amount of cobalt nickel). The mixture was stirred for 1 hour, filtered, and the nickel-cobalt content in the filtrate was measured to calculate the precipitation rate of nickel-cobalt, and the test results shown in Fig. 3 were obtained.
Figure 3 Precipitation rate of Ba, Ni and Co at different pH values
â– -Ni; â—‹-Co
From the results of Fig. 3, it is known that when nickel and cobalt are precipitated by BaS, the precipitation effect is also greatly related to the pH of the raw material liquid. In the range of pH=1～3, the precipitation rate of cobalt-nickel increases significantly with the increase of pH value; when the pH value rises to between 3 and 5, the precipitation rate of cobalt-nickel can reach about 90%. .
The use of barium sulfide as a precipitant does not introduce sodium ions into the solution, but the barium is precipitated with barium sulfate and precipitated with cobalt nickel in the precipitated slag. In the subsequent recovery of cobalt and nickel, barium sulfate must be added. Separation. On the other hand, according to the results of Fig. 3, it is necessary to control the pH of the raw material liquid to be greater than 4 when precipitating nickel cobalt with BaS, and the test results of 3.1 show that this will cause a large loss of cobalt nickel and manganese. Therefore, BaS is also unsuitable as a precipitant for recovering cobalt nickel.
3. Precipitation effect of MnS on nickel and cobalt
The raw material liquid was adjusted to a different pH with calcium oxide, and then a self-made MnS solid precipitated cobalt nickel was added (the molar amount of MnS in the mouth was equal to the total molar amount of cobalt nickel). The mixture was stirred for 1 hour, filtered, and the nickel-cobalt content in the filtrate was measured to calculate the precipitation rate of nickel-cobalt, and the test results shown in Fig. 4 were obtained.
Figure 4 Precipitation rate of Ni,Co by MnS at different pH values
â– -Ni; â—‹-Co
It can be seen from the results of Fig. 4 that when nickel and cobalt are precipitated by MnS, more than 98% of cobalt nickel in the raw material liquid can be precipitated and concentrated in the pH less than 2, and no new impurity ions are introduced into the solution and the precipitated slag. Or other sediments. At the same time, according to the test results of 3.1, in such a low pH range, the loss of cobalt, nickel and manganese in the solution is not caused. Therefore, MnS is a relatively suitable precipitant for recovering cobalt nickel from a manganese-containing solution.
Fourth, the conclusion
(1) When the cobalt-nickel is precipitated and precipitated from the low-grade manganese oxide ore by the reduction roasting sulfuric acid leaching, the initial pH of the raw material liquid is lower than 2, which is favorable for preventing the formation of hydroxide precipitates of cobalt nickel and manganese. loss.
(2) Precipitating nickel and cobalt with Na 2 S, BaS and MnS precipitants respectively. When the pH values ​​are higher than 3.5, 4 and 2 respectively, the precipitation rates of cobalt nickel are 97%, 86% and 99% respectively. However, Na2S, BaS will introduce impurities into the raw material liquid or precipitated slag, and at the same time, the loss of cobalt nickel and manganese will be caused by the high initial pH value of the solution, so it is not suitable as a precipitant for recovering cobalt nickel.
(3) When nickel and cobalt are precipitated by MnS, more than 98% of the cobalt nickel in the raw material liquid can be precipitated and concentrated in the pH value less than 2, and no new impurities are introduced into the solution and the precipitated slag, and It causes loss of cobalt, nickel and manganese in the solution, so MnS is a suitable precipitant for recovering cobalt nickel from the manganese-containing solution.
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