Non-ferrous metal ore flotation production process emit large amounts of wastewater containing residual mineral processing reagents, and harm to the environment has been valued by the people. The recycling of ore dressing wastewater is considered to be one of the most effective methods. As the ore dressing wastewater contains residual ore dressing chemicals and other impurities, improper reuse will cause a decline in the beneficiation index. Especially in the process of flotation of colored polymetallic ore, the decline of this index is more obvious. Hunan a lead zinc ore in the mining of ore than 6 × 104 t, present, the plant processing capacity of more than 200 t / d. The main products are lead and zinc concentrates. The water used for the selection of the plant is mainly taken from natural water, and the water consumption is about 1200t/d. As the mine is located in a water-deficient area, the problem of water competition with agriculture has been very prominent over the years. The wastewater from the plant is discharged into the natural water body through the tailings pond. The content of fluorine and lead in the wastewater exceeds the national industrial wastewater discharge standard, and the pollution to the surrounding environment is more serious. Therefore, the treatment and recycling of ore dressing wastewater has become an urgent issue for the mine. First, the production process and wastewater are selected to determine that the ore is a primary sulfide ore, and the ore contains low sulfur. The oxidation rate of lead and zinc ore is also low. Is selected from a conventional plant flotation process, process shown in Figure 1, processing agents used are: 25 # aerofloat, butyl xanthate, sodium carbonate, zinc sulfate, copper sulfate, # 2 oil. After the whole plant wastewater is checked, the discharge of each batch of wastewater is shown in Table 1. The water quality characteristics of the wastewater discharged from the plant are shown in Table 2.

Figure 1 Production process flow chart of the plant selection Table 1 Waste water discharge of the plant

Table 2 Water quality characteristics of wastewater discharged from the plant

The plant used 25# black medicine in the on-site production. If the wastewater is reused, it will lead to the accumulation of phenol in the wastewater. Considering that after the reuse of wastewater, some of the tailings reservoir overflow water may be discharged during the prosperous season, resulting in phenol pollution. Therefore, the 25# black medicine was eliminated in the test, and the lead flotation was replaced by the ethyl yellow medicine. In the test, the conditions of the new water beneficiation, the tailings overflow overflow and the sub-system backwater beneficiation were carried out, and the whole process closed-circuit flotation test was carried out. The closed circuit test indicators are shown in Table 3.

Table 3 New water and wastewater reuse mineral processing closed-circuit test indicators%

It can be seen from the test results that the new water beneficiation and the two different schemes of the backwater flotation closed-circuit flotation test can obtain better indicators. During the test, the flotation phenomenon was normal and easy to control, indicating that both wastewater reuse schemes are feasible. However, in terms of production process, the tailings reservoir overflow water return scheme is simple and easy to produce and implement. Although the wastewater reuse system reuse scheme is feasible, if it is industrial application, the whole water return system is more complicated, which not only increases the investment of the fixed assets of the backwater system, but also is not conducive to the operation management of the production site. Therefore, it is more reasonable to use the tailings reservoir overflow water return scheme in the industry. Third, the wastewater reuse industrial test tailings reservoir overflow water full return scheme is shown in Figure 2. In the industrial test, the 25# black medicine was eliminated, and the pollution of phenol in the waste water was eliminated. The water quality of the wastewater was basically stable after 5 days of circulation (see Table 4), and the impurity content in the wastewater no longer increased. The results of industrial tests show that after the ore dressing wastewater is reused, the ore dressing index has reached the beneficiation index before the wastewater reuse (see Table 5), which has no negative impact on production. At the same time, in addition to natural losses such as evaporation and infiltration, the ore dressing wastewater is basically returned to the plant for use, eliminating environmental pollution. According to statistics, the recycling rate of ore dressing wastewater is 76%.

Fig.2 Scheme for full return of overflow water in tailings pond Table 4 Water quality characteristics of overflowing pond tailings after wastewater reuse mg/L

Table 5 Industrial trial results of mineral processing wastewater reuse

IV. Economic Benefits Due to the fact that there are more flotation reagents remaining in the ore dressing wastewater, after the wastewater is reused in the plant, the consumption of the chemicals is significantly reduced. After calculation, the cost of chemicals can be saved by 1.15×104 yuan per year (see Table 6). . At the same time, it can save more than 2.2×104t of new water every year and save water cost by 1.1×104 yuan.

Table 6 Comparison of new water and wastewater dressing agents

V. Conclusion The reuse of ore dressing wastewater is the simplest and most effective method for treating non-ferrous polymetallic ore dressing wastewater. The test proves that for a lead-zinc ore beneficiation wastewater in Xiangzhong, after using the tailings pond overflow water full return scheme for reuse, by adjusting the ore dressing agent, the ore dressing index is not affected, and the beneficiation wastewater closed cycle can be basically realized, and the wastewater reuse The rate is over 75%, which eliminates the pollution of wastewater to the environment. At the same time, it can save the ore dressing pharmacy and water fee by 2.25×104 yuan per year, which has obvious environmental and economic benefits.

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