Treatment and reuse technology of mineral processing wastewater from lead-zinc sulfide mine?

Domestic lead and zinc resources are rich and widely distributed. However, more than 9% of the deposits are rich in minerals, most of which are mainly low-grade and complex in composition, mainly lead-zinc deposits, accompanied by more than 50 elements such as copper, silver and gold. During the mineral processing of lead-zinc sulfide ore, the water discharge is large, and the wastewater formed is seriously polluted, which seriously damages the water environment. Therefore, the recycling of mineral processing wastewater is the key to the resource utilization of mineral processing wastewater at present, and even relates to the sustainable development of mines.

A, lead-zinc ore dressing technology

Flotation is the basic requirement of lead-zinc sulfide ore dressing in China at present, and various technological levels are constantly improved, including various steps in ore dressing, mainly including ore crushing, grinding, lead flotation, zinc-sulfur mixed flotation, zinc-sulfur separation, concentrate concentration and filtration. Products include lead concentrate, zinc concentrate and sulfur concentrate. In the current production process, various resources, including xanthate, black powder, sodium thiosulfate, sodium sulfide, sodium cyanide, sodium silicate, copper sulfate, ethidium nitride, lime, sodium carbonate, zinc sulfate and sodium sulfite, are continuously integrated to improve the separation level of various zinc ores.

Second, the characteristics of lead-zinc sulfide ore dressing wastewater

2. 1 Large amount of wastewater.

Lead-zinc sulfide ore dressing consumes a lot of water, and the lead-zinc ore treated by flotation method needs 4 ~ 6m2 of water per kloc-0/t. Medium-sized mines with production scale 1000 tons/day need 4000~6000m2 of water every day. Even if the recycling rate of wastewater is 75%, the daily wastewater discharge will reach about 1000m2. Based on 300d a year, it is estimated that the annual wastewater discharge will reach about 40. 1 10,000.

2.2 The composition of wastewater is complex

The composition of lead-zinc ore dressing wastewater is complex, mainly containing heavy metal ions and mineral processing reagents. The main harmful substances in mineral processing wastewater are heavy metal ions and various organic and inorganic flotation reagents used in ore flotation, including highly toxic cyanide and cyanochrome compounds. Wastewater also contains various insoluble coarse and fine dispersed impurities. Mineral processing wastewater usually contains sulfate, chloride or hydroxide of sodium, magnesium and calcium. The acid in mineral processing wastewater is mainly formed by mixing sulfur-containing minerals with water and air oxidation.

2.3 High suspended particle content

Lead-zinc mineral processing wastewater contains complex components such as heavy metal ions and mineral processing reagents. Mine washing wastewater, concentrate concentration and dehydration wastewater, tailings water and wet dust removal wastewater, accident discharge wastewater, etc. , containing a large number of insoluble coarse and fine impurities, especially tailings water and concentrated water with high suspended solids content. Because the wastewater contains heavy metal ions and mineral processing reagents, as well as dissolved sulfates, chlorides or hydroxides of sodium, magnesium and calcium, the total dissolved solids content of the wastewater is high.

2.4 It has certain toxicity.

The xanthate residue in lead-zinc ore dressing wastewater is not only accompanied by odor, but also has certain toxicity. Studies have confirmed that even if a small amount of xanthate remains in wastewater, it will affect the water quality and form a pungent smell. Moreover, xanthate seriously poisons mammals and is highly toxic to fish. Cyanide, heavy metal ions, etc. Regulators in wastewater are highly toxic. But also can enter the human body through the food chain, which seriously threatens human health. However, the suspended solids will interfere with the living conditions of aquatic organisms, such as blocking fish gills and affecting the photosynthesis of algae. If the concentration of suspended solids is too high, it may also cause river siltation, and irrigation with it will cause soil hardening. If it is used as domestic water, suspended matter is a kind of uncomfortable substance, and it is also a carrier of bacteria and viruses, which is potentially harmful to human body. Even if there are heavy metal compounds in suspended solids, they will be released into water under certain conditions (the pH value of water decreases, the ionic strength changes, and the concentration of organic chelating agents changes, etc. ).

Three, lead zinc sulfide mineral processing wastewater treatment

3. 1 For reference.

Considering the high content of pollutants in lead-zinc ore dressing wastewater. The treatment methods that can be used for reference can be divided into the following categories: first, physical treatment, precipitation, flotation, filtration, etc. The second is chemical treatment, adsorption, oxidation, neutralization, etc. Three kinds, biochemical, anaerobic treatment, aerobic treatment and so on.

3.2 Treatment process flow

Lead and zinc sulfide wastewater contains a lot of heavy metals, suspended solids and strong bubbles. Coagulation-oxidation is a treatment process that can be tried, and it will basically meet the discharge standards. The wastewater discharged into the tailings pond is discharged up to the standard through DH value recovery, natural purification and tailings adsorption. The specific treatment process, wastewater-tailings pond-natural purification -pH adjustment-standard discharge; Or; Wastewater-coagulation-sedimentation-oxidation -pH adjustment-recovery. After the above treatment, the emission requirements can basically be met.

3.3 Processing equipment and facilities

3.3. 1 thickener

The concentration of tailings discharged from lead-zinc beneficiation is generally low. Usually, a thickener or thickener is built in or near the concentrator to dehydrate the tailings, and the tailings sand is precipitated to form an underflow and discharged into the tailings pond. Clear water overflows from the upper part of the thickener and is reused. After the overflow water of thickener is treated, the backwater rate can generally reach 40% ~ 70%.

3.3.2 tailings pond

In lead-zinc ore dressing, tailings pond is the most common form. After the discharged tailings are treated by the tailings pond, some water seeps into the cracks of the tailings pond, some water naturally degrades in the tailings pond, and some water evaporates in the tailings pond. However, in practical application, there is a problem of leakage, which directly pollutes the underground aquifer and should be paid attention to.

Four, lead zinc sulfide mineral processing wastewater recovery application technology

4. 1 direct recycling application

The direct recovery of mineral processing wastewater will be used in the original separation operation according to the characteristics of wastewater quality, which greatly reduces the cost of reagent selection. Moreover, the tailings concentrated wastewater contains a large number of foaming agents, sulfate ions and so on. It is directly used in sulfur separation operation, which increases the cost of sulfur separation by reducing the price. In addition, mineral processing wastewater is rich in traditional Chinese medicine, and harmful substances also account for the majority. Direct reuse without treatment will directly affect the ore separation index, increase the components contained in metals and reduce the accuracy of concentrate quality. Therefore, direct use in zinc selection will affect the zinc selection index, and direct use or use in lead selection will affect the main taste of lead selection. Moreover, the water reuse facilities in the subsystem are complex, the stability of water use is not strong, and the operation and production are difficult to control.

4.2 Moderate therapeutic application

In the application of recovery of mineral processing wastewater from lead-zinc sulfide mine, moderate treatment and reuse of wastewater is the most effective way to solve wastewater pollution. At present, there are two basic treatment forms: first, the wastewater is reused for mineral processing after being treated by treatment facilities; Second, the tailings pond is clarified, precipitated, oxidized and self-purified. Considering the separation of lead and zinc in mineral processing wastewater, the pH value is generally high. Therefore, it is necessary to add an appropriate amount of acid to the tailings pond and fine-tune it for mineral processing production.

At present, the basic principle of pollution control of lead-zinc sulfide mineral processing wastewater is to reduce environmental pollution after treatment. Physical, chemical and biological methods can be considered to ensure the purification index of discharged sewage and reduce the pollution to the surrounding environment. Combined with various treatment measures, the measures of giving priority to recycling part of wastewater and moderately treating the remaining wastewater and reusing it will greatly improve the reuse rate of wastewater, reduce the pollution of wastewater to the environment, and be more conducive to saving production costs.

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