The main pollutants in mine wastewater:
1. Organic pollutants. The decay of plants in mine wastewater ponds and tailings ponds may cause high organic content in wastewater. The wastewater discharged from mineral processing plants, coal washing plants, and analysis laboratories contains organic substances such as phenol, cresol, and naphthol, which are harmful to aquatic organisms. Extremely harmful.
2. Oil pollutants. Oil pollutants are common pollutants in mines. The oily wastewater immerses into the pores to form an oil film, which can block the soil structure, is not conducive to the growth of plants, and even makes crops die. The oil film on the water hinders the transfer of oxygen in the atmosphere to the water body, so that the water body cannot get oxygen, and the aquatic organisms die due to lack of oxygen, Application of polyacrylamide in mineral processing plant.
3. Acid and alkali pollution. Acid-base pollution is a common phenomenon in water pollution. After acid-base wastewater is discharged into the water body, the pH value of the water body changes, inhibits the growth of bacteria and microorganisms, prevents the self-purification of water bodies, can also corrode ships and hydraulic structures, and destroy normal Ecological cycle.
4. Oxide. Oxides are highly toxic, and most people will die if they mistakenly take about 0.1g of sodium cyanide or potassium cyanide. Sensitive people can kill even 0.06g. When the CN- content in the water reaches 0.3-0.5mg/L, it can kill the fish.
There are many methods for treating mine wastewater, which can be roughly divided into two categories, one is chemical treatment methods, and the other is physical treatment methods. The chemical treatment includes neutralization method, oxidation method, reduction method, flocculation method, ion exchange method and so on. Physical treatment methods include gravity sedimentation, activated carbon adsorption, evaporation, and reverse osmosis. The following mainly introduces the chemical treatment methods of mine wastewater.
1. Neutralization method, which neutralizes mine wastewater with excessive acidity or alkalinity. Usually lime and limestone are used to neutralize acidic wastewater, and acid is used to neutralize alkaline wastewater. The obtained by-products can be soluble or insoluble in water. For example, the use of soda ash to neutralize sulfuric acid to obtain soluble sodium sulfate, while the use of lime to obtain poorly soluble calcium sulfate. When carbonates such as soda ash or limestone are used to neutralize the acid, carbon dioxide is released, which can cause foam and other related problems. If there are both acidity and alkalinity in mine wastewater, we must try to mix these wastewater. The use of limestone to neutralize acid sewage has a wide range of raw materials and low unit alkalinity cost, so this method can indeed be used. However, for a fixed bed composed of limestone blocks or particles, it will be affected by metal ions, phosphates, fluorides, oils and greasy, etc., which will reduce the neutralization effect, such as the formation of insoluble metal oxide coatings, or oil And the coverage of greasy substances, etc., this is also a problem that needs attention. Hill and Wilmos of the United States have made a comment. They believe that the method of neutralization with limestone seems to be limited to water with a divalent iron content of less than 50-100 mg/liter, because the concentration of divalent iron is higher. It takes a long time to oxidize under high conditions, whether it is aerated first or aerated later. When the concentration of ferrous iron is lower than 50-100 mg/L, the neutralization of tumbling and spraying limestone is feasible. Expanded bed, tumbling and spray-like systems are suitable for treating acidic mine wastewater containing ferric iron. The abrasion that occurs in the expanded bed or roller mill helps to remove the continuously generated iron oxide coating. The sprayed limestone must have enough fineness to ensure a considerable reaction rate before the surface deposits on the particles are formed. Lime is used to neutralize acid wastewater. Its reaction rate is greater than that of limestone, and it is more widely used. It is used in the form of quicklime or hydrated lime. The cost per unit of alkalinity of quicklime is relatively low, and it requires a considerable maturation device when it is used and needs to be taken care of. This is not economical for small-scale processing. When using lime to neutralize solutions containing sulfates, phosphates, fluorides and certain metals, the nature of the sludge and scaling must be considered.
2. Oxidation method and reduction method. Oxidation method is to oxidize wastewater through chemical treatment methods such as blowing air, wet burning or chlorination. Chlorine can be used as an oxidant in wastewater treatment, and other chemical oxidants are also used. For example, oxygen itself is sometimes an effective oxidant, or catalysts can be used to increase its oxidizing ability. Moreover, it is not too expensive to generate large amounts of oxygen on site. Ozone can also be used to destroy cyanide and phenols, but because of the high cost of generating ozone on site, its use is limited. The reduction method uses less than the oxidation reaction in the process of treating wastewater. Several commonly used waste water reducing agents are ferrous chloride and ferrous sulfate (obtained from pickling waste liquid), sodium metabisulfite, hydrogen sulfide and sulfur dioxide.
3. Flocculation, colloid, is composed of tiny particles with a diameter of 0.001 to 1.0 microns evenly distributed in a uniform medium. The coagulation process of flocculation is to neutralize the charge of the particles by adding chemicals and destroy the stability of the system, thereby removing colloids from the water. Because colloids are usually negatively charged, multivalent cations are often added to the system. The agglomeration process is divided into two stages. First, add chemicals to neutralize and cause agglomeration of particles, and then add flocculants and some chemicals to strengthen the structure, size and density of the coagulum. Adding the following three flocculants helps to improve the floc structure. The first is a weighting agent, such as bentonite, kaolin, and jiaolin, with a concentration of 5-10%. The second type is adsorbents, such as various grades of powdered carbon and various grades of activated alumina. The third type is polymer electrolytes, inorganic polymer electrolytes, which are activated silica prepared by partially neutralizing sodium silicate with acidic reagents such as chlorine or alumina; organic polymer electrolytes are of various molecular weights and different Charged organic polymer.
4. Ion exchange method. Ion exchange method is another method to remove certain metal ions from sewage. When the ion exchange resin has a strong selective effect on the ions to be removed, the ion exchange method is particularly effective. The ions will be concentrated on the resin, as long as it is washed and recovered with a small amount of regenerant solution, or simply treated. However, only a few metals can be industrially produced by ion exchange, including very precious metals and cheaper metals such as copper and zinc. The ion exchange method can be effectively used to remove calcium sulfate in mine wastewater. Using this method no longer produces liquid waste, but it will encounter separation problems.
Mine wastewater treatment generally uses anionic polyacrylamide. Dissolve the solid particles in a 1%‰o-5%o concentration aqueous solution before use to quickly take effect. When dosing, a step-by-step method should be adopted. Slowly throw it into the water, then disperse it evenly in the water
The addition of solution polyacrylamide is generally 0.5%-1%o aqueous solution, but in the case of high suspension concentration and high viscosity, it is recommended to further dilute to 0.1%o, so that it is easy to mix and give full play to the effect， Application of polyacrylamide in mineral processing plant。
The molecular weight of the cation is smaller than that of the anion, so the viscosity of the cation is also weaker than the viscosity of the anion. Therefore, the concentration standards of cations and non-ions are slightly higher than that of anions. (According to the situation, the turbidity of the concentration can also be adjusted appropriately according to the concentration of the water. The turbidity of the concentration can be appropriately adjusted to high or low. The low turbidity can be appropriately adjusted to increase the concentration). The recommended concentration of 5‰-1% PAM has a good and stable application effect in mine wastewater treatment. It has the advantages of low investment in wastewater treatment, small footprint, fast wastewater treatment response, low operating cost, strong broad spectrum, large operational flexibility, strong sterilization and bathing ability, no secondary pollution, fast solid-liquid separation, good water effluent effect, etc. Features, can realize waste water reuse and waste water resource utilization. PAM can not only treat sewage but also save water resources, and has good economic and social benefits.