Combined treatment method for sodium chloride-containing wastewater generated in dressing and smelting of rare earth

Abstract

The invention relates to a combined treatment method for sodium chloride-containing wastewater generated in dressing and smelting of rare earth. According to the method, a series of desalination and concentration treatments such as deoiling, neutralizing, homogenizing, aeration, flocculation, ultrafiltration, nanofiltration, reverse osmosis, electroosmosis and MVR (mitral valve replacement) concentration are carried out on the wastewater, so that recyclable purified water is obtained; ammonium bicarbonate is added into the sodium chloride extracted from the wastewater, so that the sodium salt can be converted and regenerated into sodium bicarbonate, sodium carbonate and ammonium chloride products for dressing and smelting of the rare earth. According to the method, the recovery rate of the wastewater is high, the effluent quality is stable, the conversion rate of the sodium salt is high, and no three wastes are discharged; production equipment is compact, simple to operate, and easy to realize automation control; the problem that the sodium chloride-containing wastewater and other similar industrial wastewater generated in dressing and smelting of rare earth are difficult to recycle is solved.

Description

technical field [0001] The invention belongs to the technical fields of environmental engineering and chemical engineering, and in particular relates to a wastewater treatment method. Background technique [0002] A large amount of sodium chloride-containing wastewater is produced in the process of rare earth separation, smelting, extraction and separation. The main pollutants in the water are sodium chloride salts, the concentration range is between 400.0-140000.0mg / l, and the calcium and magnesium ions are 440.0-2000.0mg / l l, fluoride ion 1.0-20.0mg / l, other heavy metal ions accumulatively 10.0-80.0mg / l, oil extractant and other organic pollutants 20.0-3000.0mg / l, COD500.0-5000.0mg / l, the composition of the wastewater is complex , cannot be effectively treated with conventional water treatment processes and technologies. [0003] It is known that the rare earth smelting and separation process can use industrial grade ammonium bicarbonate (NH 4 HCO 3 ), heavy alkali (NaH...

AI Technical Summary

Problems solved by technology

Because ammonium bicarbonate is used as rare earth metal saponification agent, large discharge and low concentration ammonium chloride wastewater will be generated, causing ammonia nitrogen pollution in the water environment and difficult to effectively control; therefore, the use of ammonium salt as a dressing and smelting agent is limited

[0004] Chinese patent CN1646429A discloses a treatment method for electrolytic alkali production after extraction and separation of high-concentration sodium chloride wastewater; this inventive technology is not applicable to the treatment of low-concentration sodium chloride-containing wastewater

However, this method needs to be co-produced with a synthetic ammonia plant, and high-purity solid NaCl must be selected as a raw material to produce soda ash; and the industrial production of combined soda production requires a large amount of processing, a large investment in plant construction, and complex process equipment.

Therefore, it is not practical and feasible to directly use the combined soda production method for the treatment of sodium chloride-containing wastewater from rare earth dressing and smelting, and it cannot fundamentally solve the reduction and zero discharge of sodium chloride wastewater.

[0006] Although the sodium chloride salt in the waste water can be crystallized by using the traditional evaporation and concentration process and equipment, the economic value of the sodium chloride salt extracted and separated from the waste water is very low and there is no sales market, which will cause enterprises to The operating cost of treating this kind of wastewater treatment is too high to bear

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