Tandem resource recovery and deep defluorination method for fluorine-containing waste liquid

Abstract

The invention discloses a fluorine-containing waste liquid tandem type resource recovery and deep defluorination method which comprises the following steps: detecting fluorine-containing waste liquid, and dividing the fluorine-containing waste liquid according to different [F-]; [F-] gt; introducing the liquid with the fluorine ion concentration of 2,000-10,000 mg / L into a first crystallizer, adding a first medicament, and reacting and crystallizing to obtain a sodium fluoride crystal and a liquid with the fluorine ion concentration of 2,000-10,000 mg / L; the liquid is introduced into a second crystallizer, a second agent is added, reaction crystallization is conducted, and cryolite crystals and liquid with the fluorine ion concentration being 100-2000 mg / L are obtained; the liquid is introduced into a third crystallizer, a third agent is added, reaction crystallization is conducted, and calcium fluoride crystals and liquid with the fluorine ion concentration being 10-100 mg / L are obtained; and introducing the liquid into a defluorination device, adsorbing and defluorinating, and discharging after reaching the standard. The sodium fluoride and cryolite recovered by the method have high additional values, the use of dilution water is reduced, and the yield of solid waste is reduced.

Description

Technical Field

[0001] The invention belongs to the field of wastewater and waste liquid resource recovery and treatment, and specifically relates to a method for serial resource recovery and deep defluorination of fluorine-containing waste liquid. Background Art

[0002] In many industrial production processes, such as chemical, electronic, metallurgical, photovoltaic and other industries, a large amount of high-concentration fluorine-containing waste liquid is generated. If fluoride is discharged directly without effective treatment, it will cause serious harm to the environment and human health. The traditional treatment method is mainly flocculation and sedimentation, which reacts fluorine-containing waste liquid with excessive soda lime and adds flocculants to convert it into solid waste, which will lead to waste of fluorine resources and difficulties in solid waste treatment.

[0003] In order to realize the recycling of fluorine resources, the method of crystallization recovery of calcium fluoride is usually adopted. However, due to the extremely low solubility of calcium fluoride in water, it is easy to generate fine crystals, resulting in low product purity and difficult separation and recovery. Especially for high-concentration fluorine-containing waste liquid, a large amount of dilution water is required, resulting in an increase in the amount of waste liquid treated and an increase in the operating load of the equipment. Moreover, the market price of calcium fluoride is low, usually 1,000 to 3,000 yuan per ton, and the recovery economy is not good. At the same time, the fluorine content in the tail water is still difficult to meet the direct discharge standard.

[0004] Therefore, it is urgent to develop new process routes to improve the value of fluorine resource recovery products and reduce the amount of solid waste and waste liquid treatment while meeting the increasingly high emission targets. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for serial resource recovery and deep defluorination of fluorine-containing waste liquid.

[0006] The technical solution of the present invention is summarized as follows:

[0007] A method for serial resource recovery and deep defluorination of fluorine-containing waste liquid, comprising the following steps:

[0008] 1) Detection of fluorine-containing wastewater, according to [F - ] are different, and the fluorine-containing waste liquid is divided into: [F - ]>10000mg / L of liquid; 10000mg / L≥[F - ]>2000mg / L of liquid; 2000mg / L≥[F - ]>100mg / L of liquid; 100mg / L≥[F - ]>10mg / L of liquid;

[0009] 2) [F -]>10000mg / L liquid is passed into the first crystallizer, the first reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain sodium fluoride crystals and 10000mg / L≥[F - ]>2000mg / L liquid; the first reagent is sodium hydroxide, sodium carbonate or sodium bicarbonate;

[0010] 3) 10000mg / L≥[F - ]>2000mg / L of liquid is passed into the second crystallizer, the second reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain cryolite crystals and 2000mg / L≥[F - ]>100mg / L liquid; the second agent is sodium aluminate, or sodium aluminate generated by the reaction of sodium hydroxide and aluminum hydroxide;

[0011] 4) 2000mg / L≥[F - ]>100mg / L of liquid is passed into the third crystallizer, the third reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain calcium fluoride crystals and 100mg / L≥[F - ]>10mg / L of liquid; the third agent is at least one of calcium chloride, calcium oxide and calcium hydroxide;

[0012] 5) 100mg / L≥[F - Liquids with fluorine content >10mg / L are passed into the defluorination device for adsorption and defluorination. The fluorine content in the effluent is <1mg / L, meeting the discharge standards.

[0013] Preferably, the first crystallizer is a stirred crystallizer or a fluidized bed crystallizer; the second crystallizer is a stirred crystallizer or a fluidized bed crystallizer; and the third crystallizer is a stirred crystallizer or a fluidized bed crystallizer.

[0014] Advantages of the present invention:

[0015] Compared with calcium fluoride, the sodium fluoride and cryolite recovered by the method of the present invention are fluorine-containing products with high added value, and their market price is 4,000 to 8,000 yuan per ton. Based on the significant differences in the solubility of the three, sodium fluoride> cryolite> calcium fluoride, the present invention establishes a series crystallization recovery strategy to recover fluorine resources step by step, significantly improving the added value of products and the economic benefits of wastewater treatment. By connecting the defluorination device in series, the end guarantee is carried out to ensure the safety of the effluent. The sodium fluoride and cryolite recovered by the method of the present invention have high added value, reduce the use of dilution water, and cut down on the output of solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of a method for serial resource recovery and deep defluorination of fluorine-containing waste liquid. DETAILED DESCRIPTION

[0017] The fluorine-containing waste liquid used in the present invention is collected from an integrated circuit factory. The present invention does not limit the source of the fluorine-containing waste liquid. Other industries such as chemical, electronic, metallurgical, photovoltaic and other industries that produce a large amount of high, medium and low concentration fluorine-containing waste liquid can be treated by the method of the present invention.

[0018] The present invention will be further described below in conjunction with specific embodiments.

[0019] Example 1

[0020] A method for serial resource recovery and deep defluorination of fluorine-containing waste liquid, see Figure 1 , including the following steps:

[0021] 1) Detection of fluorine-containing wastewater, according to [F - ] are different, and the fluorine-containing waste liquid is divided into: [F - ]>10000mg / L of liquid; 10000mg / L≥[F - ]>2000mg / L of liquid; 2000mg / L≥[F - ]>100mg / L of liquid; 100mg / L≥[F - ]>10mg / L of liquid;

[0022] 2) [F - ] is 50080mg / L and is passed into the first crystallizer (a stirred crystallizer or a fluidized bed crystallizer), and the first reagent (a sodium hydroxide aqueous solution with a mass concentration of 30%) is added, and the reaction is carried out, crystals are precipitated, and solid-liquid separation is performed to obtain sodium fluoride crystals and [F - ] is 5081mg / L of liquid (10000mg / L≥[F - ]>2000mg / L liquid); the first agent can also be a sodium carbonate aqueous solution with a mass concentration of 15% or a sodium bicarbonate aqueous solution with a mass concentration of 30%, or a sodium hydroxide aqueous solution, a sodium carbonate aqueous solution or a sodium bicarbonate aqueous solution of other concentrations;

[0023] 3) [F - ] is 5081 mg / L and is passed into the second crystallizer (fluidized bed crystallizer, stirring crystallizer can also be used), and the second reagent (aqueous solution of sodium aluminate with a mass concentration of 10%) is added, and the reaction is carried out, crystals are precipitated, and solid-liquid separation is performed to obtain cryolite crystals and [F - ] is 509mg / L of liquid (2000mg / L≥[F - ]>100mg / L liquid); the second agent can also be sodium aluminate generated by the reaction of sodium hydroxide and aluminum hydroxide in a molar ratio of 1:1, and then prepared into a sodium aluminate aqueous solution with a mass concentration of 10%;

[0024] 4) [F - ] is 509 mg / L and is passed into the third crystallizer (fluidized bed crystallizer, stirring crystallizer can also be used), and the third reagent (a calcium chloride aqueous solution with a mass concentration of 3%) is added, reacted, crystals are precipitated, and solid-liquid separation is performed to obtain calcium fluoride crystals and [F - ] is 15.2mg / L (100mg / L≥[F - ]>10mg / L liquid); the third agent can also be calcium oxide, calcium hydroxide or a mixture of calcium oxide and calcium hydroxide;

[0025] 5) [F - ] is 15.2mg / L and then passed into the defluorination device for adsorption and defluorination. - ] is 0.8mg / L, meeting the emission standards.

[0026] The direct emission standard of fluoride in the Electronic Industry Water Pollutant Emission Standard (GB 39731-2020) is less than 10 mg / L.

[0027] The defluorination device is filled with The defluorination adsorption resin is composed of an adsorption tank, a filtration unit, and a water distribution device.

[0028] According to the fluoride ion concentration of the fluoride-containing waste liquid detected in step 1), the above appropriate steps are selected. For example, when the fluoride ion concentration range is >10000 mg / L, steps 2), 3), 4), and 5) are sequentially adopted to complete the entire fluoride-containing waste liquid series resource recovery and deep defluorination; if the fluoride ion concentration is 10000 mg / L or less, for example, a liquid with a fluoride ion concentration of 6000 mg / L, steps 3), 4), and 5) are adopted to complete the entire fluoride-containing waste liquid series resource recovery and deep defluorination.

Claims

1. A method for serial resource recovery and deep defluorination of fluorine-containing waste liquid, characterized in that The steps include: 1) Detection of fluorine-containing wastewater, according to [F - ] are different, and the fluorine-containing waste liquid is divided into: [F - ]>10000mg / L of liquid; 10000mg / L≥[F - ]>2000mg / L of liquid; 2000mg / L≥[F - ]>100mg / L of liquid; 100mg / L≥[F - ]>10mg / L of liquid; 2) [F - ]>10000mg / L liquid is passed into the first crystallizer, the first reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain sodium fluoride crystals and 10000mg / L≥[F - ]>2000mg / L liquid; the first agent is sodium hydroxide, sodium carbonate or sodium bicarbonate; 3) 10000mg / L≥[F - ]>2000mg / L of liquid is passed into the second crystallizer, the second reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain cryolite crystals and 2000mg / L≥[F - ]>100mg / L liquid; the second agent is sodium aluminate, or sodium aluminate generated by the reaction of sodium hydroxide and aluminum hydroxide; 4) 2000mg / L≥[F - ]>100mg / L of liquid is passed into the third crystallizer, the third reagent is added, the reaction is carried out, crystals are precipitated, and the solid-liquid separation is carried out to obtain calcium fluoride crystals and 100mg / L≥[F - ]>10mg / L of liquid; the third agent is at least one of calcium chloride, calcium oxide and calcium hydroxide; 5) 100mg / L≥[F - Liquids with fluorine content >10mg / L are passed into the defluorination device for adsorption and defluorination. The fluorine content in the effluent is <1mg / L, meeting the discharge standards.

2. The method according to claim 1 is characterized in that the first crystallizer is a stirred crystallizer or a fluidized bed crystallizer; the second crystallizer is a stirred crystallizer or a fluidized bed crystallizer; and the third crystallizer is a stirred crystallizer or a fluidized bed crystallizer.

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