CN101555053B - A composite coagulant and treatment method that can be used to treat rare earth high-concentration ammonia nitrogen wastewater and recover industrial-grade ammonium chloride - Google Patents

Abstract

The invention provides a composite coagulant and a treatment method which can be used for treating rare earth high-concentration ammonia nitrogen wastewater to recover industrial-grade ammonium chloride and a treatment method, belonging to the technical fields of chemical environmental protection and resource recovery. The composite coagulant is a mixture of ammonium oxalate, ammonium sulfate, heavy metal precipitant DTCR and polyacrylamide (PAM). The treatment method of using composite coagulant to treat wastewater is as follows: the wastewater first passes through the grease trap and the air flotation chamber to remove the oily substances in the wastewater, then enters the pH adjustment sedimentation tank to adjust the pH to 7.5-8.5, and then enters the coagulation sedimentation tank, adding Composite coagulant, the wastewater after coagulation and precipitation enters the pH adjustment tank to adjust the pH to 2.5-4, and the wastewater after pH adjustment enters the activated carbon filter tower for adsorption and filtration, and then evaporates and concentrates under negative pressure conditions. The composite coagulant used in the invention has simple processing method, low cost and good effect. The treatment method in the invention has short process flow, simple and easy treatment, not only solves the problem of high-concentration ammonia nitrogen wastewater pollution, but also recovers valuable substances.

Description

A composite coagulant and treatment method that can be used to treat rare earth high-concentration ammonia nitrogen wastewater and recover industrial-grade ammonium chloride

technical field

The invention relates to a coagulant and a treatment method that can be used for treating rare earth high-concentration ammonia nitrogen wastewater to recover industrial-grade ammonium chloride, and belongs to the technical fields of chemical environmental protection and resource recovery.

Background technique

Rare earth wet smelting adopts extraction process to separate components. This process requires a large amount of lye to participate in the reaction. Considering the production cost, most enterprises currently use ammonia water for saponification. If the waste water generated is not treated, it will be discharged directly. It will bring extremely serious ammonia nitrogen pollution to the discharged water. High-concentration ammonia-nitrogen wastewater is the focus and difficulty in the treatment of rare earth smelting enterprises. At present, there are many treatment processes for this type of wastewater. The mature technologies and methods that can be used to treat ammonia-nitrogen wastewater at home and abroad at this stage and are in the research and development stage mainly include: Evaporation and crystallization, reverse osmosis desalination, electrodialysis, soil irrigation; air stripping (or steam stripping), chemical precipitation, breakpoint chlorination, emulsion membrane adsorption separation, adsorption, ion exchange, advanced catalytic oxidation, There are more than ten kinds of high-gravity denitrification methods, biochemical treatment methods, etc., but only a few of them can be really used in industrial applications.

Due to the large difference in the nature of wastewater discharged from different process stages in rare earth smelting, the concentration of ammonia nitrogen varies from high to low. According to the concentration of ammonia nitrogen in wastewater, it can be divided into three different concentrations of wastewater: high concentration ammonia nitrogen wastewater greater than 10000mg/L (rare earth soap wastewater, ammonium bicarbonate precipitation mother liquor), medium concentration ammonia nitrogen wastewater of 500-10000mg/L and less than 500mg/L Low concentration ammonia nitrogen wastewater. For ammonia nitrogen wastewater with a high concentration of more than 10000mg/L, it is most economically feasible to use the evaporation crystallization method. The evaporation crystallization method has been widely used in water treatment and chemical industries at home and abroad, and the technology is mature and reliable.

Recovering ammonium salt (ammonium chloride) by evaporation and crystallization can offset equipment operating costs, but due to the high content of oils, extractants, heavy metals and other impurities in wastewater, traditional sodium hydroxide is used as a precipitant to remove heavy metals and evaporate to crystallize , although most of the heavy metals can be removed, sodium is also introduced at the same time, which reduces the product purity and seriously affects the quality and sales of recovered ammonium salt products. The removal effect of heavy metals and other impurities is poor, and the recovered products should only be agricultural grade, and the price of agricultural grade ammonium chloride sold on the market is only half of the industrial grade, so how to reduce impurities in wastewater during pretreatment, so that It will be a very economical treatment method to recover industrial grade ammonium chloride after evaporation and crystallization.

Contents of the invention

An object of the present invention is to provide a composite coagulant capable of removing impurities such as heavy metals in rare earth high-concentration ammonia nitrogen wastewater.

Another object of the present invention is to provide a treatment method for using the composite coagulant to treat rare earth high-concentration ammonia nitrogen wastewater and recover industrial-grade ammonium chloride, which not only achieves the purpose of treating wastewater but also recovers valuable resources.

The object of the present invention is achieved by the following technical solutions: the composite coagulant is a mixed solution of ammonium oxalate, ammonium sulfate, heavy metal precipitant DTCR and polyacrylamide (PAM). According to the weight ratio of the four kinds of medicines: ammonium oxalate: ammonium sulfate: DTCR: PAM=0.6～3:0.4～1.5:1:0.01～0.03 Weigh the medicines and dissolve them in water, then mix and stir them evenly, and prepare the four kinds of medicines. A mixed solution with a mass concentration of 3.5% to 10%. Rare earth high-concentration ammonia nitrogen wastewater contains more oils, extractants, heavy metal elements and calcium ions. This composite coagulant is used to treat wastewater. Ammonium oxalate provides oxalate ions to precipitate calcium ions in wastewater, and ammonium sulfate provides sulfate ions. To remove barium ions in wastewater, DTCR strongly chelates heavy metal ions to form insoluble matter, which can form good flocculation, resulting in rapid sedimentation, and achieve the purpose of removing heavy metal ions. Polyacrylamide forms a "bridge" between the adsorbed particles ", to generate larger flocs, which is conducive to the sinking of particles and can effectively adsorb organic matter.

In order not to bring in other impurities when treating wastewater, the heavy metal precipitant DTCR in the composite coagulant of the present invention is: chelating group-NH-CSSNH ₄ type.

The treatment method and steps of using composite coagulant to treat waste water and recover industrial grade ammonium chloride are as follows:

a. The rare earth high-concentration ammonia nitrogen wastewater first enters the grease trap, so that the slick oil in the rare earth wastewater and the larger oil droplets in the dispersed oil rise to the surface, and the oil is scraped by the oil scraper to achieve the purpose of removing the slick oil, and then the wastewater Enter the air flotation chamber, and remove the emulsified oil and hydrophobic fine suspended solids in the wastewater by air flotation.

b. The degreased waste water enters the pH adjustment sedimentation tank, then adds concentrated ammonia water with a concentration of 25% to 30% to the waste water to adjust the pH to 7.5 to 8.5, and then adds 1 to 2g of PAM to each ^m3 of waste water to stir the reaction 10-15 minutes, stand still for 35-50 minutes, the generated sludge is discharged through the sludge discharge pipe at the bottom of the tank, and the supernatant and sludge filtrate enter the coagulation sedimentation tank.

c. Add 3-15L compound coagulant to the coagulation-sedimentation tank per ^m3 of wastewater, stir rapidly for 5-10min, then stir slowly for 10-15min and then let it stand for 30-40min. The generated sludge passes through the bottom of the pool The supernatant and sludge filtrate enter the pH adjustment tank, and then add concentrated hydrochloric acid with a mass concentration of 30% to 38% to the wastewater to adjust the pH to 2.5 to 4.

d. After adjusting the pH, the wastewater enters the activated carbon filter tower, and the filtration rate is controlled to be 3-5m/h to absorb and filter the residual heavy metals and trace oils in the wastewater. After the activated carbon treatment, the wastewater enters the evaporation and crystallization tower. Concentrate by evaporation under negative pressure.

Beneficial effects of the present invention:

a, the composite coagulant treatment method used in the present invention is simple, and cost is low, and after a treatment under the situation that multiple heavy metal ions can coexist, make various heavy metal ions and calcium ions in the wastewater reach a very small amount, even if It can also fully exert its effect on salts complexed with heavy metals (such as NH ₃ ), and has the characteristics of coarse flocs, fast sedimentation, fast dehydration, easy post-treatment, less sludge, stable and non-toxic, and does not bring other impurities into wastewater , No secondary pollution and other characteristics.

b, the process flow of the treatment method in the present invention is short, and the treatment is simple and easy. The ammonium chloride recovered by evaporation and crystallization of the waste water treated by the method can reach industrial-grade qualified products, and obtain great economic benefits at a relatively low cost. The profit not only solves the problem of high-concentration ammonia nitrogen wastewater pollution, but also recovers valuable substances, achieving high economic and environmental benefits.

Description of drawings

Fig. 1 is a schematic flow chart of a treatment method for recovering industrial-grade ammonium chloride from rare-earth high-concentration ammonia-nitrogen wastewater using a composite coagulant of the present invention.

Detailed ways

The technical solutions of the present invention will be further described in detail below in conjunction with the examples, and the scope of protection of the present invention is not limited to the following specific embodiments.

Examples of composite coagulants are as follows:

Example 1

Weigh 600g of ammonium oxalate, 200g of ammonium sulfate, 200g of heavy metal precipitant DTCR and 3g of PAM respectively, and then dissolve them in 13L of water in turn, stir and mix evenly to prepare a composite coagulant with a total mass concentration of 7.1%.

Example 2

Weigh 450g of ammonium oxalate, 150g of ammonium sulfate, 200g of heavy metal precipitant DTCR and 2g of PAM, and then dissolve them in 13L of water in turn, stir and mix evenly to prepare a composite coagulant with a total mass concentration of 5.8%.

The embodiment of the treatment method of using composite coagulant to process rare earth high concentration ammonia nitrogen wastewater to reclaim industrial grade ammonium chloride is as follows:

The numbers of the composite coagulants prepared in the above two application examples are sequentially No. 1 composite coagulant and No. 2 composite coagulant for treating sewage. The wastewater is taken from rare earth soap wastewater and ammonium bicarbonate precipitation mother liquor in a rare earth smelter, and its water quality characteristics are as follows:

Table 1 Water quality of rare earth soap wastewater (pH=0.47, [Cl ^- ]=96800mg/L, unit is mg/L)

_NH4 ⁺ oil Ca ²⁺ Na ⁺ Al ³⁺ Mn ²⁺ Cu ²⁺ Zn ²⁺ Pb ²⁺ Ba ²⁺ Cr ³⁺ Ni ²⁺ 48050 1580.5 200 42 56.3 twenty four 3.7 17 67.8 242 1.6 2.1

Table 2 Water Quality of Ammonium Bicarbonate Precipitation Mother Liquor (pH=6.47, [Cl ^- ]=27730mg/L, unit is mg/L)

_NH4 ⁺ oil Ca ²⁺ Na ⁺ Al ³⁺ Mn ²⁺ Cu ²⁺ Zn ²⁺ Pb ²⁺ Ba ²⁺ Cr ³⁺ Ni ²⁺ 13152 80.5 0.3 18.6 16.3 0.5 2.7 36 0.18 0.9 2.1 2

Example 3

a. Take 1m ³ rare earth soap wastewater and enter it into the slanted plate grease trap first, the wastewater residence time is 2.5h, make the slick oil in the rare earth wastewater and the oil droplets with larger particles in the dispersed oil rise to the surface, scrape off the upper layer of slick oil, Then the wastewater enters the jet-type air flotation chamber, and the emulsified oil and hydrophobic fine solid suspended matter in the wastewater are removed by air flotation. After this step, the content of oil and extractant is 80mg/L.

B, the waste water after degreasing enters the pH adjustment sedimentation tank, then adding 16L concentration to the waste water is the strong ammonia water of 30% to adjust the pH to be 8, then adds 1.5g PAM to the waste water and stirs the reaction for 15min, and leaves standstill for 40min, the produced The sludge is discharged through the sludge discharge pipe at the bottom of the tank, and the supernatant and sludge filtrate enter the coagulation sedimentation tank.

c. Add 13L No. 1 composite coagulant to the coagulation sedimentation tank, stir rapidly for 10 minutes, then stir slowly for 15 minutes and then let it stand for 40 minutes. The generated sludge is discharged through the sludge discharge pipe at the bottom of the tank, and the supernatant and sludge The filtrate enters the pH adjustment tank, and then 7L of concentrated hydrochloric acid with a mass concentration of 35% is added to the waste water to adjust the pH to 3.

d. After adjusting the pH, the wastewater enters the activated carbon filter tower, and the filtration rate is controlled to 3m/h to absorb and filter the residual heavy metals and trace oils in the wastewater. After the activated carbon treatment, the wastewater enters the evaporation crystallization tower under negative pressure. Concentrated by evaporation. The ammonia nitrogen concentration of the obtained distilled water is 13.5 mg/L, and the amount of ammonium chloride obtained is 150 kg, and the quality is shown in Table 3.

Table 3 gained ammonium chloride analysis data table

Industrial grade ammonium chloride index name First grade Qualified product The resulting ammonium chloride Ammonium chloride (NH ₄ Cl) content (on a dry basis), %, ≥ 99.3 99.0 99.1 Moisture,%, ≤ 0.7 1.0 - Residue on ignition, %, ≤ 0.4 0.4 0.38 Iron (Fe) content, %, ≤ 0.001 0.003 0.0025 Heavy metal (calculated as Pb) content, %, ≤ 0.0005 0.001 0.0008 Sulfate (as SO ₄ ) content, %, ≤ 0.02 - 0.01 pH value (200g/L solution, temperature 25°C) 4.0～5.8 4.0～5.8 4.9

Example 4

a. According to the actual amount of wastewater (4:1) of rare earth soap wastewater and ammonium bicarbonate precipitation mother liquor, ^1m3 mixed wastewater is first entered into the inclined plate grease trap, and the residence time of wastewater is 2.5h, so that the slick oil and dispersed oil in the wastewater The oil droplets with larger particles rise to the surface, scrape off the upper oil slick, and then the wastewater enters the jet-type air flotation chamber, and the emulsified oil and hydrophobic fine solid suspended matter in the wastewater are removed by air flotation. After this step, the oil and extracted The dose content is 73mg/L.

B, the waste water after degreasing enters the pH adjustment sedimentation tank, then adding 13L concentration to the waste water is the strong ammonia water of 30% to adjust the pH to be 8.05, then adds 1.5g PAM to the waste water and stirs the reaction for 15min, and leaves standstill for 40min, the produced The sludge is discharged through the sludge discharge pipe at the bottom of the tank, and the supernatant and sludge filtrate enter the coagulation sedimentation tank.

c. Add 13L No. 2 compound coagulant to the coagulation sedimentation tank, stir rapidly for 10 minutes, then stir slowly for 15 minutes and then let it stand for 40 minutes. The generated sludge is discharged through the sludge discharge pipe at the bottom of the tank, and the supernatant and sludge The filtrate enters the pH adjustment tank, and then 5.7 L of concentrated hydrochloric acid with a mass concentration of 35% is added to the waste water to adjust the pH to 3.1.

d. After adjusting the pH, the wastewater enters the activated carbon filter tower, and the filtration rate is controlled to 3m/h to absorb and filter the residual heavy metals and trace oils in the wastewater. After the activated carbon treatment, the wastewater enters the evaporation crystallization tower under negative pressure. Concentrated by evaporation. The ammonia nitrogen concentration of the obtained distilled water is 10.5 mg/L, and the amount of ammonium chloride obtained is 135 kg, and the quality is shown in Table 4.

Table 4 gained ammonium chloride analysis data table

Industrial grade ammonium chloride index name First grade Qualified product The resulting ammonium chloride Ammonium chloride (NH ₄ Cl) content (on a dry basis), %, ≥ 99.3 99.0 99.2 Moisture,%, ≤ 0.7 1.0 - Residue on ignition, %, ≤ 0.4 0.4 0.35

Iron (Fe) content, %, ≤ 0.001 0.003 0.0015 Heavy metal (calculated as Pb) content, %, ≤ 0.0005 0.001 0.0008 Sulfate (as SO ₄ ) content, %, ≤ 0.02 - 0.02 pH value (200g/L solution, temperature 25°C) 4.0～5.8 4.0～5.8 4.3

Claims (3)

1. one kind is used to handle the compound coagulant that rare-earth highly concentrated ammonia nitrogen waste water reclaims industrial grade ammonium chloride, it is characterized in that: this compound coagulant is the mixed solution of ammonium oxalate, ammonium sulfate, heavy metal precipitator DTCR and polyacrylamide (PAM), by four kinds of medicament weight proportions promptly: it is soluble in water that ammonium oxalate: ammonium sulfate: DTCR: PAM=0.6～3: 0.4～1.5: 1: 0.01～0.03 takes by weighing medicament, mixing and stirring then is mixed with four kinds of medicament total mass concentrations and is 3.5%～10% mixed solution.

2. one kind is used the described compound coagulant of claim 1 to handle the treatment process that rare-earth highly concentrated ammonia nitrogen waste water reclaims industrial grade ammonium chloride, it is characterized in that:

A, rare-earth highly concentrated ammonia nitrogen waste water at first enter oil trap, make that the bigger oil droplet of particle rises to the surface in oil slick in the RE waste water and the dispersed oil, by the Oil scraper frizing to reach the purpose of removing oil slick, waste water enters gas-floating chamber then, by oil in water emulsion and the trickle suspended solid of hydrophobicity in the air supporting removal waste water;

B, the waste water after oil removing enter the pH regulator settling tank, and adding concentration then and be 25%～30% strong aqua in waste water, to regulate pH be 7.5～8.5, again to every m ³Add 1～2g PAM stirring reaction, 10～15min in the waste water, leave standstill 35～50min, the shore pipe of the mud of generation at the bottom of the pond discharged, and supernatant liquor and mud filtrate enter coagulative precipitation tank;

C, in the coagulative precipitation tank by every m ³Add 3～15L compound coagulant in the waste water, stir 5～10min fast, leave standstill 30～40min after stirring 10～15min at a slow speed then, the shore pipe of the mud that produces at the bottom of the pond discharged, supernatant liquor and mud filtrate enter the pH regulator pond, and adding mass concentration then and be 30%～38% concentrated hydrochloric acid in waste water, to regulate pH be 2.5～4;

D, the waste water after regulating pH enter active carbon filter tower again, and the control filtering velocity is 3～5m/h, and heavy metal and the micro-oily substance of remnants enter evaporating and crystallizing tower evaporation concentration under condition of negative pressure again through the waste water after the activated carbon treatment in absorption and the filtered wastewater.

3. according to claim 1 being used to handled the compound coagulant that rare-earth highly concentrated ammonia nitrogen waste water reclaims industrial grade ammonium chloride, and it is characterized in that: the heavy metal precipitator DTCR in the compound coagulant is: chelate group-NH-CSSNH ₄Pattern.

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