CN112158931A - Method for removing calcium and magnesium in ammonium chloride wastewater - Google Patents
Method for removing calcium and magnesium in ammonium chloride wastewater Download PDFInfo
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- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 title claims abstract description 172
- 235000019270 ammonium chloride Nutrition 0.000 title claims abstract description 86
- 239000002351 wastewater Substances 0.000 title claims abstract description 72
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 239000011575 calcium Substances 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 48
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 239000011777 magnesium Substances 0.000 title claims abstract description 32
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 32
- 229910052791 calcium Inorganic materials 0.000 title claims abstract description 31
- 239000000243 solution Substances 0.000 claims abstract description 70
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims abstract description 45
- 235000019838 diammonium phosphate Nutrition 0.000 claims abstract description 45
- 239000007788 liquid Substances 0.000 claims abstract description 43
- 239000007787 solid Substances 0.000 claims abstract description 39
- 239000012452 mother liquor Substances 0.000 claims abstract description 35
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims abstract description 30
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims abstract description 30
- 239000001099 ammonium carbonate Substances 0.000 claims abstract description 30
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 24
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 24
- 238000000926 separation method Methods 0.000 claims abstract description 14
- 239000010413 mother solution Substances 0.000 claims abstract description 7
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 37
- 229910001425 magnesium ion Inorganic materials 0.000 claims description 37
- 229910001424 calcium ion Inorganic materials 0.000 claims description 35
- 238000001704 evaporation Methods 0.000 claims description 17
- 230000001105 regulatory effect Effects 0.000 claims description 17
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 16
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 16
- 150000002910 rare earth metals Chemical class 0.000 claims description 16
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims description 15
- 238000001914 filtration Methods 0.000 claims description 14
- 239000002699 waste material Substances 0.000 claims description 14
- 238000006243 chemical reaction Methods 0.000 claims description 11
- 238000003723 Smelting Methods 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 8
- 230000008025 crystallization Effects 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 6
- 230000003750 conditioning effect Effects 0.000 claims description 5
- 239000005696 Diammonium phosphate Substances 0.000 description 10
- 239000000395 magnesium oxide Substances 0.000 description 10
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 10
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 8
- 239000000292 calcium oxide Substances 0.000 description 6
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 6
- 230000008020 evaporation Effects 0.000 description 6
- 238000001223 reverse osmosis Methods 0.000 description 4
- 229910019142 PO4 Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000001488 sodium phosphate Substances 0.000 description 2
- 229910000162 sodium phosphate Inorganic materials 0.000 description 2
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- MXZRMHIULZDAKC-UHFFFAOYSA-L ammonium magnesium phosphate Chemical compound [NH4+].[Mg+2].[O-]P([O-])([O-])=O MXZRMHIULZDAKC-UHFFFAOYSA-L 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 208000028659 discharge Diseases 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229940085991 phosphate ion Drugs 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000012716 precipitator Substances 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- 239000000344 soap Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052567 struvite Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
- C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Removal Of Specific Substances (AREA)
Abstract
The invention discloses a method for removing calcium and magnesium in ammonium chloride wastewater, which comprises the following steps: 1) adjusting the pH value of the ammonium chloride wastewater by using ammonia water to obtain a first adjusting solution, then reacting the first adjusting solution with an ammonium bicarbonate solid or an ammonium bicarbonate solution, and carrying out solid-liquid separation to obtain a first solid and a first mother solution; 2) and adjusting the pH value of the first mother liquor by using ammonia water to obtain a second adjusting solution, then reacting the second adjusting solution with diammonium hydrogen phosphate solid or diammonium hydrogen phosphate solution, and carrying out solid-liquid separation to obtain a second solid and a second mother liquor. The method of the invention can obviously reduce the cost.
Description
Technical Field
The invention relates to a method for removing calcium and magnesium ions, in particular to a method for removing calcium and magnesium in ammonium chloride wastewater.
Background
The extraction link and the carbon precipitation link in the rare earth smelting process both generate a large amount of ammonium chloride waste liquid. And a part of production enterprises adopt a multi-effect evaporation mode to recover the ammonium chloride. The content of calcium oxide (CaO) in the ammonium chloride waste liquid is about 1.0g/L, and the content of magnesium oxide (MgO) in the ammonium chloride waste liquid is about 1.0 g/L. As the system is evaporated for a long time, the content of calcium oxide (CaO) in the formed ammonium chloride concentrated water reaches 50-70 g/L, and the content of magnesium oxide (MgO) reaches 30-50 g/L, thus seriously affecting the evaporation efficiency of the system. The phenomena of small crystallization particles of the system, difficult crystallization of the system, crystallization hanging of a shutter of a cooling tower, wall hanging of the system, agglomeration of three effects and the like are caused. Because the calcium and magnesium pretreatment process is not available, the ammonium chloride concentrated water in the system can only be discharged regularly, which not only reduces the working efficiency, but also increases unnecessary working procedures and wastes a large amount of time.
CN1552638A discloses an ammonium chloride wastewater zero discharge treatment process. Comprises that ammonium chloride solution enters a pretreatment device to ensure that the treated water quality SDI is less than 3 and the turbidity is less than 0.1 NTU. Entering a multistage multi-section reverse osmosis membrane group. The concentration of the ammonium chloride in the concentrated water treated by the reverse osmosis membrane group can reach 5-8%. And (4) the concentrated water from the reverse osmosis device enters a distillation evaporation device for further concentration until the concentration of ammonium chloride is 36-45%. And (3) further concentrating the treated ammonium chloride concentrated solution, cooling and crystallizing the ammonium chloride concentrated solution in a crystallizing device to produce ammonium chloride, treating the crystallized mother solution by a decalcification and magnesium removal device, returning the crystallized mother solution to an evaporating device, and circularly concentrating the crystallized mother solution and the concentrated effluent of the reverse osmosis membrane group in the evaporating device. However, the patent document does not mention how to remove calcium and magnesium.
CN103964588A discloses a method for separating calcium ions and magnesium ions in ammonium chloride wastewater. Adding soluble phosphate into the wastewater to introduce phosphate radical, generating crystal form precipitates of calcium phosphate and magnesium ammonium phosphate, and carrying out solid-liquid separation to further remove calcium and magnesium ions in the wastewater. The soluble phosphate is diammonium hydrogen phosphate or sodium phosphate. However, the amount of diammonium phosphate or sodium phosphate used in this patent document is very large, which is 0.9 to 1.1 times of the theoretical consumption of diammonium phosphate by calcium and magnesium ions in ammonium chloride wastewater, resulting in high cost.
Weidi et al (analysis and control of influence factors of a process for removing calcium and magnesium by diammonium phosphate, rare earth, vol.39, 5 th stage, 10 months in 2018) studied that saponification wastewater generated by a rare earth extraction and separation process aiming at an ammonium soap system can be pretreated by an environment-friendly process by using diammonium phosphate as a precipitator so as to reduce the concentration of calcium and magnesium ions in the wastewater. Research shows that the optimal process control conditions are as follows: after the pH value of the reaction system is adjusted to 7.5, the diammonium hydrogen phosphate with the theoretical calculation amount is added, and the reaction is carried out for 15min at normal temperature by using stirring strength as high as possible under the condition allowed by equipment conditions, so that the removal rate of calcium and magnesium ions is high. However, the diammonium phosphate used in the document is large in dosage and high in cost.
Disclosure of Invention
In view of the above, the present invention provides a method for removing calcium and magnesium from ammonium chloride wastewater. The removal method reduces the dosage of diammonium hydrogen phosphate and obviously reduces the cost on the basis of ensuring the removal rate of calcium and magnesium. Furthermore, the residual concentration of phosphate ions in the treated ammonium chloride wastewater obtained by the invention is low. The purpose of the invention is realized by the following technical scheme.
The invention provides a method for removing calcium and magnesium in ammonium chloride wastewater, which comprises the following steps:
1) adjusting the pH value of the ammonium chloride wastewater by using ammonia water to obtain a first adjusting solution, then reacting the first adjusting solution with an ammonium bicarbonate solid or an ammonium bicarbonate solution, and carrying out solid-liquid separation to obtain a first solid and a first mother solution;
wherein, in the ammonium chloride wastewater, the CaO content is more than 30g/L, and the MgO content is more than 15 g/L;
2) adjusting the pH value of the first mother liquor by using ammonia water to obtain a second adjusting solution, then reacting the second adjusting solution with diammonium hydrogen phosphate solid or diammonium hydrogen phosphate solution, and carrying out solid-liquid separation to obtain a second solid and a second mother liquor; and in the second mother liquor, the concentration of phosphate ions is less than or equal to 1 g/L.
According to the method for removing calcium and magnesium in ammonium chloride wastewater provided by the invention, preferably, in the step 1), the concentration of the ammonia water is 10-25 wt%, and the pH value is adjusted to 6-9.
According to the method for removing calcium and magnesium from ammonium chloride wastewater, preferably, in the step 1), ammonium bicarbonate solid is adopted to react with the first regulating solution, and the amount of the ammonium bicarbonate solid is 75-180% of the mass of the ammonium bicarbonate theoretically consumed by calcium ions and magnesium ions in the first regulating solution.
According to the method for removing calcium and magnesium in ammonium chloride wastewater, preferably, in the step 1), the reaction time is 25-95 min, and the reaction temperature is 15-40 ℃.
According to the method for removing calcium and magnesium in ammonium chloride wastewater provided by the invention, preferably, in the step 2), the concentration of the ammonia water is 10-25 wt%, and the pH value is adjusted to 6-9.
According to the method for removing calcium and magnesium in ammonium chloride wastewater, preferably, in the step 2), a diammonium hydrogen phosphate solution is adopted to react with the second regulating solution, the concentration of the diammonium hydrogen phosphate solution is 350-500 g/L, and the using amount of diammonium hydrogen phosphate is 50-90% of the mass of diammonium hydrogen phosphate theoretically consumed by calcium ions and magnesium ions in the second regulating solution.
According to the method for removing calcium and magnesium from ammonium chloride wastewater, in the step 2), preferably, a diammonium hydrogen phosphate solution is dropwise added into the second regulating solution at a constant speed.
According to the method for removing calcium and magnesium in ammonium chloride wastewater, the dropping time in the step 2) is preferably 5-60 min.
According to the method for removing calcium and magnesium in ammonium chloride wastewater, preferably, in the step 2), the reaction time is 25-95 min, and the reaction temperature is 15-40 ℃.
According to the method for removing calcium and magnesium in ammonium chloride wastewater, preferably, in the step 1) and the step 2), the solid-liquid separation is filtration; the ammonium chloride wastewater is concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth; the second mother liquor can be used for recovering ammonium chloride through evaporative crystallization.
The method adopts a two-step method to remove calcium and magnesium ions, namely, ammonium bicarbonate is used for removing part of the calcium and magnesium ions, and then diammonium hydrogen phosphate is used for removing part of the calcium and magnesium ions. The method of the invention can greatly reduce the dosage of diammonium hydrogen phosphate on the basis of ensuring the removal rate of calcium and magnesium ions, thereby obviously reducing the cost. Moreover, the residual concentration of phosphate ions in the obtained mother liquor can be greatly reduced.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
The method for removing calcium and magnesium in ammonium chloride wastewater comprises the following steps: (1) a step of reacting with ammonium bicarbonate; and (2) a step of reacting with diammonium hydrogen phosphate. As described in detail below.
< step of reaction with ammonium bicarbonate >
And adjusting the pH value of the ammonium chloride wastewater by using ammonia water to obtain a first adjusting solution.
The ammonium chloride waste water is concentrated waste water obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth. In the ammonium chloride wastewater, the CaO content is more than 30g/L, and the MgO content is more than 15 g/L. Preferably, the CaO content is greater than 40g/L and the MgO content is greater than 20 g/L. More preferably, the CaO content is 50g/L or more and the MgO content is 30g/L or more. Under the normal condition, the efficiency of an evaporation system is greatly reduced due to the higher concentration of calcium and magnesium ions in the concentrated wastewater of ammonium chloride, and the concentrated water of ammonium chloride in the system can only be discharged regularly, so that the working efficiency is reduced, and the resource waste is caused. The inventor discovers through research and experiments that the recycling of the ammonium chloride wastewater can be realized by effectively removing calcium and magnesium ions in the ammonium chloride wastewater.
The concentration of the ammonia water may be 10 to 25 wt%, preferably 12 to 25 wt%, and more preferably 15 to 25 wt%.
The pH value of the first adjusting liquid can be 6-9, preferably 7-9, and more preferably 8-9. By controlling the pH range of the first control solution in this manner, the removal rate of calcium and magnesium ions can be improved.
In the invention, the first regulating solution reacts with ammonium bicarbonate solid or ammonium bicarbonate solution, and solid-liquid separation is carried out to obtain first solid and first mother solution. Preferably, the first conditioning liquid is reacted with an ammonium bicarbonate solid. According to one embodiment of the present invention, ammonium bicarbonate solid is added to the first conditioning solution to perform the reaction. The reaction time is 25-95 min, preferably 30-90 min, and more preferably 30-60 min. The reaction temperature is 15-40 ℃, preferably 15-35 ℃, and more preferably 20-30 ℃.
The dosage of the ammonium bicarbonate is 75-180%, preferably 100-160%, and more preferably 120-160% of the mass of the ammonium bicarbonate theoretically consumed by the calcium ions and the magnesium ions in the first regulating solution. This ensures the removal rate of calcium and magnesium ions. The amount of calcium ions and magnesium ions in the first regulating solution is the amount of calcium ions and magnesium ions in the ammonium chloride wastewater.
The solid-liquid separation is not particularly limited, and filtration is preferable.
The first solid is the resulting calcium and magnesium containing material. In the first mother liquor, the content of CaO and the content of MgO are both reduced to a certain extent. If the ammonium bicarbonate is simply adopted to remove calcium ions and magnesium ions in the ammonium chloride wastewater, the removal rate of the calcium ions and the magnesium ions is low, especially the removal rate of the magnesium ions is low, and the target effect cannot be achieved.
< step of reacting with diammonium phosphate >
And adjusting the pH value of the first mother liquor by using ammonia water to obtain a second adjusting solution.
The concentration of the ammonia water may be 10 to 25 wt%, preferably 15 to 25 wt%, and more preferably 15 to 20 wt%.
The pH value of the second regulating solution can be 6-9, preferably 7-9, and more preferably 8-9. By controlling the pH value of the second adjusting liquid to this range, the removal rate of calcium and magnesium ions can be improved.
In the invention, the second regulating solution reacts with diammonium hydrogen phosphate solid or diammonium hydrogen phosphate solution, and solid-liquid separation is carried out to obtain a second solid and a second mother liquor. Preferably, the second conditioning solution is reacted with a solution of diammonium phosphate. According to one embodiment of the invention, the diammonium hydrogen phosphate solution is dropwise added into the second regulating solution at a constant speed for reaction. The dripping time is 5-60 min, preferably 10-50 min, and more preferably 15-40 min. The reaction time is 25-95 min, preferably 30-90 min, and more preferably 30-60 min. The reaction temperature is 15-40 ℃, preferably 15-35 ℃, and more preferably 20-30 ℃. Thus being beneficial to improving the removal rate of calcium and magnesium ions.
The dosage of the diammonium phosphate is 50-90%, preferably 60-90%, and more preferably 65-80% of the mass of the diammonium phosphate theoretically consumed by calcium ions and magnesium ions in the second regulating solution. Because the industrial price of the diammonium hydrogen phosphate is higher, the cost for removing the ammonium chloride wastewater by simply adopting the diammonium hydrogen phosphate is higher. Through research and experiments, the inventor finds that ammonium bicarbonate can be used for removing a part of calcium and magnesium ions in the ammonium chloride wastewater, and then diammonium hydrogen phosphate is used for removing the calcium and magnesium ions in the first mother liquor (namely the second regulating solution). Therefore, the integral removal rate of calcium and magnesium ions can be ensured, and the cost can be obviously reduced. But also can control the residual quantity of phosphate ions in the obtained second mother liquor after treatment, and ensure the normal operation of the subsequent process. The method has guiding significance for actual production.
The solid-liquid separation is filtration. The second solid is the resulting material containing calcium and magnesium ions.
The second mother liquor can be used for recovering ammonium chloride through evaporative crystallization. Because the content of calcium ions and magnesium ions in the second mother liquor is greatly reduced, the evaporation efficiency is basically not influenced when evaporation crystallization is carried out. Can realize the recycling of the ammonium chloride waste water and save resources. In addition, because the residual concentration of phosphate ions in the second mother liquor is low, when the second mother liquor is evaporated, crystallized and recycled to ammonium chloride, recycled water can be obtained, and the recycled water can enter the front-end rare earth leaching process. If the phosphate ion concentration is high, rare earth loss will result. The reuse water obtained by the method of the invention has lower concentration of phosphate ions, and basically does not cause the loss of rare earth. Therefore, the ammonium chloride wastewater treated by the method of the invention can not only recover ammonium chloride in a normal crystallization way, but also apply the reuse water to the front-end rare earth leaching process. And the cyclic utilization of resources is realized.
In the following examples and comparative examples:
the ammonium chloride wastewater is concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth.
In the ammonium chloride wastewater, the CaO content is 50g/L, the MgO content is 25g/L, and the pH value of the ammonium chloride wastewater is 3.5.
Example 1
Adjusting the pH value of ammonium chloride wastewater (concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth) to 6 by using 20 wt% of ammonia water to obtain first adjusting liquid, then adding ammonium bicarbonate solid into the first adjusting liquid, reacting for 60min at 25 ℃, and filtering to obtain first solid and first mother liquid.
And (3) adjusting the pH value of the first mother liquor to 8 by using 20 wt% of ammonia water to obtain a second adjusting solution, then dropwise adding 400g/L of diammonium hydrogen phosphate solution into the second adjusting solution at a constant speed for 5min, reacting at 25 ℃ for 60min after the dropwise adding is finished, and filtering to obtain a second solid and a second mother liquor, wherein the concentration of phosphate ions in the second mother liquor is 1 g/L.
Example 2
Adjusting the pH value of ammonium chloride wastewater (concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth) to 8 by using 20 wt% of ammonia water to obtain first adjusting liquid, then adding ammonium bicarbonate solid into the first adjusting liquid, reacting for 60min at 25 ℃, and filtering to obtain first solid and first mother liquid.
And (3) adjusting the pH value of the first mother liquor to 9 by using 20 wt% of ammonia water to obtain a second adjusting solution, then dropwise adding 450g/L of diammonium hydrogen phosphate solution into the second adjusting solution at a constant speed for 60min, reacting at 25 ℃ for 60min after the dropwise adding is finished, and filtering to obtain a second solid and a second mother liquor, wherein the concentration of phosphate ions in the second mother liquor is 0.5 g/L.
Example 3
Adjusting the pH value of ammonium chloride wastewater (concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth) to 9 by using 20 wt% of ammonia water to obtain first adjusting liquid, then adding ammonium bicarbonate solid into the first adjusting liquid, reacting for 30min at 25 ℃, and filtering to obtain first solid and first mother liquid.
And (3) adjusting the pH value of the first mother liquor to 9 by using 20 wt% of ammonia water to obtain a second adjusting solution, then dropwise adding 450g/L of diammonium hydrogen phosphate solution into the second adjusting solution at a constant speed for 60min, reacting at 25 ℃ for 90min after the dropwise adding is finished, and filtering to obtain a second solid and a second mother liquor, wherein the concentration of phosphate ions in the second mother liquor is less than 0.01 g/L.
Example 4
Adjusting the pH value of ammonium chloride wastewater (concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth) to 8 by using 20 wt% of ammonia water to obtain first adjusting liquid, then adding ammonium bicarbonate solid into the first adjusting liquid, reacting for 60min at 25 ℃, and filtering to obtain first solid and first mother liquid.
And (3) adjusting the pH value of the first mother liquor to 8 by using 20 wt% of ammonia water to obtain a second adjusting solution, then dropwise adding 400g/L of diammonium hydrogen phosphate solution into the second adjusting solution at a constant speed for 30min, reacting at 25 ℃ for 60min after the dropwise adding is finished, and filtering to obtain a second solid and a second mother liquor, wherein the concentration of phosphate ions in the second mother liquor is less than 0.01 g/L.
Comparative example 1
Adjusting the pH value of ammonium chloride wastewater (concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth) to 5 by using 20 wt% of ammonia water to obtain first adjusting liquid, then adding ammonium bicarbonate solid into the first adjusting liquid, reacting for 60min at 25 ℃, and filtering to obtain first solid and first mother liquid.
And (3) adjusting the pH value of the first mother liquor to 5 by using 20 wt% of ammonia water to obtain a second adjusting solution, then dropwise adding 450g/L of diammonium hydrogen phosphate solution into the second adjusting solution at a constant speed, reacting for 60min at 25 ℃, and filtering to obtain a second solid and a second mother liquor, wherein the concentration of phosphate ions in the second mother liquor is 12 g/L.
TABLE 1
Note: the dosage of the ammonium bicarbonate is the mass percentage of the ammonium bicarbonate which accounts for the theoretical consumption of calcium ions and magnesium ions in the ammonium chloride wastewater. The amount of the diammonium hydrogen phosphate is the mass percentage of the diammonium hydrogen phosphate which accounts for the theoretical consumption of calcium ions and magnesium ions in the second regulating solution.
TABLE 2
Note: the cost saving ratio was based on comparative example 1.
As can be seen from the table, the method of the invention can remove most of calcium ions and magnesium ions in the ammonium chloride wastewater, and particularly, the removal rate of magnesium ions is greatly improved. Compared with the traditional method for removing calcium and magnesium ions by adopting diammonium phosphate, the method provided by the invention can obviously reduce the cost and greatly reduce the residue of phosphate ions.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (10)
1. A method for removing calcium and magnesium in ammonium chloride wastewater is characterized by comprising the following steps:
1) adjusting the pH value of the ammonium chloride wastewater by using ammonia water to obtain a first adjusting solution, then reacting the first adjusting solution with an ammonium bicarbonate solid or an ammonium bicarbonate solution, and carrying out solid-liquid separation to obtain a first solid and a first mother solution;
wherein, in the ammonium chloride wastewater, the CaO content is more than 30g/L, and the MgO content is more than 15 g/L;
2) adjusting the pH value of the first mother liquor by using ammonia water to obtain a second adjusting solution, then reacting the second adjusting solution with diammonium hydrogen phosphate solid or diammonium hydrogen phosphate solution, and carrying out solid-liquid separation to obtain a second solid and a second mother liquor; and in the second mother liquor, the concentration of phosphate ions is less than or equal to 1 g/L.
2. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 1, wherein in the step 1), the concentration of the ammonia water is 10 to 25 wt%, and the pH value is adjusted to 6 to 9.
3. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 2, wherein in the step 1), ammonium bicarbonate solid is adopted to react with the first regulating solution, and the amount of the ammonium bicarbonate solid is 75-180% of the theoretical consumption mass of ammonium bicarbonate by calcium ions and magnesium ions in the first regulating solution.
4. The method for removing calcium and magnesium in ammonium chloride wastewater according to claim 1, wherein in the step 1), the reaction time is 25-95 min, and the reaction temperature is 15-40 ℃.
5. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 1, wherein in the step 2), the concentration of the ammonia water is 10 to 25 wt%, and the pH value is adjusted to 6 to 9.
6. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 5, wherein in the step 2), a diammonium hydrogen phosphate solution is adopted to react with the second conditioning solution, the concentration of the diammonium hydrogen phosphate solution is 350-500 g/L, and the dosage of diammonium hydrogen phosphate is 50-90% of the mass of diammonium hydrogen phosphate theoretically consumed by calcium ions and magnesium ions in the second conditioning solution.
7. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 6, wherein in the step 2), a diammonium hydrogen phosphate solution is dropwise added into the second regulating solution at a constant speed.
8. The method for removing calcium and magnesium from ammonium chloride wastewater according to claim 7, wherein the dropping time in the step 2) is 5-60 min.
9. The method for removing calcium and magnesium in ammonium chloride wastewater according to claim 1, wherein in the step 2), the reaction time is 25-95 min, and the reaction temperature is 15-40 ℃.
10. The method for removing calcium and magnesium from ammonium chloride wastewater according to any one of claims 1 to 9, wherein in the step 1) and the step 2), the solid-liquid separation is filtration; the ammonium chloride wastewater is concentrated wastewater obtained by evaporating and crystallizing ammonium chloride waste liquid obtained by smelting rare earth; the second mother liquor can be used for recovering ammonium chloride through evaporative crystallization.
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| CN103964588A (en) * | 2014-04-30 | 2014-08-06 | 内蒙古包钢稀土(集团)高科技股份有限公司 | Method for separating calcium ions and magnesium ions from ammonium chloride wastewater |
| CN109867297A (en) * | 2017-12-05 | 2019-06-11 | 南风化工集团股份有限公司 | A method of with calcium and magnesium in phosphate removal sodium sulphate type bittern |
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| CN103964588A (en) * | 2014-04-30 | 2014-08-06 | 内蒙古包钢稀土(集团)高科技股份有限公司 | Method for separating calcium ions and magnesium ions from ammonium chloride wastewater |
| CN109867297A (en) * | 2017-12-05 | 2019-06-11 | 南风化工集团股份有限公司 | A method of with calcium and magnesium in phosphate removal sodium sulphate type bittern |
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