CN117383756A - Zero-emission treatment method for sulfuric acid process titanium dioxide wastewater - Google Patents
Zero-emission treatment method for sulfuric acid process titanium dioxide wastewater Download PDFInfo
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- CN117383756A CN117383756A CN202311537981.9A CN202311537981A CN117383756A CN 117383756 A CN117383756 A CN 117383756A CN 202311537981 A CN202311537981 A CN 202311537981A CN 117383756 A CN117383756 A CN 117383756A
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- reverse osmosis
- sulfuric acid
- titanium dioxide
- nanofiltration
- concentrated solution
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 title claims abstract description 80
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 57
- 239000002351 wastewater Substances 0.000 title claims abstract description 45
- 239000004408 titanium dioxide Substances 0.000 title claims abstract description 30
- 230000008569 process Effects 0.000 title claims abstract description 24
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 132
- 238000001728 nano-filtration Methods 0.000 claims abstract description 54
- 239000007788 liquid Substances 0.000 claims abstract description 52
- 239000012528 membrane Substances 0.000 claims abstract description 42
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000000706 filtrate Substances 0.000 claims abstract description 26
- 239000000126 substance Substances 0.000 claims abstract description 24
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000011575 calcium Substances 0.000 claims abstract description 19
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 19
- 238000003825 pressing Methods 0.000 claims abstract description 19
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 17
- 238000001914 filtration Methods 0.000 claims abstract description 16
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 8
- 238000000926 separation method Methods 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 4
- 235000010215 titanium dioxide Nutrition 0.000 claims description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 40
- 229910001424 calcium ion Inorganic materials 0.000 claims description 35
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 27
- 239000002455 scale inhibitor Substances 0.000 claims description 22
- 230000001276 controlling effect Effects 0.000 claims description 18
- 230000001105 regulatory effect Effects 0.000 claims description 15
- 238000000108 ultra-filtration Methods 0.000 claims description 14
- 150000002500 ions Chemical class 0.000 claims description 13
- 238000006386 neutralization reaction Methods 0.000 claims description 13
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 12
- 238000011084 recovery Methods 0.000 claims description 11
- 238000004064 recycling Methods 0.000 claims description 9
- 239000013067 intermediate product Substances 0.000 claims description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical group [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 6
- 239000011574 phosphorus Substances 0.000 claims description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims description 6
- 239000001488 sodium phosphate Substances 0.000 claims description 6
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 claims description 6
- 230000002378 acidificating effect Effects 0.000 claims description 4
- 239000012141 concentrate Substances 0.000 claims description 3
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 claims description 3
- 229910000403 monosodium phosphate Inorganic materials 0.000 claims description 3
- 235000019799 monosodium phosphate Nutrition 0.000 claims description 3
- 235000011007 phosphoric acid Nutrition 0.000 claims description 3
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 claims description 3
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 claims description 3
- 229910000162 sodium phosphate Inorganic materials 0.000 claims description 3
- 235000011008 sodium phosphates Nutrition 0.000 claims description 3
- 229940048086 sodium pyrophosphate Drugs 0.000 claims description 3
- 235000019818 tetrasodium diphosphate Nutrition 0.000 claims description 3
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 3
- 238000001704 evaporation Methods 0.000 abstract description 4
- 230000008020 evaporation Effects 0.000 abstract description 4
- 150000003017 phosphorus Chemical class 0.000 abstract description 3
- 238000006073 displacement reaction Methods 0.000 abstract 1
- -1 sulfate radicals Chemical class 0.000 description 37
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 29
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical class [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 21
- 239000012065 filter cake Substances 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 238000001556 precipitation Methods 0.000 description 9
- 239000005997 Calcium carbide Substances 0.000 description 8
- CLZWAWBPWVRRGI-UHFFFAOYSA-N tert-butyl 2-[2-[2-[2-[bis[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]amino]-5-bromophenoxy]ethoxy]-4-methyl-n-[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]anilino]acetate Chemical compound CC1=CC=C(N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)C(OCCOC=2C(=CC=C(Br)C=2)N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)=C1 CLZWAWBPWVRRGI-UHFFFAOYSA-N 0.000 description 8
- 238000004537 pulping Methods 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 6
- 229910001415 sodium ion Inorganic materials 0.000 description 6
- 229910001425 magnesium ion Inorganic materials 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- CADZRPOVAQTAME-UHFFFAOYSA-L calcium;hydroxy phosphate Chemical compound [Ca+2].OOP([O-])([O-])=O CADZRPOVAQTAME-UHFFFAOYSA-L 0.000 description 4
- 208000028659 discharge Diseases 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000010802 sludge Substances 0.000 description 4
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- 150000001450 anions Chemical class 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000002893 slag Substances 0.000 description 3
- 229910000406 trisodium phosphate Inorganic materials 0.000 description 3
- 235000019801 trisodium phosphate Nutrition 0.000 description 3
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 235000012255 calcium oxide Nutrition 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010612 desalination reaction Methods 0.000 description 2
- 239000010440 gypsum Substances 0.000 description 2
- 229910052602 gypsum Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-L Phosphate ion(2-) Chemical compound OP([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-L 0.000 description 1
- VDIQGOWLVYFDOU-UHFFFAOYSA-H [Ca+]O.[Ca+]O.[Ca+]O.[O-]P([O-])([O-])=O Chemical compound [Ca+]O.[Ca+]O.[Ca+]O.[O-]P([O-])([O-])=O VDIQGOWLVYFDOU-UHFFFAOYSA-H 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 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
- 238000004140 cleaning Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 229960004887 ferric hydroxide Drugs 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229910001414 potassium ion Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 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
- 238000004065 wastewater treatment Methods 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
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- 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
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
-
- 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
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- 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
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- 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
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- 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
- C02F2101/20—Heavy metals or heavy metal compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a method for zero emission treatment of sulfuric acid process titanium dioxide wastewater, which comprises the following steps: s1, neutralizing sulfuric acid process titanium dioxide wastewater by adopting a calcium-containing alkaline substance, and then press-filtering the neutralized material; s2, performing precise filtration on the filter liquor after filter pressing, and then concentrating the filter liquor in a reverse osmosis system to obtain reverse osmosis concentrated liquor I and reverse osmosis clear liquor I; s3, adding the reverse osmosis concentrated solution I into a phosphoric acid source for displacement reaction, and then carrying out solid-liquid separation; s4, sequentially treating the filtrate obtained after the solid-liquid separation in the step S3 through a nanofiltration system and a reverse osmosis system. The method utilizes the membrane system and the phosphorus salt to remove calcium on the premise of not utilizing evaporation concentration, realizes zero emission of titanium dioxide wastewater by the sulfuric acid method, and creates certain benefits.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for zero discharge treatment of sulfuric acid process titanium dioxide wastewater.
Background
A large amount of wastewater is generated in the production process of titanium dioxide by the sulfuric acid method, and the wastewater contains more sulfate radicals, calcium ions, iron ions and the like, so that the wastewater can be regarded as saturated calcium sulfate solution, and the common treatment method in the prior art is direct discharge or membrane treatment. In the discharging process, partial calcium sulfate crystals can be separated out from the pipeline due to the reduction of the temperature, so that the pipeline is blocked, and the cleaning difficulty of the pipeline is increased; with the continuous improvement of environmental protection requirements, the external discharge is not allowed in many cases, so that membrane treatment and MVR treatment are needed, a certain amount of concentrated water can be generated by a common membrane treatment system, zero emission cannot be completely achieved, MVR is needed to be utilized for distilling the concentrated water, and after salt in the concentrated water is separated out, evaporated condensate water is recycled; however, this treatment mode can cause higher treatment cost, and simultaneously, because both membrane treatment and MVR have higher requirements on water quality, for example, because of the existence of concentrated solution in a membrane treatment system, the front end is required to remove easily-scaling substances, and MVR also needs to remove easily-scaling substances in order to maximally utilize heat energy, and meanwhile, MVR also has certain requirements on salinity, the higher the content of salt impurities, or the more the variety of salinity, the higher the requirements on components such as MVR crystallizer.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provides a method for zero discharge treatment of titanium dioxide wastewater by a sulfuric acid method.
The invention aims at realizing the following technical scheme:
a method for zero emission treatment of sulfuric acid process titanium dioxide wastewater comprises the following steps:
s1, neutralizing titanium dioxide wastewater by a sulfuric acid method by adopting a calcium-containing alkaline substance, controlling the pH of a terminal point to be 8-9, and then press-filtering the neutralized material;
s2, performing precise filtration on the filtrate subjected to the filter pressing in the step S1, adjusting the pH value of the filtrate subjected to the precise filtration to be 6.0-7.0, and concentrating the filtrate in a reverse osmosis system to obtain reverse osmosis concentrated solution I and reverse osmosis clear solution I; controlling the reverse osmosis recovery rate to be 40-60%;
s3, regulating the pH value of the reverse osmosis concentrated solution I to 10.5-12.0, adding a phosphoric acid source into the reverse osmosis concentrated solution I with the pH value regulated for reaction, keeping the pH value of a system to be more than or equal to 10.5 in the reaction process, and then carrying out solid-liquid separation; the reverse osmosis clear liquid I is used as washing water of a titanium white intermediate product to return to a titanium white production section;
s4, adjusting the pH value of the filtrate obtained after the solid-liquid separation in the step S3 to 6-7, and introducing the filtrate into a nanofiltration membrane system for treatment to obtain nanofiltration concentrated solution and nanofiltration clear solution, wherein the nanofiltration clear solution is treated by a reverse osmosis system to obtain reverse osmosis concentrated solution II and reverse osmosis clear solution II;
s5, recycling the nanofiltration concentrated solution to the step S1; recycling the reverse osmosis concentrated solution II to the step S2; recycling the reverse osmosis clear liquid II to the titanium white production section.
Preferably, in the neutralization reaction in step S1, the calcium-containing alkaline substance is first pulped with the nanofiltration concentrate.
Preferably, the precise filtration in step S2 includes filtration using a multi-media filter and an ultrafiltration membrane system in sequence, wherein the pore size of the ultrafiltration membrane system is not more than 50nm.
Preferably, before the step S2 and the step S4 are processed by adopting a reverse osmosis system, a scale inhibitor is added into raw water, and the adding amount of the scale inhibitor is 3-10 mg/L.
Preferably, the scale inhibitor is a phosphorus-containing scale inhibitor.
Preferably, the alkaline pH adjusting substances in the steps S2 to S4 are NaOH and/or KOH, and the acidic pH adjusting substances are sulfuric acid.
Preferably, the phosphoric acid source is added in the step S3 in a molar ratio of Ca ions in the system: the molar ratio of P ions is (1.33-2): 1.
Preferably, the phosphoric acid source in step S3 is one or more combinations selected from the group consisting of:
phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium pyrophosphate.
Preferably, step S4 adopts a two-stage reverse osmosis system to process, and the nanofiltration solution is firstly processed by a 1-stage reverse osmosis system to obtain a 1-stage reverse osmosis clear solution and a 1-stage reverse osmosis concentrated solution; the 1-level reverse osmosis clear liquid is treated by a 2-level reverse osmosis system to obtain the reverse osmosis concentrated liquid II and the reverse osmosis clear liquid II; the stage 1 reverse osmosis concentrate is recycled to step S2.
The method utilizes the membrane system and the phosphorus salt to remove calcium on the premise of not utilizing evaporation concentration, realizes zero emission of titanium dioxide wastewater by the sulfuric acid method, and creates certain benefits.
Detailed Description
The application provides a method for zero emission treatment of sulfuric acid process titanium dioxide wastewater, which comprises the following steps:
s1, neutralizing titanium dioxide wastewater by a sulfuric acid method by adopting a calcium-containing alkaline substance, and controlling the pH value of a terminal point to be 8-9; the sulfuric acid process titanium white waste water is acidic, and the calcium-containing alkaline substance is adopted to neutralize H in the waste water + Impurities such as iron ions and Al ions in the sulfate radical and wastewater to generate calcium sulfate, ferric hydroxide and aluminum hydroxide precipitate; the calcium-containing alkaline substance can be quicklime, calcium oxide, carbide slag, etc.; then press-filtering the neutralized material to obtain press-filtered filtrate; the water quality after neutralization is measured, the calcium ion concentration is 300-1200 mg/L, the sulfate radical content is 1500-10000 mg/L, the Fe ion content is 0-5 mg/L, the magnesium ion content is 10-500 mg/L, and the sodium ion content is 1000-5000 mg/L. The filter cake can be recycled as titanium gypsum byproduct.
The step adopts the substances such as NaOH and KOH for neutralization, but the cost of the substances such as NaOH and KOH is lower, which is more beneficial to mass production, and because of sulfate radical, if the substances such as NaOH are utilized for neutralization, sodium ions, potassium ions and the like cannot be precipitated at all, the substances exist in the solution, which can cause higher salt content and higher requirement on a subsequent membrane treatment system.
S2, precisely filtering the filter pressing filtrate, wherein the filter pressing filter cloth is easy to damage in the filter pressing process, and the particle size of particles trapped by the filter pressing is larger, so that precise filtration is needed to fully ensure suspended matters to be removed; the precise filtration preferably comprises the steps of sequentially adopting a multi-medium filter and an ultrafiltration membrane system for treatment, wherein the aperture of the ultrafiltration membrane system is not more than 50nm, removing small particulate matters in the wastewater, regulating the pH value of the filtrate to be 6.0-7.0, and then concentrating the filtrate in a reverse osmosis system to obtain reverse osmosis concentrated solution I and reverse osmosis clear solution I; the reverse osmosis recovery rate is controlled to be 40-60%, the wastewater is concentrated through reverse osmosis, the ion concentration in reverse osmosis concentrated solution I, especially calcium, is greatly improved compared with raw water, the subsequent reaction of a phosphoric acid source and calcium ions is convenient, the water quality of reverse osmosis clear solution I is greatly improved compared with the water quality after neutralization, and the reverse osmosis clear solution I can be returned to a titanium white production section, for example, the reverse osmosis clear solution I can be used as intermediate product washing water.
The effect of adjusting the pH before reverse osmosis treatment is: since the neutralization pH in step S1 is alkaline, the filtrate in this step is alkaline, and under alkaline conditions, metal ions and part of anions in the filtrate precipitate or are converted into anions more likely to form precipitates, and the pH is reversely adjusted to inhibit the metal ions from precipitating in the form of hydroxide under alkaline conditions, and at the same time, anions more likely to form precipitates, such as phosphate or carbonate, can be converted into hydrogen phosphate or bicarbonate with higher water solubility.
S3, regulating the pH value of the reverse osmosis concentrated solution I to 10.5-12.0; adding a phosphoric acid source into the reverse osmosis concentrated solution I with the pH value adjusted for reaction, controlling the reaction time to be 0.5-2 h, keeping the pH value of the system to be more than or equal to 10.5 in the reaction process, converting calcium phosphate generated under alkaline conditions into hydroxy calcium phosphate with smaller solubility, further removing calcium, and then carrying out solid-liquid separation;
s4, adjusting the pH value of the filtrate after solid-liquid separation to 6-7, wherein the pH value adjustment function is the same as that of the step S2, then, the filtrate enters a nanofiltration membrane system for treatment to obtain nanofiltration concentrated solution and nanofiltration filtrate, and the nanofiltration clear solution is treated by a two-stage reverse osmosis system to obtain reverse osmosis concentrated solution II and reverse osmosis clear solution II;
after the phosphoric acid source is added, most of calcium ions in the wastewater are removed, sulfate radical plasma is also contained in the wastewater, firstly, nanofiltration membrane treatment is adopted, high-valence sulfate radical ions are trapped in nanofiltration concentrated solution, the recovery rate of a nanofiltration membrane system is 75-85%, the desalination rate is 85-95%, a small amount of calcium ions and more sulfate radicals are contained in nanofiltration clear liquid, finally, reverse osmosis is adopted for concentration treatment, sulfate radicals in the wastewater are fully removed, the reverse osmosis recovery rate is 85-95%, and the obtained reverse osmosis clear liquid II is basically free of sulfate radicals and calcium ions and can be recycled as a finished product washing water for use in a titanium white production section.
S5, the nanofiltration concentrated solution contains a small amount of calcium ions and a large amount of sulfate radicals, the nanofiltration concentrated solution is recycled to the step S1, and the calcium-containing alkaline substances are pulped; when the nanofiltration concentrated solution is adopted for pulping, sulfate radicals and calcium ions in the concentrated solution can generate calcium sulfate, calcium sulfate precipitation can be generated after the calcium sulfate in the solution is saturated, the calcium sulfate precipitation can not be dissolved again when the calcium sulfate precipitation is neutralized with the titanium dioxide wastewater of the sulfuric acid method, and the calcium sulfate precipitation enters the neutralization slag in the neutralization process, so that only the slag quantity is increased, the neutralization filtrate can not be influenced, and the recycling of the nanofiltration concentrated solution is realized. And (2) recycling the reverse osmosis concentrated solution II to the step (S2), mixing with the ultrafiltration clear solution, and re-entering a reverse osmosis system for treatment.
According to the method, the characteristic that the solubility of the calcium hydroxy phosphate is smaller than that of calcium sulfate is utilized, sulfate radical in waste water is replaced by phosphate radical, calcium ions in the waste water are fully removed in a calcium hydroxy phosphate precipitation mode, different membrane treatment systems are respectively adopted for treatment before and after phosphoric acid replacement treatment, suspended particles in filter pressing solution are removed by precise filtration before replacement treatment, and then reverse osmosis membrane treatment is adopted for enriching calcium ions in the filter pressing solution, but sulfate radical is enriched at the same time, so that reverse osmosis recovery rate is controlled, and calcium sulfate solids are not precipitated on the concentrated water side; after the replacement treatment, firstly, a nanofiltration membrane is adopted to recycle part of sulfate radicals, and then reverse osmosis is utilized to enrich impurity ions in clear liquid, so that the sulfate radicals in a reverse osmosis system before the replacement can be enriched on the concentrated water side of the nanofiltration membrane first, thereby obtaining nanofiltration clear liquid with better water quality, and the concentrated water quality of the nanofiltration clear liquid enters the reverse osmosis system again and is better than that of the nanofiltration clear liquid which directly enters the reverse osmosis membrane for treatment without passing through the nanofiltration membrane. The obtained clear liquid basically contains no calcium ions and sulfate ions, and can be recycled to the titanium white production section, and the concentrated liquid contains more sulfate ions, but is pulped with calcium-containing alkaline substances, so that zero emission of wastewater is realized.
The desalination rate in the wastewater is higher after the phosphoric acid source replacement, nanofiltration and reverse osmosis treatment, so that an MVR evaporation concentration system in the prior art is not needed, and the energy is greatly saved. Specifically, due to the existence of the nanofiltration membrane, the sulfate ions enriched in the reverse osmosis concentrated solution I are further enriched, and sulfate ions in the nanofiltration concentrated solution can be separated out in a precipitation form by mixing and pulping the nanofiltration concentrated solution and a calcium-containing alkaline substance, and the enriched metal ions in the nanofiltration concentrated solution can also be separated out in a hydroxide form, which is equivalent to that most of ions in the nanofiltration concentrated solution exist in a solid in a precipitation form such as titanium gypsum or hydroxide, so that the water quality produced by a membrane treatment system is better, and MVR (mechanical vapor recompression) is not required to be adopted for treating the concentrated water. The salt content in the reverse osmosis concentrated solution II is lower than that in the ultrafiltration clear solution, and the reverse osmosis concentrated solution II is subjected to recycling and the ultrafiltration clear solution re-enters a reverse osmosis system for treatment, so that the salt content in the reverse osmosis concentrated solution II is also removed. Therefore, the method utilizes the membrane system and the phosphorus salt to remove calcium on the premise of not utilizing evaporation concentration, realizes zero emission of titanium dioxide wastewater by the sulfuric acid method, and creates certain benefits.
Preferably, before the step S2 and the step S4 are processed by adopting a reverse osmosis system, a proper amount of scale inhibitor is added into raw water, the addition amount of the scale inhibitor is 3-10 mg/L, and the precipitation and precipitation in waste water are prevented, so that a membrane system is blocked.
Preferably, the scale inhibitor is a phosphorus-containing scale inhibitor.
The alkaline pH adjusting substances in the steps S3 and S4 are NaOH and/or KOH, and the acidic pH adjusting substances are sulfuric acid.
Preferably, the phosphoric acid source is added in an amount based on the molar Ca ions in the system: the molar ratio of P ions is (1.33-2): 1.
Preferably, the phosphoric acid source is one or a combination of more selected from the group consisting of:
phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium pyrophosphate.
Preferably, step S4 adopts a two-stage reverse osmosis system for treatment, and the nanofiltration liquid is firstly treated by a 1-stage reverse osmosis system to obtain a 1-stage reverse osmosis clear liquid and a 1-stage reverse osmosis concentrated liquid; treating the 1-level reverse osmosis clear liquid by a 2-level reverse osmosis system to obtain reverse osmosis concentrated liquid II and reverse osmosis clear liquid II; the 1-stage reverse osmosis concentrated solution is recycled to the step S2, and is mixed with the ultrafiltration clear solution to be re-sent to a reverse osmosis system for treatment, so that the salt in the 1-stage reverse osmosis concentrated solution is also removed.
Example 1
1. Neutralizing sulfuric acid process titanium dioxide wastewater and calcium carbide sludge, wherein in the sulfuric acid process titanium dioxide wastewater, the Fe ion content is 3.3g/L, the calcium ion content is 162mg/L, the magnesium ion content is 419mg/L, the sodium ion content is 450mg/L, the sulfate radical content is 3200mg/L, the end point pH is controlled to be 8.5, and the water quality components after neutralization are as follows: the Fe ion content is 3mg/L, the Ca ion content is 605mg/L, the Mg ion content is 89mg/L, the Na ion content is 600mg/L, and the sulfate radical content is 3400mg/L;
2. after reaching the end pH, carrying out filter pressing on the system, and regulating the pH value of filter pressing filtrate to 6.2 by utilizing sulfuric acid after sequentially entering a multi-medium filter and an ultrafiltration membrane system;
3. adding a scale inhibitor, wherein the adding amount of the scale inhibitor is 8mg/L, then entering a reverse osmosis membrane system, controlling the reverse osmosis recovery rate to be 45%, and controlling the calcium ion concentration in the obtained reverse osmosis concentrated solution I to be 1089mg/L and the sulfate radical concentration to be 6120mg/L; the concentration of calcium ions in the reverse osmosis clear liquid I is 13mg/L, the sulfate radical content is 75mg/L, and the reverse osmosis clear liquid I returns to the titanium white production section and is used as intermediate product washing water (the intermediate product washing water requires the iron content to be less than or equal to 30 mg/L);
4. the pH of the reverse osmosis concentrated solution I is regulated to 11.0 by NaOH, and the molar ratio of calcium to phosphorus is 2:1, adding trisodium phosphate, and reacting for 1h, wherein the concentration of calcium ions in the reaction clear liquid is 10mg/L;
5. carrying out filter pressing on a system after the reaction, selling an obtained filter cake (the main component is calcium hydroxy phosphate), regulating the pH value of the filter cake to 6.2 through sulfuric acid, adding 5mg/L of scale inhibitor into the filter cake, separating the filter cake by a nanofiltration membrane, wherein the sulfate radical content in the nanofiltration concentrated solution is 22032mg/L, the calcium ion content in the nanofiltration concentrated solution is 36mg/L, the concentrated solution is returned to calcium carbide mud for pulping, the calcium ion concentration in the nanofiltration clear solution is 1.3mg/L, and the sulfate radical concentration in the nanofiltration clear solution is 816mg/L; the nanofiltration solution continuously enters a two-stage reverse osmosis membrane treatment system for concentration to obtain reverse osmosis clear solution II and reverse osmosis concentrated solution II, wherein the calcium ion content in the reverse osmosis clear solution II is 0.0mg/L, the sulfate radical content in the reverse osmosis concentrated solution II is 0.1mg/L, the sulfate radical content in the reverse osmosis concentrated solution II is 38mg/L, the nanofiltration concentrated solution enters calcium carbide mud for pulping, the reverse osmosis concentrated solution II is used as raw water, the raw water enters a front-end reverse osmosis system, the conductivity of the reverse osmosis clear solution II is 45um/cm (for washing water used by a finished product, the required washing water conductivity is less than or equal to 70 um/cm), and the raw water is used as washing water for a titanium white finished product to remove titanium white.
Example 2
1. Neutralizing titanium dioxide wastewater and calcium carbide sludge by a sulfuric acid method, controlling the pH of a terminal point to be 8.5, and controlling the water quality components after neutralization: the Fe ion content is 5mg/L, the Ca ion content is 821mg/L, the Mg ion content is 23mg/L, the Na ion content is 900mg/L, and the sulfate radical content is 3500mg/L;
2. after reaching the end pH, carrying out filter pressing on the system, and regulating the pH value of filter pressing filtrate to 6.0 by utilizing sulfuric acid after sequentially entering a multi-medium filter and an ultrafiltration membrane system;
3. adding a scale inhibitor, wherein the adding amount of the scale inhibitor is 8mg/L, then entering a reverse osmosis membrane system, controlling the reverse osmosis recovery rate to be 45%, and controlling the concentration of calcium ions in the obtained reverse osmosis concentrated solution I to be 1477mg/L and the concentration of sulfate radicals to be 6300mg/L; the concentration of calcium ions in the reverse osmosis clear liquid I is 18mg/L, the sulfate radical content is 78mg/L, and the reverse osmosis clear liquid I is used as intermediate product washing water to return to the titanium white production section;
4. the pH of the reverse osmosis concentrated solution I is regulated to 11.0 by NaOH, and the molar ratio of calcium to phosphorus is 1.8:1, adding trisodium phosphate, and reacting for 1h, wherein the concentration of calcium ions in the reaction clear liquid is 13mg/L;
5. carrying out filter pressing on a system after the reaction, selling an obtained filter cake (the main component is calcium hydroxy phosphate), regulating the pH value of the filter cake to 6.2 through sulfuric acid, adding 5mg/L of scale inhibitor into the filter cake, separating the filter cake by a nanofiltration membrane, wherein the sulfate radical content in the nanofiltration concentrated solution is 12600mg/L, the calcium ion content in the nanofiltration concentrated solution is 47mg/L, returning the concentrated solution to calcium carbide mud for pulping, the calcium ion concentration in the nanofiltration clear solution is 1.7mg/L, and the sulfate radical concentration in the nanofiltration clear solution is 470mg/L; the nanofiltration filtrate is continuously fed into a two-stage reverse osmosis membrane treatment system for concentration, so as to obtain reverse osmosis clear liquid II and reverse osmosis concentrated liquid II, wherein the calcium ion content in the reverse osmosis clear liquid II is 0.0mg/L, the sulfate radical content in the reverse osmosis concentrated liquid II is 0.1mg/L, the sulfate radical content in the reverse osmosis concentrated liquid II is 21mg/L, the nanofiltration concentrated liquid enters into calcium carbide mud for pulping, the reverse osmosis concentrated liquid II is used as raw water, the raw water enters into a front-end reverse osmosis system, the conductivity of the reverse osmosis clear liquid II is 55um/cm, and the reverse osmosis clear liquid II is used as titanium white finished product washing water to remove titanium white working sections.
Comparative example 1
1. Neutralizing titanium dioxide wastewater and calcium carbide sludge by a sulfuric acid method, and controlling the pH value of the end point to be 8.8;
2. after reaching the end-point pH value, carrying out filter pressing on the system, wherein the concentration of calcium ions in filter pressing filtrate is 736ppm, the sulfate radical content is 1890mg/L, and after sequentially entering a multi-medium and ultrafiltration membrane system, regulating the pH value to 6.1 by utilizing sulfuric acid;
3. adding a scale inhibitor, wherein the adding amount of the scale inhibitor is 8mg/L, entering a reverse osmosis system, controlling the reverse osmosis recovery rate to be 65%, and entering a membrane treatment system, wherein the recovery rate is higher, ions are separated out in a crystal form after enrichment, so that the membrane treatment system is blocked, the operation pressure is increased, and the normal operation cannot be performed.
Comparative example 2
1. Neutralizing titanium dioxide wastewater and calcium carbide sludge by a sulfuric acid method, controlling the pH of a terminal point to be 8.5, and controlling the water quality components after neutralization: the Fe ion content is 5mg/L, the Ca ion content is 821mg/L, the Mg ion content is 23mg/L, the Na ion content is 900mg/L, and the sulfate radical content is 3500mg/L;
2. after reaching the end pH, carrying out filter pressing on the system, and regulating the pH value of filter pressing filtrate to 6.0 by utilizing sulfuric acid after sequentially entering a multi-medium filter and an ultrafiltration membrane system;
3. adding a scale inhibitor, wherein the adding amount of the scale inhibitor is 8mg/L, then entering a reverse osmosis membrane system, controlling the reverse osmosis recovery rate to be 45%, and controlling the concentration of calcium ions in the obtained reverse osmosis concentrated solution I to be 1477mg/L and the concentration of sulfate radicals to be 6300mg/L; the concentration of calcium ions in the reverse osmosis clear liquid I is 18mg/L, the sulfate radical content is 78mg/L, and the reverse osmosis clear liquid I is used as intermediate product washing water to return to the titanium white production section;
4. the pH of the reverse osmosis concentrated solution I is regulated to 9.0 by NaOH, and the molar ratio of calcium to phosphorus is 1.8:1, trisodium phosphate is added, and after the reaction is carried out for 1h, the content of calcium ions is 957mg/L, and the calcium ions in the system can not be sufficiently removed when the pH is lower.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. The method for zero emission treatment of the sulfuric acid process titanium dioxide wastewater is characterized by comprising the following steps of:
s1, neutralizing titanium dioxide wastewater by a sulfuric acid method by adopting a calcium-containing alkaline substance, controlling the pH of a terminal point to be 8-9, and then press-filtering the neutralized material;
s2, performing precise filtration on the filtrate subjected to the filter pressing in the step S1, adjusting the pH value of the filtrate subjected to the precise filtration to be 6.0-7.0, and concentrating the filtrate in a reverse osmosis system to obtain reverse osmosis concentrated solution I and reverse osmosis clear solution I; controlling the reverse osmosis recovery rate to be 40-60%;
s3, regulating the pH value of the reverse osmosis concentrated solution I to 10.5-12.0, adding a phosphoric acid source into the reverse osmosis concentrated solution I with the pH value regulated for reaction, keeping the pH value of a system to be more than or equal to 10.5 in the reaction process, and then carrying out solid-liquid separation; the reverse osmosis clear liquid I is used as washing water of a titanium white intermediate product to return to a titanium white production section;
s4, adjusting the pH value of the filtrate obtained after the solid-liquid separation in the step S3 to 6-7, and introducing the filtrate into a nanofiltration membrane system for treatment to obtain nanofiltration concentrated solution and nanofiltration clear solution, wherein the nanofiltration clear solution is treated by a reverse osmosis system to obtain reverse osmosis concentrated solution II and reverse osmosis clear solution II;
s5, recycling the nanofiltration concentrated solution to the step S1; recycling the reverse osmosis concentrated solution II to the step S2; recycling the reverse osmosis clear liquid II to the titanium white production section.
2. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
in the step S1, when neutralization reaction is carried out, firstly, the nanofiltration concentrated solution is adopted to pulp the calcium-containing alkaline substance.
3. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
and step S2, the precise filtration comprises the steps of sequentially adopting a multi-medium filter and an ultrafiltration membrane system, wherein the aperture of the ultrafiltration membrane system is not more than 50nm.
4. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
before the step S2 and the step S4 are treated by adopting a reverse osmosis system, adding a scale inhibitor into raw water, wherein the adding amount of the scale inhibitor is 3-10 mg/L.
5. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater according to claim 4, which is characterized in that,
the scale inhibitor is a phosphorus-containing scale inhibitor.
6. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
and S2-S4, wherein the alkaline pH adjusting substance is NaOH and/or KOH, and the acidic pH adjusting substance is sulfuric acid.
7. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
the adding amount of the phosphoric acid source in the step S3 is calculated according to the mole of Ca ions in the system: the molar ratio of P ions is (1.33-2): 1.
8. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
the phosphoric acid source in the step S3 is one or more combination selected from the following substances:
phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium pyrophosphate.
9. The method for zero-emission treatment of sulfuric acid process titanium dioxide wastewater, which is characterized in that,
step S4, adopting a two-stage reverse osmosis system to process, wherein the nanofiltration liquid is firstly processed by a 1-stage reverse osmosis system to obtain a 1-stage reverse osmosis clear liquid and a 1-stage reverse osmosis concentrated liquid; the 1-level reverse osmosis clear liquid is treated by a 2-level reverse osmosis system to obtain the reverse osmosis concentrated liquid II and the reverse osmosis clear liquid II; the stage 1 reverse osmosis concentrate is recycled to step S2.
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