CN114716085B - Recycling method of waste water in production of silicon-aluminum inorganic coated titanium dioxide - Google Patents

Recycling method of waste water in production of silicon-aluminum inorganic coated titanium dioxide Download PDF

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CN114716085B
CN114716085B CN202210355620.1A CN202210355620A CN114716085B CN 114716085 B CN114716085 B CN 114716085B CN 202210355620 A CN202210355620 A CN 202210355620A CN 114716085 B CN114716085 B CN 114716085B
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water
nanofiltration
filtrate
titanium dioxide
reverse osmosis
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CN114716085A (en
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刘明明
杜玮辰
张旭
陈爽
孙妍妍
刘雨
易凡丰
余阳阳
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Haining Lanti New Material Co ltd
Zhejiang Hengyi Petrochemical Research Institute Co Ltd
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Haining Lanti New Material Co ltd
Zhejiang Hengyi Petrochemical Research Institute Co Ltd
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    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
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    • C02F1/00—Treatment of water, waste water, or sewage
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    • 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
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    • 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
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    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
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    • 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
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    • 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
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • 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
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    • 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
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • 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
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Abstract

The invention relates to the field of titanium white production wastewater treatment, and discloses a recycling method of silicon-aluminum inorganic coated titanium white production wastewater, which comprises the following steps: adjusting the pH value of the waste water in the production of the silicon-aluminum inorganic coated titanium dioxide to 7-8, performing flocculation precipitation, removing a first precipitate by sedimentation, and performing adsorption filtration on the obtained first supernatant to obtain filtrate; blowing air into the filtrate to perform precipitation reaction, and recovering a second precipitate to obtain a second supernatant; ultrafiltering the second supernatant to obtain ultrafiltered water and ultrafiltered concentrated water; nanofiltration is carried out on ultrafiltration produced water to obtain nanofiltration produced water and nanofiltration concentrated water; recrystallizing the nanofiltration concentrated water to obtain sodium sulfate. The method can effectively remove the main waste in the waste water of the silicon-aluminum inorganic coated titanium dioxide production, and the recovered aluminum hydroxide and sodium sulfate do not need further purification, and new waste is not introduced in the process of recovering the aluminum hydroxide, so that the waste water treatment flow can be shortened, and the energy consumption and the cost are reduced.

Description

Recycling method of waste water in production of silicon-aluminum inorganic coated titanium dioxide
Technical Field
The invention relates to the field of titanium white production wastewater treatment, in particular to a recycling method of silicon-aluminum inorganic coated titanium white production wastewater.
Background
The nano titanium dioxide has higher color fastness and hiding power, so the nano titanium dioxide becomes a matting agent material which is most widely applied in the chemical fiber industry at present. In the field of matting agents special for chinlon, nano titanium dioxide is easy to agglomerate due to small size, large specific surface area and higher surface energy, and is unfavorable for being well dispersed in polymer fibers, so that a spinneret plate and a pipeline are blocked, and the fiber forming quality, spinning performance and dyeing performance are deteriorated. In order to prevent titanium dioxide from agglomerating in the polymerization production process and also to shield the photocatalytic activity of titanium dioxide, the existing titanium dioxide matting agent special for chinlon needs to further coat and modify the surface of the titanium dioxide matting agent. Inorganic oxides such as SiO 2 、Al 2 O 3 、ZrO 2 、MnO 2 、MoO 3 、CeO 2 The single component or the mixed component is used for researching the inorganic coating of the titanium dioxide, wherein the SiO with the lowest production cost and the most obvious effect is produced 2 、Al 2 O 3 The bilayer encapsulation process is most widely used in the industry.
However, the silicon-aluminum double-layer coating process can generate a large amount of salt-containing wastewater in the coating and slurry cleaning processes, which not only causes excessive consumption and waste of pure water and increases the coating cost, but also increases the environmental protection threat due to the post-treatment discharge of a large amount of wastewater. The patent with publication number CN108328780A discloses a method and a device for recycling titanium dioxide wastewater, and the specific method is as follows: carrying out solid-liquid separation on wastewater in the process of preparing titanium dioxide by using a chlorination method; adding a desilication agent and/or an aluminum removal agent, carrying out precipitation reaction, and carrying out solid-liquid separation and removal on the obtained precipitate; after the pH was adjusted to 1-6, the solution was fed into an ion exchange resin to remove impurity ions, thereby obtaining purified NaCl brine. Wherein the desilicating agent and/or the aluminum removing agent is selected from magnesium chloride and/or calcium chloride. According to the method, magnesium chloride and/or calcium chloride are used for removing sodium silicate and sodium metaaluminate in titanium dioxide wastewater, so that the recovered aluminum hydroxide contains calcium carbonate, magnesium silicate and/or calcium silicate, pure aluminum hydroxide can be obtained only by further purification, and the added excessive magnesium chloride and/or calcium chloride also needs to be removed by further treatment, so that the wastewater treatment process is complex, and the energy consumption and the cost are high.
Disclosure of Invention
In order to solve the technical problems, the invention provides a recycling method of waste water in the production of the silicon-aluminum inorganic coated titanium dioxide. The method can effectively remove the main waste in the waste water of the silicon-aluminum inorganic coated titanium dioxide production, and the recovered aluminum hydroxide and sodium sulfate do not need further purification, and new waste is not introduced in the process of recovering the aluminum hydroxide, so that the waste water treatment flow can be shortened, and the energy consumption and the cost are reduced.
The specific technical scheme of the invention is as follows:
a recycling method of waste water in the production of silicon-aluminum inorganic coated titanium dioxide comprises the following steps:
(1) And (3) physical and chemical treatment: adjusting the pH value of the waste water in the production of the silicon-aluminum inorganic coated titanium dioxide to 7-8, performing flocculation precipitation, removing a first precipitate by sedimentation, and performing adsorption filtration on the obtained first supernatant to obtain filtrate;
(2) Bubbling reaction: blowing air into the filtrate to perform precipitation reaction, and recovering a second precipitate to obtain a second supernatant;
(3) Membrane separation and concentration: ultrafiltering the second supernatant to obtain ultrafiltered water and ultrafiltered concentrated water; nanofiltration is carried out on ultrafiltration produced water to obtain nanofiltration produced water and nanofiltration concentrated water;
(4) And (5) recrystallizing: recrystallizing the nanofiltration concentrated water to obtain sodium sulfate.
In the waste water of the silica-alumina inorganic coated titanium dioxide production (including waste water generated in the coating process and slurry cleaning waste water after coating), main wastes comprise titanium dioxide solid small particles, sulfate ions, metaaluminate ions, silicate ions, phosphate ions and the like. The invention realizes the recycling of the waste water in the production of the silicon-aluminum inorganic coated titanium dioxide through the following processes: (1) The suspended titanium dioxide small particles, phosphate radicals and silicate ions in the wastewater can be removed by sedimentation through regulating the pH and flocculating settling; filtering the first supernatant to remove non-settled particles, and adsorbing to remove residual phosphate ion and silicate ionThe method comprises the steps of carrying out a first treatment on the surface of the (2) Air is blown into the filtrate obtained after filtration, and carbon dioxide in the air is utilized to convert metaaluminate into aluminum hydroxide precipitate, so that the recovery of aluminum hydroxide can be realized; (3) Sequentially performing ultrafiltration, nanofiltration and reverse osmosis on the second supernatant of the recovered aluminum hydroxide, and respectively removing particles, macromolecules, divalent ions and monovalent ions; the nanofiltration water is low-salt water, and can be recycled as the cleaning water of the titanium pigment slurry; (4) The nanofiltration concentrated water contains a large amount of Na 2 SO 4 Na can be recovered by recrystallization 2 SO 4 The water left after recrystallization is desalted water, and can be recycled as deionized water (such as the preparation of raw materials and auxiliary materials in the production process of titanium dioxide).
In the process, the phosphate radical and the silicate radical are removed by physical and chemical treatment, so that the pollution of the recovered aluminum hydroxide and sodium sulfate can be avoided, and the recovered aluminum hydroxide and sodium sulfate do not need further purification. The main components in the wastewater after physical and chemical treatment are sulfate ions and metaaluminate ions, and because both the sulfate ions and the metaaluminate ions can be intercepted by a membrane system, the invention carries out bubbling reaction before membrane separation and concentration to realize separate recovery of aluminum hydroxide and sodium sulfate, and reduces the pressure of the membrane system, thereby prolonging the service life of the membrane and saving the cost of the membrane.
In addition, the method converts the metaaluminate in the wastewater into the aluminum hydroxide precipitate by bubbling air, so that the introduction of impurities such as insoluble carbonates (such as calcium carbonate and magnesium carbonate in the patent CN 108328780A) and the like into the aluminum hydroxide precipitate can be avoided, and new wastes such as soluble calcium salts (such as magnesium chloride and calcium chloride in the patent CN 108328780A) and the like can not be introduced into the wastewater, and the new wastes are not required to be further treated and removed, so that the wastewater treatment flow can be shortened, and the energy consumption and the cost can be reduced.
Preferably, in the step (3), after nanofiltration produced water and nanofiltration concentrated water are obtained, reverse osmosis is carried out on the nanofiltration produced water to obtain reverse osmosis produced water and reverse osmosis concentrated water; in the step (4), the nanofiltration concentrated water and the reverse osmosis concentrated water are recrystallized to obtain sodium sulfate.
The nanofiltration product water can be recycled for cleaning the titanium dioxide slurry and can be fed through reverse osmosisOne-step recovery of Na 2 SO 4 . The reverse osmosis produced water is desalted water, and can be recycled as deionized water (such as the preparation of raw materials and auxiliary materials in the titanium dioxide production process); the reverse osmosis concentrated water contains a large amount of Na 2 SO 4 Na can be recovered by recrystallization 2 SO 4 . According to the actual requirements of the preparation water of raw materials and auxiliary materials and the cleaning water of the titanium dioxide slurry in the titanium dioxide production process, the nanofiltration water production can be distributed, and the effective preparation of backwater resources can be realized.
Preferably, in the step (2), the specific process of blowing air into the filtrate to perform precipitation reaction comprises the following steps: firstly controlling the temperature to be 20-40 ℃, controlling the air pressure above the liquid level of the filtrate to be 2-6bar, and blowing air into the filtrate for 2-5h; then maintaining the temperature at 20-40deg.C, controlling the air pressure above the liquid level of the filtrate at 0.8-1.2bar, and bubbling air into the filtrate for 1-2h.
The invention adopts a step-by-step precipitation reaction method, and has the following functions: in the first stage, adopting larger air pressure to dissolve carbon dioxide in the air into water to form carbonic acid, and then reacting with metaaluminate ions to generate aluminum hydroxide precipitate; in the second stage, the small air pressure is adopted, so that excessive carbonic acid and bicarbonate ions in water can be converted into carbon dioxide again, the carbon dioxide is carried out along with the blown air, and sodium sulfate after recrystallization can be prevented from containing sodium carbonate and sodium bicarbonate impurities.
Preferably, in the step (2), the gas overflowed from the filtrate is dried and then reblowed into the filtrate.
Preferably, in the step (2), air is blown into the filtrate through a gas distributor; the gas distributor is provided with a plurality of gas outlets; the aperture of the air outlet of the air distributor is small in inside and large in outside.
The gas outlet outer diffusion type radiation structure (namely, the caliber is set to be small inside and large outside) of the gas distributor can avoid scaling of the gas outlet.
Further, a transverse baffle is arranged above the gas distributor.
The air blown from the gas distributor is diffused to the surrounding after colliding with the transverse baffle plate, and in this way, the gas stroke can be expanded, so that the air is fully contacted with the filtrate, and the recovery rate of the metaaluminate in the filtrate is improved.
Preferably, in step (1), H is used in a concentration of 1-4wt% 2 SO 4 The pH value of the waste water produced by the silica-alumina inorganic coated titanium dioxide is adjusted to 7-8 by the solution and/or NaOH solution with the concentration of 1-4wt%.
Preferably, in the step (1), flocculation precipitation is carried out by adding a flocculating agent and a coagulant aid; the addition amounts of the flocculant and the coagulant aid are respectively 200-600mg/L and 1-10mg/L.
The flocculant can be one or more of ferric sulfate, polymeric aluminum chloride, ferric chloride and polymeric aluminum sulfate; the coagulant aid can be one or more of polyacrylamide, sodium alginate and polysilicic acid. The flocculant and coagulant aid are preferably polyaluminium sulphate, polyaluminium chloride and polyacrylamide.
Preferably, in the step (1), the specific process of adsorption filtration includes the following steps: the first supernatant sequentially passes through an activated carbon packing layer, a zeolite packing layer, an anthracite packing layer and a quartz sand packing layer.
Preferably, in the step (3), an ultrafiltration membrane with a pore diameter of 40-200nm is adopted, the pressure is 0.2-0.6MPa, and the treated water amount is 10-30m 3 /h。
More than 96% of divalent ions can be trapped by ultrafiltration, and the ultrafiltration yielding water is low-salt water with the conductivity of less than 10 mu S/cm.
Preferably, in the nanofiltration process, a nanofiltration membrane with a molecular weight cut-off of 150-300Da is adopted, the pressure is 0.8-2MPa, and the water yield of a single membrane is 2-10m 3 /h。
Through nanofiltration, more than 98% of monovalent cations can be trapped, and ultrafiltration water is desalted water with the conductivity less than or equal to 1 mu S/cm.
Preferably, in the reverse osmosis process, the pressure is 1-4MPa, and the water yield of a single membrane is 0.5-1.5m 3 /h。
Preferably, the method is carried out by adopting a silicon-aluminum inorganic coated titanium dioxide production wastewater treatment line; the silicon-aluminum inorganic coated titanium dioxide production wastewater treatment line comprises a materialization treatment unit, a bubbling reaction unit, a membrane separation concentration unit and a recrystallization unit which are connected in sequence; the bubbling reaction unit comprises a bubbling reactor, one or more gas distributors are arranged in the bubbling reactor, and a plurality of gas outlets are arranged on each gas distributor; the membrane separation concentration unit comprises an ultrafilter, a nanofiltration device and a reverse osmosis device which are sequentially connected, and the ultrafilter is connected with the bubbling reactor; the recrystallization unit comprises an evaporator, and the nanofiltration device and the reverse osmosis device are connected with the evaporator.
Further, the physical and chemical treatment unit comprises a pH adjusting tank, a first-stage reaction tank, a first-stage sedimentation tank, a second-stage reaction tank, a second-stage sedimentation tank and a filter which are sequentially connected; the pH regulating tank is connected with the acid adding device and the alkali adding device; the first-stage reaction tank and the second-stage reaction tank are connected with a flocculating agent feeding device and a coagulant aid feeding device; the filter is connected to the bubble reactor.
Further, the number of the gas distributors in the bubbling reactor is 3, and the gas distributors are respectively arranged at the bottom, the middle and the upper part of the bubbling reactor.
Compared with the prior art, the invention has the following advantages:
(1) The method can effectively remove the titanium dioxide solid small particles, sulfate ions, metaaluminate ions, silicate ions and phosphate ions in the waste water of the silicon-aluminum inorganic coated titanium dioxide production, and realize the recycling of aluminum hydroxide and sodium sulfate; in addition, the recycled nanofiltration produced water can be recycled as titanium dioxide slurry cleaning water, and the reverse osmosis produced water and the water left after recrystallization can be recycled as deionized water, so that the effective preparation of backwater resources can be realized;
(2) The recovered aluminum hydroxide and sodium sulfate do not contain phosphate, silicate, calcium carbonate, magnesium carbonate and other impurities, and further purification is not needed, so that the method has the advantages of short wastewater treatment flow, low energy consumption and low cost;
(3) The method converts the metaaluminate into the aluminum hydroxide by adopting an air blowing method, and can avoid introducing new wastes into the wastewater, thereby simplifying the wastewater treatment process and reducing the energy consumption and the cost; and by adopting a high-pressure and low-pressure step precipitation reaction method, the residues of carbonic acid and bicarbonate in the wastewater can be reduced, and sodium sulfate after recrystallization is prevented from containing sodium carbonate and sodium bicarbonate impurities.
Detailed Description
The invention is further described below with reference to examples.
General examples
A recycling method of waste water in the production of silicon-aluminum inorganic coated titanium dioxide comprises the following steps:
(1) And (3) physical and chemical treatment: with H in a concentration of 1-4wt% 2 SO 4 After the pH value of the waste water produced by the silica-alumina inorganic coated titanium dioxide production is regulated to 7-8 by the solution and/or NaOH solution with the concentration of 1-4wt%, respectively adding flocculating agent and coagulant aid in the dosage of 200-600mg/L and 1-10mg/L for flocculation precipitation, then settling to remove first precipitate, and sequentially passing the obtained first supernatant through an active carbon filler layer, a zeolite filler layer, an anthracite filler layer and a quartz sand filler layer to obtain filtrate;
(2) Bubbling reaction: controlling the temperature to be 20-40 ℃, controlling the air pressure above the liquid level of the filtrate to be 2-6bar, and blowing air into the filtrate for 2-5h through a gas distributor, wherein the gas distributor is provided with a plurality of air outlets with small caliber and large inner diameter and large outer diameter, and a transverse baffle is arranged above the gas distributor; then maintaining the temperature at 20-40 ℃, controlling the air pressure above the liquid level of the filtrate to be 0.8-1.2bar, and blowing air into the filtrate for 1-2h through a gas distributor; recovering a second precipitate formed in the filtrate to obtain a second supernatant;
(3) Membrane separation and concentration: ultrafiltering the second supernatant with ultrafilter membrane with pore size of 40-200nm under pressure of 0.2-0.6MPa and treated water volume of 10-30m 3 And (h) obtaining ultrafiltration produced water and ultrafiltration concentrated water; nanofiltration of ultrafiltration water with molecular weight cut-off of 150-300Da and pressure of 0.8-2MPa, and water yield of 2-10m 3 And (h) obtaining nanofiltration produced water and nanofiltration concentrated water;
(4) And (5) recrystallizing: recrystallizing the nanofiltration concentrated water to obtain sodium sulfate.
Optionally, in the step (3), after nanofiltration produced water and nanofiltration concentrated water are obtained, reverse osmosis is carried out on the nanofiltration produced water, the pressure is 1-4MPa, and the water yield of a single membrane is 0.5-1.5m 3 And (h) obtaining reverse osmosis produced water and reverse osmosis concentrated water; in the step (4), the nanofiltration concentrated water and the reverse osmosis concentrated water are recrystallized to obtain sodium sulfate.
Example 1
The treatment line for the waste water in the production of the silicon-aluminum inorganic coated titanium dioxide comprises a materialization treatment unit, a bubbling reaction unit, a membrane separation concentration unit and a recrystallization unit which are sequentially connected, wherein the specific structure of each unit is as follows:
a physical and chemical treatment unit: comprises a pH adjusting tank, a first-stage reaction tank, a first-stage sedimentation tank, a second-stage reaction tank, a second-stage sedimentation tank and a filter which are connected in sequence. The pH adjusting tank is connected with the acid adding device and the alkali adding device. The first-stage reaction tank and the second-stage reaction tank are connected with a flocculating agent feeding device and a coagulant aid feeding device. The primary sedimentation tank and the secondary sedimentation tank are both inclined tube sedimentation tanks; and sediment outlets of the primary sedimentation tank and the secondary sedimentation tank are connected with a plate-and-frame filter press. The filter is internally and respectively provided with a quartz sand packing layer, an anthracite packing layer, a zeolite packing layer and an active carbon packing layer from bottom to top, the total stacking height of the 4 packing layers is 1.5m, and the stacking density is 1g/cm 3 。
Bubbling reaction unit: including bubble reactors. The bubble reactor is connected with a filter. The bottom, the middle and the upper part of the bubbling reactor are respectively provided with a gas distributor; each gas distributor is provided with a plurality of gas outlets with small caliber and large inner diameter and large outer diameter; a transverse baffle is arranged above each gas distributor. The gas distributor is a rotary gas distributor. The bubbling reactor is insulated by an external jacket.
Membrane separation concentration unit: comprises an ultrafilter, a nanofiltration device and a reverse osmosis device which are connected in sequence. The ultrafilter is connected with the bubbling reactor. In the ultrafilter, the average pore diameter of the ultrafilter membrane is 100nm. The nanofiltration comprises 5 nanofiltration membranes with a molecular weight cut-off of 200Da connected in series. The reverse osmosis device comprises 5 reverse osmosis membranes which are connected in series and have a desalination rate of more than or equal to 98 percent.
And (3) a recrystallization unit: including the evaporator. The nanofiltration device and the reverse osmosis device are connected with an evaporator. The evaporator is a multi-effect forced circulation evaporator.
By adopting the treatment line, the reuse of the production wastewater of the silicon-aluminum inorganic coated titanium dioxide is carried out through the following steps that the wastewater treatment capacity is 40t/d:
(1) And (3) physical and chemical treatment:
(1.1) mixing the waste water produced in the production of the silicon-aluminum inorganic coated titanium dioxide (including the waste water produced in the coating process and the slurry cleaning waste water after coating) by 10m 3 The flow of/h is led into a pH adjusting tank, 4wt percent of H is added into the pH adjusting tank through an acid adding device 2 SO 4 A solution, the pH of which is adjusted to 8;
(1.2) introducing the effluent of the pH regulating tank into a first-stage reaction tank, and respectively adding polyaluminum chloride (flocculant) and polyacrylamide (coagulant aid) into the first-stage reaction tank in the addition amount of 300mg/L and 2 mg/L through a flocculant adding device and a coagulant aid adding device to perform flocculation precipitation;
(1.3) introducing the effluent of the first-stage reaction tank into a first-stage sedimentation tank for sedimentation, and introducing the precipitate into a plate-and-frame filter press for concentration;
(1.4) introducing the supernatant in the primary sedimentation tank into a secondary reaction tank, and respectively adding polyaluminium sulfate (flocculant) and polyacrylamide (coagulant aid) into the secondary reaction tank according to the adding amount of 100mg/L and 1 mg/L for flocculation precipitation;
(1.5) introducing the effluent of the secondary reaction tank into a secondary sedimentation tank for sedimentation, and introducing the sediment into a plate-and-frame filter press for concentration;
(1.6) passing the supernatant in the secondary sedimentation tank from top to bottom through a filter to obtain a filtrate;
(2) Bubbling reaction: introducing filtrate into a bubbling reactor, controlling the temperature to be 30 ℃, and bubbling air into the filtrate through a gas distributor for 2.5h at a flow rate of 400L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 4bar in the process; then maintaining the temperature at 30 ℃, and blowing air into the filtrate through a gas distributor for 1h at a flow rate of 400L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 1bar in the process; recovering a second precipitate (i.e., aluminum hydroxide) formed in the filtrate to obtain a second supernatant;
(3) Membrane separation and concentration:
(3.1) introducing the second supernatant into an ultrafilter, controlling the pressure to 0.2MPa and the treated water amount to 10m 3 And (h) obtaining ultrafiltration produced water and ultrafiltration concentrated water;
after a period of treatment, when the ultrafiltration membrane flux drops by 20%, the ultrafiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at the flow rate of 4000L/h; then backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, and backwashing for 1h by using a 10mg/L sodium hypochlorite solution, wherein the operation pressure is 0.1MPa; finally backwashing for 30min by using deionized water;
(3.2) introducing ultrafiltration water into a nanofiltration device, controlling the pressure to be 0.8MPa, and controlling the water yield of a single membrane to be 2m 3 And (h) obtaining nanofiltration produced water and nanofiltration concentrated water; recycling 50% nanofiltration product water as titanium dioxide slurry cleaning water;
after a period of treatment, when the nanofiltration membrane flux drops by 10% or the desalination rate drops by 10%, the nanofiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(3.3) introducing the rest 50% nanofiltration water into a reverse osmosis device, controlling the pressure to be 2.5MPa, and controlling the water yield of a single membrane to be 1m 3 And (h) obtaining reverse osmosis produced water and reverse osmosis concentrated water; the reverse osmosis produced water is used as deionized water to be reused for preparing raw materials and auxiliary materials in the titanium dioxide production process;
after a period of treatment, when the flux of the reverse osmosis membrane is reduced by 10% or the desalination rate is reduced by 10%, the reverse osmosis membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(4) And (5) recrystallizing: introducing nanofiltration concentrated water and reverse osmosis concentrated water into an evaporator, adjusting the evaporation speed to 300L/h, and recrystallizing to obtain sodium sulfate, wherein the detected purity is 98.5%; and recycling water left after recrystallization as deionized water to prepare raw materials and auxiliary materials in the titanium dioxide production process.
Example 2
The processing line in this embodiment differs from embodiment 1 only in that: in the nanofiltration device, the number of nanofiltration membranes is 4; in the reverse osmosis device, the number of reverse osmosis membranes is 7.
By adopting the treatment line in the embodiment, the reuse of the production wastewater of the silicon-aluminum inorganic coated titanium dioxide is carried out through the following steps of:
(1) And (3) physical and chemical treatment:
(1.1) treating waste water produced in the production of the silicon-aluminum inorganic coated titanium dioxide (including waste water produced in the coating process and slurry cleaning waste water after coating) with the concentration of 20m 3 The flow of/h is led into a pH adjusting tank, 4wt percent of H is added into the pH adjusting tank through an acid adding device 2 SO 4 A solution, the pH of which is adjusted to 8;
(1.2) introducing the effluent of the pH regulating tank into a first-stage reaction tank, and respectively adding polyaluminum chloride (flocculant) and polyacrylamide (coagulant aid) into the first-stage reaction tank in the adding amounts of 400mg/L and 3 mg/L through a flocculant adding device and a coagulant aid adding device to perform flocculation precipitation;
(1.3) introducing the effluent of the first-stage reaction tank into a first-stage sedimentation tank for sedimentation, and introducing the precipitate into a plate-and-frame filter press for concentration;
(1.4) introducing the supernatant in the primary sedimentation tank into a secondary reaction tank, and respectively adding polyaluminium sulfate (flocculant) and polyacrylamide (coagulant aid) into the secondary reaction tank according to the adding amount of 100mg/L and 1 mg/L for flocculation precipitation;
(1.5) introducing the effluent of the secondary reaction tank into a secondary sedimentation tank for sedimentation, and introducing the sediment into a plate-and-frame filter press for concentration;
(1.6) passing the supernatant in the secondary sedimentation tank from top to bottom through a filter to obtain a filtrate;
(2) Bubbling reaction: introducing filtrate into a bubbling reactor, controlling the temperature to be 20 ℃, and bubbling air into the filtrate through a gas distributor for 3h at a flow rate of 500L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 4bar in the process; then maintaining the temperature at 30 ℃, and blowing air into the filtrate through a gas distributor for 2h at a flow rate of 500L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 0.8bar in the process; recovering a second precipitate (i.e., aluminum hydroxide) formed in the filtrate to obtain a second supernatant;
(3) Membrane separation and concentration:
(3.1) introducing the second supernatant into an ultrafilter, controlling the pressure to 0.3MPa and the treated water amount to 15m 3 And (h) obtaining ultrafiltration produced water and ultrafiltration concentrated water;
after a period of treatment, when the ultrafiltration membrane flux drops by 20%, the ultrafiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at the flow rate of 4000L/h; then backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, and backwashing for 1h by using a 10mg/L sodium hypochlorite solution, wherein the operation pressure is 0.1MPa; finally backwashing for 30min by using deionized water;
(3.2) introducing ultrafiltration water into a nanofiltration device, controlling the pressure to be 1MPa, and controlling the water yield of a single membrane to be 5m 3 And (h) obtaining nanofiltration produced water and nanofiltration concentrated water; recycling 50% nanofiltration product water as titanium dioxide slurry cleaning water;
after a period of treatment, when the nanofiltration membrane flux drops by 10% or the desalination rate drops by 10%, the nanofiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(3.3) introducing the rest 50% nanofiltration water into a reverse osmosis device, controlling the pressure to be 4MPa, and controlling the water yield of a single membrane to be 1.5m 3 And (h) obtaining reverse osmosis produced water and reverse osmosis concentrated water; the reverse osmosis produced water is used as deionized water to be reused for preparing raw materials and auxiliary materials in the titanium dioxide production process;
after a period of treatment, when the flux of the reverse osmosis membrane is reduced by 10% or the desalination rate is reduced by 10%, the reverse osmosis membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(4) And (5) recrystallizing: introducing nanofiltration concentrated water and reverse osmosis concentrated water into an evaporator, adjusting the evaporation speed to 300L/h, and recrystallizing to obtain sodium sulfate, wherein the detected purity is 98.7%; and recycling water left after recrystallization as deionized water to prepare raw materials and auxiliary materials in the titanium dioxide production process.
Example 3
The processing line in this embodiment differs from embodiment 1 only in that: in the filter, the total stacking height of the 4 packing layers is 2m; in the nanofiltration device, the number of nanofiltration membranes is 6; in the reverse osmosis device, the number of reverse osmosis membranes is 10.
By adopting the treatment line in the embodiment, the reuse of the production wastewater of the silicon-aluminum inorganic coated titanium dioxide is carried out through the following steps that the wastewater treatment capacity is 120t/d:
(1) And (3) physical and chemical treatment:
(1.1) mixing the waste water produced in the production of the silicon-aluminum inorganic coated titanium dioxide (including the waste water produced in the coating process and the slurry cleaning waste water after coating) with the water of 30m 3 The flow of/h is led into a pH adjusting tank, 4wt percent of H is added into the pH adjusting tank through an acid adding device 2 SO 4 A solution, the pH of which is adjusted to 8;
(1.2) introducing the effluent of the pH regulating tank into a first-stage reaction tank, and respectively adding polyaluminum chloride (flocculant) and polyacrylamide (coagulant aid) into the first-stage reaction tank in the adding amounts of 500mg/L and 4 mg/L through a flocculant adding device and a coagulant aid adding device to perform flocculation precipitation;
(1.3) introducing the effluent of the first-stage reaction tank into a first-stage sedimentation tank for sedimentation, and introducing the precipitate into a plate-and-frame filter press for concentration;
(1.4) introducing the supernatant in the primary sedimentation tank into a secondary reaction tank, and respectively adding polyaluminium sulfate (flocculant) and polyacrylamide (coagulant aid) into the secondary reaction tank in the addition amount of 150mg/L and 1 mg/L for flocculation precipitation;
(1.5) introducing the effluent of the secondary reaction tank into a secondary sedimentation tank for sedimentation, and introducing the sediment into a plate-and-frame filter press for concentration;
(1.6) passing the supernatant in the secondary sedimentation tank from top to bottom through a filter to obtain a filtrate;
(2) Bubbling reaction: introducing filtrate into a bubbling reactor, controlling the temperature to be 20 ℃, and bubbling air into the filtrate through a gas distributor for 3.5h at a flow rate of 600L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 5bar in the process; then maintaining the temperature at 30 ℃, and blowing air into the filtrate through a gas distributor for 1h at a flow rate of 600L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 1.2bar; recovering a second precipitate (i.e., aluminum hydroxide) formed in the filtrate to obtain a second supernatant;
(3) Membrane separation and concentration:
(3.1) introducing the second supernatant into an ultrafilter, controlling the pressure to 0.6MPa and the amount of treated water to 30m 3 And (h) obtaining ultrafiltration produced water and ultrafiltration concentrated water;
after a period of treatment, when the ultrafiltration membrane flux drops by 20%, the ultrafiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at the flow rate of 4000L/h; then backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, and backwashing for 1h by using a 10mg/L sodium hypochlorite solution, wherein the operation pressure is 0.1MPa; finally backwashing for 30min by using deionized water;
(3.2) introducing ultrafiltration water into a nanofiltration device, controlling the pressure to be 1MPa, and controlling the water yield of a single membrane to be 5m 3 And (h) obtaining nanofiltration produced water and nanofiltration concentrated water; recycling 50% nanofiltration product water as titanium dioxide slurry cleaning water;
after a period of treatment, when the nanofiltration membrane flux drops by 10% or the desalination rate drops by 10%, the nanofiltration membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(3.3) introducing the rest 50% nanofiltration water into a reverse osmosis device, controlling the pressure to be 4MPa, and controlling the water yield of a single membrane to be 1.5m 3 And (h) obtaining reverse osmosis produced water and reverse osmosis concentrated water; the reverse osmosis produced water is used as deionized water to be reused for preparing raw materials and auxiliary materials in the titanium dioxide production process;
after a period of treatment, when the flux of the reverse osmosis membrane is reduced by 10% or the desalination rate is reduced by 10%, the reverse osmosis membrane is backwashed as follows: firstly, backwashing with deionized water, and backwashing for 15min at a flow rate of 2000L/h; backwashing for 1h by using a mixed solution of 2wt% of citric acid and 0.4wt% of hydrochloric acid, wherein the operation pressure is 0.3MPa; finally backwashing for 30min by using deionized water;
(4) And (5) recrystallizing: introducing nanofiltration concentrated water and reverse osmosis concentrated water into an evaporator, adjusting the evaporation speed to 400L/h, and recrystallizing to obtain sodium sulfate, wherein the detected purity is 98.0%; and recycling water left after recrystallization as deionized water to prepare raw materials and auxiliary materials in the titanium dioxide production process.
Example 4
This embodiment differs from embodiment 2 only in that: in the reverse osmosis device, the number of reverse osmosis membranes is 4; in the step (3.2), 80% nanofiltration water is used as titanium dioxide slurry cleaning water for recycling; in the step (3.3), the rest 20 percent nanofiltration water is introduced into a reverse osmosis device, and the water yield of a single membrane is 1m 3 /h。
Example 5
This embodiment differs from embodiment 2 only in that: in the reverse osmosis device, the number of reverse osmosis membranes is 5; in the step (3.2), the 60% nanofiltration water is used as the cleaning water of the titanium pigment slurry for recycling; in step (3.3), the remaining 40% of nanofiltration product water is passed into a reverse osmosis vessel.
Comparative example 1
This comparative example differs from example 1 only in that: changing the step (2), introducing the filtrate into a bubbling reactor, controlling the temperature to be 30 ℃, and bubbling air into the filtrate through a gas distributor for 3.5h at a flow rate of 400L/h while stirring, wherein the air pressure above the liquid level of the filtrate is controlled to be 4bar in the process; recovering a second precipitate (i.e., aluminum hydroxide) formed in the filtrate to obtain a second supernatant.
According to detection, in the comparative example, the purity of sodium sulfate obtained by recrystallization in the step (4) is 93.8%, which is obviously lower than that of the example 1. The adoption of the step-by-step precipitation reaction method of the invention is helpful for improving the purity of sodium sulfate, and the reason is that: in the first stage, adopting larger air pressure to dissolve carbon dioxide in the air into water to form carbonic acid, and then reacting with metaaluminate ions to generate aluminum hydroxide precipitate; in the second stage, the small air pressure is adopted, so that excessive carbonic acid and bicarbonate ions in water can be converted into carbon dioxide again, the carbon dioxide is carried out along with the blown air, and sodium sulfate after recrystallization can be prevented from containing sodium carbonate and sodium bicarbonate impurities.
Test case
In examples 1 to 5, the pH, silicon content, aluminum content and conductivity of wastewater (untreated silicoalumino-inorganic coated titanium pigment production wastewater), low-salt water (nanofiltration water) and demineralized water (mixture of reverse osmosis water production and water remaining after recrystallization) were measured, and the total water return rate was calculated as total water return rate=total volume of recovered low-salt water and demineralized water/volume of wastewater×100%. The results are shown in Table 1.
TABLE 1
Figure BDA0003582401590000111
Data analysis:
from table 1, it can be seen that after the wastewater from the production of the silica-alumina inorganic coated titanium dioxide is treated in examples 1-5, various indexes of the obtained low-salt water and desalted water all meet the relevant standards of the reuse water, and the wastewater reuse rate is as high as 96% or more, which indicates that the invention can effectively remove the waste in the wastewater from the production of the silica-alumina inorganic coated titanium dioxide, realize the effective preparation of the backwater resource, and have substantial application effects.
In addition, the invention can distribute nanofiltration produced water (examples 2, 4 and 5) according to the actual requirements of the preparation water of raw materials and auxiliary materials and the cleaning water of the titanium pigment slurry in the titanium pigment production process, thereby realizing the effective preparation of backwater resources.
The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent transformation of the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims (9)

1. The method for recycling the silicon-aluminum inorganic coated titanium dioxide production wastewater is characterized by comprising the following steps of:
(1) And (3) physical and chemical treatment: adjusting the pH value of the waste water in the production of the silicon-aluminum inorganic coated titanium dioxide to 7-8, performing flocculation precipitation, removing a first precipitate by sedimentation, and performing adsorption filtration on the obtained first supernatant to obtain filtrate; the waste water produced by the silica-alumina inorganic coated titanium dioxide comprises titanium dioxide solid small particles, sulfate ions, metaaluminate ions, silicate ions and phosphate ions;
(2) Bubbling reaction: blowing air into the filtrate to perform precipitation reaction, and recovering a second precipitate to obtain a second supernatant; the specific process of blowing air into the filtrate to carry out precipitation reaction comprises the following steps: firstly controlling the temperature to be 20-40 ℃, controlling the air pressure above the liquid level of the filtrate to be 2-6bar, and bubbling air into the filtrate to be 2-5h; then maintaining the temperature at 20-40deg.C, controlling the air pressure above the liquid level of the filtrate at 0.8-1.2bar, and blowing air into the filtrate at 1-2h;
(3) Membrane separation and concentration: ultrafiltering the second supernatant to obtain ultrafiltered water and ultrafiltered concentrated water; nanofiltration is carried out on ultrafiltration produced water to obtain nanofiltration produced water and nanofiltration concentrated water;
(4) And (5) recrystallizing: recrystallizing the nanofiltration concentrated water to obtain sodium sulfate.
2. The recycling method according to claim 1, wherein in the step (3), after nanofiltration produced water and nanofiltration concentrated water are obtained, reverse osmosis is performed on the nanofiltration produced water to obtain reverse osmosis produced water and reverse osmosis concentrated water; in the step (4), the nanofiltration concentrated water and the reverse osmosis concentrated water are recrystallized to obtain sodium sulfate.
3. The recycling method according to claim 1, wherein in the step (2), the gas overflowed from the filtrate is re-blown into the filtrate after being dried.
4. The recycling method according to claim 1, wherein in the step (2), air is blown into the filtrate through a gas distributor; the gas distributor is provided with a plurality of gas outlets; the aperture of the air outlet of the air distributor is small in inside and large in outside.
5. The recycling method of claim 4, wherein a transverse baffle is provided above the gas distributor.
6. The recycling method according to claim 1, wherein in the step (1), the specific process of the adsorption filtration comprises the steps of: the first supernatant sequentially passes through an activated carbon packing layer, a zeolite packing layer, an anthracite packing layer and a quartz sand packing layer.
7. The recycling method according to claim 2, characterized in that in step (3):
in the ultrafiltration process, an ultrafiltration membrane with the aperture of 40-200nm is adopted, the pressure is 0.2-0.6MPa, and the treated water amount is 10-30m 3 /h; and/or
In the nanofiltration process, a nanofiltration membrane with the molecular weight cut-off of 150-300 and Da is adopted, the pressure is 0.8-2MPa, and the water yield of a single membrane is 2-10m 3 /h; and/or
In the reverse osmosis process, the pressure is 1-4MPa, and the water yield of a single membrane is 0.5-1.5m 3 /h。
8. The recycling method according to any one of claims 1 to 7, characterized in that the treatment of the waste water from the production of silica-alumina inorganic coated titanium dioxide is carried out by a treatment line; the silicon-aluminum inorganic coated titanium dioxide production wastewater treatment line comprises a materialization treatment unit, a bubbling reaction unit, a membrane separation concentration unit and a recrystallization unit which are connected in sequence; the bubbling reaction unit comprises a bubbling reactor, one or more gas distributors are arranged in the bubbling reactor, and a plurality of gas outlets are arranged on each gas distributor; the membrane separation concentration unit comprises an ultrafilter, a nanofiltration device and a reverse osmosis device which are sequentially connected, and the ultrafilter is connected with the bubbling reactor; the recrystallization unit comprises an evaporator, and the nanofiltration device and the reverse osmosis device are connected with the evaporator.
9. The recycling method according to claim 8, wherein the physicochemical treatment unit comprises a pH adjusting tank, a primary reaction tank, a primary sedimentation tank, a secondary reaction tank, a secondary sedimentation tank and a filter which are connected in sequence; the pH regulating tank is connected with the acid adding device and the alkali adding device; the first-stage reaction tank and the second-stage reaction tank are connected with a flocculating agent feeding device and a coagulant aid feeding device; the filter is connected to the bubble reactor.
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