CN112250211A

CN112250211A - Method for treating and recovering titanium white effluent by sulfuric acid process

Info

Publication number: CN112250211A
Application number: CN202010966413.0A
Authority: CN
Inventors: 伍佳
Original assignee: Cnmc Guangxi Pgma Co ltd
Current assignee: Cnmc Guangxi Pgma Co ltd
Priority date: 2020-09-15
Filing date: 2020-09-15
Publication date: 2021-01-22
Anticipated expiration: 2040-09-15
Also published as: CN112250211B

Abstract

The invention discloses a method for treating and recovering titanium white effluent by a sulfuric acid process, which comprises the following steps: adding a strong alkali solution into the sulfuric acid process titanium dioxide discharged water; stirring and filtering; adding an oxalic acid solution into the first filtrate, stirring and filtering; adding a strong alkali solution into the second filtrate, and adjusting the pH to 6-9; wherein, the strong base is one or the combination of more of KOH and NaOH. The method is convenient to operate and good in treatment effect, so that the treated water can be directly reused in the metatitanic acid washing process, the titanium dioxide prepared by salt treatment, filter pressing, calcination and grinding of the metatitanic acid after washing is qualified in water dispersibility, the pigment performance is normal, and zero discharge of discharged water can be realized; meanwhile, the method has the advantages of simple process flow, stable treatment effect, less equipment investment, no secondary pollution, low treatment cost, considerable economic benefit and wide market prospect.

Description

Method for treating and recovering titanium white effluent by sulfuric acid process

Technical Field

The invention relates to the field of wastewater treatment. More particularly, the invention relates to a method for treating and recycling titanium white effluent produced by a sulfuric acid process.

Background

At present, most of titanium dioxide factories in China adopt sulfuric acid process production, a large amount of acid wastewater is produced in the production process, and the main pollution factor is H₂SO₄、TiOSO₄、FeSO₄. Most of the waste water treatment of titanium dioxide factory adopts calcium carbonate to neutralize H₂SO₄、TiOSO₄Then using lime milk to neutralize FeSO₄Filter pressing to obtain titanium gypsum and filtrate, aerating the filtrate to obtain trace Fe in the filtrate²⁺Oxidation to Fe (OH)₃The precipitate is formed by the precipitation of the mixture,finally, clarifying to obtain the external drainage, wherein the indexes are as follows: pH 6-9, COD_cr＝10～20mg/l，NH₃-N≤1mg/l，SS＝5～20mg/l，Mg²⁺＝100～200mg/l，Ca²⁺＝500～600mg/l，SO₄ ^2-1600-2000 mg/l, and the balance Fe²⁺，Ti⁴⁺，Al³⁺，Cu²⁺，Zn²⁺，Mn²⁺，Pb²⁺，Cd²⁺，Cr⁶⁺，F^-，As⁶⁺The detection value of the equal elements is extremely low, and reaches the GB8978-1996 emission standard.

From the analysis of the external drainage index, except for Mg²⁺，Ca²⁺，SO4^2-The main reason for this result is that calcium carbonate and lime milk are used as raw materials for wastewater neutralization, and Mg with higher concentration is introduced²⁺，Ca² ⁺Neutralizing the MgSO formed in the reaction₄，CaSO₄·2H₂O itself has a certain solubility in water, so that the discharged water contains Mg with higher concentration²⁺，Ca²⁺，SO₄ ^2-. It is the effluent that contains a relatively high concentration of Mg²⁺，Ca²⁺If the titanium pigment is returned to the metatitanic acid washing procedure for use, the prepared titanium pigment contains higher calcium and magnesium, and finally the water dispersibility of the titanium pigment is too low, so that the application performance of the pigment is greatly reduced.

Therefore, how to effectively reduce Mg in the wastewater discharged by the sulfate process titanium dioxide²⁺，Ca²⁺Concentration of Mg reaching clean water for production²⁺≤10mg/l，Ca²⁺The standard of less than or equal to 10mg/l is adopted, so that the treated discharged water can return to the titanium white production line, the requirement of the metatitanic acid washing process with the highest water utilization standard of the titanium white production line is met, the finally obtained product of the titanium white production line is qualified in quality, the discharged water zero discharge can be realized, and the problem that the comprehensive utilization of the titanium white wastewater needs to be solved urgently is formed.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

The invention also aims to provide a method for treating and recycling the titanium white effluent by the sulfuric acid process, which has convenient operation and good treatment effect, so that the treated water can be directly reused in the metatitanic acid washing procedure, the titanium white powder prepared by salt treatment, filter pressing, calcining and grinding of the metatitanic acid after washing is qualified in water dispersibility, the pigment performance is normal, and zero discharge of the effluent can be realized; meanwhile, the method has the advantages of simple process flow, stable treatment effect, less equipment investment, no secondary pollution, low treatment cost, considerable economic benefit and wide market prospect.

To achieve these objects and other advantages in accordance with the present invention, there is provided a method for activated sulfuric acid process titanium dioxide effluent treatment recovery, comprising:

s1, adding a strong alkali solution into the sulfuric acid process titanium dioxide discharged water, and adjusting the pH to 10-14; stirring and filtering to obtain a first solid and a first filtrate, wherein the concentration of magnesium ions in the first filtrate is less than or equal to 10 mg/l;

s2, adding oxalic acid solution into the first filtrate, adjusting the pH to 1-4, stirring, and filtering to obtain a second solid and a second filtrate, wherein the concentration of magnesium ions in the second filtrate is less than or equal to 10mg/l, and the concentration of calcium ions in the second filtrate is less than or equal to 10 mg/l.

S3, adding a strong alkali solution into the second filtrate, and adjusting the pH to 6-9.

Preferably, the indexes of the titanium white effluent discharged by the sulfuric acid process reach GB8978-1996 discharge standard, and specifically comprise the following steps: pH 6-9, Mg²⁺＝100～200mg/l，Ca²⁺＝500～600mg/l，SS＝10～20mg/l。

Preferably, the strong base of the strong base solution is one or more of KOH and NaOH.

Preferably, the mass concentration of the strong alkali solution is 10-1000 g/l.

Preferably, the mass concentration of the oxalic acid solution is 10-100 g/l.

Preferably, when the strong alkali solution is added in S1, the oxalic acid solution is added in S2, and the strong alkali solution is added in S3, the blowing operation is performed to the solution to be added.

Preferably, S4 is further included after S3, S4 is specifically flocculation purification, polyaluminium chloride is added into the discharged water treated in the step S3, and then purification is carried out through sand filtration.

Preferably, the water purified by sand filtration is Mg²⁺≤10mg/l，Ca²⁺≤10mg/l，SS≤10mg/l。

The invention at least comprises the following beneficial effects:

the method comprises the following steps of reasonably removing magnesium ions and calcium ions, adjusting the whole external drainage system to a proper pH value by using strong base, completely precipitating the magnesium ions in the external drainage to reach a concentration standard of less than or equal to 10mg/l, meeting the magnesium ion content grade of tap water, and filtering and separating the magnesium hydroxide precipitate generated by reaction from the system in time to reduce the anti-dissolution probability of the generated magnesium hydroxide precipitate;

the pH value of the system is adjusted to be proper in acidity by oxalic acid, calcium ions are precipitated at the same time, the calcium ions in the system can be precipitated in a calcium oxalate form at one time, and the obtained calcium oxalate is filtered and separated from the system under an acidic condition, so that the calcium ions and the magnesium ions can achieve a good separation effect;

adjusting the water from which the calcium ions are removed to be neutral, so that the discharged water obtained after treatment can return to a titanium dioxide production line, reaches the metatitanic acid washing procedure with the highest water standard of the titanium dioxide production line, is adjusted to be neutral water, and can supply the surplus water to other posts for use; the content of calcium and magnesium ions in the treated discharged water is lower than the conventional tap water standard, so that the finally obtained product is qualified in quality, the zero discharge of the discharged water in a titanium dioxide factory can be realized, and the problem of comprehensive utilization of the titanium dioxide wastewater is solved;

compared with the existing membrane separation means, the concentration of calcium and magnesium ions in water to be treated is limited, for example, in order to reach the filtration standard in the Kjeldahl membrane filtration technology, the content of calcium and magnesium ions which can be treated is not more than 20mg/l, otherwise, the membrane separation method can generate larger use burden on a filtration membrane and reduce the service life of the filtration membrane; meanwhile, because the industrial water consumption of the titanium white is large, usually 10 tons is taken as a unit, and the treatment cost is higher by adopting a filtering membrane, the titanium white is not suitable for large-scale industrial production treatment;

the existing patent adopts strong alkali and calcium carbide milk to remove calcium and magnesium ions, and the content of the obtained calcium and magnesium ions does not meet the requirement of the calcium and magnesium ion content of tap water; calcium ions and magnesium ions cannot be removed as completely as possible, and other metal ions can be introduced, so that the finally obtained treated water is not suitable for the metatitanic acid washing procedure with the highest water standard of a titanium white production line, the production target of titanium white is not reached, and the discharged water cannot be recycled;

the method adopts a chemical precipitation means, firstly removes magnesium ions and then calcium ions according to a specified operation sequence, and reasonably controls the pH value to ensure that the content of the calcium and magnesium ions in the sulfate process titanium dioxide discharged water reaches a lower level and meets the tap water standard; the treated discharged water can return to the metatitanic acid washing production line for reuse, so that the effects of environmental protection and water resource saving are achieved; compared with other means except calcium and magnesium ions, such as membrane separation, ion exchange and the like, the technology of the invention has the advantage of treating large-scale external drainage, and has low treatment cost and good operation, and the treatment effect can reach or even be lower than the requirement of the calcium and magnesium ion content of tap water.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is an operation flow chart of a method for treating and recovering titanium white effluent by a sulfuric acid process in the technical scheme of the invention.

Detailed Description

The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.

As shown in FIG. 1, in the following examples, the KOH solutions were added in a concentration of 150 g/l; the concentration of the added oxalic acid solution is 100 g/l; the concentration of NaOH solution is 150 g/l; wherein, the solute of KOH solution and NaOH solution is made of raw materials, the strong base content is more than or equal to 99%, and the oxalic acid content of the solute oxalic acid in the oxalic acid solution is more than or equal to 99%.

Hair brushIn the light of the above, the indexes of the treated titanium white effluent by the sulfuric acid process all reach the discharge standard of GB8978-1996, and specifically comprise the following steps: pH 6-9, Mg²⁺＝100～200mg/l，Ca²⁺＝500～600mg/l，SS＝10～20mg/l。

< example 1>

A method for treating and recycling the titanium white by a sulfuric acid method comprises the following steps:

taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 7, Mg²⁺＝160mg/l，Ca²⁺＝550mg/l，SS＝15mg/l；

Starting mechanical stirring while blowing air, pumping sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding KOH solution, adjusting the pH to 11, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain first filtrate and first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝8mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting the pH to 2, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝4mg/l；Mg²⁺＝8mg/l；

Starting mechanical stirring while blowing air, adding a KOH solution, and adjusting the pH to 7;

adding polyaluminium chloride with the quality reaching GB15892-2009 standard, and purifying by sand filtration to prepare purified water;

wherein the content of calcium and magnesium ions in the purified effluent is Mg²⁺＝8mg/l；Ca²⁺＝4mg/l；SS＝6mg/l。

Return to reuse

After purified water is prepared, returning the purified water to a titanium white production line for a metatitanic acid washing procedure; the titanium dioxide prepared by salt treatment, filter pressing, calcining and grinding of the washed titanium white is qualified in water dispersibility, the pigment performance is normal, and zero discharge of discharged water is realized.

Transferring the purified water to a titanium dioxide production line to obtain the final titanium dioxide water dispersibility of 80%;

the performance indexes of the titanium dioxide pigment are as follows: the L value was 98.4, and the decoloring force was 103%.

< example 2>

taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 7.5, Mg²⁺＝170mg/l，Ca²⁺＝560mg/l，SS＝18mg/l；

Starting mechanical stirring while blowing air, pumping sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding KOH solution, adjusting the pH to 12.5, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a first filtrate and a first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝5mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting pH to 1.5, stirring for 30 min, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝2mg/l；Mg²⁺＝5mg/l；

Starting mechanical stirring while blowing air, adding a KOH solution, and adjusting the pH to 7.5;

wherein the content of calcium and magnesium ions in the purified effluent is Mg²⁺＝5mg/l；Ca²⁺＝2mg/l；SS＝3mg/l。

Return to reuse

Transferring the purified water to a titanium dioxide production line to obtain the final titanium dioxide water dispersibility which is 82%;

the performance indexes of the titanium dioxide pigment are as follows: the L value was 98.5, and the decoloring force was 103%.

< example 3>

taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 8.5, Mg²⁺＝165mg/l，Ca²⁺＝580mg/l，SS＝16mg/l；

Starting mechanical stirring while blowing air, pumping sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding KOH solution, adjusting the pH to 11.5, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a first filtrate and a first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝7mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding an oxalic acid solution with oxalic acid content of more than or equal to 99%, adjusting the pH value to 1.8, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝3mg/l；Mg²⁺＝7mg/l；

Starting mechanical stirring while blowing air, adding a KOH solution, and adjusting the pH to 7.2;

wherein the content of calcium and magnesium ions in the purified effluent is Mg²⁺＝7mg/l；Ca²⁺＝3mg/l；SS＝2mg/l。

Return to reuse

the performance indexes of the titanium dioxide pigment are as follows: the L value was 98.5, and the decoloring force was 104%.

< example 4>

taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 7.5, Mg²⁺＝155mg/l，Ca²⁺＝540mg/l，SS＝14mg/l；

Starting mechanical stirring while blowing air, pumping sulfate process titanium dioxide discharged water into a reaction barrel, adding NaOH solution, adjusting pH to 12, stirring for 30 minutes, and performing solid-liquid separation by a membrane filter press to obtain first filtrate and first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝6mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting the pH to 2.2, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝5mg/l；Mg²⁺＝6mg/l；

Starting mechanical stirring while blowing air, adding a NaOH solution, and adjusting the pH to be 8;

the method comprises the steps of adding polyaluminum chloride with the quality meeting the GB15892-2009 standard, purifying by sand filtration to prepare purified water, washing with metatitanic acid, performing salt treatment, filter pressing, calcining and grinding to prepare titanium dioxide with qualified water dispersibility and normal pigment performance, and realizing zero discharge of discharged water.

The content of calcium and magnesium ions in the purified water is as follows: mg (magnesium)²⁺＝6mg/l；Ca²⁺＝5mg/l；SS＝4mg/l；

Transferring the purified water to a titanium dioxide production line to obtain the final titanium dioxide water dispersibility of 81 percent;

< example 5>

taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 8, Mg²⁺＝175mg/l，Ca²⁺＝570mg/l，SS＝17mg/l；

Starting mechanical stirring while blowing air, pumping sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding NaOH solution, adjusting pH to 13, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain first filtrate and first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝4mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting the pH to 1.6, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝3mg/l；Mg²⁺＝4mg/l；

Starting mechanical stirring while blowing air, adding NaOH solution, and adjusting the pH value to 7.8;

The content of calcium and magnesium ions in the purified water is as follows: mg (magnesium)²⁺＝4mg/l；Ca²⁺＝3mg/l；SS＝5mg/l；

< example 6>

taking sulfate process titanium white external drainage, wherein the indexes are as follows: the pH value is 7, and the pH value is 7,Mg²⁺＝160mg/l，Ca²⁺＝550mg/l，SS＝15mg/l；

starting mechanical stirring while blowing air, pumping sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding KOH solution, adjusting the pH to 10, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain first filtrate and first solid, wherein the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝9mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting the pH to 1, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝2mg/l；Mg²⁺＝9mg/l；

Starting mechanical stirring while blowing air, adding a KOH solution, and adjusting the pH to be 6;

wherein the content of calcium and magnesium ions in the purified effluent is Mg²⁺＝9mg/l；Ca²⁺＝2mg/l；SS＝6mg/l。

Return to reuse

< example 7>

Starting mechanical stirring while blowing air, pumping the sulfuric acid process titanium dioxide discharged water into a reaction barrel, adding a KOH solution, adjusting the pH to 14, stirring for 30 minutes, and performing solid-liquid separation through a membrane filter press to obtain a first filtrate and a first solid, wherein most of the first solid is Mg (OH)₂(ii) a Detecting the content of magnesium ions in the first filtrate to obtain Mg²⁺＝3mg/l；

Starting mechanical stirring while blowing air, pumping the first filtrate into a reaction barrel, adding oxalic acid solution, adjusting the pH to 4, stirring for 30 minutes, and performing solid-liquid separation by using a membrane filter press to obtain a second filtrate and a second solid, wherein the majority of the second solid is CaC₂O₄(ii) a The detection shows that the contents of calcium and magnesium ions in the second filtrate are respectively Ca²⁺＝9mg/l；Mg²⁺＝3mg/l；

Starting mechanical stirring while blowing air, adding a KOH solution, and adjusting the pH to 9;

wherein the content of calcium and magnesium ions in the purified effluent is Mg²⁺＝3mg/l；Ca²⁺＝9mg/l；SS＝5mg/l。

Return to reuse

Comparative test example

And (3) external drainage: taking sulfate process titanium white external drainage, wherein the indexes are as follows: pH 7.5, Mg²⁺＝170mg/l，Ca²⁺560mg/l, SS 18 mg/l; labeled example 2; KOH 150 g/l; NaOH 150 g/l; h₂C₂O₄＝100g/l；H₂SO₄＝100g/l；Ca(OH)₂＝50g/l；Na₂CO₃＝50g/l；

The treatment conditions were changed in the standard example of example 2, and a comparative experiment was carried out;

the concentration detection of magnesium ions and calcium ions is carried out in an analysis and measurement laboratory of Guangxi Chinese colored group (Guangxi) Pinggui flying saucer, Inc., the detection means is acid-base titration, and the concrete operation is as follows:

calcium ion detection

The principle is as follows: in a strong alkaline solution with the pH value of more than 12, triethanolamine is used as a masking agent, a calcium indicator is used, and an EDTA standard solution is titrated to blue as an end point;

reagent: 0.002mol/l EDTA standard solution;

a potassium hydroxide aqueous solution with the mass concentration of 20 percent;

0.1g of calcium indicator and 10g of potassium sulfate are mixed and ground to obtain a mixture;

calcium standard solution, weighing 1.0009g of standard CaCO dried at 110 deg.C₃Dissolve in 15mL (1+4) of HCl and dilute to 1000mL with water and shake. 10ml of the extract is taken, diluted to 1000ml by water and shaken up for standby. This solution (1 ml) ═ 0.1. mu. molCa

Methyl red, 1g/L ethanol solution;

1+2 triethanolamine: taking 1 part of triethanolamine and 2 parts of H₂And mixing the phases O and O.

And (3) an analysis step:

calibration of EDTA standard solution:

20ml of calcium standard solution is taken into a 250ml conical flask, and 80ml of H is added₂O, add 10ml of ph 10 buffer, 2ml of (1+2) triethanolamine, add 2 drops of mixing indicator, and titrate to pure blue with EDTA standard solution.

T＝(0.1×20)÷(C-b)

Wherein, 0.1-equivalent hardness μmol/ml of the standard solution;

20-draw up calcium standard solution to mention ml;

consumption of EDTA volume ml at C-calibration;

b-blank consumption EDTA volume ml

Sample detection:

taking 100ml of a water sample to be detected, adding 10ml of 20% NaOH, adding 5ml of (1+2) triethanolamine, adding a small amount of calcium indicator, titrating by using an EDTA standard until pure blue is used as an end point, and simultaneously carrying out a blank experiment;

calcium ion concentration μmol/L ═ (((a-b) × T) ÷ 100) × 1000;

wherein, a-the water sample consumes the volume ml of EDTA;

b-blank consumption of EDTA volume ml;

the titer of T-EDTA on calcium hardness is mol/ml;

magnesium ion detection

The principle is as follows: titrating an EDTA standard solution to pure blue to obtain the hardness in water under the condition of mixing an acid chrome blue K-naphthol green B indicator in a pH (potential of hydrogen) 10 aqueous solution, titrating the EDTA standard solution to pure blue by using a (1+2) triethanolamine as a masking agent in a strong alkaline solution with the pH being more than 12, titrating the EDTA standard solution to pure blue by using a calcium indicator to obtain the calcium ion concentration in the water, wherein the difference between the calcium ion concentration and the calcium ion concentration is magnesium ion concentration. (ii) a

Reagent: 0.002mol/LEDTA standard solution;

a potassium hydroxide aqueous solution with a mass concentration of 20%;

Methyl red, 1g/L ethanol solution;

1+2 triethanolamine: taking 1 part of triethanolamine and 2 parts of H₂Mixing the phases O and O;

0.002mol/L EDTA standard solution;

ammonia-ammonium buffer solution: pH 10 with 20g NH₄Dissolving Cl in 100ml of water, adding 150ml of ammonia water, diluting with water to 1000ml, and shaking up;

an acid chrome blue K-naphthol green B indicator, wherein 0.2g of acid chrome blue K and 0.4g of naphthol green B are dissolved in 100ml of water;

1 part of 1+4HClHCl with 4 parts of H₂Mixing the phases O and O;

sample detection:

taking 100mL of a water sample to be detected, adding 10mL of buffer solution with the pH value of 10 into a conical flask, adding 5mL of (1+2) triethanolamine, adding 3 drops of an acidic chrome blue K-naphthol green B indicator, titrating to pure blue by using an EDTA standard until the end point, finishing the whole process within 5 minutes, and simultaneously carrying out a blank experiment at the temperature of not lower than 15 ℃;

water hardness calculation × μmol/L ═ (((a-b) × T) ÷ 100) × 1000;

wherein, a-the water sample consumes the volume ml of EDTA;

b-blank consumption of EDTA volume ml;

the titer of T-EDTA on calcium hardness is mol/ml;

magnesium ion concentration (. mu. mol/l) ═ total hardness of water (. mu. mol/l) -calcium ion concentration (. mu. mol/l)

The detection of water dispersibility is an enterprise standard, and the specific operation is as follows:

1. the instrument comprises the following steps: oven (105 + -2) deg.C, beaker 100mL (inner diameter 43mm), and drier;

2. procedure for the preparation of the

Weighing 100mL of a small amount of the test sample with constant weight, adding 5mL of water, accurately adding 5.000g of the test sample (accurate to 0.001g), and fully stirring and dispersing; adding 40mL of water with the temperature of 20 ℃, fully stirring and dispersing, standing for 2h, pouring out the upper layer liquid, leaving the precipitate, transferring into an oven at (105 +/-2) DEG C for drying for 2h, then cooling in a dryer, and weighing the precipitate.

3. Representation of the results

Water dispersibility calculation formula:

wherein m is₀Is the mass of the sample, g; m1 is the mass of the precipitate after constant weight, g; the arithmetic mean of the two measurements was taken.

Comparative example 1

The other conditions were the same as in example 2 except that in the effluent treatment, H was added first₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; adding KOH aqueous solution, adjusting the pH value to 12.5, stirring and filtering; finally using H₂C₂O₄Adjusting the pH value of the solution to 8 by using an aqueous solution; filtering with filter paper; during this period, the solution is added H for the first time₂C₂O₄When the solution is an aqueous solution, the solution becomes turbid, and the amount of generated precipitate is small;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝335mg/l；Mg²⁺＝6mg/l。

Comparative example 2

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added, the pH was adjusted to 10, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝3mg/l；Mg²⁺＝9mg/l。

Comparative example 3

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added, the pH was adjusted to 11, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝2mg/l；Mg²⁺＝7mg/l。

Comparative example 4

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added to adjust the pH to 14, followed by stirring and filtration; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝2mg/l；Mg²⁺＝4mg/l。

Comparative example 5

Other conditions and effectsThe same as in example 2, except that when the effluent is treated, a KOH aqueous solution is added, the pH is adjusted to 12.5, and the mixture is stirred and filtered; then adding H₂C₂O₄Adjusting the pH of the aqueous solution to 1, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝2mg/l；Mg²⁺＝5mg/l。

Comparative example 6

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added, the pH was adjusted to 12.5, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH of the aqueous solution to 2, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝3mg/l；Mg²⁺＝6mg/l。

Comparative example 7

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added, the pH was adjusted to 12.5, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 4, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝9mg/l；Mg²⁺＝6mg/l。

Comparative example 8

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added to adjust the pH to 12.5, followed by stirring and no filtration; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and not filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝52mg/l；Mg²⁺＝133mg/l。

Comparative example 9

The other conditions were the same as in example 2 except that, in the effluent treatment, an aqueous KOH solution was added to adjust the pH to 12.5, stirring without filtering; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝8mg/l；Mg²⁺＝151mg/l。

Comparative example 10

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was added, the pH was adjusted to 12.5, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and not filtering; finally, KOH aqueous solution is added to adjust the pH value to be 8, and the mixture is filtered;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝44mg/l；Mg²⁺＝5mg/l。

Comparative example 11

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous NaOH solution was added first, the pH was adjusted to 12.5, stirred and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; finally, adding NaOH aqueous solution to adjust the pH to 8, and filtering;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝3mg/l；Mg²⁺＝7mg/l。

Comparative example 12

The other conditions were the same as in example 2, except that, in the effluent treatment, an aqueous KOH solution was first adjusted to pH 12.5, stirred, and filtered; then adding H₂C₂O₄Adjusting the pH value of the aqueous solution to 1.5, stirring and filtering; that is, the final pH of the solution was 1.5;

Comparative example 13

The other conditions were the same as in example 2 except that in the effluent treatment, H was added first₂SO₄Adjusting the pH value of the solution to 4, stirring the solution, and filtering the solution without generating precipitate; then adding H₂C₂O₄Adjusting the pH of the solution to 1.5, stirring and filtering; that is, the final pH of the solution was 1.5;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝560mg/l；Mg²⁺＝170mg/l。

Comparative example 14

The other conditions were the same as in example 2 except that in the effluent treatment, H was added first₂C₂O₄Adjusting the pH value of the solution to 1.5, stirring the solution to generate precipitate, and not filtering the solution; then adding H₂SO₄Adjusting the pH value of the solution to 1, stirring, dissolving the precipitate and not filtering; that is, the final pH of the solution is 1;

Comparative example 15

Other conditions were the same as in example 2 except that Ca (OH) was added to the effluent for the treatment of the effluent₂Adjusting pH to 12.5, stirring to precipitate, and filtering; then adding Na₂CO₃Stirring and filtering the solution; the method is a conventional method for removing calcium and magnesium ions in solution, and Ca (OH) is adopted₂Firstly, magnesium ions are precipitated, and then calcium ions are precipitated by adopting sodium carbonate;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝256mg/l；Mg²⁺＝139mg/l。

Comparative example 16

Other conditions were the same as in example 2 except that Ca (OH) was added to the effluent for the treatment of the effluent₂Adjusting pH to 12.5, stirring to precipitate, and filtering; then adding H₂C₂O₄Adjusting the pH of the solution to 1.5, stirring and filtering; that is, the final pH of the solution was 1.5; the method is a conventional method for removing calcium and magnesium ions in solution, and Ca (OH) is adopted₂Firstly precipitating magnesium ions and then adopting H₂C₂O₄Precipitating calcium ions;

the content of the obtained calcium and magnesium ions is Ca by detection²⁺＝543mg/l；Mg²⁺＝134mg/l。

Comparative example 17

Simultaneously, the content of calcium and magnesium ions in the production water in the Guizhou management area of the Guangxi Zhuang autonomous region Hozhou city is detected, and the concentration of the calcium and magnesium ions is standard Ca through detection²⁺＝9.28mg/l；Mg²⁺＝8.43mg/l。

Comparative example 18

According to the method for treating the titanium white wastewater disclosed by the Chinese invention patent with the publication number of CN 106315910A.

Adding quicklime into sulfate process titanium dioxide wastewater for neutralization and aeration; then adding a flocculating agent for aggregation, coagulation and precipitation; the rest wastewater passes through an ultrafiltration membrane pool to remove colloid, insoluble substances, microorganisms and the like, so as to form inorganic salt wastewater; finally, inorganic salt in the water is removed through a reverse osmosis membrane component to form qualified industrial water.

The scheme is that the waste water is prepared by adding quicklime and aerating, and the GB8978-1996 standard is met; adding a polyaluminum trichloride flocculating agent, filtering by using an ultrafiltration membrane with the aperture of 0.001-0.1 mu m, and finally removing inorganic salt by using a reverse osmosis membrane component to obtain qualified industrial water with the pH of 6-9 and Mg²⁺≤50mg/l、Ca²⁺≤100mg/l。

Due to its Mg²⁺、Ca²⁺The concentration is higher, after the titanium pigment is used for washing titanium pigment slurry, the water dispersibility of the prepared titanium pigment is lower, the application performance of the pigment is influenced, and the obtained titanium pigment has poor quality and is not suitable for being recycled in a titanium pigment production line.

And (4) analyzing results:

comparing example 2 with comparative example 1, it can be seen that exchanging the precipitation order of calcium ions and magnesium ions has a great influence on the removal of calcium and magnesium ions; according to multiple experiments of the inventor, the reason may be that calcium and magnesium ions exist in the form of calcium sulfate and magnesium sulfate in the original discharged water, potassium hydroxide is added to adjust the solution to be alkaline, magnesium ions form magnesium hydroxide, because the magnesium hydroxide is extremely insoluble in water, the magnesium hydroxide is precipitated in the form of precipitate, and simultaneously, because the calcium sulfate is also converted into the calcium hydroxide, by comparing the solubility of the calcium ions in water of the two compounds calcium sulfate dihydrate and calcium hydroxide, it was found that, under alkaline conditions, calcium ions are more prone to exist in a mixed system in the form of calcium hydroxide, after magnesium hydroxide precipitate is separated out, the pH value is adjusted by adding oxalic acid, after the oxalic acid is added, the oxalic acid reacts with calcium hydroxide in a system, calcium ions are enabled to generate calcium oxalate sediment which is insoluble in water, so that the calcium ions are separated, and the reaction principle is an acid-base neutralization principle;

comparing example 2 with comparative examples 2 to 4, it can be seen that when KOH is used for precipitating magnesium ions, the larger the pH value is, the more beneficial the magnesium ions are to be precipitated, and meanwhile, the precipitation of calcium ions is not affected after the pH value is increased;

comparing example 2 with comparative examples 5 to 7, it can be seen that when calcium ions are precipitated by oxalic acid, the calcium ions exist in the form of calcium hydroxide, the smaller the pH value of the system is, the larger the precipitation amount of the calcium ions is, and when the pH value is about 1.5, the precipitation amount tends to be relatively kept stable;

comparing the example 2 with the comparative examples 8-10, it can be seen that if the magnesium hydroxide precipitate in the system is not removed in time, the magnesium hydroxide precipitated in the process of preparing the solution system from the alkalinity to the acidity has reverse dissolution, which causes low precipitation rate of magnesium ions; meanwhile, after the calcium hydroxide is completely precipitated, if the generated calcium oxalate is not separated in time, the generation rate of the calcium oxalate is reduced in the subsequent process of adjusting the pH value to be neutral, so that the concentration of calcium ions in the solution is increased;

comparing example 2 with comparative example 11, it can be seen that the use of different types of strong bases does not have a great influence on the removal of calcium and magnesium ions, and the concentration of the obtained calcium and magnesium ions is within an acceptable range;

comparing example 2 with comparative example 12, it can be seen that the calcium and magnesium ion content in the solution after oxalic acid treatment is lower, but the acidic water can not be used in industrial production due to the requirement of industrial water, and simultaneously, in order to not introduce other ions, the same strong base solution as the precipitated magnesium ions is used for adjusting the pH value, so that the discharged water after treatment can be used in normal industrial production;

as can be seen from comparison of example 2 and comparative examples 13 to 14, calcium oxalate is not easily generated under a strongly acidic condition, and even if a precipitate of calcium oxalate is generated first, the precipitate of calcium oxalate is dissolved after addition of a strong acid;

comparing example 2 with comparative example 15, it can be seen that comparative example 15 is a conventional method for removing calcium and magnesium ions in a system, calcium hydroxide is used for removing magnesium ions, and calcium hydroxide and calcium sulfate are precipitated by sodium carbonate, and experiments show that the method is suitable for systems containing a large amount of calcium and magnesium ions, the concentration of the removed calcium and magnesium ions is still in the range of 100-300 mg/l, the concentration of the calcium and magnesium ions cannot be removed to be less than 10mg/l, and the concentration of the calcium and magnesium ions cannot reach the standard of tap water, so that the method is not suitable for treating titanium white waste water.

Comparing example 2 with comparative example 16, it can be seen that the calcium ion content in the original system is increased by replacing the reagent for precipitating calcium ions with oxalic acid solution, because calcium hydroxide is used to remove magnesium ions in the previous stage; wherein, the calcium ions in the original system exist in the form of calcium sulfate, and the newly added calcium ions exist in the form of calcium hydroxide; when oxalic acid is used for precipitating calcium ions, the oxalic acid and calcium hydroxide are easy to react to generate precipitates, and the oxalic acid and calcium sulfate are difficult to react to generate precipitates;

comparing example 2 with comparative example 17 and comparative example 18, respectively, it is found that comparative example 17 is the content of calcium and magnesium ions in tap water in a laboratory, and the content of calcium and magnesium ions in example 2 is lower than that in tap water, thus reaching the hardness standard of tap water; the comparative example 18 is wastewater which can be discharged outside and is obtained by a conventional sewage treatment method of a titanium dioxide factory, and the method adopts a reverse osmosis membrane for treatment, so that the concentration of calcium and magnesium ions after treatment can not reach the tap water standard, and the calcium and magnesium ions are not suitable for recycling.

In conclusion, the experimental operation of the invention is simple, but the reagents for removing calcium and magnesium ions and the control of pH value are internally linked, and the inventor utilizes the slight difference of solubility between different calcium and magnesium ion precipitates, and through reasonable pH control and means, the content of calcium and magnesium ions in the wastewater discharged from a titanium dioxide factory is effectively reduced, the aim of recycling is achieved, and zero discharge of sewage is realized;

it should be noted that the exchange of the relevant steps in the implementation steps or the omission of the operation steps may bring a great influence on the result, so that the final result may not achieve the purpose of reducing the concentration of calcium and magnesium ions, so that the discharged water may not be returned to the industrial production line, and may also have a great influence on the quality of the produced titanium dioxide.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the embodiments shown and described without departing from the generic concept as defined by the claims and their equivalents.

Claims

1. The method for treating and recovering the titanium white by the sulfuric acid process is characterized by comprising the following steps of:

2. The method for treating and recovering the titanium white effluent of the sulfuric acid process according to claim 1, wherein the indexes of the titanium white effluent of the sulfuric acid process reach GB8978-1996 emission standards, which specifically comprise: pH 6-9, Mg²⁺＝100～200mg/l，Ca²⁺＝500～600mg/l，SS＝10～20mg/l。

3. The method for treating and recycling the titanium white effluent generated in the sulfuric acid process according to claim 1, wherein the strong base of the strong base solution is one or more of KOH and NaOH.

4. The method for treating and recycling the titanium white effluent generated by the sulfuric acid process according to claim 1, wherein the mass concentration of the strong alkali solution is 10-1000 g/l.

5. The method for treating and recovering the titanium white effluent produced by the sulfate process according to claim 1, wherein the mass concentration of the oxalic acid solution is 10 to 100 g/l.

6. The method for treating and recovering the exterior drainage of titanium white by sulfuric acid process according to claim 1, wherein, when the strong alkali solution is added in S1, the oxalic acid solution is added in S2 and the strong alkali solution is added in S3, air blowing operation is performed to the solution to be added.

7. The method for treating and recovering the titanium white mill effluent of the sulfuric acid process according to claim 1, wherein the step S4 is further included after S3, S4 is specifically flocculation purification, polyaluminium chloride is added to the effluent treated in the step S3, and then purification is performed by sand filtration.

8. The method for treating and recovering white titanium white effluent of sulfuric acid process according to claim 7, wherein the water purified by sand filtration is Mg²⁺≤10mg/l，Ca²⁺≤10mg/l，SS≤10mg/l。