阅读说明：本技术 一种利用含磷酸洗废液制备磷酸二氢钠的方法 (Method for preparing sodium dihydrogen phosphate by using phosphorus-containing acid pickling waste liquid ) 是由 孙志洋 戴国辉 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种利用含磷酸洗废液制备磷酸二氢钠的方法,所述方法包括如下步骤：(1)中和、过滤；(2)调节pH；(3)氧化除色、过滤；(4)浓缩；(5)冷却结晶、离心。本发明方法利用含磷酸洗废液,进行综合利用,达到资源综合利用,提高废液中磷物质的回收利用率,降低废水处置综合成本。(The invention discloses a method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid, which comprises the following steps: (1) neutralizing and filtering; (2) adjusting the pH value; (3) oxidizing, removing color and filtering; (4) concentrating; (5) cooling, crystallizing and centrifuging. The method utilizes the phosphorus-containing pickling waste liquid for comprehensive utilization, achieves comprehensive utilization of resources, improves the recovery rate of phosphorus substances in the waste liquid, and reduces the comprehensive cost of wastewater treatment.)

1. A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid is characterized by comprising the following steps:

(1) firstly, neutralizing the phosphorus-containing pickling waste liquid with an alkaline solution, and filtering;

(2) then, adding phosphoric acid into the filtrate prepared in the step (1) to adjust the pH value;

(3) then, adding hydrogen peroxide into the solution obtained in the step (2), heating, stirring, decoloring and filtering;

(4) then, concentrating the filtrate obtained in the step (3);

(5) and (5) cooling, stirring, crystallizing and centrifuging the concentrated solution obtained in the step (4) to obtain the sodium dihydrogen phosphate.

2. The method of claim 1, wherein in the step (1), the alkali solution is one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium bicarbonate solution and sodium bicarbonate solution.

3. The method according to claim 1, wherein in the step (1), the mass concentration of the alkali liquor is 10-50%.

4. The method according to claim 1, wherein in the step (1), the pH is neutralized to 9 to 10.

5. The method according to claim 1, wherein in the step (2), the pH after the adjustment is 5 to 6.

6. The method according to claim 1, wherein in the step (3), the mass concentration of the hydrogen peroxide is 20-30%.

7. The method according to claim 1, wherein the heating in step (3) is carried out at a temperature of 55 ℃ to 65 ℃ for a period of 1.5 hours to 3 hours.

8. The method according to claim 1, wherein in the step (4), the concentration is performed by distillation; the concentration ratio is 2-4: 1; concentrating until the solid content is 10-20%, and stopping concentrating.

9. The method according to claim 1, wherein in the step (5), the temperature of the crystallization is controlled to be 32 ℃ to 38 ℃ and the stirring rate is 100 r/min.

10. The method according to claim 1, characterized in that the phosphoric acid pickling waste liquid: 50-300 g/L of phosphoric acid, 3-5 g/L of thiourea, 0.1-0.5 g/L of M-P organosilicate solution and the balance of water.

Technical Field

The invention relates to the technical field of recovery and treatment of phosphoric acid pickling waste liquid, in particular to a resource recycling method of phosphoric acid pickling waste liquid.

Background

The pickling wastewater is wastewater generated when acid pickling treatment is performed with an acid such as sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, or the like, in order to remove oxides on the metal surface.

At present, because the factory adopting the strong acid pickling process such as hydrochloric acid and the like has serious problems of unqualified discharge of acid gas and waste water, the process of using the phosphoric acid pickling process gradually becomes a mainstream process in the treatment before the painting of metal equipment, the pickling waste water is generally strong in acidity, the waste water is treated mainly by a neutralization method at present, and the commonly used neutralizing agents comprise lime, dolomite, magnesium oxide and the like.

The treatment of the pickling waste liquid by adopting the neutralization method can generate a large amount of salt, and the treatment cost is high. In recent years, with the enhancement of environmental awareness, regulations increasingly restrict various indexes of acid pickling waste water, simple neutralization treatment is performed, heavy metals in acid pickling waste liquid are difficult to remove, and resource waste is caused.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for preparing sodium dihydrogen phosphate by using a phosphorus-containing pickling waste liquid. The method utilizes the steps of neutralization, filtration, pH adjustment, oxidation and color removal, filtration, concentration, crystallization recovery and the like to recycle the pickling waste liquid.

The technical scheme of the invention is as follows:

a method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) firstly, neutralizing the phosphorus-containing pickling waste liquid with an alkaline solution, and filtering;

(2) then, adding phosphoric acid into the filtrate prepared in the step (1) to adjust the pH value;

(3) then, adding hydrogen peroxide into the solution obtained in the step (2), heating, stirring, decoloring and filtering;

(4) then, concentrating the filtrate obtained in the step (3);

(5) and (5) cooling, stirring, crystallizing and centrifuging the concentrated solution obtained in the step (4) to obtain the sodium dihydrogen phosphate.

In the step (1), the alkali liquor is one or more of a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution, a potassium bicarbonate solution and a sodium bicarbonate solution.

In the step (1), the mass concentration of the alkali liquor is 10-50%.

In the step (1), the pH value is neutralized to 9-10.

In the step (2), the pH value is 5-6 after adjustment.

In the step (3), the mass concentration of the hydrogen peroxide is 20-30%.

In the step (3), the heating temperature is 55-65 ℃ and the time is 1.5-3 h.

In the step (4), the concentration is distillation concentration; the concentration ratio is 2-4: 1; concentrating until the solid content is 10-20%, and stopping concentrating.

In the step (5), the crystallization temperature is controlled to be 32-38 ℃, and the stirring speed is 100r/min

The phosphorus-containing pickling waste liquid: 50-300 g/L of phosphoric acid, 3-5 g/L of thiourea, 0.1-0.5 g/L of M-P organosilicate solution and the balance of water.

The beneficial technical effects of the invention are as follows:

1. the method utilizes the phosphoric acid pickling waste liquid, only uses conventional equipment, reduces equipment input cost, reduces treatment cost, has simple process, easy operation, reduces the skill requirement on workers, adjusts the pH to be strong alkalinity by utilizing different solubilities of different pH values during neutralization so as to reduce the impurities in the pickling waste liquid to the minimum, and adjusts the pH value back after filter pressing, thereby being beneficial to improving the qualification rate of finished products of sodium dihydrogen phosphate.

2. The method of the invention adds hydrogen peroxide and maintains a certain temperature to decolor the solution, reduce or remove the chroma of the sodium dihydrogen phosphate solution and further improve the qualification rate of the finished sodium dihydrogen phosphate product.

3. The method adopts the treatments of neutralization, filtration, pH regulation, oxidation and color removal, filtration, concentration, cooling crystallization and centrifugation, and the components in the pickling waste liquid are fully and reasonably recycled through the treatment of the steps, so that the medicament cost for directly neutralizing the waste liquid and the solid landfill cost are reduced, the problems existing in the treatment process of the pickling waste liquid are solved, the resources are recycled to the maximum extent, the pollutants discharged into the environment are minimized, and the comprehensive treatment cost is reduced.

Detailed Description

The present invention will be described in detail with reference to examples.

Example 1

A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) taking 500ml of phosphoric acid pickling waste liquid (the acidity of raw phosphoric acid is 15%, the character is reddish brown turbid liquid, the COD is 16000ppm, thiourea is 3g/L, and the M-P organosilicone hydrochloric acid solution is 0.2g/L), slowly adding a sodium hydroxide solution with the mass concentration of 10%, neutralizing the pH value to 10, and filtering to obtain reddish brown filtrate;

(2) slowly adding phosphoric acid with the mass concentration of 15% into the filtrate obtained in the step (1), and adjusting the pH value back to 5;

(3) after the pH is adjusted, slowly adding 10ml of hydrogen peroxide with the mass concentration of 30%, heating in a water bath to 60 ℃, maintaining, stirring for 3 hours, closing the water bath after the solution becomes colorless, and performing suction filtration to obtain colorless filtrate;

(4) distilling the filtrate at 100 deg.C and-0.06 MPa until the concentration ratio is 3, stopping distillation, pouring the distillation mother liquor into a beaker, stirring, cooling for crystallization, and centrifuging to obtain sodium dihydrogen phosphate crystal. The detection of the finished product shows that the content of the sodium dihydrogen phosphate is 98 percent.

(5) The COD of the distilled fraction is 1500mg/L, the index is reduced, and the salt is recovered, so that the salt content in the wastewater is reduced, and the residue generated in the common neutralization process is avoided.

Example 2

A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) taking 1000ml of phosphoric acid pickling waste liquid (the acidity of raw phosphoric acid is 14%, the character is reddish brown turbid liquid, the COD is 15500ppm, thiourea is contained in 4g/L, and the mass concentration of M-P organosilicone hydrochloric acid solution is 0.5g/L), slowly adding 13% sodium hydroxide solution, neutralizing the pH value to 10, and filtering to obtain reddish brown filtrate;

(2) slowly adding phosphoric acid with the mass concentration of 15% into the filtrate obtained in the step (1), and adjusting the pH value back to 5;

(3) after the pH is adjusted, slowly adding 20ml of hydrogen peroxide with the mass concentration of 30%, heating in a water bath to 58 ℃, maintaining, stirring for 2 hours, closing the water bath after the solution becomes colorless, and performing suction filtration to obtain colorless filtrate;

(4) distilling the filtrate at 100 deg.C and-0.06 MPa until the concentration ratio is 3.5, stopping distillation, pouring the distillation mother liquor into a beaker, stirring, cooling for crystallization, and centrifuging to obtain sodium dihydrogen phosphate crystal. The content of sodium dihydrogen phosphate in the finished product is 97 percent.

(5) The COD of the distilled fraction is 1300mg/L, the index is reduced, and the salt is recovered, so that the salt content in the wastewater is reduced, and the residue generated in the common neutralization process is avoided.

Example 3

A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) taking 2000ml of phosphoric acid pickling waste liquid (the acidity of raw phosphoric acid is 15%, the character is reddish brown turbid liquid, the COD is 13000ppm, the content of thiourea is 3.5g/L, and the content of M-P organosilicone hydrochloric acid solution is 0.5g/L), slowly adding 13% by mass of sodium hydroxide solution, neutralizing the pH value to 9.5, and filtering to obtain reddish brown filtrate;

(2) slowly adding phosphoric acid with the mass concentration of 15% into the filtrate obtained in the step (1), and adjusting the pH value back to 5.5;

(3) after the pH is adjusted, slowly adding 45ml of hydrogen peroxide with the mass concentration of 30%, heating in a water bath to 60 ℃, maintaining, stirring for 5 hours, closing the water bath after the solution becomes colorless, and performing suction filtration to obtain colorless filtrate;

(4) distilling the filtrate at 100 deg.C and-0.06 MPa until the concentration ratio is 3, stopping distillation, pouring the distillation mother liquor into a beaker, stirring, cooling for crystallization, and centrifuging to obtain sodium dihydrogen phosphate crystal. The detection of the finished product shows that the content of the sodium dihydrogen phosphate is 98 percent.

(5) The COD of the distilled fraction is 1600mg/L, the index is reduced, and the salt is recovered, so that the salt content in the wastewater is reduced, and the residue generated in the common neutralization process is avoided.

Comparative example 1

A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) taking 500ml of phosphoric acid pickling waste liquid (the acidity of raw phosphoric acid is 14%, the character is reddish brown turbid liquid, the COD is 15500ppm, thiourea is contained in 4g/L, and the M-P organosilicone hydrochloric acid solution is 0.5g/L), slowly adding a sodium hydroxide solution with the mass concentration of 13%, neutralizing the pH value to 10, and filtering to obtain reddish brown filtrate;

(2) slowly adding phosphoric acid with the mass concentration of 15% into the filtrate obtained in the step (1), and adjusting the pH value back to 5; performing suction filtration to obtain filtrate which is reddish brown clear liquid;

(3) distilling the filtrate at 100 deg.C and-0.06 MPa until the concentration ratio is 3, stopping distillation, pouring the distillation mother liquor into a beaker, stirring, cooling for crystallization, and centrifuging to obtain sodium dihydrogen phosphate crystal. The content of sodium dihydrogen phosphate in the finished product is 88 percent, the crystal color is reddish, the index of the finished product does not reach the standard, and the part needs to be regarded as next generation. The fraction COD was 4500 mg/L.

Comparative example 2

A method for preparing sodium dihydrogen phosphate by using phosphoric acid pickling waste liquid comprises the following steps:

(1) taking 500ml of phosphoric acid pickling waste liquid (the acidity of raw phosphoric acid is 15%, the character is reddish brown turbid liquid, the COD is 16000ppm, thiourea is 3g/L, and the M-P organosilicone hydrochloric acid solution is 0.2g/L), slowly adding a sodium hydroxide solution with the mass concentration of 10%, neutralizing the pH value to 7, and filtering to obtain dark brown filtrate;

(2) slowly adding phosphoric acid with the mass fraction of 15% into the filtrate obtained in the step (1), and adjusting the pH value back to 5;

(3) after the pH is adjusted, slowly adding 10ml of hydrogen peroxide with the mass concentration of 30%, heating the mixture to 60 ℃ in a water bath, maintaining the temperature, stirring the mixture for 2 hours until the solution is slightly brown, closing the water bath, and performing suction filtration to obtain a slightly brown clear solution;

(4) distilling the filtrate at 100 deg.C and-0.06 MPa until the concentration ratio is 3.5, stopping distillation, pouring the distillation mother liquor into a beaker, stirring, cooling for crystallization, and centrifuging to obtain sodium dihydrogen phosphate crystal with light gray color. The content of the sodium dihydrogen phosphate in the finished product is 78 percent, the index of the finished product does not reach the standard, and the part needs to be regarded as next generation. The fraction COD was 3800 mg/L.