Method for preparing polyferric sulfate from yellow ferrous iron

Abstract

The invention relates to the technical field of mother liquor treatment, and provides a method for preparing polyferric sulfate by using yellow ferrous iron, which comprises the following steps: adding lime milk into acid wastewater, neutralizing in a water bath for a period of time, sequentially carrying out first-stage neutralization and second-stage neutralization during neutralization, concentrating slurry obtained by the second-stage neutralization, and reacting with the yellow ferrous iron to obtain primary jellyfish liquid; and then adding modified polyacrylamide into the monojellyfish liquid for settling, and compounding the monojellyfish liquid obtained after settling with yellow ferrous iron to prepare the polymerized ferrous sulfate. On one hand, organic combination of treatment of waste by waste on yellow ferrous iron and waste water neutralization slurry is achieved, and the jellyfish liquid is prepared; on the other hand, the monojellyfish liquid and the yellow ferrous iron are compounded to prepare the polymerized ferrous sulfate, so that the use way of the yellow ferrous iron can be increased, and considerable economic benefits are brought to enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of mother liquor treatment, and in particular to a method for preparing polyferric sulfate by utilizing ferrous yellow. Background Art

[0002] During the production of titanium dioxide by sulfuric acid method, the filtrate containing a large amount of impurities is obtained by filtering the metatitanic acid slurry after hydrolysis, which is called waste sulfuric acid. Waste sulfuric acid contains 20% to 30% dilute sulfuric acid. The precipitate precipitated by the treatment of waste acid is commonly known as concentrated slag (i.e. ferrous yellow), and the main components of ferrous yellow are ferrous sulfate monohydrate and sulfuric acid. According to statistics, about 1.15 tons of ferrous yellow are produced for every ton of titanium dioxide by sulfuric acid method. Due to the high content of free sulfuric acid in ferrous yellow, it is difficult to recycle the ferrous yellow produced by waste acid concentration.

[0003] In the existing technology, ferrous iron is used for acid production or other ways to recover iron resources. However, the equipment and technology requirements for ferrous iron are high, and the cost of ferrous iron is also a big problem. In addition, free sulfuric acid gradually precipitates during the stacking process of ferrous iron, which brings great pressure to the disposal of enterprises and the local environment.

[0004] At present, the main utilization of ferrous iron is to prepare polyferric sulfate and sell it in small quantities. However, due to the high residual sulfuric acid content in ferrous iron, it must be used in combination with a monohydrate with low acid and high iron content when preparing polyferric sulfate. Affected by the output of the monohydrate, the use of ferrous iron is greatly restricted.

[0005] Therefore, it is necessary to recycle and reuse the existing waste, which is crucial to achieve sustainable development. Summary of the invention

[0006] The inventor innovatively proposed that if ferrous yellow can be used to prepare a monohydrate solution, and then the monohydrate solution is compounded with ferrous yellow to prepare polyferrous sulfate, it can increase the use of ferrous yellow and bring considerable economic benefits. Based on this, the purpose of the present invention is to provide a method for preparing polyferric sulfate using ferrous yellow, which, on the one hand, realizes the organic combination of ferrous yellow and wastewater neutralization slurry to treat waste with waste, and obtains a monohydrate solution; on the other hand, the monohydrate solution is compounded with ferrous yellow to prepare polyferrous sulfate, which can increase the use of ferrous yellow and bring considerable economic benefits to the enterprise.

[0007] The embodiments of the present invention are achieved through the following technical solutions:

[0008] A method for preparing polyferric sulfate using ferrous iron, comprising the following steps:

[0009] S1. Neutralization slurry:

[0010] Add the ash milk to the acidic wastewater, neutralize it in a water bath at 40-60°C for 0.5-1.5h, and control the neutralization pH value in stages. Specifically, the pH value in the first stage of neutralization is 0.5-4, and the end point pH value is 4-4.5; the pH value in the second stage of neutralization is 4-9, and the end point pH value is 8.5-9; the second stage of neutralization slurry obtained after the second stage of neutralization is concentrated, and the iron content can be concentrated to more than 3%, which lays a good foundation for preparing a monohydrate with low acid and high iron content, and the slurry has an extremely low solid-liquid ratio, and no liquid return process is required, which greatly improves the work efficiency and product purity;

[0011] The second-stage neutralization slurry is concentrated by sedimentation to above 24.5%. Preferably, the concentration of the neutralization slurry is controlled at about 25%. The water content in the neutralization slurry is reduced to control the iron content of the system, and a mother liquor with suitable acidity and iron content is prepared.

[0012] S2, monohydrate:

[0013] Add the second-stage neutralization slurry to ferrous yellow, and neutralize for 0.5-1.5 hours at room temperature to obtain a monohydrate liquid;

[0014] During the neutralization reaction, the pH value of the neutralization endpoint is controlled between 1.2 and 2; preferably, the pH value is controlled between 1.2 and 1.25, and the optimal value is 1.25; thereby, a monohydrate with low acid and high iron content is obtained. Since the residual sulfuric acid in ferrous yellow is high, the monohydrate can be compounded with ferrous yellow to prepare polyferric sulfate with composite use requirements, thereby meeting the production needs of the enterprise, obtaining economic benefits, complying with the standards for waste discharge, and meeting the needs of green and sustainable development.

[0015] S3, Polyferrous Sulfate:

[0016] Modified polyacrylamide is added to the monohydrate solution for sedimentation, and the monohydrate solution obtained after sedimentation is compounded with ferrous iron to prepare polyferrous sulfate.

[0017] On the one hand, the invention realizes the organic combination of ferrous yellow and the neutralized slurry in wastewater to treat waste with waste, thereby preparing monohydrate; on the other hand, the monohydrate is compounded with ferrous yellow to prepare polyferrous sulfate, which can increase the use of ferrous yellow and bring considerable economic benefits to the enterprise.

[0018] Since the metatitanic acid contained in the monohydrate liquid will have an adverse effect on the color of the newly prepared polyferric sulfate, it is necessary to remove the metatitanic acid in the monohydrate liquid. Therefore, the present invention uses modified polyacrylamide to precipitate the monohydrate liquid to remove the metatitanic acid. Specifically, the preparation method of the modified polyacrylamide includes the following steps:

[0019] (1) Add a certain amount of deionized water to a flask, then add a certain amount of amylose to the deionized water and mix, and stir magnetically at 100-300°C for 1 hour to obtain a first liquid; then add a certain amount of amylopectin to the deionized water and mix, and stir magnetically at 5-20°C for 1 hour to obtain a second liquid; mix the first liquid and the second liquid and cool them to room temperature, add a certain amount of initiator solution to the flask, and react for 10 minutes under magnetic stirring to fully activate the free radicals. Then continue to add a certain amount of a mixed solution of acrylamide monomer and cationic monomer to the flask and react for 3 hours. After the polymerization reaction is completed, cool the colloidal product to room temperature, add a certain amount of anhydrous ethanol while stirring, and precipitate a white or light yellow cationic starch-based flocculant. After filtering the crude product, put it into a vacuum drying oven at 300°C and dry it to constant weight. After purification, the grafted polymer is obtained;

[0020] Amylose is a linear polysaccharide with a large number of glucose units in its molecular structure. In hot water, amylose dissolves to form a transparent, viscous solution. Amylopectin is a branched polysaccharide with a large number of branches in its molecular structure. In cold water, amylopectin forms a colloid with high viscosity.

[0021] (2) Take 2.0 g of the grafted polymer and dissolve it in 500 mL of deionized water, stirring continuously. After it is completely dissolved, add 2.0 g of a di-long chain quaternary ammonium salt and stir the mixture at 80° C. for 7 days. Then pour the solution into a dialysis bag, place the dialysis bag in deionized water with a stirring system and stir for 14 days to allow the unreacted di-long chain quaternary ammonium salt to diffuse into the deionized water through the dialysis bag. Then, after purification and drying, the modified polyacrylamide is obtained.

[0022] The modified polyacrylamide of the invention is grafted with amylose and amylopectin and then polymerized with a quaternary ammonium salt, so that the polymerization of the modified polyacrylamide is more stable, and a large amount of positive charges can be evenly loaded on the surface, thereby enhancing the bridging effect and adsorption effect thereof, so that the suspended metatitanic acid particles are agglomerated and flocculated, and then precipitated. Meanwhile, a large amount of positive charges of the modified polyacrylamide destroy the stability of the suspended metatitanic acid particles by neutralizing the electrical property, thereby improving the sedimentation effect of the metatitanic acid.

[0023] Furthermore, di-long-chain quaternary ammonium salts include: bis(decyldimethyl)ammonium bromide, bis(decyldimethyl)ammonium chloride, dimethylbenzyl ammonium chloride, bis(dodecyldimethyl)ethylenediammonium bromide, 2-(2-phenoxyethoxy)ethyltrimethylammonium chloride, and a mixture of alkyldimethylbenzylammonium chloride and octyldecyldimethylammonium chloride.

[0024] Furthermore, the initiator is ammonium cerium nitrate, ammonium persulfate, or potassium persulfate.

[0025] Furthermore, the cationic monomer is dimethyldiallylammonium chloride, allyltrimethylammonium chloride and 3-acrylamidopropyltrimethylammonium chloride.

[0026] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0027] 1. On the one hand, the present invention realizes the organic combination of ferrous yellow and the neutralized slurry in wastewater to treat waste with waste, and obtains monohydrate; on the other hand, the monohydrate is compounded with ferrous yellow to prepare polyferrous sulfate, which can increase the use of ferrous yellow and bring considerable economic benefits to the enterprise.

[0028] 2. The modified polyacrylamide of the present invention is grafted with amylose and amylopectin and then polymerized with a quaternary ammonium salt, so that the polymerization of the modified polyacrylamide is more stable, and a large amount of positive charges can be evenly loaded on the surface, thereby enhancing its bridging effect and adsorption effect, so that the suspended titanic acid particles are agglomerated and flocculated, and then settled. At the same time, the large amount of positive charges of the modified polyacrylamide destroy the stability of the suspended titanic acid particles by neutralizing the charge, thereby improving the settling effect of the titanic acid. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0030] Example 1

[0031] A method for preparing polyferric sulfate using ferrous iron, comprising the following steps:

[0032] S1. Neutralization slurry:

[0033] Add the ash emulsion into the acidic wastewater, neutralize it in a water bath at 50℃ for 1h, and control the neutralization reaction in stages. Specifically, the neutralization is carried out in two stages. The pH value of the first stage is 0.5-4, and the end point pH value is 4; then the second stage is carried out. The pH value of the second stage is 4-9, and the end point pH value is 9; the second stage neutralization slurry obtained after the second stage neutralization is concentrated to 25%, at which time the iron content is concentrated to 2.97%, and the slurry solid-liquid ratio is extremely low.

[0034] S2, monohydrate:

[0035] Add the second-stage neutralization slurry to the ferrous iron, and carry out a neutralization reaction at room temperature for 1 hour to obtain a monohydrate solution; during the neutralization reaction, the neutralization endpoint pH value is controlled to be 1.25;

[0036] S3, Polyferrous Sulfate:

[0037] Modified polyacrylamide is added to the monohydrate solution for sedimentation, and the monohydrate solution obtained after sedimentation is compounded with ferrous iron to prepare polyferrous sulfate.

[0038] Specifically, the preparation method of modified polyacrylamide comprises the following steps:

[0039] (1) Add 500 mL of deionized water to a flask, then add 10 g of amylose to the deionized water and mix, and stir magnetically at 150°C for 1 hour to obtain a first liquid; then add 10 g of amylopectin to 500 mL of deionized water and mix, and stir magnetically at 15°C for 1 hour to obtain a second liquid; mix the first liquid and the second liquid and cool them to room temperature, add 30 g of initiator solution to the flask, react under magnetic stirring for 10 minutes, and then continue to add a mixed solution of 5 g of acrylamide monomer and 5 g of cationic monomer to the flask to react for 3 hours. After the polymerization reaction is completed, cool to room temperature, add 50 mL of anhydrous ethanol while stirring, precipitate the starch-based flocculant, filter, put it in a vacuum drying oven at 300°C and dry it to constant weight, and obtain a grafted polymer after purification;

[0040] (2) Take 2.0 g of the grafted polymer and dissolve it in 500 mL of deionized water, stirring continuously. After it is completely dissolved, add 2.0 g of dimethylbenzyl ammonium chloride and stir the mixture at 80° C. for 7 days. Then pour the solution into a dialysis bag, place the dialysis bag in deionized water with a stirring system and stir for 14 days to allow the unreacted dimethylbenzyl ammonium chloride to diffuse into the deionized water through the dialysis bag. Then, after purification and drying, the modified polyacrylamide is obtained.

[0041] By analyzing the thick slurry of monohydrate liquor after sedimentation, it can be concluded that the thick slurry of monohydrate liquor can be used to prepare trivalent titanium and recover TiO 2 The mass is about 240 tons / year, and the benefit of recycled titanium is about 2.16 million yuan / year.

[0042] Example 2

[0043] A method for preparing polyferric sulfate using ferrous iron, comprising the following steps:

[0044] S1. Neutralization slurry:

[0045] Add the ash emulsion into the acidic wastewater, neutralize in a water bath at 50°C for 1 hour, and control the neutralization reaction in stages. Specifically, the neutralization is carried out in two stages, the pH value of the first stage is 0.5-4, and the end point pH value is 4.5; then the second stage is carried out, the pH value of the second stage is 4-7, and the end point pH value is 8.5; the second stage neutralization slurry obtained after the second stage neutralization is concentrated to 25%;

[0046] S2, monohydrate:

[0047] Add the second-stage neutralization slurry to the yellow ferrous iron, and neutralize for 1 hour at room temperature to obtain a monohydrate solution; during the neutralization reaction, the neutralization end point pH value is controlled to be 1.25;

[0048] S3, Polyferrous Sulfate:

[0049] Modified polyacrylamide is added to the monohydrate solution for sedimentation, and the monohydrate solution obtained after sedimentation is compounded with ferrous iron to prepare polyferrous sulfate.

[0050] Specifically, the preparation method of modified polyacrylamide comprises the following steps:

[0051] (1) Add 500 mL of deionized water to a flask, then add 10 g of amylose to the deionized water and mix, and stir magnetically at 130°C for 1 hour to obtain a first liquid; then add 10 g of amylopectin to 500 mL of deionized water and mix, and stir magnetically at 10°C for 1 hour to obtain a second liquid; mix the first liquid and the second liquid and cool them to room temperature, add 40 g of initiator solution to the flask, and react for 10 minutes under magnetic stirring. Then continue to add a certain amount of a mixed solution of acrylamide monomer and cationic monomer to the three-necked flask and react for 3 hours. After the polymerization reaction is completed, cool to room temperature, add 50 mL of anhydrous ethanol while stirring, precipitate the starch-based flocculant, filter, put it in a vacuum drying oven at 300°C and dry it to constant weight, and after purification, obtain a grafted polymer;

[0052] (2) Take 2.0 g of the grafted polymer and dissolve it in 500 mL of deionized water, stirring continuously. After it is completely dissolved, add 2.0 g of dimethyl ammonium chloride and stir at 80° C. for 7 days. Then pour the solution into a dialysis bag, place the dialysis bag in deionized water with a stirring system and stir for 14 days to allow the unreacted dimethyl ammonium chloride to diffuse into the deionized water through the dialysis bag. Then, after purification and drying, the modified polyacrylamide is obtained.

[0053] By analyzing the thick slurry of monohydrate liquor after sedimentation, it can be concluded that the thick slurry of monohydrate liquor can be used to prepare trivalent titanium and recover TiO 2 The quality is about 235 tons / year, and the benefit of recycled titanium is about 2.115 million yuan / year.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the polyacrylamide in S3 is not modified, that is, ordinary polyacrylamide is used.

[0056] TiO can be recovered by analyzing the thick slurry of monohydrate liquor after sedimentation. 2 The quality is extremely low, and it can be concluded that the monohydrate slurry cannot meet the requirements for the preparation of trivalent titanium.

[0057] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing polyferric sulfate using ferrous iron, characterized in that: The following steps are involved: S1. Neutralization slurry: Adding ash milk into acidic wastewater, and carrying out primary neutralization and secondary neutralization reactions in sequence under water bath conditions, taking the secondary neutralization slurry obtained after the secondary neutralization for sedimentation, and concentrating it to more than 24.5%; S2, monohydrate: Adding the second-stage neutralization slurry into ferrous iron, and neutralizing and reacting for a period of time at room temperature to obtain a monohydrate liquid; S3, Polyferrous Sulfate: Modified polyacrylamide is added to the monohydrate solution for sedimentation, and the monohydrate solution obtained after sedimentation is compounded with ferrous iron to prepare polyferrous sulfate.

2. The method for preparing polyferric sulfate using ferrous iron according to claim 1, characterized in that: In S1, the pH value during the first stage of neutralization is 0.5-4, and the end point pH value is 4-4.5; the pH value during the second stage of neutralization is 4-9, and the end point pH value is 8.5-9.

3. The method for preparing polyferric sulfate using ferrous iron according to claim 1, characterized in that: In S2, during the neutralization reaction, the neutralization endpoint pH value is controlled between 1.2-2.

4. The method for preparing polyferric sulfate using ferrous iron according to claim 1, characterized in that: In S3, the solid-to-liquid ratio of modified polyacrylamide to monohydrate is 10-20 mg / L.

5. The method for preparing polyferric sulfate using ferrous iron according to claim 1, characterized in that: The preparation method of the modified polyacrylamide comprises the following steps: (1) adding a certain amount of amylose to water, mixing, and magnetically stirring for a period of time under high temperature conditions to obtain a first liquid; then adding a certain amount of amylopectin to deionized water, mixing, and magnetically stirring for a period of time under low temperature conditions to obtain a second liquid; mixing the first liquid and the second liquid and cooling to room temperature to obtain a colloidal solution; adding a certain amount of initiator solution to the colloidal solution, stirring for a period of time, and then adding a certain amount of a mixed solution of acrylamide monomer and cationic monomer to react for a period of time, after the polymerization reaction is completed, adding a certain amount of anhydrous ethanol to the colloidal product while stirring, precipitating a starch-based flocculant, and drying and purifying to obtain a graft polymer; (2) The grafted polymer is dissolved in water, and then a di-long chain quaternary ammonium salt is added. After stirring for a period of time, the solution is dialyzed, and then purified and dried to obtain modified polyacrylamide.

6. The method for preparing polyferric sulfate using ferrous iron according to claim 5, characterized in that: The reaction temperature of step (1) under high temperature conditions is 100-300°C, and the reaction temperature under low temperature conditions is 5-20°C.

7. The method for preparing polyferric sulfate using ferrous yellow according to claim 5, characterized in that: The mass ratio of the amylose, amylopectin, initiator, acrylamide monomer and cationic monomer is 1:1:2-4:0.5-1:0.5-1.

8. The method for preparing polyferric sulfate using ferrous iron according to claim 5, characterized in that: The di-long-chain quaternary ammonium salt includes any one or more of bis(decyldimethyl)ammonium bromide, bis(decyldimethyl)ethylenediammonium bromide, 2-(2-phenoxyethoxy)ethyltrimethylammonium chloride, and a mixture of alkyldimethylbenzylammonium chloride and octyldecyldimethylammonium chloride.

9. The method for preparing polyferric sulfate using ferrous iron according to claim 5, characterized in that: The initiator is ammonium cerium nitrate, ammonium persulfate, and potassium persulfate.

10. The method for preparing polyferric sulfate using ferrous yellow according to claim 5, characterized in that: The cationic monomers are dimethyldiallylammonium chloride, allyltrimethylammonium chloride and 3-acrylamidopropyltrimethylammonium chloride.