Method for recycling glass thinning etching waste liquid and waste residues

Abstract

The invention relates to the technical field of industrial wastewater resourceful treatment, and provides a glass thinning etching waste liquid and waste residue resourceful method which comprises the following steps: treating glass thinning etching waste liquid by adopting a sodium chloride precipitation method to obtain first filter residue and first filtrate; neutralizing the glass thinning etching waste residues with ammonia water to obtain second filter residues and second filtrate; adding the second filter residue into the first filtrate, adding a part of the second filtrate, and stirring for reaction to obtain a third filter residue and a third filtrate; adding sodium fluosilicate seed crystals and sodium chloride into the third filtrate, and reacting to obtain fourth filter residues and fourth filtrate; lime is added into the fourth filtrate to adjust the pH value to be 11 or above, meanwhile, a modified flocculant accounting for 1-5% of the mass of the fourth filtrate is added, and a fifth filter residue and a fifth filtrate are obtained through a reaction; synergistic recycling of the glass thinning etching waste liquid and waste residues can be achieved, and particularly step-by-step recycling of the glass thinning etching waste residues can be achieved.

Description

A method for resource utilization of glass thinning etching waste liquid and residue Technical Field

[0003] This invention relates to the field of industrial wastewater resource utilization technology, and more specifically, to a method for the resource utilization of glass thinning etching waste liquid and waste residue. Background Technology

[0005] In the manufacturing process of substrate glass for electronic products such as mobile phones, tablets, and LCD displays, thinning is a crucial step, directly impacting product quality. Currently, acid etching is a commonly used method for glass thinning. Its main principle is to react HF-containing acid with SiO2 and other metal oxides in the glass, causing surface peeling and achieving thinning. Glass thinning etching solutions typically use a mixed acid system, primarily composed of hydrofluoric acid, sulfuric acid, hydrochloric acid, or nitric acid. Adding sulfuric acid, hydrochloric acid, or nitric acid to the etching solution increases the hydrogen ion concentration, improving etching efficiency, and also dissolves some metal fluoride precipitates, thus ensuring a smooth glass surface.

[0006] The composition of substrate glass typically falls into three main categories based on its properties: the first is the alkali aluminosilicate system, the second is the borosilicate system, and the third is the soda-lime glass system. Soda-lime glass systems generally use ammonium bifluoride as the etchant, while alkali aluminosilicate systems, due to their more robust glass network, often require the more reactive hydrofluoric acid as the primary etchant. A typical composition of alkali aluminosilicate glass is SiO2, Na2O, Al2O3, K2O, MgO, and CaO. During etching, the generated SiF4 can further react with excess HF to form fluorosilicic acid. Since Na2SiF6, K2SiF6, MgF2, AlF3, Na3AlF6, CaF2, and CaSO4·2H2O are all sparingly soluble, the H2SiF6 generated in the etching solution, as well as the residual HF and H2SO4 in the system, will react with the generated Na+, K+, Al3+, Mg2+, and Ca2+ to form corresponding precipitates.

[0007] As the reaction proceeds, the acid concentration in the glass thinning etching solution gradually decreases, with HF decreasing the fastest. Simultaneously, H₂SiF₆ and corresponding precipitates gradually accumulate in the system. When the precipitates accumulate to a certain level, they hinder the continued etching of the glass by HF, necessitating treatment as waste. This type of waste (especially glass thinning etching residue) is characterized by high acidity and complex composition, and is generally treated using lime neutralization. This not only wastes a large amount of valuable resources, but also generates 3-5 tons of waste residue per ton of this type of waste, resulting in very high treatment costs.

[0008] To address this issue, some research has been conducted on the resource recovery of glass thinning etching waste liquid. For example, patents CN102745837A and CN109626646A respectively use alkali metal inorganic salts and alkali metal organic salts to remove fluorosilicic acid from the glass thinning etching waste liquid. The remaining liquid is then replenished with fresh acid and reused in the original production line. The former also performs alkaline conversion on the obtained fluorosilicates to obtain silica gel and metal fluorides for utilization. However, online reuse technology is often not feasible because the waste-generating units have high requirements for the impurity composition of the etching solution.

[0009] Patent CN110976076A utilizes glass thinning waste liquid to purify iron oxide-impregnated quartz sand, obtaining high-quality quartz sand products that meet the requirements for ultra-white photovoltaic rolled glass. However, the technology for purifying iron oxide-impregnated quartz sand is relatively niche, cannot process glass thinning etching waste liquid on a large scale, and also requires separate disposal of secondary waste.

[0010] Patent CN104071820A involves adding solid sodium fluoride to the etching solution of waste LCD panel glass, which converts the fluorosilicic acid and fluoroaluminic acid in the etching solution into sodium fluorosilicate and sodium fluoroaluminate, and releases hydrofluoric acid. Then, ammonia water is added to react and filter out the insoluble matter. Lime is added to the filtrate to neutralize it and obtain calcium fluoride product with a purity of over 95%. However, the method of adding sodium fluoride to remove silicon and then preparing calcium fluoride will have poor economic benefits because the purchase cost of sodium fluoride raw material is higher than the sales cost of calcium fluoride. Summary of the Invention

[0012] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for the resource utilization of glass thinning etching waste liquid and waste residue, which can realize the synergistic resource utilization of glass thinning etching waste liquid and waste residue, especially the stepwise resource utilization of glass thinning etching waste residue.

[0013] The embodiments of the present invention are achieved through the following technical solutions:

[0014] A method for resource recovery of glass thinning etching waste liquid and residue includes the following steps:

[0015] (1) The glass thinning etching waste liquid was treated by sodium chloride precipitation to obtain the first filter residue and the first filtrate;

[0016] (2) The glass was thinned by using ammonia water to obtain the second filter residue and the second filtrate;

[0017] (3) The second filter residue is added to the first filtrate, and a portion of the second filtrate is added. After stirring and reacting, the third filter residue and the third filtrate are obtained.

[0018] (4) Add sodium fluorosilicate seeds and sodium chloride to the third filtrate, and react to obtain the fourth filter residue and the fourth filtrate;

[0019] (5) Add lime to the fourth filtrate to adjust the pH value to above 11, and at the same time pass steam to strip away most of the ammonia gas. Then add 1-5% of its mass of modified flocculant to react and obtain the fifth filter residue, the fifth filtrate and the first waste gas.

[0020] The modified flocculant contains magnesium ions, phosphate ions, calcium ions and aluminum ions;

[0021] The preparation method of the modified flocculant includes the following steps:

[0022] 1) Mix raw material A containing magnesium ions, raw material B containing phosphate ions, raw material C containing calcium ions, and raw material D containing aluminum ions with deionized water, and then disperse them in a solvent to obtain the first mixture.

[0023] 2) Add β-cyclodextrin to the first mixture, let stand, and dry to obtain the second mixture;

[0024] 3) Add deionized water to graphene oxide, mix well, slowly add ammonium dihydrogen phosphate, heat, stir, filter, add ammonium persulfate in small amounts several times, react with heating, add deionized water and dilute hydrochloric acid; then concentrate the obtained solution to 2~5 mg / mL, then concentrate to 10~50 mg / mL, stir evenly, and let stand in the dark for 24~48 h to obtain graphene oxide colloid.

[0025] 4) Mix the graphene oxide colloid with the second mixture, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid well, and then dry and cool to obtain the modified flocculant.

[0026] (6) The fifth filter residue is mixed and reacted with the third filter residue and then used as a building material raw material;

[0027] The second filtrate can be mixed with hydrofluoric acid to adjust the pH value, and then evaporated to obtain ammonium fluoride or ammonium bifluoride products.

[0028] The first waste gas can be recycled to neutralize the glass thinning etching waste residue at the front end;

[0029] The fifth filtrate can be mixed with an acidic solution to adjust the pH to 5-7, and then evaporated to obtain calcium chloride product.

[0030] The main components of the fifth filter residue are calcium fluoride and calcium sulfate (alkaline), which can be mixed with the third filter residue (acidic) and used as building materials; the main component of the first waste gas is ammonia, which can be recycled for front-end neutralization of glass thinning etching waste; the main components of the second filtrate are ammonium fluoride and excess ammonia water, which can be adjusted to different pH values ​​by adding hydrofluoric acid, and evaporated to obtain ammonium fluoride or ammonium bifluoride products; the main components of the fifth filtrate are calcium chloride and calcium hydroxide, which can be adjusted to pH 5-7 by adding hydrochloric acid, and evaporated to obtain calcium chloride products.

[0031] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0032] 1. The processing method of this invention utilizes the characteristics of the glass thinning etching waste liquid and waste residue to realize the resource utilization of the main components fluorine and silicon; in particular, it can realize the step-by-step recovery of glass thinning etching waste residue to obtain high-value sodium fluorosilicate, ammonium fluoride or ammonium bifluoride and calcium chloride products, thus realizing step-by-step resource utilization.

[0033] 2. In the final treatment of the filtrate, this invention adds a modified flocculant and excess lime, uses magnesium ions, phosphate ions, and aluminum ions to assist precipitation, and utilizes β-cyclodextrin to coat the filtrate, forming a particle structure with a three-dimensional cavity inside. This allows the flocculent precipitate to be encapsulated within the cavity in a manner similar to phagocytosis, thus precipitating rapidly. More importantly, this invention uses graphene oxide as the particle structure after β-cyclodextrin loading, resulting in a larger specific surface area and adsorption capacity, and providing more attachment sites. This allows for the loading of more fluoride and ammonium ions, increasing the removal efficiency of ammonia nitrogen, while also increasing the adsorption performance of fluoride, accelerating precipitation and resource utilization. Detailed Implementation

[0035] This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this invention will be thorough and complete.

[0036] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] A method for resource recovery of glass thinning etching waste liquid and residue includes the following steps:

[0039] (1) Add 5-10% sodium fluorosilicate seed crystals to the glass thinning etching waste liquid, and then add a sodium chloride solution with a concentration of 5-20% and an excess sodium chloride coefficient of 1-1.2. React for 0.5-1h, and then filter by pressure to obtain the first filter residue (mainly sodium fluorosilicate product) and the first filtrate (mainly hydrochloric acid, hydrofluoric acid, sulfuric acid and a small amount of unreacted fluorosilicic acid).

[0040] (2) The glass thinning etching waste residue is neutralized with ammonia water with a concentration of 5-20%, the pH is adjusted to 8.0-9.5, the reaction is stirred for 0.5-2.0h, and then filtered to obtain the second filter residue and the second filtrate. The main components of the second filtrate are ammonium fluoride and excess ammonia water. Hydrofluoric acid is added to adjust the pH value to different values, and ammonium fluoride or ammonium bifluoride products are obtained by evaporation and crystallization. The main components of the second filter residue are silicon dioxide and a small amount of calcium sulfate, calcium fluoride, magnesium fluoride, aluminum fluoride and cryolite, etc. The glass thinning etching waste residue is neutralized with ammonia water, and the fluorosilicic acid and fluorosilicate in the waste residue are converted into silicon dioxide and fluorides (ammonium fluoride and a small amount of sodium fluoride, potassium fluoride, etc.).

[0041] (3) All the second filter residue is added to the first filtrate, and a portion of the second filtrate is added. The amount of the second filtrate added is 40-60% of the yield of the second filtrate. The mixture is stirred and reacted for 0.5-2.0 hours. After pressure filtration, the third filter residue and the third filtrate are obtained. The main components of the third filter residue are calcium sulfate, calcium fluoride, magnesium fluoride, aluminum fluoride and cryolite. The main components of the third filtrate are fluorosilicic acid, hydrochloric acid, ammonium chloride, sulfuric acid and a small amount of unreacted hydrofluoric acid. The second filter residue uses the acidity of the first filtrate and the fluoride in the second filtrate to dissolve the main component silicon dioxide, convert it into fluorosilicic acid, and separate it from insoluble impurities.

[0042] (4) First, add 5-10% of sodium fluorosilicate seed crystals to the third filtrate, then add a sodium chloride solution with a concentration of 5-20%, the excess sodium chloride coefficient is 1-1.2, and react for 0.5-1h. After the reaction is completed, the fourth filter residue (mainly sodium fluorosilicate product) and the fourth filtrate are obtained. The main components of the fourth filtrate are hydrochloric acid, ammonium chloride, sulfuric acid, hydrofluoric acid and a small amount of unreacted fluorosilicic acid.

[0043] (5) Add lime to the fourth filtrate to adjust the pH value to above 11, and simultaneously pass steam to strip ammonia for 0.5 to 1.0 h. Then add 1 to 5% of the mass of the modified flocculant and react for 0.5 h. After pressure filtration, the fifth filter residue, the fifth filtrate and the first waste gas are obtained. The main components of the fifth filter residue are calcium fluoride, calcium sulfate and excess calcium hydroxide (alkaline). After mixing with the third filter residue (acidic), it can be used as building material. The main component of the first waste gas is ammonia. After water absorption, it can be reused in the front end to neutralize the glass thinning etching waste residue. The main components of the fifth filtrate are calcium chloride and calcium hydroxide. Hydrochloric acid can be added to adjust the pH to 5 to 7 and evaporate to obtain calcium chloride product. By adding modified flocculant and excess lime to the fourth filtrate, not only can the fluoride and sulfate in it be removed, but also the calcium chloride and ammonium chloride can be separated by stripping ammonia. Thus, high-purity calcium chloride product is obtained by evaporation and crystallization. At the same time, the recovered ammonia water can be recycled.

[0044] Specifically, the modified flocculant contains magnesium ions, phosphate ions, calcium ions, and aluminum ions;

[0045] The preparation method of the modified flocculant includes the following steps:

[0046] 1) Mix raw material A containing magnesium ions, raw material B containing phosphate ions, raw material C containing calcium ions, and raw material D containing aluminum ions in a mass ratio of 1:1:1-2:3-5, then add 5-15 times the mass of deionized water and mix. Then disperse the mixture in a solvent, such as anhydrous ethanol, to obtain the first mixture.

[0047] 2) Add 1-2 times the mass of β-cyclodextrin to the first mixture, let stand, and dry to obtain the second mixture;

[0048] 3) Add 5-10 times the amount of deionized water to graphene oxide, mix well, and then slowly add 0.2-0.5 times the amount of ammonium dihydrogen phosphate. After heating, stirring, and filtering, add ammonium persulfate in small amounts several times, such as in 3 slow additions. The mass of ammonium persulfate is 0.5-1.5 times the mass of graphene oxide. After heating and reacting, add 50-100 times the amount of deionized water and 2-5 times the amount of dilute hydrochloric acid. Then concentrate the obtained solution to 2-5 mg / mL, and then concentrate it to 10-50 mg / mL. Stir well, and let it stand in the dark for 24-48 hours to obtain graphene oxide colloid.

[0049] 4) Mix the graphene oxide colloid with the second mixture at a mass ratio of 2-5:1, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid well, and then dry and cool to obtain the modified flocculant.

[0050] Among them, raw material A can be selected from magnesium chloride and magnesium citrate, raw material B can be selected from sodium hydrogen phosphate and potassium hydrogen phosphate, raw material C can be selected from calcium chloride, and raw material D can be selected from polyaluminum chloride;

[0051] Most importantly, this step involves adding a modified flocculant to the feed liquid after stripping and deammoniation of the fourth filtrate. This allows the residual ammonium ions in the feed liquid to react with the flocculant to form magnesium ammonium phosphate precipitate, thus more thoroughly removing ammonium ions. Simultaneously, it can also react with fluoride ions to form calcium fluoride precipitate, thereby specifically removing ammonium and fluoride ions from the filtrate and precipitating pollutants to treat the wastewater. Considering the relatively long settling time of particles and the electrostatic repulsion effect of the generated calcium fluoride particles during flocculation, the inventors have chosen a magnesium ion-modified flocculant in this invention. The precipitate is aided by phosphate and aluminum ions, and coated with β-cyclodextrin to form a particle structure with a three-dimensional cavity inside. This structure can encapsulate the flocculent precipitate in a manner similar to phagocytosis, thus precipitating it quickly. More importantly, this invention uses graphene oxide as the particle structure after β-cyclodextrin loading, which results in a larger specific surface area and adsorption capacity, and provides more attachment sites. This allows for the loading of more fluoride and ammonium ions, increasing the removal efficiency of ammonia nitrogen, while also increasing the adsorption performance of fluoride, accelerating precipitation and resource utilization.

[0052] Compared with existing technologies, this invention can achieve the synergistic resource utilization of glass thinning etching waste liquid and waste residue, especially the stepwise resource utilization of glass thinning etching waste residue. Conventional lime neutralization methods generate approximately 3-5 tons of waste residue for every 1 ton of glass thinning etching waste residue processed. However, this invention utilizes the inherent characteristics of both waste materials to achieve the resource utilization of their main components, fluorine and silicon, reducing the final waste residue amount to less than 0.3 tons, thus achieving a waste residue reduction of over 90%.

[0053] Meanwhile, the process of this invention is simple to operate. It only requires the input of inexpensive sodium chloride and lime (ammonia water can be recycled throughout the process) to recover high-value sodium fluorosilicate, ammonium fluoride and calcium chloride products in steps. It efficiently realizes resource recycling and reuse and generates beneficial by-products.

[0054] Example 1

[0055] A method for resource recovery of glass thinning etching waste liquid and residue includes the following steps:

[0056] (1) Add 10% sodium fluorosilicate seed crystals by mass to the glass thinning etching waste liquid, and then add a sodium chloride solution with a concentration of 20% and an excess sodium chloride coefficient of 1.2. After reacting for 1 hour, filter the solution by pressure to obtain the first filter residue (mainly sodium fluorosilicate product) and the first filtrate (mainly hydrochloric acid, hydrofluoric acid, sulfuric acid and a small amount of unreacted fluorosilicic acid).

[0057] (2) The glass thinning etching residue was neutralized with 20% ammonia water, the pH was adjusted to 9.0, and the reaction was stirred for 2.0 h. After pressure filtration, the second filter residue and the second filtrate were obtained. The main components of the second filtrate were ammonium fluoride and excess ammonia water. Hydrofluoric acid was added to adjust the pH value to different values, and the ammonium fluoride or ammonium bifluoride product was obtained by evaporation and crystallization. The main components of the second filter residue were silicon dioxide and a small amount of calcium sulfate, calcium fluoride, magnesium fluoride, aluminum fluoride and cryolite, etc.

[0058] (3) All the second filter residue was added to the first filtrate, and some of the second filtrate was added. The amount of the second filtrate added was 50% of the yield of the second filtrate. The mixture was stirred and reacted for 2.0 h. After pressure filtration, the third filter residue and the third filtrate were obtained. The main components of the third filter residue were calcium sulfate, calcium fluoride, magnesium fluoride, aluminum fluoride and cryolite. The main components of the third filtrate were fluorosilicic acid, hydrochloric acid, ammonium chloride, sulfuric acid and a small amount of unreacted hydrofluoric acid.

[0059] (4) First, add 10% of sodium fluorosilicate seed crystals to the third filtrate, then add a 20% sodium chloride solution with an excess sodium chloride coefficient of 1.2. After reacting for 1 hour, the fourth filter residue (mainly sodium fluorosilicate product) and the fourth filtrate are obtained. The main components of the fourth filtrate are hydrochloric acid, ammonium chloride, sulfuric acid, hydrofluoric acid and a small amount of unreacted fluorosilicic acid.

[0060] (5) Add lime to the fourth filtrate to adjust the pH to 11, and then pass steam to strip and remove ammonia for 1.0 h. Then add 5% of the modified flocculant by mass, and filter by pressure to obtain the fifth filter residue, the fifth filtrate and the first waste gas. Specifically, the preparation method of the modified flocculant includes the following steps:

[0061] 1) Mix magnesium chloride, sodium hydrogen phosphate, calcium chloride and polyaluminum chloride in a mass ratio of 1:1:2:5, then add 10 times the mass of deionized water and mix. Then disperse the mixture in anhydrous ethanol to obtain the first mixture.

[0062] 2) Add 2 times the mass of β-cyclodextrin to the first mixture, let stand for 12 hours, and dry to obtain the second mixture;

[0063] 3) Add 10 times the amount of deionized water to graphene oxide, mix well, then slowly add 0.5 times the amount of ammonium dihydrogen phosphate, heat to 60℃, stir at a constant temperature for 2 hours, filter, and then slowly add ammonium persulfate in 3 portions, wherein the mass of ammonium persulfate is 1.5 times the mass of graphene oxide; heat to 30℃ and react at a constant temperature for 4 hours, then add 100 times the amount of deionized water and 5 times the amount of dilute hydrochloric acid; then concentrate the obtained solution to 5 mg / mL, then concentrate to 50 mg / mL, stir well, and let stand in the dark for 48 hours to obtain graphene oxide colloid solution;

[0064] 4) Mix the graphene oxide colloid with the second mixture at a mass ratio of 5:1, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid well, heat at 60°C for 3 hours, and then cool at room temperature to obtain the modified flocculant.

[0065] The fifth filter residue mainly consists of calcium fluoride, calcium sulfate, magnesium ammonium phosphate, and excess calcium hydroxide (alkaline). When mixed with the third filter residue (acidic), it can be used as building material. The first waste gas mainly consists of ammonia, which can be absorbed by water and reused to neutralize the glass thinning etching waste residue at the front end. The fifth filtrate mainly consists of calcium chloride and calcium hydroxide. Hydrochloric acid can be added to adjust the pH to 5-7, and calcium chloride product can be obtained by evaporation. The fourth filtrate, by adding excess lime, can not only remove impurities such as fluoride and sulfate, but also separate calcium chloride and ammonium chloride through stripping and ammonia removal, thereby obtaining a high-purity calcium chloride product through evaporation and crystallization. At the same time, the recovered ammonia water can be recycled, ultimately achieving a waste residue reduction of more than 90%.

[0066] Example 2

[0067] A method for resource recovery of glass thinning etching waste liquid and residue includes the following steps:

[0068] (1) Add 5% sodium fluorosilicate seed crystals by mass to the glass thinning etching waste liquid, and then add a 10% sodium chloride solution with an excess sodium chloride coefficient of 1.1. After reacting for 1 hour, filter the solution by pressure to obtain the first filter residue and the first filtrate.

[0069] (2) Neutralize the glass thinning etching residue with 10% ammonia water, adjust the pH to 9.0, stir and react for 1.0 h, and then filter by pressure to obtain the second filter residue and the second filtrate;

[0070] (3) Add all of the second filter residue into the first filtrate and add some of the second filtrate, wherein the amount of the second filtrate added is 45% of the yield of the second filtrate. Stir and react for 2.0 h, and then filter by pressure to obtain the third filter residue and the third filtrate.

[0071] (4) First, add 8% sodium fluorosilicate seed crystals by mass to the third filtrate, then add a 10% sodium chloride solution with an excess sodium chloride coefficient of 1.1, react for 1 hour, and obtain the fourth filter residue and the fourth filtrate.

[0072] (5) Add lime to the fourth filtrate to adjust the pH to 12, and then pass steam to strip and remove ammonia for 1.0 h. Then add 3% of the modified flocculant by mass, react for 1 h, and filter by pressure to obtain the fifth filter residue, the fifth filtrate, and the first waste gas. Specifically, the preparation method of the modified flocculant includes the following steps:

[0073] 1) Mix magnesium chloride, sodium hydrogen phosphate, calcium chloride and polyaluminum chloride in a mass ratio of 1:1:2:4, then add 10 times the mass of deionized water and mix. Then disperse the mixture in anhydrous ethanol to obtain the first mixture.

[0074] 2) Add 1.5 times the mass of β-cyclodextrin to the first mixture, let stand for 12 hours, and dry to obtain the second mixture;

[0075] 3) Add 5 times the amount of deionized water to graphene oxide, mix well, then slowly add 0.5 times the amount of ammonium dihydrogen phosphate, heat to 70℃, stir at a constant temperature for 2 hours, filter, and slowly add ammonium persulfate in 3 portions, where the mass of ammonium persulfate is 0.8 times the mass of graphene oxide; heat to 30℃ and react at a constant temperature for 4 hours, then add 100 times the amount of deionized water and 5 times the amount of dilute hydrochloric acid; then concentrate the obtained solution to 5 mg / mL, then concentrate to 30 mg / mL, stir well, and let stand in the dark for 48 hours to obtain graphene oxide colloid solution;

[0076] 4) Mix the graphene oxide colloid with the second mixture at a mass ratio of 5:1, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid well, heat at 60°C for 3 hours, and then cool at room temperature to obtain the modified flocculant.

[0077] Example 3

[0078] A method for resource recovery of glass thinning etching waste liquid and residue includes the following steps:

[0079] (1) Add 8% sodium fluorosilicate seed crystals by mass to the glass thinning etching waste liquid, then add 8% sodium chloride solution with an excess sodium chloride coefficient of 1, react for 0.5 h, and then filter by pressure to obtain the first filter residue and the first filtrate.

[0080] (2) Neutralize the glass thinning etching residue with 5% ammonia water, adjust the pH to 8.0, stir and react for 0.5 h, and then filter by pressure to obtain the second filter residue and the second filtrate;

[0081] (3) Add all of the second filter residue to the first filtrate and add some of the second filtrate, wherein the amount of the second filtrate added is 40% of the yield of the second filtrate. Stir and react for 2.0 h, and then filter by pressure to obtain the third filter residue and the third filtrate.

[0082] (4) First, add 5% sodium fluorosilicate seed crystals by mass to the third filtrate, then add a 5% sodium chloride solution with an excess sodium chloride coefficient of 1, and react for 1 hour to obtain the fourth filter residue and the fourth filtrate.

[0083] (5) Add lime to the fourth filtrate to adjust the pH to 11, and then pass steam to strip and remove ammonia for 1.0 h. Then add 2% of the modified flocculant by mass, react for 0.5 h, and filter by pressure to obtain the fifth filter residue, the fifth filtrate, and the first waste gas. Specifically, the preparation method of the modified flocculant includes the following steps:

[0084] 1) Mix magnesium chloride, sodium hydrogen phosphate, calcium chloride and polyaluminum chloride in a mass ratio of 1:1:2:3, then add 10 times the mass of deionized water and mix. Then disperse the mixture in anhydrous ethanol to obtain the first mixture.

[0085] 2) Add 2 times the mass of β-cyclodextrin to the first mixture, let stand for 12 hours, and dry to obtain the second mixture;

[0086] 3) Add 6 times the amount of deionized water to graphene oxide, mix well, then slowly add 0.3 times the amount of ammonium dihydrogen phosphate, heat to 50℃, stir at a constant temperature for 2 hours, filter, and slowly add ammonium persulfate in 3 portions, where the mass of ammonium persulfate is 0.9 times the mass of graphene oxide; heat to 30℃ and react at a constant temperature for 4 hours, then add 100 times the amount of deionized water and 5 times the amount of dilute hydrochloric acid; then concentrate the obtained solution to 5 mg / mL, then concentrate to 20 mg / mL, stir well, and let stand in the dark for 48 hours to obtain graphene oxide colloid solution;

[0087] 4) Mix the graphene oxide colloid with the second mixture at a mass ratio of 2:1, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid well, heat at 60°C for 3 hours, and then cool at room temperature to obtain the modified flocculant.

[0088] Example 4

[0089] The difference between this embodiment and embodiment 1 is that: in step (2), the concentration of ammonia is 15%; in step (3), the amount of the second filtrate replenished is 55% of the yield of the second filtrate; and in step (4), the concentration of sodium chloride solution is 10%.

[0090] Example 5

[0091] The difference between this embodiment and embodiment 1 is that in step (5), when the modified flocculant is prepared, raw material A is magnesium citrate and raw material B is potassium hydrogen phosphate.

[0092] Example 6

[0093] The difference between this embodiment and embodiment 1 is that in step (5), when the modified flocculant is prepared, in step (3), during gradient concentration, it is first concentrated to 4.5 mg / mL and then concentrated to 25 mg / mL.

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that it does not include step (2), that is, the glass thinning etching waste residue is directly mixed with the first filtrate for subsequent processing, and lime is added in step (5) to adjust the pH value to 7.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that no modified flocculant was added in step (5).

[0098] Comparative Example 3

[0099] This comparative example uses the traditional quicklime neutralization method to treat glass thinning etching waste liquid and waste residue. Specifically, 800g of quicklime is added to 500g of glass thinning etching waste liquid and 500g of glass thinning etching waste residue, stirred and reacted for 2 hours, and then filtered to obtain filter residue and filtrate.

[0100] Experimental Example 1

[0101] It should be noted that the glass thinning etching waste liquid used in the above embodiments and comparative examples are all from the same batch.

[0102] The filtrates and filter cakes obtained in the examples and comparative examples were analyzed, and the results are shown in Table 1.

[0103] Test method:

[0104] 1. For specific analysis methods of sodium fluorosilicate content, please refer to "GB / T 23936-2018 Industrial Sodium Fluorosilicate" for testing.

[0105] 2. The fluoride content analysis method shall be in accordance with GB / T 7484-1987 Determination of Fluoride in Water by Ion Selected Electrode Method.

[0106] 3. The analysis method for ammonia nitrogen content shall be in accordance with the "HJ 537-2009 Determination of Ammonia Nitrogen in Water - Distillation-Neutralization Titration Method".

[0107] 4. The analytical method for calcium chloride content shall be in accordance with GB / T 26520-2021 Industrial Calcium Chloride.

[0108] Table 1 - Analysis results of filtrate and filter cake at each stage of Examples 1-3 and Comparative Examples

[0109]

[0110] As shown in Table 1, in the embodiments of the present invention, the recovery rates of fluorine and silicon and the reduction of waste residue are both high, and the purity of the obtained sodium fluorosilicate can meet the requirements of the standard GB / T 23936-2018 Industrial Sodium Fluorosilicate. At the same time, ammonium fluoride or ammonium bifluoride, calcium chloride and other products can be produced as by-products.

[0111] In Comparative Example 1, because the glass thinning etching waste residue was not ammonified, the fluorosilicate precipitate in the waste residue could not be converted into silicon dioxide that is soluble in hydrofluoric acid and could only be treated as waste residue. Therefore, its fluorine and silicon recovery rate and waste residue reduction value were lower than those of the Example. Moreover, the purity of sodium fluorosilicate in the fourth filter residue was low because it was not effectively purified.

[0112] In Comparative Example 2, the lack of modified flocculant resulted in a higher moisture content in the sludge, leading to a lower waste reduction than in the Example. Additionally, the higher fluoride and ammonia nitrogen content in the fifth filtrate would moderately affect the purity of the subsequent calcium chloride product.

[0113] In Comparative Example 3, only harmless treatment was carried out, with no resource-based products, and the amount of waste residue increased rather than decreased, with an increase of up to 1.4 times.

[0114] In summary, the processing method of this invention utilizes the characteristics of the glass thinning etching waste liquid and residue to achieve the resource utilization of its main components, fluorine and silicon; in particular, it can achieve the step-by-step recovery of glass thinning etching waste residue to obtain high-value sodium fluorosilicate, ammonium fluoride or ammonium bifluoride and calcium chloride products, thus realizing step-by-step resource utilization.

[0115] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for resource utilization of glass thinning etching waste liquid and residue, characterized in that, The process includes the following steps: (1) treating the glass thinning etching waste liquid with sodium chloride precipitation to obtain the first filter residue and the first filtrate; (2) neutralizing the glass thinning etching waste residue with ammonia water to obtain the second filter residue and the second filtrate; (3) adding the second filter residue to the first filtrate and adding a portion of the second filtrate, stirring and reacting to obtain the third filter residue and the third filtrate; (4) adding sodium fluorosilicate seed crystals and sodium chloride to the third filtrate, reacting to obtain the fourth filter residue and the fourth filtrate; (5) adding lime to the fourth filtrate to adjust the pH value to above 11, and simultaneously introducing steam for stripping and ammonia removal, and then adding 1-5% of its mass of modified flocculant, reacting to obtain the fifth filter residue, the fifth filtrate and the first waste gas.

2. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 1, characterized in that, In step (1), 5-10% sodium fluorosilicate seed crystals are added to the glass thinning etching waste liquid, followed by a sodium chloride solution with a concentration of 5-20% and an excess sodium chloride coefficient of 1-1.

2. After the reaction, the first filter residue and the first filtrate are obtained.

3. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 1, characterized in that, In step (2), the glass thinning etching residue is neutralized with ammonia water with a concentration of 5-20%, and the pH is adjusted to 8.0-9.

5. After the reaction, the second filter residue and the second filtrate are obtained.

4. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 1, characterized in that, In step (3), the amount of the second filtrate added is 40-60% of the yield of the second filtrate.

5. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 1, characterized in that, In step (4), 5-10% sodium fluorosilicate seed crystals by mass are first added to the third filtrate, followed by a sodium chloride solution with a concentration of 5-20%, and the excess sodium chloride coefficient is 1-1.

2.

6. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 1, characterized in that, The preparation method of the modified flocculant includes the following steps: 1) Mix raw material A containing magnesium ions, raw material B containing phosphate ions, raw material C containing calcium ions, and raw material D containing aluminum ions with deionized water, and then disperse them in a solvent to obtain a first mixture; 2) Add β-cyclodextrin to the first mixture, let it stand and dry to obtain a second mixture; 3) Add deionized water to graphene oxide, mix well, slowly add ammonium dihydrogen phosphate, heat, stir, filter, add ammonium persulfate in small amounts several times, react with heating, add deionized water and dilute hydrochloric acid; then concentrate the obtained solution in a gradient, stir evenly, let it stand in the dark to obtain graphene oxide colloid; 4) Mix the graphene oxide colloid with the second mixture, sonicate and centrifuge, discard the supernatant, retain the mixture, shake the colloid evenly, and then dry and cool to obtain the modified flocculant.

7. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 6, characterized in that, In step 1), the mass ratio of raw material A, raw material B, raw material C, and raw material D is 1:1:1~2:3~5.

8. The method for resource utilization of glass thinning etching waste liquid and residue according to claim 6, characterized in that, In step 2), the mass of the β-cyclodextrin is 1 to 2 times the mass of the first mixture.

9. The method for resource utilization of glass thinning etching waste liquid and waste residue according to claim 6, characterized in that, In step 3), the amount of ammonium dihydrogen phosphate added is 0.2 to 0.5 times the mass of graphene oxide; the amount of ammonium persulfate added is 0.5 to 1.5 times the mass of graphene oxide; during gradient concentration, it is first concentrated to 2 to 5 mg / mL, and then concentrated to 10 to 50 mg / mL.

10. The method for resource utilization of glass thinning etching waste liquid and waste residue according to claim 6, characterized in that, In step 4), the mass ratio of the graphene oxide solution to the second mixture is 2~5:1.

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