47results about "Fluosilicic acid" patented technology

A phosphor composition includes a red phosphor material having a red decay rate and a green phosphor material having a green decay rate. The red phosphor material includes a Mn4+ doped phosphor of Formula I and a Eu3+ doped uranium phosphor, and a difference between the red decay rate and the green decay rate is no more than 7 ms, AxMFy:Mn4+ (I), wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is an absolute value of a charge of the MFy ion; and y is 5, 6 or 7. A device is also provided.

The invention relates to the technical field of industrial solid waste resource utilization, and particularly discloses a fluorine-containing silicon slag recycling process which comprises five steps of fluorine-containing silicon slag raw material pretreatment, acid leaching fluorine extraction, ammonium fluosilicate preparation, nanometer silica gel purification and wastewater recycling. Fluorine in the fluorine-containing silicon slag is converted into ammonium fluosilicate solid to be recycled, fluorine in the fluorine-containing silicon slag is converted into sodium silicate to be manufactured into nano silica gel to be recycled, only feeding reaction is needed in the whole process, then filtering is conducted, the technological process is simple, and the treatment efficiency of the fluorine-containing silicon slag is improved. 0.3 ton of ammonium fluosilicate (the market price is 8000 yuan / ton) and 0.2 ton of nano silica gel (the market price is 15000 yuan / ton) can be produced from each ton of fluorine-containing silicon slag, and huge economic value can be brought to factories.

The invention belongs to the field of inorganic chemical industry, and particularly relates to a method and a system for efficiently utilizing a phosphate fertilizer byproduct, the method comprises the following steps: carrying out acidolysis on fluosilicic acid with the concentration of more than or equal to 45% wt and concentrated sulfuric acid to generate a mixed solution of silicon tetrafluoride gas and fluorosulfonic acid; the mass ratio of the fluosilicic acid to the concentrated sulfuric acid is controlled to be 1: (4-15); pyrolyzing the obtained fluorosulfonic acid to generate dilute sulphuric acid, hydrogen fluoride and water vapor, forming 98% concentrated sulphuric acid from part of dilute sulphuric acid and fuming sulphuric acid, drying hydrogen fluoride to obtain crude hydrogen fluoride gas, and condensing and rectifying to obtain anhydrous hydrogen fluoride; the rest dilute sulphuric acid is partially compounded and then returned for acidolysis, and the rest dilute sulphuric acid is used for producing white carbon black and flows back to a wet-process phosphoric acid system; and circularly absorbing the obtained silicon tetrafluoride gas by using secondary concentrated fluosilicic acid to obtain fluosilicic acid with the mass concentration of more than or equal to 45%, recycling the fluosilicic acid for acidolysis reaction, and modifying the concentrated by-product silicon dioxide to obtain the high-activity white carbon black. The problems of energy consumption and cost are solved, and efficient circulation and poly-generation of fluorine and silicon resources are achieved in the whole process.

The invention relates to a method for preparing high-purity fluosilicate by taking industrial fluorine-containing sludge as a raw material. Comprising the following steps: slurrying calcium fluoride sludge, acidifying with inorganic acid, adding an adsorbent, and filtering; adding soluble salt into the filtrate to carry out crystallization reaction and adjusting the pH value; and cooling, filtering, washing and drying to obtain a target product. Solid waste resource utilization is achieved, the product purity is larger than or equal to 98%, and energy consumption is reduced by 60% or above compared with a traditional process.

The present invention relates to the field of water treatment, and discloses a method for resource recycling and reuse of fluorine-containing waste acid and recovery equipment. The equipment includes a fluorine-containing waste acid regulating water tank, a mixing reactor, a fully automatic drum microfilter, an inorganic membrane separation device and a control module. The fluorine-containing waste acid is first pre-treated in the regulating water tank, and then sequentially processed through the mixing reactor reaction, the fully automatic drum microfilter solid-liquid separation, and the inorganic membrane separation device for deep treatment to achieve waste acid resource recycling; the method steps cover the waste acid pretreatment, reaction treatment, solid-liquid separation, and membrane separation treatment links, and are precisely controlled using a sequential control algorithm and a PID control algorithm. The dosage of the reagent and the pressure adjustment are calculated according to specific formulas, respectively, and the influence of historical data is fully considered, so that the treatment process can be controlled more accurately; the invention can efficiently remove fluorosilicic acid impurities, effectively solve the problem of fluorine-containing waste acid treatment, and provide strong support for related enterprises to reduce costs and achieve green production.

The invention belongs to the field of waste liquid recycling, and discloses a method for preparing potassium fluosilicate by using mixed waste acid, which comprises the following steps: S1, silica fume acidification pretreatment: soaking silica fume in an acid solution for acidification, carrying out precipitation separation on the silica fume, drying, and grinding to obtain acidified silica fume; s2, mixing the raw materials: uniformly mixing the acidified silica fume and the silicon dioxide powder; s3, preparation of fluosilicic acid: adding a mixture of acidified silica fume and silicon dioxide powder into the mixed waste acid, and uniformly stirring by a mechanical stirrer; and S4, preparation of potassium fluosilicate: adding a potassium chloride saturated solution into the fluosilicic acid solution to generate potassium fluosilicate precipitate. The method has the advantages and effects of being high in fluorine ion utilization efficiency, low in production cost and high in finished product purity.

This invention belongs to the field of fly ash treatment technology, specifically disclosing a method for separating potassium and sodium from fly ash, including the following steps: adjusting the acid concentration in the fly ash washing solution to 40-65% and the temperature to 40-65℃, adding a sodium precipitating agent and maintaining the reaction temperature, and filtering to obtain sodium salt and potassium-containing waste liquid. This invention utilizes precipitation to recover sodium ions from fly ash washing solution. After filtration, sodium salt precipitate and potassium-containing waste liquid are obtained. During this process, the reaction is controlled under acidic conditions to prevent potassium ion precipitation. At 40-60℃, the sodium precipitating agent reacts with sodium ions to obtain sodium salt precipitate with large crystals, which allows for more convenient and thorough filtration, resulting in better separation of potassium and sodium ions in the fly ash washing solution. The sodium salt precipitate is further washed with a displacement agent to replace the potassium ions attached to the surface of the sodium salt precipitate with sodium, improving the purity of the sodium salt product. Finally, multiple water washings are performed to reduce the acidity of the sodium salt precipitate, resulting in a sodium salt product with stable quality.

The invention relates to the field of photovoltaic production, in particular to a photovoltaic wastewater treatment method which comprises the following steps: mixing fluorine-containing wastewater with waste acid to obtain fluorine ion wastewater; adding waste silicon dioxide powder into the fluorine ion wastewater to obtain fluosilicic acid wastewater; adding an alkaline sodium source into the fluosilicic acid wastewater to obtain sodium fluosilicate wastewater; and carrying out separation treatment on the sodium fluosilicate wastewater, and extracting bottom-layer jelly to obtain sodium fluosilicate and photovoltaic treatment water. According to the method, waste acid and waste silicon dioxide powder generated in the photovoltaic production process are both utilized, the fluorine content in the wastewater is greatly reduced while no extra chlorine-containing fluorine removal agent is added, fluorine is extracted as a by-product with high purity, photovoltaic wastewater pollution is reduced, the environmental friendliness is improved, and meanwhile, the energy consumption is reduced. The wastewater treatment cost is further reduced, and potential profits are created.

Provided are a liquid dispersion of fluoride particles, which has low viscosity and excellent dispersibility, and is suitable for producing an optical film such as an antireflection film; a method for producing the same; and an optical film using the same. The liquid dispersion of fluoride particles according to the present invention is that in which particles of a fluoride represented by the chemical formula AxCFy (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) are dispersed in an aprotic organic solvent having a relative permittivity of 5 to 40, and the optical film according to the present invention is produced by using the liquid dispersion of fluoride particles.

The invention discloses a method for synergistically preparing and purifying sodium fluosilicate by using fluorine-containing waste acid and fly ash. The method comprises the following steps: crushing household garbage incineration fly ash, pulping, pickling, and carrying out solid-liquid separation to obtain crude calcium water; sequentially carrying out heavy metal removal, denitrification, oxidation and neutralization treatment on the crude calcium water, and carrying out solid-liquid separation to obtain refined calcium water; carrying out primary calcium removal treatment on the obtained refined calcium water, and carrying out solid-liquid separation to obtain crude brine; carrying out deep calcium removal treatment on the crude brine to obtain refined brine mainly containing sodium chloride; pretreating the fluorine-containing waste acid to obtain a fluosilicic acid solution; mixing and reacting the fluosilicic acid solution with refined salt water, controlling the pH value of a reaction system to be less than 2, and performing solid-liquid separation to obtain crude sodium fluosilicate; and carrying out multistage countercurrent oxidation washing on the crude sodium fluosilicate, and drying to obtain a sodium fluosilicate product. And resource comprehensive utilization of the fluorine-containing waste acid and the fly ash is realized.

The invention relates to the technical field of chemical raw material production, and particularly discloses a potassium fluosilicate synthesis device and a synthesis method thereof. The device comprises a box body, a feeding mechanism, a mixing mechanism, a multi-stage detection mechanism and an adjusting mechanism. The feeding mechanism realizes accurate proportioning and conveying of fluosilicic acid solution and sylvite solution (such as potassium chloride and potassium sulfate solution) through a plurality of independent conveying pumps. The mixing mechanism adopts a multi-stage disc type reaction tube, a bending part and an inner diameter expansion design, so that fluosilicate (SiF) and potassium ions (K) fully react to generate potassium fluosilicate (K2SiF6) precipitate, and an electric heating tube synchronously regulates and controls the reaction temperature (40-80 DEG C). And the multi-stage detection mechanism performs three-stage pH real-time detection on the slurry through the three detection boxes connected in series and the rotary mixing shaft, so that the detection precision is improved. And dynamically adjusting the pH value to a target range (5.5-6.5) through an acid adding pipe (such as injection of hydrochloric acid) or an alkali adding pipe (such as injection of a sodium hydroxide solution) according to a detection result.

This invention discloses a method for separating fluorosilicic acid and hydrofluoric acid using an anion exchange membrane, comprising the following steps: adding a flocculant to a fluorosilicic acid-hydrofluoric acid mixture, aging it, then adding a desulfurizing agent to carry out a desulfurization reaction to obtain a mixed solution, adding the mixed solution to the feed side of an anion exchange membrane for membrane separation, and obtaining a hydrofluoric acid solution with a mass concentration of 2-30% on the clear water side after separation. This invention uses a flocculant to rapidly settle solids such as sodium fluorosilicate and potassium fluorosilicate in the fluorosilicic acid-hydrofluoric acid mixture, uses a desulfurizing agent to remove sulfuric acid, and then uses an anion exchange membrane to effectively separate fluorosilicic acid and hydrofluoric acid in the fluorosilicic acid-hydrofluoric acid mixed solution. The hydrofluoric acid separated by membrane separation has high purity and high output value, increases the utilization rate of by-product hydrofluoric acid, and reduces costs.

The invention relates to the technical field of calcium superphosphate preparation and fluorine resource recycling, in particular to a method for preparing calcium superphosphate and co-producing fluosilicic acid by using wet-process phosphoric acid sludge acid filter residues, which comprises the following steps: carrying out filter pressing on wet-process phosphoric acid sludge acid to prepare clear liquid and acid sludge, and returning the clear liquid to a clear acid tank; acidifying the acid sludge with sulfuric acid and repulping to obtain a mixture A; filtering and washing the mixture A to obtain filter residues B and filtrate C; the filter residue B is subjected to acidolysis again with concentrated sulfuric acid under the conditions of high temperature and negative pressure, gas generated by acidolysis is washed and absorbed to prepare fluosilicic acid D, a solid-liquid mixture E left after acidolysis and the filtrate C are mixed and react with the pretreated phosphate tailings in proportion to obtain a transition product G, and after a curing reaction is conducted at the temperature of 50-60 DEG C, a single superphosphate product H is obtained; a feasible way is provided for comprehensive utilization of the wet-process phosphoric acid sludge and the phosphate tailings, the channel of the superphosphate raw material is widened, and the recycling efficiency of fluorine resources is improved.

The invention relates to a semiconductor industry ammonium sulfate solid recycling method, which comprises: (1) mixing a sodium-containing ammonium sulfate solid and an ammonium sulfate solution at a temperature of 60-85 DEG C to obtain a saturated ammonium sulfate solution at a temperature of 60-85 DEG C; (2) carrying out cooling crystallization on the saturated ammonium sulfate solution, and carrying out solid-liquid separation to obtain refined ammonium sulfate and a first mother solution; (3) adjusting the pH value of the first mother liquor to be alkaline, and performing heavy metal impurity removal to obtain impurities and second mother liquor; and recycling the second mother liquor according to the sodium content in the second mother liquor. According to the method provided by the invention, a high-purity ammonium sulfate product can be obtained; and the discharge of mother liquor can be reduced, a sodium fluosilicate byproduct can be produced, the utilization rate of resources is improved, and the economic requirement and the environmental protection requirement are both considered.

The present invention provides a method for recovering fluorine in a wet-process phosphoric acid production process using flash evaporation and cooling coupled with cyclone flow. The method comprises: subjecting a slurry obtained from the acid hydrolysis of phosphate rock to flash evaporation and cooling for crystallization to obtain a flashed slurry; and subjecting the obtained flashed slurry to cyclone separation to recover fluorosilicate particles. The method, provided herein, utilizes flash evaporation and cooling coupled with cyclone separation to separate and recover fluorine from the acid hydrolysis of phosphate rock into large-particle fluorosilicates. The process is simple and easy to operate, and without the need for the addition of any chemical reagents, the method achieves excellent fluorine recovery, with a recovery rate exceeding 32.4%. This method can effectively reduce the fluorine content in phosphogypsum and phosphoric acid produced during the wet-process phosphoric acid production process and facilitates the subsequent recycling of fluorine resources.

The present invention relates to the technical field of water treatment, more specifically, it relates to a kind of resource treatment method of BOE waste liquid, and its technical scheme key points are, comprise the following steps: S1, sodium salt solution is added to BOE waste liquid to react, obtain sodium fluorosilicate and the first waste liquid;S2, aluminum salt solution is added to the first waste liquid, and pH is adjusted to 4-7, and cryolite and the second waste liquid are obtained;S3, defluorinating agent and heavy capture agent are added to the second waste liquid, and the first waste residue and the third waste liquid are obtained;S4, pH of the third waste liquid is adjusted to 2-4, evaporation crystallization is carried out, and evaporation condensation water and concentrated liquid are obtained;S5, the concentrated liquid is pumped into cooling crystallization tank and cooled, centrifuged, and ammonium salt and final mother liquor are obtained;S6, the third waste liquid and the final mother liquor are returned to the S1 and the S2 for circulation. The present invention can realize the resource recovery of components in BOE waste liquid, and has the advantages of obtaining high-value sodium fluorosilicate, cryolite and agricultural grade ammonium salt products.

The application discloses a preparation method and application of ferrous hexafluorosilicate and iron-silicon composite material, and adopts hydrofluoric acid and ferrosilicon alloy to prepare ferrous hexafluorosilicate in one step; the difficulty of the application lies in controlling the content of the hydrofluoric acid and the weight of the ferrosilicon alloy, and regulating a certain proportion to achieve balance; although the hydrofluoric acid is highly toxic, the method can achieve good effects by using a small amount of the hydrofluoric acid, and can adopt the excessive ferrosilicon alloy to minimize environmental pollution and be more friendly to the environment; when the prepared ferrous hexafluorosilicate is used as a negative material of a lithium ion battery, irreversible lithium fluorosilicate can be effectively relieved, thereby being favorable to lithium ion embedding and discharging, better relieving volume expansion caused in the charging and discharging process, maintaining the stability of a pole piece structure, greatly improving the electrochemical performance of the lithium ion battery, improving the specific capacity of the battery, and being capable of well reducing the production cost of the lithium ion.

The present application belongs to the technical field of waste liquid treatment, and particularly relates to a graphite purification waste liquid treatment method and a treatment system. The present application introduces a pre-acid pickling system to utilize waste acid twice, reduces the amount of acid used in the acid pickling process of graphite purification, improves the use efficiency of acid liquid, thereby reducing the cost of the graphite purification process and significantly enhancing the overall economy. The present application also introduces a sodium fluorosilicate production line, effectively realizing the resource utilization of residual fluorosilicic acid and fluorosilicate in waste water. Not only can the operation cost of reagents in the subsequent water treatment process be effectively reduced, but also the produced sodium fluorosilicate can be sold to improve economic benefits. An evaporation crystallization system is used to crystallize and recover valuable salts in waste water. The obtained crystalline salt can be further used as a raw material for other products. The treatment system provided by the present application can realize the resource utilization and recycling of waste acid and waste water, and achieve zero emission.

The invention discloses a method for utilizing de-heavy residue from wet-process phosphoric acid, comprising the following steps: step 1), grinding and finely grinding low-grade phosphate ore; step 2), adding the powdered material in step 1), mixing and placing the mixture in a disc pelletizing machine for pelletizing; heating the dried pellets with conventional yellow phosphorus furnace charge, condensing volatilized arsenic sulfide and lead sulfide through a flue gas heat exchanger, and enriching them to obtain arsenic-lead dust; step 6), raising the furnace temperature in step 5) to 1300° C. to 1600° C., condensing P vapor and SiF4 gas generated by the high-temperature reaction through spraying water, and collecting them; step 7), performing solid-liquid separation of the solid yellow phosphorus collected in step 6) and liquid H2SiF6 to obtain a main product, yellow phosphorus, and a by-product, H2SiF6. The preparation of the pellets according to the invention does not require the addition of an additional binder or sintering, has low energy consumption, and has better effects; the invention can separate and enrich As and Pb elements in the de-heavy residue without causing phosphorus loss, and the arsenic-lead dust can be used as a raw material for lead smelting.

The invention discloses a method for recovering fluorosilicate from high-purity quartz sand pickling wastewater, and belongs to the field of fluorosilicate recovery technology. The method of the present invention comprises the following steps: S1 high-purity quartz sand is pickled with hydrofluoric acid (ultrapure);S2 pickling is press-filtered to pickling solution after the pickling is completed to obtain fine quartz sand solid and fluorosilicic acid filtrate;S3 fluorosilicic acid filtrate is stirred and heated up and concentrated and then continues to add inorganic alkali solution for sedimentation, until the mixed solution pH is 7.2-7.5 and stops adding inorganic alkali solution;S4 carries out press-filtration to the mixed solution after sedimentation, collects filter cakes to dryness and obtains fluorosilicate. The fluorosilicate purity obtained by applying this method to reclaim is high and the recovery rate is high, and it is achieved that waste resources can be reused, and environmental protection is achieved, with the characteristics of green environmental protection economy.

The invention discloses a preparation method of phosphorus ore defluorination and low-power-consumption yellow phosphorus. The preparation method comprises the steps of first-stage reaction, batching and balling, second-stage reaction, tail gas purification and electric furnace reduction. The method comprises the following steps: by taking medium-low-grade complex collophanite, phosphoric acid, low-silicon high-calcium phosphorite and calcium carbonate or calcium oxide as raw materials, carrying out a first-stage reaction by regulating the ratio of CaO to P2O5 in a mixture for one time; regulating and controlling the ratio of CaO / P2O5 to SiO2 / CaO for the second time, pelletizing, and calcining to carry out a second-stage reaction. The reaction gas is silicon tetrafluoride, and is used for preparing anhydrous hydrogen fluoride and other fluorine-containing products after being purified; the reaction solid phase is low-fluorine high-grade phosphorite, when the phosphorite is used for preparing yellow phosphorus, the fluorine overflow rate and the dust rate are greatly reduced, the phosphorus reduction rate is obviously improved, and the power consumption of the yellow phosphorus is obviously reduced. The technology is a preferred route for energy conservation and consumption reduction of yellow phosphorus and efficient recovery of fluorine resources; meanwhile, phosphorus, fluorine and silicon elements in the middle-low-grade complex collophanite can be directly utilized in a high-valued mode, and a new route is opened up for efficient utilization of a large amount of low-grade complex collophanite in China.

The invention discloses a method for recovering fluorine and phosphorus resources in dilute phosphoric acid defluorination residues by a fractional precipitation method. The method comprises the following steps: reacting the defluorination residues with sulfuric acid and process water to form slurry A; carrying out filter pressing and solid-liquid separation on the slurry A to obtain calcium sulfate and a solution containing phosphorus and fluorine; adding active silicon powder and sodium carbonate into the solution containing phosphorus and fluorine to react for 50-90 minutes, and precipitating fluorine element to form slurry B; carrying out filter pressing separation on the slurry B to obtain defluorinated phosphoric acid and a fluorine-containing precipitate; and re-pulping and recrystallizing the fluorine-containing precipitate, then centrifugally separating and washing to obtain a sodium fluosilicate semi-finished product, and drying to obtain a sodium fluosilicate product. According to the method, calcium is precipitated through sulfuric acid, fluorine is precipitated through active silicon and sodium carbonate, defluorinated slurry is re-pulped, and recrystallization is conducted in sequence, the process is simple, the cost is low, the method is environmentally friendly, calcium, fluorine and phosphorus are precipitated in sequence, high-value phosphorus and fluorine resources are efficiently recycled, the purity of sodium fluosilicate is larger than or equal to 99%, calcium hydrophosphate meets the feed-grade standard, and pollution of the fluorine resources to the environment is reduced.

The invention discloses a rare earth smelting fluorine-containing tail gas resource recycling system and method. The system comprises an acid removal device, a tail gas recycling module, a tail gas acid concentration module and a tail gas treatment module. The deacidification device is used for removing sulfuric acid mist entrained in fluorine-containing tail gas and purifying hydrogen fluoride and silicon tetrafluoride tail gas; a gas inlet of the tail gas recovery module is communicated with a gas outlet of the deacidification device; the tail gas acid concentration module comprises a concentration tower, a concentration tower circulating pump, a concentration tower reboiler, a concentration tower condenser, a vacuum unit and a tail gas acid output assembly; the bottom of the concentration tower reboiler is communicated with the concentration tower, the bottom of the concentration tower is connected with the concentration tower circulating pump, the concentration tower circulating pump is connected with the top of the concentration tower reboiler, the top of the concentration tower is connected with the top of the concentration tower condenser, and the bottom of the concentration tower condenser is connected with the tail gas acid output assembly. The fluorine-containing tail gas recovery problem in the rare earth concentrate sulfuric acid slurrying decomposition process is solved, and the high-concentration fluorine-silicon mixed acid is obtained after acid removal and concentration.

Described herein is a method for chemically breaking down per- and polyfluoroalkyl substances (PFAs), whereby to convert the PFAs to products that are more friendly to the environment than are per- and polyfluoroalkyl substances. Also described are compositions containing PFAs and components that under the conditions described herein effect such breakdown, as well as an apparatus that can be used to effect the chemical transformation.

The invention relates to the technical field of industrial waste resource utilization, and particularly discloses a method for producing sodium fluosilicate by using fluorine-containing silicon slag and etching waste liquid, which comprises the following steps: firstly, adding the fluorine-containing silicon slag into the etching waste liquid to dissolve silicon dioxide in hydrofluoric acid to generate fluosilicic acid; reacting purchased sodium salt with fluosilicic acid to generate sodium silicate precipitate, and performing suction filtration, washing and drying to obtain a sodium fluosilicate product. The etching waste acid containing hydrofluoric acid and the fluorine-containing silicon slag are co-treated, hydrofluoric acid reacts with silicon dioxide to generate fluosilicic acid, then sodium salt reacts with fluosilicic acid to prepare a sodium fluosilicate product, and the component complementarity of the fluorine-containing silicon slag and the etching waste liquid is utilized, so that waste is treated with waste, and the raw material cost is reduced.

The invention relates to the technical field of phosphorus chemical industry and three-waste resourceful treatment, and discloses a silicon dioxide-assisted phosphoric acid concentration fluorine recovery process, which comprises the following steps: mixing anhydrous hydrogen fluoride byproduct silicon slag with dilute phosphoric acid to prepare slurry with the solid content of 9.0-9.5%; after being homogenized by a buffer tank, the slurry is premixed and diluted on line through a dilute phosphoric acid branch, and is injected into a concentration system; in the concentration process, silicon dioxide is used for promoting hydrogen fluoride to be converted into volatile silicon tetrafluoride to escape and be recycled. In order to solve the scaling problem in the conveying process, a double-pipeline switching mechanism is established, and 3%-5% dilute sulphuric acid is used for conducting periodic acid pickling maintenance on a shutdown pipeline. Through dynamic flow control, the fluorine recovery rate is greatly improved while the solid content of the concentrated phosphoric acid product is ensured to be qualified, the problems that pipelines are easy to block and fluorine resources are wasted in the traditional process are solved, and efficient resource utilization of the silicon slag is realized.

Described herein is a method for chemically breaking down per- and polyfluoroalkyl substances (PFAs), whereby to convert the PFAs to products that are more friendly to the environment than are per- and polyfluoroalkyl substances. Also described are compositions containing PFAs and components that under the conditions described herein effect such breakdown, as well as an apparatus that can be used to effect the chemical transformation.

The invention discloses a resource recycling process of a sodium hydrogenfluoride mother liquor byproduct, and belongs to the technical field of fluorine chemical industry waste liquid treatment. The process comprises the following three steps: firstly, preparing a sodium fluoride crystal by regulating the molar ratio of Na to F to be (1.05-1.08): 1, optimizing a feeding mode and adding a seed crystal; secondly, regulating the molar ratio of F to Si to be (6-9): 1 by using the sodium fluoride mother liquor, and adding white carbon black to prepare sodium fluosilicate; and finally, treating the F-containing waste liquid by compounding quick lime and slaked lime, regulating the molar ratio of Ca to F to be (2.1-2.5): 1, and reacting for 1-2 hours under the conditions of 50-70 DEG C and 300-400 r / min, so that the F content in the wastewater is less than or equal to 10 mg / L and the ammonia nitrogen content is less than or equal to 15 mg / L. According to the process, the total fluorine recovery rate is larger than or equal to 99%, the silicon recovery rate is larger than or equal to 95%, the main content of prepared sodium fluoride is larger than or equal to 98%, the main content of sodium fluosilicate is larger than or equal to 98%, and efficient resource utilization of sodium hydrogenfluoride mother liquor byproducts is achieved.

The present invention discloses a process for concentrating fluorosilicic acid, comprising the following steps: S1, subjecting a fluorosilicic acid solution having a mass concentration of less than 25% to cyclic gas-liquid contact with a first gas-phase heat medium and separating water vapor to obtain a primary concentrated fluorosilicic acid having a temperature of 40 to 70°C and a mass concentration of 30 to 35%; S2, subjecting the primary concentrated fluorosilicic acid in S1 to cyclic gas-liquid contact with a second gas-phase heat medium and separating water vapor to obtain a secondary concentrated fluorosilicic acid having a temperature of 20 to 40°C; wherein the temperature of the primary concentrated fluorosilicic acid is greater than that of the secondary concentrated fluorosilicic acid. The present invention employs two staged concentrations, the two concentrations being process flows and process technical parameters selected based on the differences in the stability of fluorosilicic acid under different conditions, thereby achieving an overall optimal concentration concentration, concentration time, and fluorine yield.

The invention discloses a method for in-situ deposition of silicon dioxide in a SiF4 absorption tower, which comprises the following steps: primarily separating a fluorosilicic acid solution discharged from the SiF4 absorption tower and slurry formed by silica gel particles by a plate-and-frame filter press to obtain a silica gel filter cake and a fluorosilicic acid solution, preparing the silica gel filter cake into a sizing material, and feeding the sizing material into a ball mill for wet grinding, then adding a modifier for surface activity modification to prepare a high-activity seed crystal; high-activity crystal seeds are added into the SiF4 absorption tower, so that SiO2 newly generated in the tower is preferentially deposited on the surfaces of the high-activity crystal seeds, and finally large-particle silica gel particles are formed; the silica gel particles and the fluosilicic acid solution discharged by the SiF4 absorption tower are filtered and separated from SiF4 to obtain a silica gel filter cake and a fluorine-silicon prepared solution, and the silica gel filter cake is returned to the step 1). The process is simple, the filter pressing resistance and time are remarkably reduced, and fluosilicic acid residues in a filter cake are reduced.