Method for preparing white carbon black from fluorine-containing silicon slag

Abstract

The invention relates to the technical field of resource recovery, in particular to a method for preparing white carbon black from fluorine-containing silicon slag. The invention provides a method for preparing white carbon black from fluorine-containing silicon slag, which comprises the following steps: drying the fluorine-containing silicon slag to obtain coarse silicon slag; mixing and reacting the coarse silicon slag with an alkaline solution, and carrying out solid-liquid separation to obtain a first solution; adding benzenesulfonic acid into the first solution for reaction, performing solid-liquid separation on reactants to obtain colloid, and washing and drying the colloid to obtain the white carbon black. According to the preparation method, the recovery rate of silicon in the fluorine-containing silicon slag can be increased through the steps of drying treatment, alkaline leaching with the alkaline solution, reaction with benzenesulfonic acid and the like, the prepared white carbon black is high in purity, low in fluorine content and high in specific surface area, and the production cost can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of resource recovery, and particularly to a method for preparing white carbon black from fluorosilicate slag. Background Art

[0002] At present, the production of anhydrous hydrogen fluoride by the fluorosilicic acid method has received increasing attention. However, a large amount of fluorosilicate slag will be generated during the production of anhydrous hydrogen fluoride using fluorosilicic acid. When decomposing H 2 SiF 6 to produce anhydrous hydrogen fluoride by the sulfuric acid method, 0.625 tons of fluorosilicate slag will be generated for every 1 ton of anhydrous hydrogen fluoride produced. In addition, fluorosilicate slag will also be generated during the production of phosphate fertilizers and fluoride salts. Fluorosilicate slag belongs to industrial waste, which is strongly acidic and toxic, and is likely to pollute the environment and threaten human health. However, it has not been effectively treated at present and is mainly treated by stacking, resulting in serious waste of resources.

[0003] The content of SiO 2 in fluorosilicate slag is high, and SiO 2 in it can be recovered to prepare white carbon black. In the prior art, the main method for producing white carbon black is the acid method. The acid method is to react fluorosilicate slag with a strong alkaline solution to obtain a sodium silicate solution, and then react the sodium silicate solution with an acid to prepare white carbon black. Among them, sulfuric acid, hydrochloric acid, carbonic acid, etc. are often used as acidifying agents. Although these acidifying agents can effectively promote the hydrolysis and precipitation reactions of sodium silicate, there are also some disadvantages: for example, sulfuric acid has strong corrosiveness, the reaction is violent and difficult to control; hydrochloric acid has strong volatility and corrosiveness, and the reaction rate is fast and it is difficult to control the particle size and morphology; the reaction of carbonic acid is slow, resulting in an extended reaction time, and the precipitation effect is poor, resulting in incomplete precipitation. Moreover, when using these common acids as acidifying agents, the by-product sodium salts produced have a low value rate. In addition, in the conventional recovery method, white carbon black is prone to agglomeration, resulting in a small specific surface area of white carbon black, making it difficult for the obtained white carbon black product to meet the usage requirements in some fields (such as rubber, coatings, etc.), greatly narrowing the application scope of the recovered white carbon black. Therefore, it is urgent to develop a method for preparing white carbon black from fluorosilicate slag to realize the recycling of fluorosilicate slag, obtain high-quality white carbon black, and reduce production costs at the same time. Summary of the Invention

[0004] The purpose of the present application is to provide a method for preparing white carbon black from fluorosilicate slag, so as to improve the recovery rate of silicon, prepare white carbon black with high purity, low fluorine content and high specific surface area, and reduce production costs. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a method for preparing white carbon black from fluorosilicate slag, which includes the following steps:

[0006] (1) Dry the fluorosilicate slag to obtain crude silicon slag;

[0007] (2) Mix the crude silicon slag with an alkaline solution and react, followed by solid-liquid separation to obtain a first solution.

[0008] (3) Add benzenesulfonic acid to the first solution for reaction to obtain a reactant. Separate the solid and liquid of the reactant to obtain a colloid, wash and dry the colloid to obtain white carbon black.

[0009] In some embodiments of the present application, in step (3), add benzenesulfonic acid to the first solution at a temperature of 30°C to 50°C until the pH of the solution is 1 to 3, and then carry out aging after heating to obtain the colloid.

[0010] In some embodiments of the present application, the temperature of the aging is 80°C to 110°C, and the time of the aging is 1 h to 4 h.

[0011] In some embodiments of the present application, in step (3), the benzenesulfonic acid is an aqueous solution of benzenesulfonic acid, the mass fraction of the aqueous solution of benzenesulfonic acid is 4.9% to 19.6%, and the aqueous solution of benzenesulfonic acid is added to the first solution by dropping. When the pH of the solution ≤ 7, the dropping rate of the aqueous solution of benzenesulfonic acid is 1 mL / (200 mL·min) to 2 mL / (200 mL·min) until the pH of the solution is 1 to 3, and then stop dropping.

[0012] In some embodiments of the present application, in step (1), the temperature of the drying treatment is 60°C to 180°C, and the time of the drying treatment is 4 h to 12 h.

[0013] In some embodiments of the present application, in step (1), the drying treatment is divided into a first drying stage and a second drying stage. The temperature of the first drying stage is T1, 60°C ≤ T1 ≤ 120°C, and the time of the first drying stage is t1, 2 h ≤ t1 ≤ 4 h; the temperature of the second drying stage is T2, 120°C < T2 ≤ 180°C, and the time of the second drying stage is t2, 2 h ≤ t2 ≤ 8 h.

[0014] In some embodiments of the present application, in step (2), the alkaline solution is selected from at least one of sodium hydroxide solution or potassium hydroxide solution; the concentration of the alkaline solution is 140 g / L to 250 g / L, and the alkaline solution and the crude silicon slag are mixed at a liquid-solid ratio of 8 mL / g to 13 mL / g.

[0015] In some embodiments of the present application, in step (2), the alkaline solution is selected from sodium hydroxide solutions, the concentration of the sodium hydroxide solution is 180 g / L to 200 g / L, and the sodium hydroxide solution and the crude silicon slag are mixed at a liquid-solid ratio of 8 mL / g to 13 mL / g.

[0016] In some embodiments of the present application, in step (2), the temperature of the reaction is 65 °C to 105 °C, and the reaction time is 0.5 h to 4 h.

[0017] In some embodiments of the present application, in step (2), the reaction is carried out under ultrasonic conditions, and the ultrasonic frequency is 20 kHz to 40 kHz.

[0018] In some embodiments of the present application, in step (3), the drying temperature is 100 °C to 150 °C.

[0019] Advantages of the present application:

[0020] The present application provides a method for preparing white carbon black from fluorine-containing silicon slag, which includes the following steps: drying the fluorine-containing silicon slag to obtain crude silicon slag; mixing the crude silicon slag with an alkaline solution and reacting, followed by solid-liquid separation to obtain a first solution; adding benzenesulfonic acid to the first solution for reaction to obtain a reactant, subjecting the reactant to solid-liquid separation to obtain a colloid, and washing and drying the colloid to obtain white carbon black. The preparation method of the present application can improve the recovery rate of silicon in the fluorine-containing silicon slag through steps such as drying treatment, alkaline solution leaching, and reaction with benzenesulfonic acid, and the prepared white carbon black has high purity, low fluorine content, high specific surface area, and can also reduce production costs.

[0021] Of course, it is not necessary for any product or method implementing the present application to simultaneously achieve all the above-mentioned advantages. Detailed implementation manners

[0022] The technical solutions in the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0023] The first aspect of the present application provides a method for preparing white carbon black from fluorine-containing silicon slag, which includes the following steps:

[0024] (1) Drying the fluorine-containing silicon slag to obtain crude silicon slag;

[0025] (2) Mixing the crude silicon slag with an alkaline solution and reacting, followed by solid-liquid separation to obtain a first solution;

[0026] (3) Add benzenesulfonic acid to the first solution for reaction to obtain a reaction product. Separate the solid and liquid of the reaction product to obtain a colloid, and wash and dry the colloid to obtain white carbon black.

[0027] Fluorine in the fluorosilicate slag mainly exists in the forms of free fluorine and lattice fluorine. Among them, free fluorine is mainly fluorosilicic acid adhering to the surface of silica, and lattice fluorine is that fluorine in the solution occupies the position of oxygen element during the crystallization of silica, and fluorine exists in silica in the form of crystal defects. If only through simple drying, water washing, etc., only the free fluorine attached to the surface of silica can be removed, and the lattice fluorine cannot be removed. It is found that first drying the fluorosilicate slag can effectively remove the free fluorine on the surface of the fluorosilicate slag and the moisture in the fluorosilicate slag, which is beneficial to reducing the dosage of the subsequent alkaline solution; then mixing the obtained crude silica slag with the alkaline solution, the silica in the crude silica slag reacts with the alkaline solution to generate silicate, so that the lattice fluorine is leached out and becomes free fluorine, and the leached free fluorine can be removed through subsequent treatment steps, which is beneficial to reducing the fluorine content in the white carbon black product and improving the purity of white carbon black.

[0028] More importantly, in step (3) of the present application, benzenesulfonic acid is selected as the acidifying agent. On the one hand, benzenesulfonic acid can promote the hydrolysis of silicate to generate white carbon black, and the hydrolysis reaction of benzenesulfonic acid and silicate is relatively mild, which can reduce the situation of local reaction overheating, is beneficial to regulating the particle size of white carbon black and increasing the specific surface area of white carbon black; on the other hand, in the early stage of the acidification reaction, benzenesulfonic acid first reacts with the remaining alkaline solution in the first solution, and the generated sodium benzenesulfonate or potassium benzenesulfonate can be used as a surfactant and participate in the acidification reaction stage. Sodium benzenesulfonate or potassium benzenesulfonate adsorbs on the surface of white carbon black to form a protective film to prevent particle agglomeration, thereby improving the dispersibility of white carbon black in the solution, and is beneficial to preparing a white carbon black product with uniform particle size, good dispersibility and large specific surface area. That is, the present application selects benzenesulfonic acid as the acidifying agent, which not only plays an acidifying role on sodium silicate or potassium silicate, but also the generated sodium benzenesulfonate or potassium benzenesulfonate has the function of a surfactant, and can effectively increase the specific surface area of white carbon black without adding an additional surfactant. In addition, compared with common surfactants, such as cetyltrimethylammonium bromide, sodium benzenesulfonate or potassium benzenesulfonate is easier to be removed from the surface of white carbon black during the washing process to obtain high-purity white carbon black, and sodium benzenesulfonate or potassium benzenesulfonate, as a by-product after the reaction, has good biodegradability, has less impact on the environment, and has high recycling value.

[0029] The preparation method of the present application can improve the recovery rate of silicon in the fluorosilicate slag through steps such as drying treatment, alkaline solution alkali leaching, and acidification reaction with benzenesulfonic acid, and the prepared white carbon black has high purity, low fluorine content and high specific surface area, and can also reduce the production cost.

[0030] In step (2) of the present application, in addition to containing SiO 2 in the crude silicon slag, it may also contain HF, H 2 SiF 6 and so on. For example, when the alkaline solution is selected as sodium hydroxide solution, the reaction between the crude silicon slag and the sodium hydroxide solution is as follows: .

[0031] Furthermore, in step (3) of the present application, when benzenesulfonic acid is added to the first solution, the reaction that occurs is as follows: .

[0032] In some embodiments of the present application, in step (3), benzenesulfonic acid is added to the first solution at a temperature of 30°C to 50°C until the pH of the solution is 1 to 3, and after heating, aging is carried out to obtain the colloid. For example, when adding benzenesulfonic acid to the first solution, the temperature can be 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C or a range composed of any two of these values; the pH of the solution is adjusted to 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3 or a range composed of any two of these values. Controlling the temperature of the first solution to 30°C to 50°C for preheating is beneficial to accelerating the acidification reaction process, and the obtained silicic acid colloid (SiO 2 ·H 2 O) is not easily agglomerated. At the same time, controlling the pH to 1 to 3 can also reduce the agglomeration of the silicic acid colloid, further improve the specific surface area, which is beneficial to further improving the specific surface area of the finally obtained white carbon black product, and is beneficial to the hydrolysis of silicate in the solution to be converted into silicic acid colloid (SiO 2 ·H 2 O).

[0033] In some embodiments of the present application, the temperature of the aging is 80°C to 110°C, and the time of the aging is 1 h to 4 h. For example, the temperature of the aging can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or a range composed of any two of these values; the time of the aging can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h or a range composed of any two of these values. The aging process can be carried out under stirring, and the present application does not particularly limit the rotation speed of the stirring, as long as the purpose of the present application can be achieved. For example, the rotation speed of the stirring is 200 rpm to 800 rpm. By controlling the temperature and time of the aging within the scope of the present application, it is beneficial to improve the dispersibility of the silicic acid colloid, reduce agglomeration, and thus is beneficial to improving the specific surface area of the white carbon black.

[0034] In some embodiments of the present application, in step (3), the benzenesulfonic acid is an aqueous solution of benzenesulfonic acid, and the mass fraction of the aqueous solution of benzenesulfonic acid is 4.9% to 19.6%. The aqueous solution of benzenesulfonic acid is added to the first solution by dropwise addition. When the pH of the solution ≤ 7, the dropping rate of the aqueous solution of benzenesulfonic acid is 1 mL / (200 mL·min) to 2 mL / (200 mL·min), until the pH of the solution is 1 to 3, and then the dropping is stopped. For example, the mass fraction of the aqueous solution of benzenesulfonic acid can be 4.9%, 5%, 8%, 10%, 12%, 15%, 18%, 19.6% or a range composed of any two of these values. In the present application, the dropping rate of the aqueous solution of benzenesulfonic acid being 1 mL / (200 mL·min) to 2 mL / (200 mL·min) means that 1 mL to 2 mL of the aqueous solution of benzenesulfonic acid is dropped into every 200 mL of the first solution per minute. For example, when the first solution is 400 mL, then at this dropping rate, 2 mL to 4 mL of the aqueous solution of benzenesulfonic acid will be dropped into it per minute; when the first solution is 100 mL, then 0.5 mL to 1 mL of the aqueous solution of benzenesulfonic acid will be dropped per minute. When the pH of the solution ≤ 7, the dropping rate of the aqueous solution of benzenesulfonic acid can be 1 mL / (200 mL·min), 1.2 mL / (200 mL·min), 1.5 mL / (200 mL·min), 1.8 mL / (200 mL·min), 2 mL / (200 mL·min) or a range composed of any two of these values; the aqueous solution of benzenesulfonic acid is dropped into the first solution until the pH of the solution is 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3 or a range composed of any two of these values. When the pH of the solution > 7, the present application has no particular limitation on the rate of adding the aqueous solution of benzenesulfonic acid to the first solution, as long as the purpose of the present application can be achieved. For example, the dropping rate of the aqueous solution of benzenesulfonic acid can be 5 mL / (200 mL·min) to 10 mL / (200 mL·min). By selecting the benzenesulfonic acid within the scope of the present application and regulating the dropping rate of the aqueous solution of benzenesulfonic acid within the scope of the present application, it is beneficial to improve the dispersibility of the silica colloid and reduce aggregation, thereby being beneficial to increasing the specific surface area of the precipitated silica.

[0035] In the present application, after the first solution and benzenesulfonic acid undergo an acidification reaction in step (3), the reactants are subjected to solid-liquid separation to obtain a colloid and a filtrate. The main component of the filtrate is sodium benzenesulfonate or potassium benzenesulfonate, which has a high recycling value.

[0036] In some embodiments of the present application, in the step (1), the temperature of the drying treatment is 60°C to 180°C, and the time of the drying treatment is 4h to 12h. For example, the temperature of the drying treatment can be 60°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C or a range composed of any two of these values; the time of the drying treatment can be 4h, 5h, 8h, 10h, 12h or a range composed of any two of these values. By adjusting the temperature and time of the drying treatment within the scope of the present application, it is beneficial to remove the free fluorine on the surface of the fluorosilicate slag and the moisture in the fluorosilicate slag, which is beneficial to reducing the dosage of the subsequent alkaline solution and lowering the cost. At the same time, it is also beneficial to reduce the fluorine content in the solution in the subsequent treatment steps and is beneficial to the recycling of the by-product solution.

[0037] In some embodiments of the present application, in the step (1), the drying treatment is divided into a first drying stage and a second drying stage. The temperature of the first drying stage is T1, 60°C ≤ T1 ≤ 120°C, and the time of the first drying stage is t1, 2h ≤ t1 ≤ 4h; the temperature of the second drying stage is T2, 120°C < T2 ≤ 180°C, and the time of the second drying stage is t2, 2h ≤ t2 ≤ 8h. For example, T1 can be 60°C, 80°C, 90°C, 100°C, 110°C, 120°C or a range composed of any two of these values; t1 can be 2h, 2.5h, 3h, 3.5h, 4h or a range composed of any two of these values; T2 can be 121°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C or a range composed of any two of these values; t2 can be 2h, 3h, 4h, 5h, 6h, 7h, 8h or a range composed of any two of these values. By dividing the drying treatment into a first drying stage and a second drying stage, the first drying stage mainly removes the free fluorine on the surface of the fluorosilicate slag, and the second stage mainly removes the moisture in the fluorosilicate slag. Through the segmented drying treatment, the free fluorine and moisture in the fluorosilicate slag can be efficiently removed, and the energy consumption can be further reduced and the cost can be reduced.

[0038] In some embodiments of the present application, in step (2), the alkaline solution is selected from at least one of sodium hydroxide solution or potassium hydroxide solution; the concentration of the alkaline solution is 140 g / L to 250 g / L, and the alkaline solution and the crude silica slag are mixed at a liquid-solid ratio of 8 mL / g to 13 mL / g. For example, the concentration of the alkaline solution can be 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L or a range composed of any two of these values; the liquid-solid ratio of the alkaline solution to the crude silica slag can be 8 mL / g, 9 mL / g, 10 mL / g, 11 mL / g, 12 mL / g, 13 mL / g or a range composed of any two of these values. By selecting the alkaline solution within the scope of the present application, it is beneficial to convert silicon dioxide in the crude silica slag into silicate, and leach out the lattice fluorine in the crude silica slag to form free fluorine, and then the leached free fluorine can be removed through subsequent treatment steps, which is beneficial to reducing the fluorine content in the silica white product and improving the purity of the silica white. In the present application, the concentration of the alkaline solution refers to the mass of the solute contained in each liter of the alkaline solution.

[0039] In some embodiments of the present application, in step (2), the alkaline solution is sodium hydroxide solution, the concentration of the sodium hydroxide solution is 180 g / L to 200 g / L, and the sodium hydroxide solution and the crude silica slag are mixed at a liquid-solid ratio of 8 mL / g to 13 mL / g. For example, the concentration of the sodium hydroxide solution can be 180 g / L, 190 g / L, 200 g / L or a range composed of any two of these values; the liquid-solid ratio of the sodium hydroxide solution to the crude silica slag can be 8 mL / g, 9 mL / g, 10 mL / g, 11 mL / g, 12 mL / g, 13 mL / g or a range composed of any two of these values. By controlling the concentration of the sodium hydroxide solution and the liquid-solid ratio of the sodium hydroxide solution to the crude silica slag within the scope of the present application, it is beneficial to convert silicon dioxide in the crude silica slag into sodium silicate, and leach out the lattice fluorine in the crude silica slag to form free fluorine, and then the leached free fluorine can be removed through subsequent treatment steps, which is beneficial to reducing the fluorine content in the silica white product and improving the purity of the silica white.

[0040] In some embodiments of the present application, in step (2), the reaction temperature is 65°C to 105°C, and the reaction time is 0.5h to 4h. For example, the reaction temperature may be 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, or a range consisting of any two of the values; the reaction time may be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, or a range consisting of any two of the values. The reaction of silicon dioxide in the fluorine-containing silicon slag with sodium hydroxide is an endothermic reaction. By regulating the reaction temperature and time within the scope of the present application, it is beneficial to further promote the reaction of silicon dioxide in the fluorine-containing silicon slag with sodium hydroxide, and the silicon in the fluorine-containing silicon slag can be effectively leached and converted into sodium silicate.

[0041] In some embodiments of the present application, in step (2), the reaction is carried out under ultrasonic conditions, and the ultrasonic frequency is 20kHz~40kHz. For example, the ultrasonic frequency can be 20kHz, 25kHz, 30kHz, 35kHz, 40kHz or a range consisting of any two of these values. By applying ultrasonic waves during the reaction of fluorine-containing silicon slag and sodium hydroxide, and regulating the frequency of the ultrasonic waves within the scope of the present application, it is beneficial to destroy the agglomeration structure of the fluorine-containing silicon slag particles, accelerate the penetration of sodium hydroxide solution in the fluorine-containing silicon slag, promote the reaction of silicon dioxide in the fluorine-containing silicon slag with sodium hydroxide, and improve the conversion rate of silicon; at the same time, it promotes the leaching of lattice fluorine and converts it into free fluorine, which is beneficial to improve its defluorination effect.

[0042] In the present application, the colloid obtained in step (3) is washed to remove the sodium benzenesulfonate and fluoride ions contained in the colloid. The present application does not particularly limit the washing conditions, as long as the purpose of the present application can be achieved. In some embodiments of the present application, the colloid and ultrapure water are mixed and stirred in a mass ratio of 1: (2~5), stirred for 30min~100min, and solid-liquid separation is performed. In some embodiments of the present application, ultrasound can be applied during the washing process. In some embodiments of the present application, the number of washings can be 2~6 times.

[0043] In some embodiments of the present application, in step (3), the drying temperature is 100°C to 150°C. For example, the drying temperature may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or a range consisting of any two of these values. By adjusting the drying temperature in step (3) within the range of the present application, it is beneficial to remove moisture from white carbon black.

[0044] Example

[0045] Hereinafter, examples and comparative examples are given to illustrate the embodiments of the present application more specifically. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass. All raw materials in the examples and comparative examples of the present application are commercially available.

[0046] Test methods and equipment:

[0047] Test for the purity of silica white and the mass percentage content of fluorine element

[0048] The silica white prepared in each example and comparative example of the present application was tested by an X-ray fluorescence spectrometer to measure the mass percentage content of silicon dioxide and the mass percentage content of fluorine element in the silica white. The mass percentage content of silicon dioxide in the silica white is the purity of the silica white.

[0049] Test for the recovery rate of silicon

[0050] The crude silicon slag was sampled and tested by an X-ray fluorescence spectrometer to obtain the mass percentage content W1 of silicon element in the crude silicon slag, and the mass of the crude silicon slag was M1. The mass of silicon in the crude silicon slag was calculated as W1×M1. The silica white obtained in each example and comparative example was tested by an X-ray fluorescence spectrometer to obtain the mass percentage content W2 of silicon element in the silica white, and the mass of the silica white was M2. The mass of silicon in the silica white was calculated as W2×M2. Thus, the recovery rate of silicon was calculated as [(W2×M2) / (W1×M1)]×100%.

[0051] Test for the specific surface area of silica white

[0052] Using a specific surface area analyzer, the specific surface area of silica white was measured by the nitrogen adsorption method. Among them, the specific test was carried out according to the national standard GB / T 19587-2017 "Determination of Specific Surface Area of Solid Materials by Gas Adsorption BET Method".

[0053] Example 1

[0054] The fluorine-containing silicon slag used in the present application is a by-product in the process of producing hydrogen fluoride from fluorosilicic acid. The fluorine-containing silicon slag was sampled and subjected to thermogravimetric analysis and X-ray fluorescence spectrometer test. The main component content in the fluorine-containing silicon slag is: H 2 The mass percentage content of O is 60.59%, and the mass percentage content of SiO 2 is 28.48%, and the mass percentage content of F element is 10.61%.

[0055] (1) Take 200 g of fluorine-containing silicon slag and place it in an oven for drying treatment. First, dry it at 80 °C for 2 h, and then raise the temperature to 160 °C and dry it for 7 h to obtain crude silicon slag. In the crude silicon slag, H 2The mass percentage of O is 0.76%, and the water removal rate is 98.74%; the mass percentage of F element in the crude silicon slag is 4.03%, and the defluorination rate is 62.02%.

[0056] (2) Pour the obtained crude silicon slag into a reaction flask made of PFA (soluble polytetrafluoroethylene), and then add a sodium hydroxide solution with a concentration of 190 g / L to the above reaction flask. The liquid-solid ratio of the sodium hydroxide solution to the crude silicon slag is 10 mL / g. Stir and react at 95 °C for 1 h, while applying ultrasonic waves with a frequency of 40 kHz and a stirring rate of 500 rpm. Then, after suction filtration, the first solution is obtained.

[0057] (3) Place the first solution prepared above in a reaction flask made of PFA and heat it to 40 °C in an oil bath. After the temperature in the reaction flask reaches 40 °C, add an aqueous solution of benzenesulfonic acid with a mass fraction of 9.8% dropwise to the first solution. When the solution pH > 7, the dropping rate of the aqueous solution of benzenesulfonic acid is 8 mL / (200 mL·min). Until the solution pH ≤ 7, the dropping rate of the aqueous solution of benzenesulfonic acid is adjusted to 1 mL / (200 mL·min). When the solution pH reaches 2, stop dropping the aqueous solution of benzenesulfonic acid. Then heat it to 80 °C and carry out aging under stirring, with a stirring speed of 300 rpm and an aging time of 2 h. Then, carry out suction filtration to obtain a colloid. Wash the colloid ultrasonically with water 3 times, and then dry it at 120 °C to prepare white carbon black.

[0058] Example 2

[0059] Except that in step (3), stop dropping the aqueous solution of benzenesulfonic acid when the final pH of the solution is adjusted to 1 by adding benzenesulfonic acid, the rest is the same as in Example 1.

[0060] Example 3

[0061] Except that in step (3), stop dropping the aqueous solution of benzenesulfonic acid when the final pH of the solution is adjusted to 3 by adding benzenesulfonic acid, the rest is the same as in Example 1.

[0062] Example 4

[0063] Except that in step (3), stop dropping the aqueous solution of benzenesulfonic acid when the final pH of the solution is adjusted to 5 by adding benzenesulfonic acid, the rest is the same as in Example 1.

[0064] Example 5

[0065] Except that in step (3), when the solution pH ≤ 7, the dropping rate of the aqueous solution of benzenesulfonic acid is adjusted to 2 mL / (200 mL·min), the rest is the same as in Example 1.

[0066] Example 6

[0067] Except that in step (3), when the solution pH ≤ 7, the dropping rate of the aqueous benzenesulfonic acid solution is adjusted to 4 mL / (200 mL·min), the rest is the same as in Example 1.

[0068] Example 7

[0069] Except that in step (3), the oil bath is heated to 30 °C, and after the temperature in the reaction flask reaches 30 °C, 9.8% aqueous benzenesulfonic acid solution is added dropwise, the rest is the same as in Example 1.

[0070] Example 8

[0071] Except that in step (3), the oil bath is heated to 50 °C, and after the temperature in the reaction flask reaches 50 °C, 9.8% aqueous benzenesulfonic acid solution is added dropwise, the rest is the same as in Example 1.

[0072] Example 9

[0073] Except that in step (3), no oil bath heating is carried out, and 9.8% aqueous benzenesulfonic acid solution is added dropwise at 20 °C, the rest is the same as in Example 1.

[0074] Example 10

[0075] Except that in step (3), the aging temperature is adjusted to 110 °C and the aging time is 1 h, the rest is the same as in Example 1.

[0076] Example 11

[0077] Except that in step (3), the aging temperature is adjusted to 70 °C and the aging time is 2 h, the rest is the same as in Example 1.

[0078] Example 12

[0079] Except that in step (2), the reaction process is only stirred at 95 °C for 1 h without applying ultrasonic waves, the rest is the same as in Example 1.

[0080] Example 13

[0081] Except that in step (1), the drying treatment is directly carried out at 60 °C for 9 h without staged drying treatment, the rest is the same as in Example 1. The mass percentage of H 2 O in the obtained crude silicon slag is 47.48%, and the water removal rate is 21.64%; the mass percentage of F element in the crude silicon slag is 6.12%, and the defluorination rate is 42.32%.

[0082] Example 14

[0083] Except that in step (1), the drying treatment is directly carried out at 180 °C for 9 h without staged drying treatment, the rest is the same as in Example 1. The H in the obtained crude silicon slag 2The mass percentage content of O is 0.74%, and the water removal rate is 98.78%; the mass percentage content of F element in the crude silicon slag is 3.99%, and the defluorination rate is 62.39%.

[0084] Example 15

[0085] Except that the concentration of sodium hydroxide in step (2) is adjusted to 140 g / L, the rest is the same as in Example 1.

[0086] Example 16

[0087] Except that the concentration of sodium hydroxide in step (2) is adjusted to 250 g / L, the rest is the same as in Example 1.

[0088] Example 17

[0089] Except that the alkaline solution in step (2) is replaced with a mixed alkaline solution of sodium hydroxide and potassium hydroxide, the concentration of the alkaline solution is 190 g / L, wherein the concentration of sodium hydroxide in the alkaline solution is 80 g / L, and the concentration of potassium hydroxide in the alkaline solution is 110 g / L, the rest is the same as in Example 1.

[0090] Comparative Example 1

[0091] Except that benzenesulfonic acid is replaced with a sulfuric acid solution with a mass fraction of 9.8% in step (3), the rest is the same as in Example 1.

[0092] The purity, mass percentage content of fluorine element, specific surface area and silicon recovery rate of the precipitated silica prepared in each example and comparative example are shown in Table 1.

[0093] Table 1

[0094] It can be seen from Example 1 to Example 17 and Comparative Example 1 that the precipitated silica obtained by the preparation method of the present application has high purity, low fluorine content, high specific surface area, and high silicon recovery rate. In Comparative Example 1, sulfuric acid was used as the acidifying agent instead of benzenesulfonic acid, and the obtained precipitated silica had a lower specific surface area. It shows that benzenesulfonic acid is selected as the acidifying agent in the preparation method of the present application, which not only plays an acidifying role on sodium silicate, but also the generated sodium benzenesulfonate has the function of a surfactant, and the specific surface area of precipitated silica can be effectively increased without adding an additional surfactant.

[0095] In step (3), adding benzenesulfonic acid to adjust the pH value of the solution will affect the specific surface area of silica and the recovery rate of silicon. As can be seen from Examples 1 to 4, when adding benzenesulfonic acid to adjust the pH of the solution within the range of 1 to 3, it is beneficial to further increase the specific surface area of silica and the recovery rate of silicon, and the obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0096] In step (3), when the pH of the solution ≤ 7, the dropping rate of the aqueous benzenesulfonic acid solution will affect the specific surface area of silica. As can be seen from Examples 1, 5 and 6, by controlling the dropping rate of the aqueous benzenesulfonic acid solution within the range of 1 mL / (200 mL·min) to 2 mL / (200 mL·min), it is beneficial to further increase the specific surface area of silica, and the obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0097] In step (3), the temperature when adding the benzenesulfonic acid solution to the first solution will affect the specific surface area of silica. As can be seen from Examples 1, 7 to 9, by controlling the temperature when adding benzenesulfonic acid to the first solution within the range of 30°C to 50°C, it is beneficial to further increase the specific surface area of silica, and the obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0098] In step (3), the aging temperature and aging time will affect the specific surface area of silica. As can be seen from Examples 1, 10 and 11, by controlling the aging temperature within the range of 80°C to 110°C and the aging time within the range of 1 h to 4 h, it is beneficial to further increase the specific surface area of silica, and the obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0099] In step (2), the reaction conditions after adding the alkaline solution will affect the fluorine leaching rate and the recovery rate of silicon. As can be seen from Examples 1 and 12, by applying ultrasonic waves during the reaction process in step (2), this is beneficial to the leaching of fluorine and can increase the recovery rate of silicon. The obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0100] In step (2), the concentration of the alkaline solution will affect the fluorine leaching rate and the recovery rate of silicon. As can be seen from Examples 1, 15 to 17, by controlling the concentration of the alkaline solution within the range of 140 g / L to 250 g / L, it is beneficial to increase the recovery rate of silicon. The obtained silica has a higher purity, lower fluorine content, higher specific surface area, and also a higher recovery rate of silicon.

[0101] In step (1), the drying process will affect the water content and fluorine content in the crude silicon slag. It can be seen from Example 1, Example 13, and Example 14 that by dividing the drying process into two stages, the free fluorine and moisture in the fluorine-containing silicon slag can be efficiently removed, which is also conducive to further reducing energy consumption and cost.

[0102] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing white carbon black from fluorine-containing silicon slag, characterized in that: The following steps are involved: (1) Drying the fluorine-containing silicon slag to obtain crude silicon slag; (2) mixing and reacting the crude silicon slag with an alkaline solution, and performing solid-liquid separation to obtain a first solution; (3) adding benzenesulfonic acid to the first solution to react and obtain a reactant, performing solid-liquid separation on the reactant to obtain a colloid, and washing and drying the colloid to obtain white carbon black.

2. The method according to claim 1, characterized in that In the step (3), benzenesulfonic acid is added to the first solution at a temperature of 30° C. to 50° C. until the pH value of the solution is 1 to 3, and the solution is aged after heating to obtain the colloid.

3. The method according to claim 2, characterized in that The aging temperature is 80° C. to 110° C., and the aging time is 1 h to 4 h.

4. The method according to claim 1, characterized in that: In the step (3), the benzenesulfonic acid is an aqueous solution of benzenesulfonic acid, the mass fraction of the aqueous solution of benzenesulfonic acid is 4.9% to 19.6%, and the aqueous solution of benzenesulfonic acid is added to the first solution by dropwise addition. When the pH value of the solution is ≤7, the dropwise addition rate of the aqueous solution of benzenesulfonic acid is 1mL / (200mL·min) to 2mL / (200mL·min), and the dropwise addition is stopped until the pH value of the solution is 1 to 3.

5. The method according to any one of claims 1 to 4, characterized in that In the step (1), the temperature of the drying treatment is 60° C. to 180° C., and the time of the drying treatment is 4 h to 12 h.

6. The method according to claim 5, characterized in that In the step (1), the drying process is divided into a first drying stage and a second drying stage. The temperature of the first drying stage is T1, 60°C ≤ T1 ≤ 120°C, and the time of the first drying stage is t1, 2h ≤ t1 ≤ 4h; the temperature of the second drying stage is T2, 120°C < T2 ≤ 180°C, and the time of the second drying stage is t2, 2h ≤ t2 ≤ 8h.

7. The method according to any one of claims 1 to 4, characterized in that In the step (2), the alkaline solution is selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution; The concentration of the alkaline solution is 140 g / L to 250 g / L, and the alkaline solution is mixed with the crude silicon slag at a liquid-to-solid ratio of 8 mL / g to 13 mL / g.

8. The method according to any one of claims 1 to 4, characterized in that In the step (2), the alkaline solution is selected from a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 180 g / L to 200 g / L, and the sodium hydroxide solution is mixed with the crude silicon slag at a liquid-to-solid ratio of 8 mL / g to 13 mL / g.

9. The method according to any one of claims 1 to 4, characterized in that In the step (2), the reaction temperature is 65°C to 105°C, and the reaction time is 0.5h to 4h.

10. The method according to any one of claims 1 to 4, characterized in that In the step (2), the reaction is carried out under ultrasonic conditions, and the ultrasonic frequency is 20kHz~40kHz.

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