Process for deep removal of aluminum and / or silicon from high-base, low-aluminum, low-silicon solutions

Abstract

The invention belongs to the technical field of deep purification of solutions, and discloses a deep removal process for aluminum, silicon and aluminum and silicon in a high-alkali, low-aluminum and low-silicon solution. The preparation method comprises the following steps: mixing a magnesium compound or a calcium compound or a magnesium and calcium compound with a part of high-alkali, low-aluminum and low-silicon solutions for size mixing, heating and reacting to obtain an aluminum-removing or silicon-removing or silicon-aluminum-removing additive; the method comprises the following steps: adding an additive for removing aluminum or silicon or removing silicon and aluminum into a high-alkali, low-aluminum and low-silicon solution, heating, and reacting, so as to deeply remove aluminum or silicon or silicon and aluminum in alkali liquor. The process disclosed by the invention is wide in application range, good in removal effect of aluminum or silicon or silicon and aluminum, and capable of realizing cyclic utilization of the alkali liquor.

Description

Technical Field

[0001] The invention belongs to the technical field of deep solution purification, and in particular relates to deep removal of aluminum and / or silicon in high-alkali, low-aluminum, and low-silicon solutions. Background Art

[0002] In the process of coal chemical deashing, direct alkali leaching can significantly remove the ash in the coal and obtain high-purity coal with an ash content of less than 1%. However, the alkali solution after alkali leaching contains aluminum and silicon components. 2 O 3 、SiO 2 The concentration is about 3-10g / L, and the causticity ratio is very high (a k >80~100), if it is directly returned for circulating deashing, it will seriously affect the subsequent alkaline leaching deashing effect. Therefore, before the alkali solution enters the circulating deashing, the silicon and aluminum components in the alkali solution need to be deeply removed. In addition, a large amount of high caustic ratio alkali solution is produced during the fly ash alkali leaching pre-desiliconization and bauxite chemical beneficiation process, in which the concentrations of silicon and aluminum ions are relatively low. The circulation of the alkali solution needs to be deeply purified to remove the silicon and aluminum components.

[0003] A lot of research has been conducted at home and abroad on the desiliconization of strongly alkaline sodium aluminate solutions. The main methods include dilution and thermal insulation desiliconization, sodium silicate slag desiliconization, and lime deep desiliconization. However, the sodium aluminate solutions treated by these desiliconization methods have high alkali and aluminum concentrations. Usually, Na 2 O k 、Al 2 O 3 The concentration is above 100g / L, even more than 200g / L, and the caustic ratio is a k Usually between 1.4 and 1.8, while SiO 2 The concentration is 2~5g / L.

[0004] Dilution and thermal desiliconization refers to adding red mud washing liquid to the sodium aluminate slurry after high temperature dissolution to adjust the Na 2 O k To medium concentration level (<150g / L), due to the SiO 2 The equilibrium concentration decreases, and sodium silicon slag will precipitate out at a certain temperature and stirring for a period of time. Although this method has a low cost, the desiliconization efficiency is low and is limited by the equilibrium concentration of sodium silicon slag. The solution SiO 2 The concentration usually drops to about 0.5~1g / L.

[0005] The principle of adding sodium silicate slag to desiliconize is to avoid the difficulty of forming the nucleus of hydrated sodium aluminosilicate (sodium silicate slag) and increase the crystal surface area, thereby increasing the speed and depth of desiliconization. 2 O•Al 2 O3 • xSiO 2 • nH 2 O) and their stability order in sodium aluminate solution are as follows: amorphous < A-type zeolite < sodalite (embedded chloride) < nosean (embedded sulfate) < cancrinite (embedded carbonate). Regarding the mechanism of action of the seed crystal, it is generally considered to be based on crystallographic principles. At the same time, the seed crystal provides active sites, promoting the precipitation of silicate ions in the supersaturated silica solution, so that the silicon in the solution is transferred from the liquid phase to the solid phase and removed. By using this method, the removal of silicon in sodium aluminate solution under normal pressure can be achieved, and the cost is relatively low.

[0006] Patent CN101397604A discloses a method for purifying lye after leaching bauxite with high-concentration lye for pre-desilication. This method can remove most of the silicon dioxide in the lye by adding sodium silicon slag or red mud waste residue seeds to the lye and stirring and crystallizing for 1 to 20 hours, so that the lye can be recycled. Among them, the weight ratio of the seed crystal to the alkali solution is 1-3:10, and the Al 2 O 3 content in the solution before desilication is 22.6 g / L, and the SiO 2 content is 21.5 g / L, which can be reduced to 7.5 g / L and 6.5 g / L after desilication. This method can recycle the lye for chemical beneficiation and desilication of bauxite, but this method only has a certain removal effect on lye containing high concentrations of silicon and aluminum.

[0007] During the desilication process of adding lime (lime milk) to sodium aluminate solution, calcium hydroaluminate is first formed, and at the same time, the silicate ions in the solid solution are fixed to form hydrogarnet (3CaO•Al 2 O 3 • xSiO 2 •(6 - 2x)H 2 O). Compared with sodium silicon slag, hydrogarnet has a lower equilibrium solubility and better stability in sodium aluminate solution, and can achieve deep desilication of sodium aluminate solution. Under the condition of deep desilication at 85-95 °C, the SiO 2 concentration in sodium aluminate solution can be reduced to less than 0.1 g / L, and the silicon modulus can be increased to more than 1000. The formation of hydrogarnet reduces the silicon concentration in the solution, achieving the purpose of deep desilication of sodium aluminate solution. The speed at which SiO 3 2- enters calcium hydroaluminate and replaces the OH - ions depends on process conditions such as the microstructure of calcium hydroaluminate, the concentration of silicon dioxide in the solution, the desilication temperature, and the lime addition amount. With the increase of the lime addition amount, the silicon modulus of the desilicated semen can reach a very high value (even 10000), and the SiO 2The concentration can even be reduced to below 0.01g / L.

[0008] Patent CN1907857A discloses a method for desiliconizing circulating mother liquor in Bayer process production. The method adds lime milk to the circulating mother liquor (caustic ratio is about 3) for desiliconization, so that the silicon in the solution reacts with the lime milk to form calcium silicon slag precipitation, and then solid-liquid separation is performed. The separated alkali liquor can enter the circulating mother liquor system through evaporation and concentration. The applicable solution SiO 2 The concentration is 0.8~1.6g / L, while Al 2 O 3 The content is about 90g / L, the amount of effective calcium added to the lime milk is 1-20g / L, and the product after desiliconization is hydrated garnet. This method has a good effect on the desiliconization of alkali solution in the alumina process, but because the formation of hydrated garnet has requirements on temperature, time and silicon and aluminum concentration in the solution, it is not suitable for the purification of alkali solution containing low concentrations of silicon and aluminum.

[0009] Patent CN117865195A discloses a method for producing aluminum oxide involving calcification dissolution and causticization circulation of alkali solution, which mainly includes high-pressure alkali leaching, carbonation decomposition of alkali leaching solution and causticization of slaked lime. Aluminum hydroxide and carbonated decomposition solution are obtained by carbonation decomposition of the leached alkali solution. Aluminum hydroxide is roasted to obtain aluminum oxide. Slaked lime is added to the carbonated decomposition solution for causticization. The amount of addition is calculated based on the molar ratio of calcium oxide in slaked lime to carbonate in the carbonated decomposition liquid phase of 1.1:1. After causticization, a recyclable sodium hydroxide solution is obtained. However, the process involves high pressure, carbonation, roasting and other processes, with complicated steps and high energy consumption.

[0010] Xu Yingpeng et al. (Reference: Synergistic desiliconization effect of silicon slag and lime on silicon-containing alkali solution [J]. Journal of Guizhou University (Natural Science Edition), 2020, 37(03): 36-41.) After the silicon slag was roasted at 600°C, 25 g / L was added to the alkali solution for desiliconization. The concentration of the silicon-containing alkali solution was 106 g / L, and the initial SiO 2 The concentration is 8g / L, and the desiliconization rate is 66.67%. When 25g / L of roasted silicon slag and CaO with a calcium-silicon ratio of 1 are mixed and added, the desiliconization rate reaches 93%, and it is found that CaO and silicon slag have a synergistic desiliconization effect during the desiliconization process. The desiliconized alkali liquid can be recycled, but this process only purifies the silicon in the silicon-containing alkali liquid, and there are problems such as large amount of lime added, high energy consumption and low process efficiency.

[0011] Wang Zhongming et al. (Reference: Hydrothermal synthesis of wollastonite from alkali-containing sodium silicate solution [J]. Bulletin of the Silicate Society, 2017, 36(10): 3446-3451) used a hydrothermal synthesis method to prepare wollastonite from silicon-containing high-caustic ratio alkali solution at normal pressure. When the SiO2 content in the silicon-containing alkali solution was controlled, the wollastonite 2Concentration 40g / L, Al 2 O 3 When the concentration is 0.98g / L, under the conditions of calcium-silicon ratio of 1.0, temperature of 98℃ and reaction time of 5h, the silicon precipitation rate is more than 95%, and the roasting product is wollastonite. However, this process still only involves the removal of silicon in the alkali solution, and does not take into account the simultaneous removal of silicon and aluminum, and cannot be used for the purification and regeneration cycle of coal deashing alkali solution.

[0012] In summary, there are many different solution systems in the existing alkali solution purification process. Among them, the purification of sodium aluminate solution in alumina production follows the principle of only desiliconization, which only involves desiliconization with sodium silicon slag and deep desiliconization with calcium silicon slag; and the silicon-containing alkali solution with high alkali concentration can be regenerated and circulated by adding lime, and the silicon in the silicon-containing alkali solution is purified due to the formation of wollastonite, and there are requirements for the concentration of silicon and aluminum in the solution. The alkali solution obtained in the processes of deep purification of alkali leaching deashing in the coal industry to produce ultra-pure carbon materials, pre-desiliconization of fly ash alkali leaching, and chemical beneficiation of bauxite has the characteristics of high alkali, low aluminum, and low silicon solutions, high causticity ratio, different solution systems, and large differences in composition and structure. Affected by the equilibrium concentration of sodium silicon slag and calcium silicon slag in the alkali solution, only part of the SiO in the solution can be removed. 2 , it is not possible to simultaneously purify and remove Al from the solution 2 O 3 Therefore, the secondary alkali solution (containing silicon and aluminum) cannot be regenerated and circulated. Therefore, how to remove low-content silicon and aluminum in high-concentration alkali solution to achieve purification and regeneration of alkali solution is a technical problem that urgently needs to be solved in the field of alkali solution purification technology. Summary of the invention

[0013] In view of the problems existing in the prior art, the first object of the present invention is to provide a process for the deep removal of aluminum in a high-alkali, low-aluminum, low-silicon solution; the second object of the present invention is to provide a process for the deep removal of silicon in a high-alkali, low-aluminum, low-silicon solution; the third object of the present invention is to provide a process for the deep removal of aluminum and silicon in a high-alkali, low-aluminum, low-silicon solution.

[0014] The high alkali, low aluminum, low silicon solution of the present invention refers to Al 2 O 3 The concentration of SiO is 3~10g / L. 2 The concentration of Na is about 3~10g / L 2 O k The concentration of the solution is 100~200g / L.

[0015] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0016] First, the present invention provides a deep removal process of aluminum in a high-alkali, low-aluminum, low-silicon solution, comprising: Step S1, mixing a magnesium compound with a portion of a high-alkali, low-aluminum, low-silicon solution, slurrying, heating, and reacting to obtain an aluminum removal additive; Step S2, adding the aluminum removal additive to the high-alkali, low-aluminum, low-silicon solution, heating and reacting.

[0017] In a further preferred embodiment, the magnesium compound is at least one of magnesium oxide and magnesium hydroxide.

[0018] In a further preferred embodiment, in step S1, the solid-to-liquid ratio of the magnesium compound to the high-alkali, low-aluminum, low-silicon solution is 1 g:1-3 mL.

[0019] In a further preferred embodiment, in step S1, the temperature to which the heating is performed is 20-100°C, and the reaction time is 0.5-3 hours. Further preferably, the temperature to which the heating is performed is 40-80°C, and the reaction time is 1-2 hours.

[0020] In a further preferred embodiment, in step S1, after the reaction is completed, solid-liquid separation is performed.

[0021] In a further preferred embodiment, in step S2, 10 to 20 g, preferably 12 to 18 g, of the aluminum removal additive is added to each liter of high alkali, low aluminum, low silicon solution.

[0022] In a further preferred embodiment, in step S2, the heating temperature is 50-150°C, preferably 70-110°C; the reaction time is 2-5h, preferably 2-4h.

[0023] In a further preferred embodiment, the step of solid-liquid separation of the slurry after the reaction in step S2 is also included. After solid-liquid separation, aluminum removal slag and purified liquid after aluminum removal are obtained. The aluminum removal slag can be used as an aluminum removal additive after acid washing.

[0024] Secondly, the present invention provides a deep removal process of silicon in a high-alkali, low-aluminum, low-silicon solution, comprising: Step S1, mixing a calcium compound with a portion of a high-alkali, low-aluminum, low-silicon solution, slurrying, heating, and reacting to obtain a silicon removal additive; Step S2, adding the silicon removal additive to the high alkali, low aluminum, low silicon solution, heating and reacting.

[0025] In a further preferred embodiment, the calcium compound is at least one of calcium oxide and calcium hydroxide.

[0026] In a further preferred embodiment, in step S1, the solid-to-liquid ratio of the calcium compound to the high-alkali, low-aluminum, low-silicon solution is 1 g:1-3 mL.

[0027] In a further preferred embodiment, in step S1, the temperature to which the heating is performed is 20-100°C, and the reaction time is 0.5-3 hours. Further preferably, the temperature to which the heating is performed is 40-80°C, and the reaction time is 1-2 hours.

[0028] In a further preferred embodiment, in step S1, after the reaction is completed, solid-liquid separation is performed.

[0029] In a further preferred embodiment, in step S2, 5 to 20 g of a silicon removal additive is added to each liter of the high-alkali, low-aluminum, low-silicon solution.

[0030] In a further preferred embodiment, in step S2, the heating temperature is 50-150°C, preferably 70-110°C; the reaction time is 2-5h, preferably 2-4h.

[0031] In a further preferred embodiment, the step of solid-liquid separation of the slurry after the reaction in step S2 is also included. After solid-liquid separation, silicon-removing slag and purified liquid after silicon removal are obtained. The silicon-removing slag can be used as a silicon-removing additive after acid washing.

[0032] Based on the same inventive concept, the present invention provides a process for deep removal of aluminum and silicon in a high-alkali, low-aluminum, low-silicon solution, comprising: Step S1, mixing a calcium compound, a magnesium compound and a part of a high-alkali, low-aluminum, low-silicon solution, slurrying, heating, and reacting to obtain a silicon-aluminum removal additive; Step S2, adding the silicon-aluminum removal additive to the high-alkali, low-aluminum, low-silicon solution, heating and reacting.

[0033] In a further preferred embodiment, the magnesium compound is at least one of magnesium oxide and magnesium hydroxide; the calcium compound is at least one of calcium oxide and calcium hydroxide.

[0034] In a further preferred embodiment, the mass ratio of the calcium compound to the magnesium compound is 1:1 to 1:3.

[0035] In a further preferred embodiment, in step S1, the solid-to-liquid ratio of the calcium compound, the magnesium compound and the high-alkali, low-aluminum, low-silicon solution is 1 g:1-3 mL.

[0036] In a further preferred embodiment, in step S1, the temperature to which the heating is performed is 20-100°C, and the reaction time is 0.5-3 hours. Further preferably, the temperature to which the heating is performed is 40-80°C, and the reaction time is 1-2 hours.

[0037] In a further preferred embodiment, in step S1, after the reaction is completed, solid-liquid separation is performed.

[0038] In a further preferred embodiment, in step S2, 10 to 20 g of the silicon-aluminum removal additive is added to each liter of the high-alkali, low-aluminum, low-silicon solution.

[0039] In a further preferred embodiment, in step S2, the heating temperature is 50-150°C, preferably 70-110°C; the reaction time is 2-5h, preferably 2-4h.

[0040] In a further preferred embodiment, the step of solid-liquid separation of the slurry after the reaction in step S2 is also included. After solid-liquid separation, silicon-aluminum-removed slag and purified liquid after silicon-aluminum-removed are obtained. The silicon-aluminum-removed slag can be used as a silicon-aluminum-removed additive.

[0041] Compared with the prior art, the above one or more technical solutions of the present invention can achieve at least one of the following beneficial effects: The deep purification process of aluminum and / or silicon provided by the present invention has a wide range of applications and can be used for the purification and regeneration of alkali liquor after coal alkali leaching deashing, alkali liquor pre-desiliconization of fly ash, and alkali liquor obtained from chemical beneficiation of low-grade bauxite, etc.

[0042] The present invention can achieve deep removal of aluminum or silicon in a high-alkali, low-aluminum, low-silicon solution, or one-time simultaneous removal of silicon and aluminum components, thereby achieving deep purification of the alkali solution, and the purified alkali solution can be recycled.

[0043] The present invention provides a complete alkali solution regeneration and recycling technology route for preparing high-purity carbon by alkali leaching deashing of coal, pre-desiliconization alkali solution of fly ash and chemical beneficiation of low-grade bauxite, and overcomes the shortcomings of existing alkali solution purification methods, provides a new purification method for low-aluminum, low-silicon, high-causticity ratio alkali solution systems, and realizes a green, economical and sustainable technology route. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The process flow chart of the embodiment of the present invention is adopted. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0047] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0048] The embodiment of the present invention adopts Figure 1 The process flow is shown.

[0049] Example 1 Lye:Al 2 O 3 The concentration is 4.89g / L, SiO 2 The concentration is 5.78g / L, Na 2 O k It is 175g / L.

[0050] (1) Magnesium oxide and alkali solution were mixed at a L / S ratio of 1.5 mL:1.0 g to prepare a slurry, reacted at 40° C. for 2.5 h, and after solid-liquid separation, an aluminum removal additive was obtained.

[0051] (2) Add 14 g of aluminum removal additive to each liter of alkaline solution, heat to 90°C and react for 2 hours. After solid-liquid separation, aluminum removal slag and aluminum removal purified liquid are obtained.

[0052] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.162g / L, SiO 2 The content is 5.47g / L.

[0053] (3) After pickling, the aluminum removal slag is returned to step (2) as an aluminum removal additive.

[0054] (4) The purified liquid after aluminum removal is returned for recycling.

[0055] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that magnesium oxide is directly used as the aluminum removal agent, and the specific steps include: Add 14g of magnesium oxide to each liter of alkaline solution, heat to 90°C and react for 2h. After solid-liquid separation, aluminum-removed slag and aluminum-removed purified liquid are obtained.

[0056] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 2.377g / L, SiO 2 The content is 5.62g / L.

[0057] Example 2 Lye:Al 2 O 3 The concentration is 6.36g / L, SiO 2 The concentration is 7.54g / L, Na 2 O k It is 195g / L.

[0058] (1) Magnesium oxide and alkali solution were mixed at a L / S ratio of 3 mL:1 g to prepare a slurry, reacted at 60° C. for 1 h, and after solid-liquid separation, an aluminum removal additive was obtained.

[0059] (2) Add 10 g of aluminum removal additive to each liter of alkaline solution, heat to 80°C and react for 4 hours. After solid-liquid separation, aluminum removal slag and aluminum removal purified liquid are obtained.

[0060] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.143g / L, SiO 2 The content is 7.39g / L.

[0061] (3) After pickling, the aluminum removal slag is returned to step (2) as an aluminum removal additive.

[0062] (4) The purified liquid after aluminum removal is returned for use in the circulation experiment.

[0063] Example 3 Lye:Al 2 O 3 The concentration is 3.78g / L, SiO 2 The concentration is 4.66g / L, Na 2 O k It is 130g / L.

[0064] (1) Magnesium hydroxide and alkali solution were mixed at a L / S ratio of 2.5 mL:1 g, reacted at 60° C. for 2 h, and solid-liquid separation was performed to obtain an aluminum removal additive.

[0065] (2) Add 16 g of aluminum removal additive to each liter of alkaline solution, heat to 75°C and react for 3 hours. After solid-liquid separation, aluminum removal slag and aluminum removal purified liquid are obtained.

[0066] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.192g / L, SiO 2 The content is 4.39g / L.

[0067] (3) After pickling, the aluminum removal slag is returned to step (2) as an aluminum removal additive.

[0068] (4) The purified liquid after aluminum removal is returned for recycling.

[0069] Example 4 Lye:Al 2 O 3 The concentration is 4.89g / L, SiO 2 The concentration is 5.78g / L, Na 2 O kIt is 175g / L.

[0070] (1) Calcium oxide and alkali solution were mixed at a L / S ratio of 2.5 mL:1.0 g to prepare a slurry, reacted at 60° C. for 1 h, and solid-liquid separation was performed to obtain a silicon removal additive.

[0071] (2) Add 9 g of desiliconizing additive to each liter of alkaline solution, heat to 85°C and react for 4 hours. After solid-liquid separation, desiliconizing slag and desiliconized purified liquid are obtained.

[0072] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 4.71g / L, SiO 2 The content is 0.124g / L.

[0073] (3) After pickling, the desiliconizing slag is returned to step (2) as a desiliconizing additive.

[0074] (4) The purified liquid after silicon removal is returned for recycling.

[0075] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that calcium oxide is directly used as a silicon removal agent, and the specific steps include: (1) Add 9 g of calcium oxide to each liter of alkaline solution, heat to 85°C and react for 4 hours. After solid-liquid separation, desiliconized slag and desiliconized purified liquid are obtained.

[0076] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 4.77g / L, SiO 2 The content is 2.326g / L.

[0077] Example 5 Lye:Al 2 O 3 The concentration is 6.36g / L, SiO 2 The concentration is 7.54g / L, Na 2 O k It is 195g / L.

[0078] (1) Calcium oxide and alkali solution were mixed at a L / S ratio of 1.5 mL:1 g to prepare a slurry, reacted at 40° C. for 3 h, and solid-liquid separation was performed to obtain a silicon removal additive.

[0079] (2) Add 15 g of desiliconizing additive to each liter of alkaline solution, heat to 140°C and react for 1 hour. After solid-liquid separation, desiliconizing slag and desiliconizing purified liquid are obtained.

[0080] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O3 The content is 6.14g / L, SiO 2 The content is 0.117g / L.

[0081] (3) After pickling, the desiliconizing slag is returned to step (2) as a desiliconizing additive.

[0082] (4) The purified liquid after silicon removal is returned for use in the circulation experiment.

[0083] Example 6 Lye:Al 2 O 3 The concentration is 3.78g / L, SiO 2 The concentration is 4.66g / L, Na 2 O k It is 130g / L.

[0084] (1) Calcium hydroxide and alkali solution were mixed at a L / S ratio of 2 mL:1 g to prepare a slurry, reacted at 50° C. for 2 h, and solid-liquid separation was performed to obtain a silicon removal additive.

[0085] (2) Add 12 g of desiliconizing additive to each liter of alkaline solution, heat to 95°C and react for 2 hours. After solid-liquid separation, desiliconizing slag and desiliconizing purified liquid are obtained.

[0086] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 3.59g / L, SiO 2 The content is 0.141g / L.

[0087] (3) After pickling, the desiliconizing slag is returned to step (2) as a desiliconizing additive.

[0088] (4) The purified liquid after silicon removal is returned for use in the circulation experiment.

[0089] Example 7 Lye:Al 2 O 3 The concentration is 8.27g / L, SiO 2 The concentration is 9.69g / L, Na 2 O k It is 150g / L.

[0090] (1) Magnesium oxide and calcium hydroxide were mixed in a mass ratio of 1:1, and then mixed with alkaline solution in a L / S ratio of 2.5 mL:1.0 g to prepare a slurry, reacted at 70° C. for 1.5 h, and after solid-liquid separation, a silicon-aluminum removal additive was obtained.

[0091] (2) Add 12 g of silicon-aluminum removal additive to each liter of alkaline solution, heat to 90°C and react for 2.5 hours. After solid-liquid separation, silicon-aluminum removal slag and silicon-aluminum removal purified liquid are obtained.

[0092] The content of aluminum and silicon in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.052g / L, SiO 2 The content is 0.084g / L.

[0093] (3) The desiliconized aluminum slag is returned to step (2) after pickling as a desiliconizing additive.

[0094] (4) The purified liquid after silicon and aluminum removal is returned for recycling.

[0095] Comparative Example 3 The difference between Comparative Example 3 and Example 7 is that magnesium oxide and calcium hydroxide are directly used as silicon-aluminum removal agents, and the specific steps include: (1) Add 6 g of magnesium oxide and 6 g of calcium hydroxide to each liter of alkaline solution, heat to 90°C and react for 2.5 hours. After solid-liquid separation, silicon-aluminum-removed slag and purified liquid after silicon-aluminum removal are obtained.

[0096] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 4.669g / L, SiO 2 The content is 3.438g / L.

[0097] Example 8 Lye:Al 2 O 3 The concentration is 3.98g / L, SiO 2 The concentration is 4.77g / L, Na 2 O k It is 115g / L.

[0098] (1) Magnesium oxide and calcium hydroxide were mixed in a mass ratio of 1:2, and then mixed with alkaline solution in a L / S ratio of 1.5 mL:1.0 g to prepare a slurry, reacted at 40° C. for 2 h, and after solid-liquid separation, a silicon-aluminum removal additive was obtained.

[0099] (2) Add 18 g of silicon-aluminum removal additive to each liter of alkaline solution, heat to 110°C and react for 2 hours. After solid-liquid separation, silicon-aluminum removal slag and silicon-aluminum removal purified liquid are obtained.

[0100] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.098g / L, SiO 2 The content is 0.042g / L.

[0101] (3) The desiliconized aluminum slag is returned to step (2) after pickling as a desiliconizing additive.

[0102] (4) The purified liquid after the removal of silicon and aluminum is returned for use in the circulation experiment.

[0103] Example 9 Lye:Al 2 O 3 The concentration is 6.65g / L, SiO 2 The concentration is 7.79g / L, Na 2 O k It is 135g / L.

[0104] (1) Magnesium oxide and calcium hydroxide are mixed in a mass ratio of 1:1.5, and then mixed with alkaline solution in a L / S ratio of 2 mL:1 g to prepare a slurry, reacted at 50° C. for 1 h, and after solid-liquid separation, a silicon-aluminum removal additive is obtained.

[0105] (2) Add 14 g of silicon-aluminum removal additive to each liter of alkaline solution, heat to 100°C and react for 3 hours. After solid-liquid separation, silicon-aluminum removal slag and silicon-aluminum removal purified liquid are obtained.

[0106] The content of silicon and aluminum in the purification liquid was tested, and the results were: Al 2 O 3 The content is 0.037g / L, SiO 2 The content is 0.016g / L.

[0107] (3) After pickling, the desiliconized aluminum slag is returned to step (2) as a desiliconized aluminum additive.

[0108] (4) The purified liquid after silicon and aluminum removal is returned for recycling.

[0109] By comparing the contents of aluminum component, silicon component, and silicon-aluminum component in the purified solution in Example 1 and Comparative Example 1, Example 4 and Comparative Example 2, and Example 7 and Comparative Example 3, it can be known that: the aluminum removal additive obtained after the magnesium compound is pretreated with alkali solution has a better aluminum removal effect than the magnesium compound; the silicon removal additive obtained after the calcium compound is pretreated with alkali solution has a better silicon removal effect than the calcium compound; the magnesium compound and the calcium compound can better remove aluminum and silicon in the alkali solution in depth and synchronously after being pretreated with alkali solution. This is because: the aluminum removal additive, silicon removal additive, and silicon-aluminum removal additive are prepared by pre-synthesizing the magnesium compound and the calcium compound with high alkali, low aluminum, and low silicon alkali solution. The synthesized additive has an unstable structure under the conditions of aluminum removal, silicon removal, and aluminum-silicon removal, and the internal structure will be reorganized. The reorganization process can form more sites for adsorbing aluminum and silicon in the alkali solution, which is better than directly adding magnesium and calcium compounds, thereby deeply removing aluminum and silicon in the solution.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for deep removal of aluminum from a high-alkali, low-aluminum, low-silicon solution, characterized in that: include: Step S1, mixing a magnesium compound with a portion of a high-alkali, low-aluminum, low-silicon solution, slurrying, heating, and reacting to obtain an aluminum removal additive; Step S2, adding the aluminum removal additive to the high-alkali, low-aluminum, low-silicon solution, heating and reacting.

2. A process for deep removal of silicon from a high-alkali, low-aluminum, low-silicon solution, characterized in that: include: Step S1, mixing a calcium compound with a portion of a high-alkali, low-aluminum, low-silicon solution, heating, and reacting to obtain a silicon removal additive; Step S2, adding the silicon removal additive to the high alkali, low aluminum, low silicon solution, heating and reacting.

3. A process for deep removal of aluminum and silicon in a high-alkali, low-aluminum, low-silicon solution, characterized in that: include: Step S1, mixing a calcium compound, a magnesium compound and a part of a high-alkali, low-aluminum, low-silicon solution, slurrying, heating, and reacting to obtain a silicon-aluminum removal additive; Step S2, adding the silicon-aluminum removal additive to the high-alkali, low-aluminum, low-silicon solution, heating and reacting.

4. The deep removal process according to claim 1, characterized in that: The magnesium compound is at least one of magnesium oxide and magnesium hydroxide; the solid-liquid ratio of the magnesium compound to the high-alkali, low-aluminum, low-silicon solution is 1g:1~3mL.

5. The deep removal process according to claim 1 or 4, characterized in that: Add 10-20 g of the aluminum removal additive to each liter of high alkali, low aluminum, and low silicon solution.

6. The deep removal process according to claim 2, characterized in that: The calcium compound is at least one of calcium oxide and calcium hydroxide; the solid-liquid ratio of the calcium compound to the high-alkali, low-aluminum, low-silicon solution is 1g:1~3mL.

7. The deep removal process according to claim 2 or 6, characterized in that: 5-20 g of the silicon removal additive is added to each liter of high alkali, low aluminum, low silicon solution.

8. The deep removal process according to claim 3, characterized in that: The mass ratio of the calcium compound and the magnesium compound is 1:1-1:3; in step S1, the solid-liquid ratio of the calcium compound, the magnesium compound and the high-alkali, low-aluminum, low-silicon solution is 1g:1-3mL.

9. The deep removal process according to claim 3 or 8, characterized in that: In step S2, 10-20 g of the silicon-aluminum removal additive is added to each liter of high-alkali, low-aluminum, low-silicon solution.

10. The deep removal process according to any one of claims 1 to 3, characterized in that: In step S1, the heating temperature is 20-100°C; in step S2, the heating temperature is 50-150°C.

11. The deep removal process according to any one of claims 1 to 3, characterized in that: In step S1, after the reaction is completed, solid-liquid separation is performed.

12. The deep removal process according to any one of claims 1 to 3, characterized in that: The method also includes the step of solid-liquid separation of the slurry after the reaction in step S2; after the solid-liquid separation, the obtained slag phase is acid-washed and used for impurity removal of high-alkali, low-aluminum, and low-silicon solution.

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