Method for removing silicon and arsenic from a metal mixture and use thereof

Abstract

The application provides a method for removing silicon and arsenic from a metal mixture and application thereof, and comprises the following steps: (1) mixing the metal mixture with lye to obtain an alkali leaching solution; (2) adding an aluminum source into the alkali leaching solution to obtain a mixed solution; (3) adding a magnesium source and a calcium source into the mixed solution in sequence for reaction, and then the reaction system is subjected to separation treatment, so that the metal mixture is removed of silicon and arsenic. The calcium aluminate method is combined with magnesium salt, and the adding sequence of the raw materials is controlled, so that the metal mixture is deeply removed of silicon and arsenic.

Description

Technical Field

[0001] This invention relates to the field of metal resource recycling technology, specifically to a method for removing silicon and arsenic from metal mixtures and its application. Background Technology

[0002] In fields such as hydrometallurgy and secondary resource recycling, it is often necessary to sort mixtures containing multiple metals to selectively extract valuable metals such as vanadium, tungsten, molybdenum, and chromium. However, these metal mixtures usually contain impurity elements such as silicon and arsenic, which enter the solution along with the valuable metals during the sorting process, forming silicates and arsenates. This not only seriously interferes with subsequent metal separation and purification processes but also increases the difficulty and cost of wastewater treatment.

[0003] To address the aforementioned problems, several solutions have been proposed in existing technologies. For example, the direct calcium addition method involves adding calcium hydroxide or calcium oxide to a metal mixture solution, utilizing the calcium ions to form insoluble calcium salt precipitates with silicate and arsenate ions, thus removing the silicon. However, this method has low silicon removal efficiency, with the silicon content in the residual liquid often exceeding 0.5 g / L, far from meeting the stringent requirements of subsequent processes. Simultaneously, calcium ions readily react with valuable metal ions such as tungstate and vanadate in the solution to form corresponding calcium salts, resulting in a valuable metal loss rate exceeding 5%. Furthermore, the arsenic removal effect is also unsatisfactory, often requiring an additional arsenic removal step. Another method uses magnesium sulfate for silicon removal, adding magnesium sulfate and adjusting the pH to around 11 to precipitate silicon as magnesium silicate. While this method has some silicon removal effect, it requires adjusting the original high-alkalinity system of the leaching solution down and then back up, increasing acid and alkali consumption and operating costs. More importantly, the introduced large amount of sulfate ions severely interferes with subsequent extraction or ion exchange separation processes, and the valuable metal loss rate still exceeds 3%. Another method employs activated aluminate adsorption, using insoluble activated aluminates as adsorbents to remove silicon and arsenic. While this method can simultaneously adsorb some silicon and arsenic, the adsorbent requires complex processes such as synthesis, granulation, drying, and calcination, resulting in high costs, difficult regeneration, and limited processing efficiency, making it unsuitable for large-scale industrial applications. Furthermore, some researchers have proposed a calcium precipitation-acid dissolution-iron salt arsenic removal method, which involves first adding calcium salts to precipitate vanadium and arsenic simultaneously, then acid dissolving the precipitate before adding iron salts to remove arsenic. This process is lengthy, involving multiple solid-liquid separation operations, which not only causes significant losses of valuable metals during multiple transfers but also generates large amounts of acidic wastewater, increasing the environmental burden.

[0004] In summary, current technologies lack a comprehensive solution that can efficiently remove silicon and arsenic from metal mixtures while maintaining low valuable metal loss rates, being easy to operate, and not introducing new interfering impurities. Therefore, it is necessary to develop a new method for removing silicon and arsenic from metal mixtures to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] To address the problems of poor silicon and arsenic removal efficiency, significant loss of valuable metals, and complex processes in existing technologies, this invention provides a method for removing silicon and arsenic from metal mixtures and its application.

[0006] According to a first aspect of the present invention, a method for removing silicon and arsenic from a metal mixture is provided, comprising the following steps: (1) A metal mixture is mixed with an alkaline solution to obtain an alkaline leaching solution, wherein the pH of the alkaline solution is ≥13 at 23℃~28℃; (2) Add an aluminum source to the alkaline leaching solution to obtain a mixed solution; (3) A magnesium source and a calcium source are added sequentially to the mixed solution to carry out the reaction. After the reaction system is separated, the metal mixture is desiliconized and dearsenicized. In steps (2) and (3), the reaction temperature of the reaction system is 90℃~95℃.

[0007] This invention employs a calcium aluminate method combined with magnesium salts, and controls the order of addition of each raw material to achieve deep silicon and arsenic removal from metal mixtures. Specifically, the inventors discovered that adding the magnesium source too early produces suspended particles (the binding constant between magnesium salts and arsenate ions is extremely low), which affects the dissolution process of the aluminum source. Adding the aluminum source first allows it to exist stably in the alkaline leaching solution, reserving aluminum elements for subsequent reactions. Adding the magnesium source after the aluminum source results in the formation of magnesium arsenate precipitates in the solution through the arsenic removal reaction. Because the arsenic content is generally low, the generated magnesium arsenate precipitates do not interfere with the subsequent reaction of adding the calcium source to precipitate silicon. On the contrary, the magnesium arsenate precipitate formed first by adding the magnesium source can pre-form precipitate nuclei for the subsequent reaction of adding the calcium source to precipitate silicon, thereby promoting the adsorption of silicon and the formation of hydrated calcium aluminosilicate precipitates. Therefore, the silicon and arsenic removal method provided by this invention helps to promote the binding reaction, accelerate precipitate formation, and achieve deep purification of silicon and arsenic.

[0008] Preferably, the metal mixture comprises a metal component and an impurity component; wherein the metal component includes elemental metals or metal compounds soluble in an alkaline solution; and the impurity component includes silicon or its compounds, and arsenic or its compounds. Silicon and arsenic in the metal mixture often interfere with the extraction of metal elements in subsequent separation steps, not only making it difficult to achieve the required purity of the final product but also easily causing problems such as equipment scaling and clogging. The silicon and arsenic removal method provided by this invention can efficiently remove these two impurity elements, thereby creating favorable conditions for the subsequent recovery of valuable metals.

[0009] On the other hand, metal mixtures may also include some elemental metals or metal compounds that are insoluble in alkaline solutions. By mixing the metal mixture with an alkaline solution and then subjecting it to conventional filtration, effective separation can be achieved between the elemental metals or metal compounds insoluble in the alkaline solution and the dissolved components (elemental metals or metal compounds soluble in the alkaline solution). Subsequent separation and purification steps can further recover and reuse the obtained elemental metals or metal compounds insoluble in the alkaline solution, which is beneficial to improving the overall resource utilization rate.

[0010] Preferably, the metal mixture includes one or more metallic elements selected from zinc, tin, lead, titanium, vanadium, tungsten, molybdenum, chromium, and manganese.

[0011] Preferably, the metal compound includes metal oxides and / or metal hydroxides.

[0012] Preferably, the alkaline leaching solution contains ≥4.5 g / L silicon and ≥0.3 g / L arsenic. Under these concentration conditions, the subsequent addition of aluminum, magnesium, and calcium sources enhances the interaction between the reactants and silicon and arsenic, promoting the formation of stable precipitates with good settling properties, thus achieving efficient impurity removal during solid-liquid separation. Furthermore, under these impurity concentration conditions, the target metal component exhibits a higher separation coefficient from impurity elements in the strongly alkaline system, resulting in a higher input-output ratio and improving the overall economic efficiency and resource utilization of the process.

[0013] Preferably, the molar ratio of aluminum in the aluminum source to silicon in the alkaline leaching solution is 1.0 to 1.1; and / or, the molar ratio of magnesium in the magnesium source to arsenic in the alkaline leaching solution is 3 to 5; and / or, the molar ratio of calcium in the calcium source to silicon in the alkaline leaching solution is 1.3 to 1.5.

[0014] By rationally controlling the ratio of aluminum, magnesium, or calcium in the reaction environment, suitable reaction kinetics are provided for the formation of silicon and arsenic-containing precipitates, enabling efficient adsorption and precipitation of silicon and arsenic. Controlling the aluminum-silicon molar ratio within a narrow range of 1.0 to 1.1 ensures sufficient reaction between aluminum ions and silicate ions to form aluminosilicate precipitates while avoiding excessive aluminum introducing new impurities or increasing alkali consumption. Controlling the magnesium-arsenic molar ratio between 3 and 5 allows magnesium salts to overcome the reaction energy barrier, promoting the formation of stable magnesium arsenates such as Mg3(AsO4)2 precipitates. Excess magnesium ions also help to encapsulate residual arsenic, further improving the arsenic removal rate. Controlling the calcium-silicon molar ratio between 1.3 and 1.5 utilizes the affinity between calcium salts and silicate ions to combine with aluminate ions to form calcium aluminosilicate precipitates. A slight excess of calcium can also synergistically precipitate some arsenic and act as a filter aid, improving the filtration performance of the residue.

[0015] Preferably, the aluminum source is at least one of aluminum oxide, aluminum hydroxide, or sodium aluminate; and / or, the magnesium source is magnesium oxide or magnesium hydroxide; and / or, the calcium source is calcium hydroxide.

[0016] When aluminum hydroxide is used as the aluminum source, it reacts with a base, causing aluminum to dissolve in the solution and providing aluminum for the subsequent silicon removal reaction. The dissolution reaction equation is: Al(OH)3 + NaOH = NaAlO2 + 2H2O.

[0017] When the magnesium source is magnesium oxide, magnesium oxide first hydrolyzes to form magnesium hydroxide (MgO + H2O → Mg(OH)2), and then reacts with arsenate to form insoluble magnesium arsenate precipitate (3Mg(OH)2 + 2Na3AsO4 → Mg3(AsO4)2↓ + 6NaOH); in addition, silicon in the solution will also occupy a small portion of magnesium to form magnesium silicate precipitate. Both of these will promote the subsequent large-scale reaction of hydrated calcium aluminosilicate.

[0018] When calcium hydroxide is used as the calcium source, the desiliconization reaction can generate a stable hydrated calcium aluminosilicate (hydrated garnet) precipitate, and simultaneously regenerate NaOH, which can be recycled for use in the preceding alkaline leaching process, reducing alkali consumption; there is no additional acid-base neutralization step, avoiding sodium salt accumulation and reducing wastewater discharge. The chemical reaction equation is as follows: 3Ca(OH)2+2NaAlO2+3Na2SiO3+4H2O=3CaO·Al2O3·3SiO2·6H2O↓+8NaOH.

[0019] Preferably, the activity of the magnesium oxide is ≥65%.

[0020] Magnesium oxide (MgO) activity specifically refers to the effective MgO content that can rapidly hydrate in aqueous solution to form magnesium hydroxide, and is directly related to crystal defect density, specific surface area, and lattice integrity. Highly active MgO has a loose lattice, numerous unsaturated surface bonds, a large specific surface area (≥100 m² / g), and a fast hydration rate; low-active MgO has a dense lattice, high crystallinity, strong surface inertness, and a slow hydration rate, or even is difficult to react. This invention uses the citric acid neutralization method (YB / T4019-2015) to determine the activity of MgO: at 30℃, the shorter the reaction time of 10% citric acid with MgO to pH=3.0, the higher the activity. Among these, MgO activity ≥65% corresponds to a citric acid reaction time ≤40s, which belongs to the high activity level in industrial applications.

[0021] This invention discovers that the surface lattice of highly active MgO is easily converted by OH groups. - The attack rapidly forms a highly adsorbent magnesium hydroxide colloid, whose surface positive charge interacts with AsO4. 3- A stable magnesium arsenate precipitate is formed. When the MgO activity is ≥65%, the resulting colloidal Mg(OH)₂ has a large specific surface area and many surface active sites, which is beneficial for AsO₄⁻.3- The adsorption and precipitation efficiency of MgO is 3 to 5 times that of crystalline MgO, resulting in a more complete and faster precipitation of arsenic. This facilitates the subsequent adsorption and precipitation of silicon, improving the overall rate and effectiveness of silicon and arsenic removal. Furthermore, highly active MgO, due to its rapid and complete hydrolysis, quickly forms a solution environment with a Mg / As molar ratio ≥3, which is conducive to building stable precipitation and preventing metastable precipitates from dissolving in subsequent processes. Simultaneously, the formation of magnesium arsenate precipitate also regenerates NaOH, maintaining system alkalinity and preventing the formation of calcium tungstate and calcium vanadate precipitates, thus preventing the loss of valuable metals. Low-activity MgO, on the other hand, undergoes incomplete hydrolysis, easily causing the system pH to drop below 13, requiring alkali replenishment, increasing costs, and compromising process stability. Moreover, MgO with an activity ≥65% exhibits good dispersibility, preventing agglomeration and blockage in feeders and pipelines, resulting in better equipment adaptability.

[0022] Preferably, the calcium source added to the reaction system is a calcium hydroxide emulsion with a mass fraction of 15-25%.

[0023] By controlling the concentration of the calcium source added to the reaction system, localized Ca2+ can be avoided. 2+ Excessive concentration can lead to the formation of precipitates such as calcium tungstate and calcium vanadate, resulting in the loss of valuable metals. Therefore, it is essential to ensure a low loss rate of valuable metals.

[0024] Preferably, the calcium hydroxide emulsion is added to the reaction system continuously and slowly using a metering pump, while simultaneously stirring uniformly. This continuous, slow addition combined with uniform stirring helps maintain a localized Ca2+ concentration of the calcium source in the reaction system. 2+ concentration.

[0025] Preferably, in step (3) above, the reaction temperature of the reaction system is 90℃~95℃, pH≥13, and the stirring speed is 80~150 rpm.

[0026] The preferred reaction environment system in this invention provides environmental support for the precipitation process during silicon and arsenic removal. In a highly alkaline environment with pH ≥ 13, the aluminum source can fully dissolve, providing an aluminum source for the subsequent combination reaction of aluminum, silicon, and calcium. At 90℃~95℃, the magnesium source arsenic removal reaction and the calcium source silicon removal reaction proceed in the direction of precipitation formation. The stirring speed is controlled at 80~150 rpm. This ensures uniform reaction of all materials without affecting the normal crystallization and precipitation of the reactants.

[0027] Preferably, the reaction system in step (3) above needs to undergo heat preservation and aging treatment before separation treatment. The heat preservation and aging treatment is to keep it at 85℃~90℃ for more than 120 minutes.

[0028] By maintaining a constant temperature and allowing the solution to settle, the initial fine crystals crystallize into larger and more complete crystal particles. High temperatures reduce solution viscosity and enhance ion diffusion and mass transfer, allowing unreacted silicate and arsenate ions to continue migrating and depositing on the crystal nucleus surface, thus further reducing the residual concentrations of silicon and arsenic to even lower levels. This settling process requires the reaction system to be naturally maintained at a constant temperature without mechanical stirring. Continuous stirring will cause shear forces to break up the growing soft aggregates or initial crystals, generating numerous small secondary crystal nuclei, which in turn leads to finer precipitate particles and an increased specific surface area, making it extremely easy for the precipitate to penetrate or clog the filter cloth during subsequent filtration. In a settled environment, particles settle naturally under gravity and slowly collide, adhere, and bridge with Brownian motion, forming dense flocs or large crystal particles, significantly improving the settling speed and filtration efficiency of the slag.

[0029] Preferably, the processing temperature of the above separation process is ≥80℃.

[0030] The separation process is controlled by pressure filtration at ≥80℃. The purpose is to rely on the fact that the solubility of silicon and arsenic-containing precipitates is low at this temperature, but the solubility of valuable metals is high, so as to separate silicon and arsenic to the greatest extent while retaining valuable metals.

[0031] According to a second aspect of the present invention, a method for removing silicon and arsenic from metal mixtures is provided for use in metal recycling.

[0032] Preferably, the application of the above method includes the metal recovery treatment of spent SCR catalysts.

[0033] Specifically, the method for removing silicon and arsenic from the aforementioned metal mixture can be applied to the metal recovery treatment of spent SCR catalysts. SCR (Selective Catalytic Reduction) denitrification catalysts are widely used in flue gas purification in industries such as power, steel, and cement. Their main active components are TiO2, V2O5, WO3, MoO3, etc., and they contain impurities such as silicon, arsenic, calcium, and magnesium. The presence of silicon and arsenic severely affects the subsequent separation and extraction of valuable metals, leading not only to substandard product purity but also to problems such as equipment scaling and clogging. The silicon and arsenic removal method provided by this invention can effectively remove these impurities from spent SCR catalysts.

[0034] Compared with the prior art, the beneficial effects of the present invention are: In the process of removing silicon and arsenic from metal mixtures, this invention employs a calcium aluminate method combined with magnesium salts. By optimizing the order of raw material addition, deep removal of silicon and arsenic from the metal mixture is achieved. Research has found that if the magnesium source is added too early, the extremely low binding constant between magnesium salts and arsenate ions easily leads to the formation of suspended particles, interfering with the dissolution process of the aluminum source. Therefore, the aluminum source is added first, ensuring its stable presence in the alkaline leaching solution and reserving active aluminum for subsequent reactions. Subsequently, the magnesium source is added, at which point magnesium arsenate precipitates are formed in the solution. These precipitates not only do not interfere with the subsequent calcium source silicon removal reaction but also act as nuclei, promoting the adsorption and formation of hydrated calcium aluminosilicate during calcium source precipitation and accelerating sedimentation. The stepwise dosing strategy provided by this invention effectively enhances precipitation kinetics, significantly improves the purification efficiency and depth of silicon and arsenic, and has the outstanding advantages of simple operation and synergistic effect. Detailed Implementation

[0035] The technical features of the technical solution provided by the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1 This embodiment describes the removal of silicon and arsenic from a metal mixture using the following method, comprising the following steps: (1) Take the SCR spent catalyst as the metal mixture to be separated, mix the metal mixture with sodium hydroxide alkaline solution (pH value of 13.5 at 25℃) and filter to obtain alkaline leaching solution; the filter residue containing metallic titanium is then sent to other separation processes. The alkaline leaching solution was tested and the specific components are as follows: calcium 0.2740 g / L, magnesium 0.1200 g / L, sodium 90.7000 g / L, potassium 0.2320 g / L, silicon 18 g / L, vanadium 2.0 g / L, arsenic 0.4 g / L, tungsten 30 g / L, molybdenum 1.5 g / L, titanium 0.1030 g / L, aluminum 0.2730 g / L, sulfate 30 g / L.

[0037] (2) Take 1L of alkaline leaching solution and pump it into the reactor. Heat it to 95℃, add 53g of 98% pure aluminum hydroxide, and stir for 45 minutes until completely dissolved to obtain a mixed solution.

[0038] (3) Maintain the temperature of the reaction system in the reactor at 95°C. First, add 1g of 90% pure lightly calcined magnesium oxide (the activity of magnesium oxide was determined to be 75%) to the reactor and stir for 5 minutes. Then, continuously add 69.2g of 95% pure calcium hydroxide (prepared as a 20% mass fraction lime slurry) to the reactor through a metering pump for 90 minutes. After the calcium and magnesium are added, keep the reactor at a constant temperature and stir for 120 minutes at a stirring speed of 120 rpm. After the reaction is completed, transfer the liquid in the reactor to a heat-insulating aging tank and keep it at 90°C for 120 minutes. Finally, filter the material in the aging tank at 80°C to obtain a filter cake containing silicon and arsenic elements and a purified liquid. Wash the filter cake twice with 80°C hot water, each time with a liquid-to-solid ratio of 3:1. The washing liquid is returned to the previous SCR waste catalyst alkaline leaching process; the purified liquid can be used for subsequent valuable metal recovery processes.

[0039] Example 2 This embodiment provides a method for removing silicon and arsenic from a metal mixture. Compared with embodiment 1, the difference in composition is that the magnesium source used in step (3) is magnesium hydroxide, and the amount added is 1.45g.

[0040] Apart from the differences mentioned above, the other materials, formulation ratios, and operating procedures used in this embodiment are consistent with those in Embodiment 1.

[0041] Example 3 This embodiment provides a method for removing silicon and arsenic from a metal mixture. Compared with Embodiment 1, the difference in composition is that the magnesium oxide used in step (3) has an activity of 55%.

[0042] Apart from the differences mentioned above, the materials, formula ratios, and operating steps used in this embodiment are consistent with those in Embodiment 1.

[0043] Example 4 This embodiment provides a method for removing silicon and arsenic from a metal mixture. Compared with Embodiment 1, the difference in composition is that the amount of lightly calcined magnesium oxide added in this embodiment is 0.6g.

[0044] Apart from the differences mentioned above, the materials, formula ratios, and operating steps used in this embodiment are consistent with those in Embodiment 1.

[0045] Example 5 This comparative example provides a method for removing silicon and arsenic from a metal mixture. The difference between this method and Example 1 is that the reaction solution is not transferred to a heat-preserving aging tank after the reaction is completed; instead, a pressure filtration process is performed directly.

[0046] Apart from the differences mentioned above, the materials, formula ratios, and operating steps used in this embodiment are consistent with those in Embodiment 1.

[0047] Comparative Example 1 This comparative example provides a method for removing silicon and arsenic from a metal mixture. Compared with Example 1, the difference in composition is that a magnesium source is first added to the reaction vessel containing an alkaline leaching solution, and then an aluminum source is added. The amounts of magnesium and aluminum sources added are the same as in Example 1.

[0048] Apart from the differences mentioned above, the materials, formulation ratios, and operating procedures used in this comparative example are consistent with those in Example 1.

[0049] Comparative Example 2 This comparative example provides a method for removing silicon from a metal mixture. The difference between this method and Example 1 is that magnesium oxide was not added in this comparative example.

[0050] Apart from the differences mentioned above, the materials, formulation ratios, and operating procedures used in this comparative example are consistent with those in Example 1.

[0051] Comparative Example 3 This comparative example provides a method for removing silicon and arsenic from a metal mixture. The difference between this method and Example 1 is that only magnesium oxide is added to the metal mixture in this comparative example.

[0052] Apart from the differences mentioned above, the materials, formulation ratios, and operating procedures used in this comparative example are consistent with those in Example 1.

[0053] Comparative Example 4 This comparative example provides a method for removing silicon and arsenic from a metal mixture. The difference between this method and Example 1 is that the pH value of the reaction system in the reactor in this comparative example is 11.

[0054] Apart from the differences mentioned above, the materials, formulation ratios, and operating procedures used in this comparative example are consistent with those in Example 1.

[0055] Comparative Example 5 This comparative example provides a method for removing silicon and arsenic from a metal mixture. Compared with Example 1, the difference in configuration is that the reaction temperature in the reactor in this comparative example is 80°C, and the temperature at which the liquid is transferred to the heat-insulating aging tank for static aging after the reaction is completed is 80°C.

[0056] Apart from the differences mentioned above, the materials, formulation ratios, and operating procedures used in this comparative example are consistent with those in Example 1.

[0057] Testing and Analysis 1. Test Object This test example uses the alkaline leaching solutions and impurity-removed solutions obtained in Examples 1-5 and Comparative Examples 1-5 as test objects to conduct relevant parameter tests.

[0058] 2. Test Content (1) The contents of elements such as Si, As, W, Mo, and V in the alkaline leaching solution and the solution after purification, as well as the pH value of the solution, were determined.

[0059] (2) The test methods are as follows: 1) The main elements of the solution are determined by ICP-OES. For specific operation, please refer to the relevant operation requirements of GB / T 36244-2018 "Inductively Coupled Plasma Atomic Emission Spectrometer"; 2) The pH value of the solution is determined by pH meter.

[0060] 3. Experimental Results The alkaline leaching solution and the purified solution obtained from the silicon and arsenic removal process of the metal mixture provided in Example 1 were tested, and the test results are shown in Table 1.

[0061] Table 1. Test results of Example 1

[0062] The removal rates of each element in the purified solutions after treatment in Examples 1-5 and Comparative Examples 1-5 were measured respectively, and are shown in Table 2. Additionally, for clear comparison, the removal rate results for Example 1 are also listed in Table 2.

[0063] Table 2. Removal rates of the purified solutions in Examples 1-5 and Comparative Examples 1-5

[0064] Analysis of the data in Table 2 reveals that the core advantage of this invention lies in the fact that by adding aluminum first and then magnesium and calcium, it achieves deep and simultaneous removal of silicon and arsenic (Si removal rate of 99.76% and As removal rate of 93.00% in Example 1), while controlling the loss of valuable metals such as tungsten, molybdenum, and vanadium to within 1%, demonstrating excellent selectivity in impurity removal. In Comparative Example 1, adding magnesium source first hinders the dissolution of aluminosilicates due to the magnesium hydroxide colloid coating of aluminum source, resulting in insufficient aluminum content in the subsequent reaction system and affecting the reaction precipitation, ultimately causing the Si removal rate in Comparative Example 1 to drop to 88.49%. Omitting the magnesium source almost completely eliminates the arsenic removal capacity of the reaction system (As removal rate of only 0.12% in Comparative Example 2), and adding only magnesium source without aluminum / calcium almost completely fails to remove silicon (Si removal rate of only 1.32% in Comparative Example 3). In Comparative Example 4, when the pH value decreased to 11, the silicon removal rate dropped to 80.43%, while the loss rate of valuable metals increased. This indicates that pH affects the solubility of the aluminum source, causing a change in the amount of hydrated calcium aluminosilicate formed after the addition of the calcium source. This alters the overall adsorption and co-precipitation performance, leading to a decrease in Si removal rate. Furthermore, because the aluminum source was not effectively dissolved, some calcium source remained after the formation of hydrated calcium aluminosilicate. This calcium residue reacted with vanadium, tungsten, and molybdenum in the system to form precipitates, increasing the loss rate of valuable metals. Similarly, in Comparative Example 5, the decrease in reaction temperature also led to a decrease in the removal rates of Si and As, while increasing the removal rate of the target metal. This may be because temperature changes alter the selectivity and precipitation equilibrium of the reactions within the system.

[0065] Furthermore, comparisons between the examples also show that different process optimization conditions will affect the removal efficiency of silicon and arsenic.

[0066] Compared to Example 1, Example 2 showed a slight decrease in silicon and arsenic removal rates, and a slight increase in valuable metal loss rates. This may be because Example 2 used commercial-grade industrial Mg(OH)2, which is mostly in crystalline form with a smaller specific surface area and higher crystallinity. In concentrated alkali, OH... - The common ion effect significantly inhibits its dissociation, Mg 2+ The release is slow, the reaction starts slowly, and the kinetics are gentle. In contrast, the lightly calcined active MgO used in Example 1 rapidly hydrates after being added to the reaction solution to generate in-situ nascent Mg(OH)2. This in-situ nascent Mg(OH)2 has smaller grain size, larger specific surface area, and higher surface energy, and is relatively less inhibited by the common ion effect of high alkali. 2+ The release rate is faster, allowing for quicker attainment of supersaturation. Because magnesium oxide has a shorter reaction time, it is more effective at removing arsenic and assisting in silicon removal, better maintaining system alkalinity, preventing the formation of calcium tungstate and calcium vanadate precipitates, and minimizing the loss of valuable metals.

[0067] In Example 3, magnesium oxide with an activity of 55% was used, and the final As removal rate was 88.42%. It can be seen that magnesium oxide with different activities will affect the As removal rate.

[0068] In Example 4, the amount of lightly calcined magnesium oxide added was lower than the molar ratio of magnesium to arsenic in the range of 3-5, which caused a decrease in the removal rates of both Si and As. This may be because the amount of magnesium source added was insufficient, resulting in a low overall magnesium ion concentration in the reaction system, a reduction in the amount of magnesium hydroxide colloid generated, and a decrease in the adsorption and co-precipitation effect.

[0069] Compared to Example 1, the aging process was omitted in Example 5, resulting in finer precipitate particles and incomplete solid-liquid separation. This led to a decrease in the removal rates of silicon and arsenic by approximately 9 and 5 percentage points, respectively.

[0070] Therefore, the above embodiments and comparative examples sufficiently demonstrate that different process optimization conditions of the present invention will also affect the removal effect of silicon and arsenic.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method for removing silicon and arsenic from a metal mixture, characterized in that, Includes the following steps: (1) A metal mixture is mixed with an alkaline solution to obtain an alkaline leaching solution, wherein the pH of the alkaline solution is ≥13 at 23℃~28℃; (2) Add an aluminum source to the alkaline leaching solution to obtain a mixed solution; (3) A magnesium source and a calcium source are added sequentially to the mixed solution to carry out the reaction. After the reaction system is separated, the metal mixture is desiliconized and dearsenicized. During steps (2) and (3), the reaction temperature of the reaction system is 90℃~95℃.

2. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The metal mixture includes a metal component and an impurity component; The metal component includes elemental metals or metal compounds that are soluble in the alkaline solution. The impurity components include silicon or its compounds, and arsenic or its compounds.

3. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The alkaline leaching solution contains ≥4.5 g / L silicon and ≥0.3 g / L arsenic.

4. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The molar ratio of aluminum in the aluminum source to silicon in the alkaline leaching solution is 1.0 to 1.

1. And / or, the molar ratio of magnesium in the magnesium source to arsenic in the alkaline leaching solution is 3 to 5; And / or, the molar ratio of calcium in the calcium source to silicon in the alkaline leaching solution is 1.3 to 1.

5.

5. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The aluminum source is at least one of aluminum oxide, aluminum hydroxide, or sodium aluminate. And / or, the magnesium source is magnesium oxide or magnesium hydroxide; And / or, the calcium source is calcium hydroxide.

6. The method for removing silicon and arsenic from a metal mixture as described in claim 4, characterized in that: The activity of the magnesium oxide is ≥65%.

7. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The calcium source added to the reaction system is a calcium hydroxide emulsion with a mass fraction of 15-25%.

8. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: Before separation, the reaction system in step (3) needs to undergo heat preservation and aging treatment. The heat preservation and aging treatment is to keep the system at 85℃~90℃ for more than 120 minutes.

9. The method for removing silicon and arsenic from a metal mixture as described in claim 1, characterized in that: The separation process is carried out at a temperature ≥80℃.

10. The method for removing silicon and arsenic from metal mixtures as described in any one of claims 1 to 9, applied to the recovery of metals.

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