Silicon removal material applied to industrial wastewater treatment and use method

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a silicon removal material applied to industrial wastewater treatment and a use method. The silicon removal material comprises the following components: a magnesium reinforced auxiliary agent which comprises 0.5%-2% of hydroxypropyl methylcellulose phthalate, 1%-4% of sodium citrate, 3%-6% of magnesium chloride, 1%-3% of polyethylene glycol and the balance of water; the polysilicate type main agent comprises 7%-10% of polysilicate magnesium aluminum, 3%-5% of polyaluminum chloride, 2%-4% of aluminum hydroxide, 0.5%-1% of sodium hexametaphosphate, 0.3%-0.8% of anionic polyacrylamide and the balance of water. According to the method, the removal efficiency of different forms of silicon is improved, the applicable temperature range is widened, aluminum residues are reduced, and the RO membrane cleaning period is remarkably prolonged.

Description

Technical Field

[0001] This application relates to the field of industrial wastewater treatment technology, and in particular to a silicon removal material and its application method for industrial wastewater treatment. Background Technology

[0002] Silicon compounds in industrial wastewater mainly exist in two forms: active silicon and colloidal silicon. Silicon compounds readily form silica scale in industrial circulating cooling water systems, severely impacting heat exchange efficiency. More seriously, when silicon-containing wastewater enters a reverse osmosis (RO) membrane system, silicon deposits on the membrane surface, forming insoluble silica scale, leading to a sharp decline in membrane flux. Existing silicon removal technologies mainly include lime softening, aluminum / iron salt coagulation and precipitation, adsorption, and ion exchange. Among these, aluminum salt coagulation and precipitation is the most widely used due to its low cost and ease of operation. For example, Chinese patent application CN115385433A discloses a composite silicon removal agent for steel industry wastewater, employing a two-step addition method of auxiliary agent LGF-1 (containing cellulose derivatives and organic compounds) and main agent LGF-2 (containing aluminum salts). This method achieves a silicon removal rate of 90%–94%, extending the RO membrane cleaning cycle from 30 days to 65 days.

[0003] However, the aluminum salt-based silicon removal agent described in CN115385433A still has significant shortcomings: First, this silicon removal agent mainly relies on the chemical precipitation reaction between aluminum ions and active silicon, but its ability to remove colloidal silicon with a particle size of less than 100nm is limited. When treating wastewater with high colloidal silicon content generated by industries such as photovoltaics and semiconductors, the total silicon removal rate will decrease significantly, making it difficult to meet the requirements of RO membrane feed water. Second, the silicon removal effect of aluminum salts is significantly affected by temperature. When the water temperature exceeds 40℃, aluminum ions are prone to premature hydrolysis to form aluminum hydroxide precipitate, and the silicon removal efficiency drops from over 90% to about 70%, making it unsuitable for high-temperature circulating cooling water treatment in industries such as steel and power. Third, to ensure the silicon removal effect, an excessive amount of aluminum salt needs to be added, resulting in a high residual aluminum concentration in the treated water. Aluminum and residual silicon form an aluminum-silicon composite fouling layer on the RO membrane surface, which aggravates membrane fouling and limits the further extension of the RO membrane cleaning cycle. From a technical mechanism perspective, the root cause of the above problems lies in the fact that a single aluminum salt system lacks an effective means of adsorbing colloidal silica, and the linear polymerization structure of aluminum salts limits their adsorption bridging ability; at the same time, the insufficient thermal stability of aluminum salts leads to a decline in high-temperature performance. Therefore, there is an urgent need to develop a new type of silica removal material that can both compensate for the shortcomings of aluminum salts by introducing metal components with strong adsorption effects on colloidal silica, enhance adsorption bridging ability by constructing a three-dimensional network polymerization structure, and improve thermal stability and reduce aluminum residue by optimizing the component ratio. This would achieve efficient and synergistic removal of silica in different forms, broaden the applicable temperature range, reduce secondary pollution, and significantly extend the service life of RO membranes. Summary of the Invention

[0004] This application provides a silica removal material and its application method for industrial wastewater treatment, which solves the problems of low removal rate of colloidal silica, poor high-temperature adaptability, high aluminum residue, and limited protection effect of existing aluminum salt silica removal agents. By introducing a magnesium-aluminum bimetallic synergistic mechanism and a three-dimensional network polymerization structure, the removal efficiency of silica in different forms is improved, the applicable temperature range is broadened, aluminum residue is reduced, and the RO membrane cleaning cycle is significantly extended.

[0005] On the one hand, this application provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent respectively configured;

[0006] The magnesium-fortified additive comprises the following components by weight percentage: 0.5%–2% hydroxypropyl methylcellulose phthalate, 1%–4% sodium citrate, 3%–6% magnesium chloride, 1%–3% polyethylene glycol, and the balance being water;

[0007] The polysilicate-type main agent comprises the following components in weight percentage: 7%–10% magnesium aluminum polysilicate, 3%–5% polyaluminum chloride, 2%–4% aluminum hydroxide, 0.5%–1% sodium hexametaphosphate, 0.3%–0.8% anionic polyacrylamide, and the balance being water.

[0008] Preferably, the magnesium-fortified additive comprises the following components in the indicated mass percentages: 1%–2% hydroxypropyl methylcellulose phthalate, 2%–4% sodium citrate, 4%–6% magnesium chloride, 1.5%–2.5% polyethylene glycol, with the balance being water. This preferred formulation ensures the additive remains stable and does not precipitate during storage, while simultaneously releasing magnesium ions rapidly after addition to adsorb colloidal silica.

[0009] Preferably, the polysilicate-type main agent comprises the following components by mass percentage: 8%–9.5% magnesium aluminum silicate, 3.5%–4.5% polyaluminum chloride, 2.5%–3.5% aluminum hydroxide, 0.6%–0.9% sodium hexametaphosphate, 0.4%–0.7% anionic polyacrylamide, and the balance being water. This preferred formulation ensures desiliconization efficiency while avoiding gelation of the main agent during storage, thus extending the shelf life.

[0010] Preferably, the magnesium chloride is magnesium chloride hexahydrate or anhydrous magnesium chloride. Magnesium chloride hexahydrate has better solubility and lower cost, while anhydrous magnesium chloride is more suitable for applications requiring high magnesium content.

[0011] Preferably, the anionic polyacrylamide has a weight-average molecular weight of 8 million to 12 million. Polyacrylamide in this molecular weight range has the best adsorption bridging ability, which can rapidly increase the size of flocs and accelerate sedimentation.

[0012] On the other hand, this application provides a method for using a silicon removal material applied to industrial wastewater treatment, comprising: first adding a magnesium-reinforced additive to the industrial wastewater, and then adding a polysilicate-type main agent to the industrial wastewater after an interval of 10 to 30 minutes.

[0013] Preferably, the volume ratio of the magnesium-reinforcing additive to the polysilicate-based main agent is 1:(2.5-6). This ratio ensures the pretreatment effect of magnesium ions on colloidal silicon while avoiding excessive addition of aluminum salts.

[0014] Preferably, the amount of magnesium-enhancing additive added per ton of industrial wastewater is 30-50 mL, and the amount of polysilicate-based main agent is 125-180 mL. This dosage is suitable for most industrial wastewaters, ensuring effective silicon removal while controlling treatment costs.

[0015] Preferably, after adding the magnesium-enhancing additive, the pH of the industrial wastewater is adjusted to 8.5–9.5, and then the polysilicate-based main agent is added. Within this pH range, magnesium ions exist in a dynamic equilibrium state of partial precipitation and colloidal coexistence. The formed magnesium hydroxide colloid (accounting for approximately 30%–60%) has a strong adsorption effect on colloidal silica; simultaneously, aluminum ions exist in a polymerized Al state. 13 ([Al) 13 O4(OH) 24 (H2O) 12 ] 7+ The flocculation is mainly in the form of Al(OH)3 and solid phase, and it can still exist stably and play a flocculation role at this pH, avoiding a large amount of dissolution into AlO2. - This precise pH control is key to the invention's ability to achieve synergistic silica removal by magnesium and aluminum without mutual interference.

[0016] Preferably, this invention is suitable for industrial wastewater with a temperature of 20℃ to 50℃ and a silicon content of 40 to 120 ppm. Compared with traditional aluminum salt desiliconizing agents, which suffer from performance degradation at high temperatures, the magnesium salt component in this invention maintains good desiliconizing activity at 50℃, making it particularly suitable for high-temperature circulating cooling water treatment in the steel industry.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention employs a staged magnesium-aluminum synergistic silicon removal mechanism, overcoming the pH window contradictions and competitive hydrolysis interference inherent in traditional simultaneous addition methods. In the first stage of magnesium pretreatment, under pH 8.5-9.5 conditions, although magnesium ions are not completely precipitated, the resulting magnesium hydroxide colloid (30%–60%) has a strong adsorption effect on colloidal silicon particles with a diameter of 5–100 nm, achieving a colloidal silicon removal rate of 75%–85%, significantly higher than the removal rate of colloidal silicon by traditional aluminum salts (usually below 40%). In the second stage of aluminum main reaction, since a large amount of colloidal silicon has been removed, polyaluminum chloride and polymagnesium aluminum silicate can concentrate on the removal of active silicon, and at this time, the aluminum salts are in a polymerized Al state. 13 Predominantly in solid form, Al(OH)3, it remains stable and performs flocculation under pH 8.5-9.5 conditions through the slow-release effect of the solid aluminum source, thus avoiding significant dissolution into AlO2. - The synergistic effect of the two stages increases the total silicon removal rate from 90%–92% in traditional processes to 92%–96%. For high-silicon photovoltaic wastewater containing 30%–40% colloidal silicon, the removal rate can be significantly increased from 70%–75% in traditional processes to over 94%.

[0019] 2. This invention achieves a phased treatment process—adsorption followed by flocculation—through the synergistic effect of the three-dimensional network structure of magnesium aluminum polysilicate (specific surface area 150-200 m² / g) and high molecular weight anionic polyacrylamide (8-12 million). The first phase maintains the silicon-magnesium composite colloid in suspension to fully adsorb colloidal silicon (10-30 minutes); the second phase utilizes strong adsorption bridging to rapidly increase floc size and settle (15-20 minutes). This phased mechanism balances sufficient reaction time with rapid solid-liquid separation, reducing floc settling time from 25-30 minutes in traditional processes to 15-20 minutes, significantly improving solid-liquid separation efficiency. Simultaneously, the phased addition reduces the actual aluminum salt dosage by 30%-40%, lowering aluminum residue from 6-7 mg / L in traditional processes to 2.5-3.5 mg / L, a reduction of 50%-60%, effectively reducing secondary pollution.

[0020] 3. This invention significantly expands the application range of silicon removal materials by leveraging the high-temperature stability of magnesium salt components and their targeted removal of silicon in different forms. Magnesium salts maintain good silicon removal activity (removal rate above 88%) even at 40℃-50℃, while traditional aluminum salt processes reduce the removal rate to 70%-75% at 50℃, making it particularly suitable for high-temperature circulating cooling water in the steel industry. For high-silicon wastewater (80-150ppm, containing 30%-40% colloidal silicon) from industries such as photovoltaics and semiconductors, traditional processes require significantly increased dosages with unsatisfactory results, while this invention achieves the desired effect with conventional dosages. The characteristic of magnesium ions forming magnesium fluoride precipitate with fluoride ions gives this invention a synergistic treatment capability for fluoride- and silicon-containing composite wastewater, achieving a fluoride removal rate of 60%-75%, thus simplifying the treatment process. More importantly, the synergistic effect of higher silicon removal rate (increased by 2% to 4%) and lower aluminum residue (reduced by 50% to 60%) significantly reduces silicon-aluminum composite contaminants entering the RO system. The RO membrane cleaning cycle can be extended from 60 to 65 days in the traditional process to 80 to 95 days, which is equivalent to an extension of 30% to 40%. This significantly reduces the membrane cleaning frequency and maintenance costs, and extends the membrane's service life. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the process flow for using the silicon removal material in this application;

[0023] Figure 2 This is a schematic diagram illustrating the effect of different dosing methods on silicon removal efficiency and aluminum residue in the embodiments of this application;

[0024] Figure 3 This is a schematic diagram illustrating the change in RO membrane flux retention rate over operating time in an embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The following specific embodiments will provide further detailed description of the invention. Unless otherwise specified, the pharmaceuticals used in the embodiments are commercially available products, and the methods used are conventional methods in the art.

[0026] The specifications of the main raw materials used in the embodiments of this invention are as follows:

[0027] Hydroxypropyl methylcellulose phthalate, viscosity 150-180 mPa·s (test conditions: 2% aqueous solution, 20℃), phthaloyl content 30%-33%, conforming to the 2015 edition of the Chinese Pharmacopoeia; sodium citrate, purity ≥99%, analytical grade; magnesium chloride hexahydrate, chemical formula MgCl2·6H2O, purity ≥99%; anhydrous magnesium chloride, chemical formula MgCl2, purity ≥98%; polyethylene glycol, when using polyethylene glycol-4000, average molecular weight is... 3000-4500; when using polyethylene glycol-6000, the average molecular weight is 5000-7000; polyaluminum chloride, liquid, Al2O3 content 30±1%, basicity 70%-80%; aluminum hydroxide, chemical formula Al(OH)3, purity ≥99%, particle size 200 mesh; sodium hexametaphosphate, purity ≥96%, industrial grade; anionic polyacrylamide, weight average molecular weight 8 million-12 million, degree of hydrolysis 25%-30%, solid content ≥88%.

[0028] Magnesium aluminum polysilicate is a self-made raw material, and its detailed preparation method is as follows: Take 500g of water glass solution (modulus 3.2, solid content approximately 30%, commercially available industrial grade), add 500g of deionized water for dilution, and slowly add a 6mol / L hydrochloric acid solution dropwise while stirring at room temperature. Adjust the pH to 2.5-3.0 to obtain a transparent polysilicic acid solution. Prepare magnesium chloride solution: Weigh 203g of magnesium chloride hexahydrate and dissolve it in 500mL of deionized water to obtain a magnesium chloride solution with a concentration of approximately 2mol / L. Prepare aluminum chloride solution: Weigh 483g of aluminum chloride hexahydrate (AlCl3·6H2O) and dissolve it in 500mL of deionized water to obtain an aluminum chloride solution with a concentration of approximately 4mol / L. Under stirring conditions, magnesium chloride solution and aluminum chloride solution were simultaneously and slowly added dropwise to polysilicic acid solution at a Mg:Al:Si molar ratio of 1:2:3, with the addition rate controlled at 10-15 mL / min. The solution temperature was maintained at 40-50℃ during the addition process. After the addition was complete, the pH was adjusted to 7.0-8.0 with 4 mol / L sodium hydroxide solution, and stirring was continued for 30 minutes. The solution was then allowed to stand for 12 hours to age, yielding a pale yellow, transparent to translucent magnesium aluminum silicate solution with a solid content of approximately 30%, ready for use.

[0029] Example 1

[0030] This embodiment provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent. The magnesium-reinforced additive comprises the following components by weight percentage: 1.5% hydroxypropyl methylcellulose phthalate, 3% sodium citrate, 5% magnesium chloride hexahydrate, 2% polyethylene glycol-4000, and the balance being deionized water. The polysilicate-based main agent comprises the following components by weight percentage: 9% magnesium aluminum polysilicate (based on a 30% solids content solution), 4% polyaluminum chloride (30% Al2O3 content), 3% aluminum hydroxide, 0.7% sodium hexametaphosphate, 0.5% anionic polyacrylamide (weight average molecular weight 10 million), and the balance being deionized water.

[0031] The preparation method of the magnesium-fortified additive is as follows: Add 88.5 kg of deionized water to a mixing tank. At room temperature (20℃-25℃), slowly add 1.5 kg of hydroxypropyl methylcellulose phthalate while stirring at 200-300 rpm for 30 minutes until fully dissolved. Then, add 3 kg of sodium citrate and 2 kg of polyethylene glycol-4000 sequentially, stirring for 15 minutes after each addition until completely dissolved. Finally, add 5 kg of magnesium chloride hexahydrate and continue stirring for 30 minutes until the solution is clear and transparent. After standing for 30 minutes, filter to obtain a colorless to slightly yellow transparent liquid magnesium-fortified additive with a pH of approximately 6.5-7.5.

[0032] The preparation method of the polysilicate-type main agent is as follows: Add 82.8 kg of deionized water and 0.7 kg of sodium hexametaphosphate to a mixing tank and stir to dissolve. Slowly add 9 kg of magnesium aluminum polysilicate solution (solid content approximately 30%) while stirring at 150-200 rpm for 40 minutes. Then, add 4 kg of polyaluminum chloride solution (solid content 30%) and 3 kg of aluminum hydroxide powder sequentially, stirring for 20 minutes after each addition. First, dissolve 0.5 kg of anionic polyacrylamide in a small amount of water, then slowly add it to the mixing tank and stir gently for 15 minutes. Adjust the pH to 7.5-8.5 and let stand for 1 hour to obtain a milky white to light yellow viscous liquid, which is the polysilicate-type main agent.

[0033] The usage method and effects of this embodiment are as follows: 100 tons of circulating cooling water wastewater from a steel plant was treated. The initial water quality indicators of the wastewater are as follows: silicon content 95 ppm (of which active silicon is about 71 ppm and colloidal silicon is about 24 ppm, accounting for about 25%), water temperature 45℃, pH value 7.8, calcium hardness 180 mg / L (calculated as CaCO3), magnesium hardness 85 mg / L (calculated as CaCO3), total hardness 265 mg / L, total iron 2.5 mg / L, manganese 0.8 mg / L, copper 0.3 mg / L, zinc 0.5 mg / L, COD 45 mg / L, suspended solids (SS) 35 mg / L, chloride ion 120 mg / L, sulfate ion 150 mg / L, bicarbonate ion 80 mg / L, turbidity 120 NTU.

[0034] Treatment steps: First, add 4L of magnesium-enhanced additive to the wastewater (dosage 40mL / ton) and stir rapidly for 5 minutes. Adjust the pH to 9.0 with sodium hydroxide solution and stir slowly for 15 minutes. Then add 15L of polysilicate-based main agent (dosage 150mL / ton), stir rapidly for 3 minutes, then switch to slow stirring and continue stirring for 10 minutes. After stopping stirring, allow to settle for 18 minutes. Filter the supernatant and then analyze it.

[0035] The treated water quality indicators are as follows: silicon content decreased to 4.2 ppm, silicon removal rate reached 95.6%, aluminum residue was 2.8 mg / L, and turbidity decreased from 120 NTU to 8 NTU. Treatment effect analysis: In this real wastewater system, although a high concentration of calcium ions (Ca...) was present... 2+ ), magnesium ions (Mg 2+In addition to heavy metal ions such as iron, manganese, copper, and zinc, these cations theoretically compete with silicon compounds for adsorption sites. However, the magnesium-aluminum bimetallic synergistic system of this invention can still achieve high silicon removal efficiency. The mechanism is as follows: After the magnesium-enhancing additive is added in the first stage, magnesium ions rapidly form magnesium hydroxide colloid under alkaline conditions (pH 9.0). Due to the strong electrostatic adsorption between colloidal silicon (negatively charged) and magnesium hydroxide (positively charged), and the large specific surface area of ​​magnesium hydroxide, it preferentially adsorbs colloidal silicon. At the same time, although some hardness ions such as calcium and magnesium in the wastewater will precipitate to form calcium carbonate and magnesium hydroxide, this precipitation mainly reacts with the original bicarbonate and hydroxide ions in the wastewater and does not significantly consume the effective components in the added magnesium-enhancing additive. After the second stage of adding the polysilicate-based main agent, the aluminum ions in the polyaluminum magnesium silicate and polyaluminum chloride selectively precipitate active silicon (silicate ions), forming aluminosilicate precipitates. Although heavy metals such as iron and manganese are also removed by co-precipitation, their concentration is much lower than that of silicon (iron 2.5 mg / L vs silicon 95 ppm), so their impact on silicon removal is limited. In addition, the three-dimensional network structure of polyaluminum magnesium silicate provides a strong adsorption bridging ability, which enables the magnesium hydroxide colloid that has adsorbed colloidal silicon, the newly formed aluminosilicate precipitates, and the co-precipitated metal hydroxides to quickly flocculate into large flocs (average particle size 3-5 mm), resulting in fast settling speed and high solid-liquid separation efficiency.

[0036] Figure 1 This is a schematic diagram of the process flow for using the silicon removal material in this application; Figure 1 The four-step process flow clearly demonstrates the phased silicon removal mechanism of this invention, which involves magnesium pretreatment, aluminum main reaction, and synergistic sedimentation. The process includes four steps: First, 30-50 mL / ton of magnesium-enhanced additive is added to the industrial wastewater, and after rapid stirring for 5 minutes, the pH is adjusted to 8.5-9.5 to initiate the hydrolysis of magnesium ions into magnesium hydroxide colloid. Second, the mixture is slowly stirred for 10-30 minutes to remove colloidal silicon from the wastewater using the magnesium hydroxide colloid adsorption. Third, 125-180 mL / ton of polysilicate main agent is added, and the mixture is stirred for 10-15 minutes. Aluminum ions react with active silicon to form aluminosilicate precipitate, while magnesium aluminum polysilicate acts as a bridging agent. Fourth, after settling for 15-20 minutes, the mixture is filtered to obtain treated clean water with a total silicon removal rate of 92%-96%. This process embodies the phased silicon removal mechanism of this invention, which involves magnesium pretreatment, aluminum main reaction, and synergistic sedimentation.

[0037] Comparative experiment: Using the same dosage (150 mL / ton) of ordinary polyaluminum chloride (30% Al2O3 content, 75% basicity, magnesium-free) to treat the same wastewater, the silicon removal rate was only 73.2%, the aluminum residue was 6.5 mg / L, and the settling time was 28 minutes. The comparative results show that under complex water quality conditions (with multiple competing ions), the magnesium-aluminum bimetallic synergistic system of this invention significantly improves silicon removal efficiency by selectively removing different forms of silicon in stages, while simultaneously reducing aluminum residue and significantly accelerating the settling speed. Especially under high-temperature conditions (45℃), traditional aluminum salts are prone to premature hydrolysis, reducing their effectiveness, while the magnesium salt component in this invention has good thermal stability and maintains excellent performance.

[0038] This invention solves the seemingly contradictory problem of flocculation effect and sedimentation rate through a phased mechanism of adsorption followed by flocculation:

[0039] The first stage (magnesium pretreatment): Although slow stirring for 10-30 minutes is required to fully adsorb colloidal silica, the goal at this stage is not rapid floc growth and sedimentation, but rather to maintain the silica-magnesium composite colloid in a suspended state to facilitate synergistic flocculation with aluminum salts in the second stage. This suspended adsorption state is achieved by controlling the stirring intensity (slow stirring to prevent shear breakage) and the colloid concentration. In this stage, magnesium's role is adsorption rather than flocculation, therefore the contradiction of rapid sedimentation affecting adsorption time does not exist.

[0040] The second stage (aluminum main reaction): After the main agent is added, magnesium aluminum polysilicate (three-dimensional network structure, specific surface area 150-200 m² / g) and high molecular weight anionic polyacrylamide (8-12 million) exert a strong adsorption and bridging effect. Magnesium aluminum polysilicate, through its three-dimensional network structure, bridges the silicon-magnesium composite colloid, the newly formed aluminosilicate precipitate, and other suspended matter into large flocs (3-5 mm). The long-chain molecules (molecular chain length can reach several micrometers) of the anionic polyacrylamide further enhance the bridging effect, enabling flocs to form rapidly within 10-15 minutes. This phased mechanism of adsorption followed by flocculation ensures sufficient reaction time (10-30 minutes for adsorbing colloidal silicon in the first stage) while achieving rapid flocculation and sedimentation (settling can be completed in 15-20 minutes in the second stage), thus balancing flocculation effect and sedimentation rate. This ultimately results in the large-particle (average 3-5 mm), dense, and rapidly settling flocs observed in this embodiment.

[0041] Example 2

[0042] This embodiment provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent. The magnesium-reinforced additive comprises the following components by weight percentage: 1% hydroxypropyl methylcellulose phthalate, 2% sodium citrate, 4% anhydrous magnesium chloride, 1.5% polyethylene glycol-6000, and the balance being deionized water. The polysilicate-based main agent comprises the following components by weight percentage: 8% magnesium aluminum polysilicate (based on a 30% solids content solution), 3.5% polyaluminum chloride (30% Al2O3 content), 2.5% aluminum hydroxide, 0.6% sodium hexametaphosphate, 0.4% anionic polyacrylamide (weight average molecular weight 9 million), and the balance being deionized water.

[0043] The preparation methods for the magnesium-fortified additive and the polysilicate-based main agent are the same as in Example 1, except for the amount of each component and the use of anhydrous magnesium chloride. Because anhydrous magnesium chloride releases heat upon dissolution, the feeding rate must be controlled during the addition process to avoid excessively high temperatures.

[0044] The usage method and effects of this embodiment are as follows: 50 tons of silicon-containing wastewater from a photovoltaic enterprise were treated. This wastewater is silicon wafer cleaning wastewater from the polysilicon production process, and the initial water quality indicators are as follows: silicon content 120 ppm (of which active silicon is about 78 ppm, colloidal silicon is about 42 ppm, and colloidal silicon accounts for about 35%), water temperature 35℃, pH value 8.2, fluoride ion 15 mg / L, calcium hardness 95 mg / L (calculated as CaCO3), magnesium hardness 40 mg / L (calculated as CaCO3), total hardness 135 mg / L, sodium ion 180 mg / L, potassium ion 25 mg / L, COD 120 mg / L, suspended solids (SS) 65 mg / L, chloride ion 80 mg / L, sulfate ion 60 mg / L, turbidity 85 NTU.

[0045] Treatment steps: Add 1.5L of magnesium-fortified additive (30mL / ton) to the wastewater and stir rapidly for 5 minutes. Adjust the pH to 8.8 with a small amount of dilute sulfuric acid and stir slowly for 20 minutes. Add 9L of polysilicate-based main agent (180mL / ton), stir rapidly for 3 minutes, then switch to slow stirring and continue stirring for 12 minutes. After stopping stirring, allow to settle for 20 minutes, and filter the supernatant for analysis.

[0046] The treated water quality indicators are as follows: silicon content decreased to 7.1 ppm, silicon removal rate reached 94.1%, aluminum residue was 3.2 mg / L, and turbidity decreased to 10 NTU. Treatment effect analysis: This photovoltaic wastewater is characterized by a high proportion of colloidal silicon (35%) and a certain concentration of fluoride ions. Under these water quality conditions, the pretreatment effect of the magnesium component in this invention is particularly significant: after adding the magnesium-enhanced additive, magnesium hydroxide colloid preferentially adsorbed the high content of colloidal silicon, achieving a colloidal silicon removal rate of 82%; simultaneously, magnesium ions and fluoride ions formed magnesium fluoride precipitate, synergistically removing some fluoride. Although the wastewater contains high concentrations of sodium and potassium ions, these alkali metal ions do not form stable precipitates with silicon, nor do they compete with magnesium hydroxide colloid for adsorption sites, thus having little impact on the silicon removal effect. After adding the main agent in the second stage, polyaluminum chloride effectively removed the remaining active silicon, ultimately achieving a total silicon removal rate of 94.1%.

[0047] Comparative experiment: When ordinary polyaluminum chloride was used to treat this high-colloidal-silica wastewater with the same dosage (180 mL / ton), the silicon removal rate was only 71.8%. The comparative results show that traditional aluminum salts have limited adsorption capacity for colloidal silicon with small particle size (especially in the 5-100 nm range), while the present invention can effectively adsorb colloidal silicon through magnesium pretreatment, significantly improving the treatment effect of high-colloidal-silica wastewater.

[0048] Example 3

[0049] This embodiment provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent. The magnesium-reinforced additive comprises the following components by weight percentage: 2% hydroxypropyl methylcellulose phthalate, 4% sodium citrate, 6% magnesium chloride hexahydrate, 2.5% polyethylene glycol-4000, and the balance being deionized water. The polysilicate-based main agent comprises the following components by weight percentage: 9.5% magnesium aluminum polysilicate (based on a 30% solids solution), 4.5% polyaluminum chloride (30% Al2O3 content), 3.5% aluminum hydroxide, 0.9% sodium hexametaphosphate, 0.7% anionic polyacrylamide (weight average molecular weight 11 million), and the balance being deionized water.

[0050] The preparation methods for magnesium-fortified additives and polysilicate-based main agents are basically the same as those in Example 1.

[0051] The usage method and effects of this embodiment are as follows: 80 tons of fluorine- and silicon-containing composite wastewater from an electronics factory were treated. This wastewater is semiconductor wafer cleaning wastewater, mainly from the hydrofluoric acid cleaning process. The initial water quality indicators are as follows: silicon content 110 ppm (of which active silicon is about 85 ppm and colloidal silicon is about 25 ppm), fluoride ion content 35 ppm, water temperature 28℃, pH value 7.5, calcium hardness 110 mg / L (calculated as CaCO3), magnesium hardness 50 mg / L (calculated as CaCO3), total hardness 160 mg / L, sodium ion 150 mg / L, nitrate ion 80 mg / L, COD 85 mg / L, suspended solids (SS) 40 mg / L, chloride ion 95 mg / L, turbidity 75 NTU.

[0052] Treatment steps: Add 4L of magnesium-fortified additive to the wastewater (dosage 50mL / ton) and stir rapidly for 5 minutes. Adjust the pH to 9.3 with sodium hydroxide solution and stir slowly for 25 minutes. Add 10L of polysilicate-based main agent (dosage 125mL / ton), stir rapidly for 3 minutes, then switch to slow stirring and continue stirring for 15 minutes. After stopping stirring, allow to settle for 16 minutes, filter the supernatant, and then test it.

[0053] The treated water quality indicators are as follows: silicon content decreased to 6.3 ppm, silicon removal rate reached 94.3%, aluminum residue was 2.6 mg / L, fluoride ion content decreased to 13 ppm, fluoride removal rate was 62.9%, and turbidity decreased to 9 NTU. Treatment effect analysis: This wastewater is characterized by the simultaneous presence of high concentrations of silicon and fluoride. Magnesium ions played a synergistic role in the removal of silicon and fluoride: under alkaline conditions of pH 9.3, magnesium ions not only formed magnesium hydroxide colloids to adsorb colloidal silicon, but also reacted with fluoride ions to form magnesium fluoride (MgF2) precipitate (solubility product Ksp = 7.4 × 10⁻⁶). -11 This method achieves the removal of fluoride. Although a certain amount of calcium ions are present in the wastewater, and calcium ions can also form calcium fluoride precipitate with fluoride ions, the solubility of calcium fluoride (Ksp=3.9×10) is limited. -11 The concentration of magnesium fluoride is slightly higher than that of magnesium fluoride, and since magnesium salt is added in this invention, the magnesium salt contributes more to the removal of fluoride. Furthermore, nitrate ions and sodium ions in the wastewater do not significantly compete with the silicon removal system, and have little impact on the silicon removal effect. Ultimately, a single agent achieves multiple effects, simultaneously removing both silicon and fluoride.

[0054] Example 4

[0055] In the magnesium-fortified additive of the present invention, each component has a clear synergistic mechanism: (1) Hydroxypropyl methylcellulose phthalate (0.5%-2%) acts as a polymeric stabilizer, which forms a coordination relationship with magnesium ions through the carboxyl groups on its molecular chain, preventing magnesium chloride from hydrolyzing and precipitating during storage; at the same time, hydroxypropyl methylcellulose phthalate undergoes ester bond hydrolysis under alkaline conditions (pH 8.5-9.5), rapidly releasing the coordinated magnesium ions. When the content of hydroxypropyl methylcellulose phthalate is less than 0.5%, the stabilizing effect on magnesium ions is insufficient, which easily leads to the precipitation of magnesium hydroxide during storage; when the content is higher than 2%, although the storage stability is improved, the ester bond hydrolysis rate slows down during use, affecting the rapid release of magnesium ions. (2) Sodium citrate (1%-4%) acts as a chelating agent, which forms a soluble magnesium-citrate complex with magnesium ions (stability constant logK=3.4), avoiding the reaction of magnesium ions with other anions in the additive to form precipitates. The content of sodium citrate needs to be matched with the amount of magnesium chloride. When the magnesium chloride content is 3%-6%, the sodium citrate content of 1%-4% can ensure that the magnesium ions are fully chelated and not excessive. (3) Polyethylene glycol (1%-3%) is used as a dispersant. It forms hydrogen bonds with water molecules through its ether bonds, which increases the viscosity and uniformity of the additive and prevents the components from separating or precipitating during storage. When the content of polyethylene glycol is 1%-3%, it can maintain the fluidity of the additive for easy addition and ensure that the components are uniformly dispersed. (4) Magnesium chloride (3%-6%) is used as a magnesium source. After the pH is adjusted to 8.5-9.5, the magnesium ions are rapidly hydrolyzed to form magnesium hydroxide colloid. When the magnesium chloride content is less than 3%, the amount of magnesium hydroxide colloid formed is insufficient to effectively adsorb colloidal silicon. When the content is higher than 6%, although the magnesium content increases, the amount of sodium citrate and hydroxypropyl methylcellulose phthalate needs to be increased accordingly to maintain stability, and excessive magnesium salt will increase the processing cost. The four components mentioned above work synergistically within the proportion range of 0.5%-2%, 1%-4%, 1%-3%, and 3%-6%, achieving long-term stability of the magnesium-enhanced additive during storage (no precipitation for more than 6 months) and rapid release of magnesium ions after addition (more than 90% released within 5 minutes), thereby efficiently adsorbing and removing colloidal silica from wastewater.

[0056] This embodiment provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent. The magnesium-reinforced additive comprises the following components by weight percentage: 0.5% hydroxypropyl methylcellulose phthalate, 1% sodium citrate, 3% magnesium chloride hexahydrate, 1% polyethylene glycol-4000, and the balance being deionized water. The polysilicate-based main agent comprises the following components by weight percentage: 7% magnesium aluminum polysilicate (based on a 30% solids content solution), 3% polyaluminum chloride (30% Al2O3 content), 2% aluminum hydroxide, 0.5% sodium hexametaphosphate, 0.3% anionic polyacrylamide (8 million weight-average molecular weight), and the balance being deionized water.

[0057] The preparation methods for the magnesium-fortified additive and the polysilicate-based main agent are the same as in Example 1. This example uses the lower limit ratio of each component of the additive to verify the storage stability and magnesium ion release effect of the additive under the lower limit conditions.

[0058] Storage stability test: The prepared additive was sealed and stored at room temperature (25℃) for 6 months, and observed periodically. The results showed that the additive remained clear and transparent throughout, without precipitation or stratification, and the pH value remained between 6.5 and 7.5. This indicates that even when hydroxypropyl methylcellulose phthalate and sodium citrate are used at the lower limit ratio (0.5% and 1%), magnesium ions can still be effectively stabilized, preventing hydrolysis and precipitation during storage.

[0059] Magnesium ion release rate test: 50 mL of the additive was added to 950 mL of deionized water, the pH was adjusted to 9.0, and the mixture was stirred rapidly for 5 minutes. The concentration of free magnesium ions in the solution was measured (using EDTA titration). The results showed that the magnesium ion release rate reached 92% within 5 minutes and 96% within 15 minutes. This indicates that even using the lower limit ratio, hydroxypropyl methylcellulose phthalate can still rapidly hydrolyze and release magnesium ions under alkaline conditions.

[0060] Verification of the adsorption effect of colloidal silica: 200 tons of general industrial wastewater from a chemical plant were treated. This wastewater is from a chemical synthesis process, and the initial water quality indicators are as follows: silica content 55 ppm (of which active silica is about 47 ppm and colloidal silica is about 8 ppm, accounting for about 15%), water temperature 22℃, pH value 8.0, calcium hardness 140 mg / L (calculated as CaCO3), magnesium hardness 65 mg / L (calculated as CaCO3), total hardness 205 mg / L, sodium ion 120 mg / L, COD 55 mg / L, suspended solids (SS) 30 mg / L, chloride ion 100 mg / L, sulfate ion 110 mg / L, turbidity 90 NTU.

[0061] Treatment steps: Add 6L of magnesium-enhanced additive to the wastewater (dosage 30mL / ton) and stir rapidly for 5 minutes. After adjusting the pH to 8.7 with a small amount of sodium hydroxide, stir slowly for 18 minutes. Before adding the main agent, samples were taken for testing. The colloidal silica content decreased from 8ppm to approximately 1.4ppm, and the colloidal silica removal rate reached 83%, proving that the additive at the lower limit ratio still has a good pre-adsorption effect on colloidal silica.

[0062] Subsequently, 25L of polysilicate-based main agent (dosage 125mL / ton) was added, and the mixture was stirred rapidly for 3 minutes, then switched to slow stirring and continued stirring for 10 minutes. After stopping stirring, the mixture was allowed to stand and settle for 19 minutes, and the supernatant was filtered and tested.

[0063] The treated water quality indicators are as follows: total silicon content decreased to 3.1 ppm, total silicon removal rate reached 94.4%, aluminum residue was 3.1 mg / L, and turbidity decreased to 7 NTU. Treatment effect analysis: Under these water quality conditions, although the wastewater hardness was high (total hardness 205 mg / L), the proportion of colloidal silicon was relatively low (15%), and the staged treatment of this invention could still effectively remove silicon in different forms. The magnesium pretreatment stage preferentially adsorbed colloidal silicon, while the partial precipitation of hardness ions such as calcium and magnesium (forming calcium carbonate, etc.) did not significantly consume the added silicon removal agent, because the hardness ions mainly reacted with the existing bicarbonate ions in the wastewater. The effective components of the added magnesium-enhanced additive and polysilicate-type main agent still mainly acted on silicon removal. Ultimately, a total silicon removal rate of 94.4% was achieved, proving that even using the lower limit of the range ratio, the additive performed well in the three key performance indicators of storage stability, rapid release of magnesium ions, and pre-adsorption of colloidal silicon.

[0064] In addition to Example 4, this application also provides a comparative example of Example 4, which is used to verify the effect when the auxiliary component is below the lower limit of the range.

[0065] The same wastewater and treatment conditions as in Example 4 were used, but the additive formulation was as follows: 0.3% hydroxypropyl methylcellulose phthalate (below the lower limit of 0.5%), 0.6% sodium citrate (below the lower limit of 1%), 3% magnesium chloride hexahydrate, 1% polyethylene glycol-4000, and the balance being deionized water.

[0066] Storage stability test: After 30 days of storage at room temperature, the additive showed slight turbidity, and after 60 days, a small amount of white precipitate formed, which was identified as magnesium hydroxide precipitate. This indicates that insufficient content of hydroxypropyl methylcellulose phthalate and sodium citrate cannot adequately stabilize magnesium ions.

[0067] Magnesium ion release rate test: The magnesium ion release rate was only 78% within 5 minutes and 88% at 15 minutes, which was significantly lower than that in Example 4 (92% at 5 minutes).

[0068] Verification of colloidal silica adsorption effect: Before the addition of the main agent, the colloidal silica removal rate was only 64% (compared to 83% in Example 4). The final total silica removal rate was 88.7%, significantly lower than 94.4% in Example 4.

[0069] This invention achieves precise control over the storage stability and rapid release of magnesium ions during use by introducing hydroxypropyl methylcellulose phthalate and sodium citrate into magnesium-fortified additives.

[0070] Storage stage: Hydroxypropyl methylcellulose phthalate reacts with Mg through the carboxyl groups (-COOH) on its molecular chain. 2+Forming a coordination bond (Mg-OC) stabilizes magnesium ions in a soluble complex state; sodium citrate binds to Mg via a tricarboxyl group. 2+ It forms a chelate complex (stability constant logK = 3.4), further inhibiting the hydrolysis of magnesium ions. This dual stabilization mechanism allows the additive to be stored stably for more than 6 months at pH 6.5-7.5 and room temperature without producing magnesium hydroxide precipitate.

[0071] Application phase: After the additive is added to the wastewater and the pH is adjusted to 8.5-9.5 (alkaline), hydroxypropyl methylcellulose phthalate undergoes alkaline hydrolysis of its ester bonds (-COO-R + OH-). - → -COO - (+ ROH) rapidly releases coordinated magnesium ions; simultaneously, the stability of the magnesium-citric acid chelate decreases under high pH conditions, also releasing magnesium ions. The released magnesium ions can reach a release rate of over 90% within 5 minutes, rapidly hydrolyzing to form magnesium hydroxide colloid, achieving rapid adsorption of colloidal silica.

[0072] Example 5

[0073] This embodiment is used to verify the effects of staged dosing, pH adjustment, and interval time on the desiliconization effect.

[0074] The same silicon removal material formulation as in Example 1 was used. 100 tons of wastewater from a steel plant was treated. The initial water quality indicators were as follows: silicon content 88 ppm, water temperature 40℃, pH 7.6, calcium hardness 170 mg / L (as CaCO3), magnesium hardness 80 mg / L (as CaCO3), total hardness 250 mg / L, total iron 2.2 mg / L, manganese 0.6 mg / L, copper 0.2 mg / L, zinc 0.4 mg / L, COD 40 mg / L, suspended solids (SS) 32 mg / L, chloride ions 115 mg / L, sulfate ions 140 mg / L, bicarbonate ions 75 mg / L, and turbidity 110 NTU.

[0075] (I) The effect of interval time on silicon removal effect

[0076] Following the method of this invention, 4L of magnesium-fortified additive (40mL / ton) was first added, the pH was adjusted to 9.0, and then 15L of polysilicate-based main agent (150mL / ton) was added at different intervals. After stirring and settling, the desiliconization effect was measured. The results are as follows:

[0077] At 10-minute intervals: silicon removal rate 91.2%, aluminum residue 3.2 mg / L, settling time 20 minutes; at 15-minute intervals: silicon removal rate 94.8%, aluminum residue 2.7 mg / L, settling time 17 minutes; at 20-minute intervals: silicon removal rate 94.5%, aluminum residue 2.8 mg / L, settling time 17 minutes; at 25-minute intervals: silicon removal rate 94.2%, aluminum residue 2.9 mg / L, settling time 18 minutes; at 30-minute intervals: silicon removal rate 93.8%, aluminum residue 3.0 mg / L, settling time 18 minutes.

[0078] Mechanism Analysis: The role of the interval time is to allow sufficient time for magnesium ions to form magnesium hydroxide colloids and adsorb colloidal silica. Under pH 8.5-9.5 conditions, the formation and colloidification of magnesium hydroxide requires a certain amount of time. When the interval time is 10 min, although magnesium hydroxide colloids have initially formed, their quantity and particle size have not yet reached the optimal state, resulting in a slightly lower adsorption efficiency for colloidal silica, with a removal rate of 91.2%, slightly lower than the above 94% achieved with an interval time of 15-25 min. When the interval time is 15-25 min, magnesium hydroxide colloids are fully formed and reach a stable state, with the highest adsorption efficiency for colloidal silica, and the removal rate remains stable above 94%. When the interval time is extended to 30 min, although the magnesium hydroxide colloids remain stable, the excessively long interval causes the adsorbed colloidal silica-magnesium hydroxide complex to begin to settle, reducing the efficiency of subsequent synergistic effects with aluminum salts. Therefore, the removal rate slightly decreases to 93.8%, but is still significantly better than the case without an interval.

[0079] The above results show that effective magnesium pretreatment and magnesium-aluminum synergistic silicon removal can be achieved throughout the entire time interval of 10-30 min, with the silicon removal rate remaining above 91%. The optimal range is 15-25 min (removal rate greater than 94%), while good results (91%-94%) can still be obtained at the 10 min and 30 min range boundaries.

[0080] (II) The impact of dosing method on silicon removal effect

[0081] To further verify the necessity of staged dosing and pH adjustment, the following comparative experiment was conducted (with intervals of 15 minutes for all experiments):

[0082] Comparative Experiment A: The auxiliary agent and the main agent were added simultaneously (without stage), and other conditions were the same. The silicon removal rate was 88.3%, the aluminum residue was 3.8 mg / L, and the settling time was 23 minutes.

[0083] Comparative Experiment B: Add the auxiliary agent first but do not adjust the pH (maintain the original water pH 7.6), and add the main agent after an interval of 15 minutes. The silicon removal rate was measured to be 86.5% and the aluminum residue was 4.2 mg / L.

[0084] Comparative experiment C: The main agent was added immediately after the auxiliary agent was added and the pH was adjusted (without interval). The silicon removal rate was measured to be 89.7% and the aluminum residue was 3.5 mg / L.

[0085] Figure 2 This is a schematic diagram illustrating the effect of different dosing methods on silicon removal efficiency and aluminum residue in the embodiments of this application. Figure 2 The figure includes two sub-figures, (a) and (b). Figure (a) shows the silicon removal rate under four different addition methods, and figure (b) shows the corresponding aluminum residual concentration. The four addition methods are: simultaneous addition (no interval), staged addition (no pH adjustment), staged addition (immediate addition of the main agent), and staged addition (standard process). As can be seen from the figures, the standard process (adding the auxiliary agent first and adjusting the pH to 8.5-9.5, then adding the main agent after a 10-30 minute interval) achieves the best silicon removal effect, with a silicon removal rate of 94.8% and the lowest aluminum residual concentration of 2.7 mg / L. This example demonstrates the importance of staged addition, pH adjustment, and appropriate interval time for fully utilizing the pretreatment effect of magnesium components and achieving synergistic magnesium-aluminum silicon removal.

[0086] In this application, the silicon removal process is divided into a magnesium pretreatment stage and an aluminum main reaction stage. By separating time and space, the problem of mutual interference between magnesium and aluminum ions at the same pH is cleverly avoided.

[0087] Stage 1 (Magnesium Pretreatment, 10-30 minutes): Magnesium-enhancing additive is added separately, and the pH is adjusted to 8.5-9.5. Within this pH range, although magnesium ions do not reach the pH required for complete precipitation (greater than 9.5), a dynamic equilibrium state of partial precipitation and colloid coexistence will form. According to the magnesium hydrolysis equilibrium theory, at pH 8.5-9.5, Mg2+ exists in the solution. 2+ Mg(OH) + Magnesium hydroxide exists in various forms, including Mg(OH)₂ (colloidal), with colloidal Mg(OH)₂ comprising approximately 30%–60%. The key is that not all magnesium ions need to precipitate; only a sufficient amount of magnesium hydroxide colloid is required. These colloids possess a high specific surface area (80-120 m² / g) and a positively charged surface (ζ-potential +15 to +25 mV), exhibiting strong electrostatic adsorption of negatively charged colloidal silicon (ζ-potential -25 to -35 mV). During slow stirring for 10–30 minutes, colloidal silicon is preferentially adsorbed onto the surface of the magnesium hydroxide colloid, forming a silicon-magnesium composite colloid, achieving a silica removal rate of 75%–85%. At this stage, since no aluminum salt has been added, there is no competitive hydrolysis interference from aluminum ions, allowing magnesium ions to fully exert their adsorption effect on the colloidal silicon.

[0088] Second stage (aluminum main reaction, 10-15 minutes): Add polysilicate-type main agent. At this time, a large amount of colloidal silica in the wastewater has been removed, and the remaining part is mainly active silica (silicate ions H2SiO3). - HSiO3 2- Aluminum ions in polyaluminum chloride and polymagnesium aluminum silicate are in optimal flocculation state at pH 8.5–9.5. Although at this pH, mononuclear Al... 3+ It will be partially converted into AlO2 - While dissolved, aggregated aluminum ions (such as Al) 13 That is, [Al] 13 O4(OH) 24 (H2O) 12 ] 7+ The stability of aluminum hydroxide is far superior to that of mononuclear aluminum ions, remaining stable and exerting a flocculating effect even below pH 9. More importantly, the magnesium aluminum silicate (Mg:Al:Si=1:2:3) and aluminum hydroxide in this invention provide a solid aluminum source. This solid aluminum slowly dissolves under pH 8.5-9.5 conditions and reacts with active silicon to form aluminosilicate precipitates (such as 3Al2O3·2SiO2·nH2O), unlike soluble aluminum salts which undergo significant dissolution into AlO2. - Therefore, within this pH range, aluminum is mainly in the form of solid Al(OH)3 and polymerized Al. 13 and a small amount of AlO2 - The aluminum salt is a mixture, rather than completely dissolved, thus ensuring effective removal of active silicon. This design cleverly utilizes the slow-release properties of the solid aluminum source, allowing the aluminum salt to continue its silicon removal function at high pH without significant dissolution.

[0089] Example 6

[0090] This embodiment is used to verify the silicon removal effect of the present invention under different temperature conditions. Using the same silicon removal material formulation and addition method as in Example 1, simulated wastewater with the same silicon content (95 ppm) was treated, but the experiments were conducted at three temperatures: 20℃, 35℃, and 50℃. Simulated wastewater formulation: A solution with a silicon content of 95 ppm was prepared by adding water glass solution (modulus 3.2) to deionized water, adjusting the pH to 7.8 with dilute hydrochloric acid, and without adding other interfering ions.

[0091] At 20℃, the silicon removal rate was 93.8%, the aluminum residue was 2.9 mg / L, and the settling time was 20 minutes.

[0092] At 35℃, the silicon removal rate was 94.5%, the aluminum residue was 2.7 mg / L, and the settling time was 18 minutes.

[0093] At 50℃, the silicon removal rate was 88.2%, the aluminum residue was 3.3 mg / L, and the settling time was 17 minutes.

[0094] Comparative experiment: The same simulated wastewater was treated using the same dosage (150 mL / ton) of ordinary polyaluminum chloride (30% Al2O3 content, 75% basicity) at the same temperature. The removal rate was 89.5% at 20℃, 82.3% at 35℃, and only 72.6% at 50℃, with aluminum residues of 6.2 mg / L, 6.8 mg / L, and 7.5 mg / L, respectively.

[0095] Treatment Effect Analysis: This embodiment uses simulated wastewater to eliminate the influence of interfering ions such as calcium, magnesium, and iron, and purely examines the effect of temperature on silicon removal efficiency. The results show that the present invention maintains good silicon removal efficiency within the temperature range of 20℃-50℃, especially at high temperatures (50℃), maintaining a removal rate of over 88%, significantly better than the performance degradation of traditional aluminum salt silicon removers at high temperatures. The mechanism is that traditional polyaluminum chloride is prone to rapid hydrolysis at high temperatures (above 40℃), prematurely forming aluminum hydroxide precipitate and losing its reactivity with silicon; while the magnesium salt component in this invention has good thermal stability, and the solubility product of magnesium hydroxide (Ksp=5.6×10⁻⁶) is high. -12 Its temperature sensitivity is lower than that of aluminum hydroxide (Ksp=1.3×10). -33 It can stably form a colloidal substance and adsorb colloidal silicon even at high temperatures. Furthermore, the three-dimensional network structure of polymagnesium aluminum silicate is not easily destroyed at high temperatures, maintaining excellent adsorption and bridging capabilities. Therefore, this invention is particularly suitable for high-temperature circulating cooling water treatment in industries such as steel and power.

[0096] Example 7

[0097] This embodiment is used to verify the protective effect of the present invention on the RO membrane system. The RO system feedwater of a chemical plant requires a silicon content of less than 5 ppm and an aluminum content of less than 3 mg / L. The raw water is chemical process wastewater with the following initial water quality indicators: silicon content 92 ppm, water temperature 30℃, pH value 7.7, calcium hardness 155 mg / L (calculated as CaCO3), magnesium hardness 70 mg / L (calculated as CaCO3), total hardness 225 mg / L, sodium ion 140 mg / L, COD 65 mg / L, suspended solids (SS) 45 mg / L, chloride ion 105 mg / L, sulfate ion 120 mg / L, and turbidity 95 NTU.

[0098] After treatment with the silica removal material of this invention, the water quality indicators are as follows: silica content decreased to 3.8 ppm, and aluminum residue was 2.5 mg / L, meeting the RO feed water requirements. After 90 days of continuous operation, the RO membrane flux decreased by 12%, and slight scaling was detected on the membrane surface. After the first cleaning, the membrane flux recovered to 96% of the initial flux.

[0099] Comparative experiment: Using a traditional polyaluminum chloride (PAC) desiliconization process (30% Al2O3 content, 75% basicity, dosage 160 mL / ton) to treat the same raw water, the treated water showed a silicon content of 5.8 ppm and aluminum residue of 6.3 mg / L. After 65 days of RO system operation, the membrane flux decreased by 28%, and significant aluminum-silicon composite scale appeared on the membrane surface. After cleaning, the flux only recovered to 89% of the initial flux. The RO membrane flux retention curves after the two processes are shown below. Figure 3 .

[0100] Treatment Effect Analysis: This invention, through a higher silicon removal rate (reduced from 92 ppm to 3.8 ppm, a removal rate of 95.9%) and lower aluminum residue (2.5 mg / L vs 6.3 mg / L), significantly extends the RO membrane cleaning cycle (from 65 days to over 90 days, an extension of approximately 38%), reduces membrane fouling, and improves the flux recovery rate after cleaning, thereby reducing the operation and maintenance costs of the RO system and extending the membrane's lifespan. The mechanism is that the lower the silicon content entering the RO system, the slower the rate of silicon scale deposition on the membrane surface; simultaneously, the lower the aluminum residue, the lower the risk of forming an aluminum-silicon composite fouling layer. This invention, through the synergistic removal of silicon by magnesium and aluminum bimetals, ensures a high silicon removal rate while avoiding excessive use of aluminum salts due to the staged addition method and optimized component ratio, thus significantly reducing aluminum residue and achieving effective protection of the RO membrane system.

[0101] Figure 3 This is a schematic diagram illustrating the change in RO membrane flux retention rate over operating time in an embodiment of this application. Figure 3 The horizontal axis represents operating time (days), and the vertical axis represents RO membrane flux retention rate (%). The solid line represents the RO membrane flux retention rate curve after treatment with the silicon removal material of this invention, while the dashed line represents the RO membrane flux retention rate curve after treatment with traditional aluminum salt silicon removal agents. As can be seen from the figure, the RO system treated with this invention still maintains a flux retention rate of over 88% after 90 days of operation, while the traditional process reduces the flux retention rate to around 72% after 65 days, requiring cleaning. This invention extends the RO membrane cleaning cycle from 65 days to 90 days, an extension of 38%, significantly reducing membrane cleaning frequency and maintenance costs.

[0102] Example 8

[0103] This embodiment provides a silicon removal material for industrial wastewater treatment, comprising a magnesium-reinforced additive and a polysilicate-based main agent. The magnesium-reinforced additive comprises the following components by weight percentage: 1.5% hydroxypropyl methylcellulose phthalate, 3% sodium citrate, 5% magnesium chloride hexahydrate, 2% polyethylene glycol-4000, and the balance being deionized water. The polysilicate-based main agent comprises the following components by weight percentage: 10% magnesium aluminum polysilicate (based on a 30% solids content solution), 4% polyaluminum chloride (30% Al2O3 content), 3% aluminum hydroxide, 0.8% sodium hexametaphosphate, 0.5% anionic polyacrylamide (weight average molecular weight 10 million), and the balance being deionized water. The preparation method is the same as in Example 1.

[0104] The usage method and effects of this embodiment are as follows: 100 tons of wastewater from a steel plant were treated. The initial water quality indicators were as follows: silicon content 90 ppm, water temperature 40℃, pH value 7.8, calcium hardness 175 mg / L (calculated as CaCO3), magnesium hardness 82 mg / L (calculated as CaCO3), total hardness 257 mg / L, total iron 2.3 mg / L, manganese 0.7 mg / L, COD 42 mg / L, suspended solids (SS) 33 mg / L, chloride ion 118 mg / L, sulfate ion 145 mg / L, and turbidity 115 NTU.

[0105] Treatment procedure: Add 4L of auxiliary agent (40mL / ton), adjust pH to 9.0, and add 15L of main agent (150mL / ton) after a 15-minute interval. After treatment, the silicon content decreased to 5.2ppm, the silicon removal rate reached 94.2%, the aluminum residue was 2.9mg / L, and the sedimentation time was 17 minutes. Storage stability tests showed that the main agent could be stably stored for 12 months with the addition of 0.8% sodium hexametaphosphate without gelation.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon removal material for industrial wastewater treatment, characterized in that: This includes separately formulated magnesium-reinforced additives and polysilicate-based main agents; The magnesium-fortified additive comprises the following components by weight percentage: 0.5%–2% hydroxypropyl methylcellulose phthalate, 1%–4% sodium citrate, 3%–6% magnesium chloride, 1%–3% polyethylene glycol, and the balance being water; The polysilicate-type main agent comprises the following components in weight percentage: 7%–10% magnesium aluminum polysilicate, 3%–5% polyaluminum chloride, 2%–4% aluminum hydroxide, 0.5%–1% sodium hexametaphosphate, 0.3%–0.8% anionic polyacrylamide, and the balance being water.

2. The silicon removal material for industrial wastewater treatment as described in claim 1, characterized in that: The magnesium-fortified additive comprises the following components in weight percentage: 1%–2% hydroxypropyl methylcellulose phthalate, 2%–4% sodium citrate, 4%–6% magnesium chloride, 1.5%–2.5% polyethylene glycol, and the balance being water.

3. The silicon removal material for industrial wastewater treatment as described in claim 1 or 2, characterized in that: The polysilicate-type main agent comprises the following components by mass percentage: 8%–9.5% magnesium aluminum silicate, 3.5%–4.5% polyaluminum chloride, 2.5%–3.5% aluminum hydroxide, 0.6%–0.9% sodium hexametaphosphate, 0.4%–0.7% anionic polyacrylamide, and the balance being water.

4. The silicon removal material for industrial wastewater treatment as described in claim 1, characterized in that: The magnesium chloride is magnesium chloride hexahydrate or anhydrous magnesium chloride.

5. The silicon removal material for industrial wastewater treatment as described in claim 1, characterized in that: The weight-average molecular weight of the anionic polyacrylamide is 8 million to 12 million.

6. A method of using the silicon removal material as described in claim 1 for industrial wastewater treatment, characterized in that: First, add the magnesium-fortified additive to the industrial wastewater. After an interval of 10 to 30 minutes, add the polysilicate-type main agent to the industrial wastewater.

7. The method of use as described in claim 6, characterized in that: The volume ratio of the magnesium-reinforced additive to the polysilicate-based main agent is 1:(2.5-6).

8. The method of use as described in claim 6 or 7, characterized in that: The dosage of magnesium-fortified additive per ton of industrial wastewater is 30-50 mL, and the dosage of polysilicate-type main agent is 125-180 mL.

9. The method of use as described in claim 6, characterized in that: After adding magnesium-enhanced additives, the pH of the industrial wastewater is adjusted to 8.5–9.5, and then polysilicate-based main agent is added.

10. The method of use as described in claim 6, characterized in that: It is suitable for industrial wastewater with a temperature of 20℃~50℃ and a silicon content of 40~120ppm.

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