What is polyaluminium chloride used for?

      Polyaluminium chloride, as an efficient inorganic polymer flocculation and water purification agent, has a wide range of applications. It can effectively destabilize, aggregate, and precipitate fine suspended particles and colloidal ions in water through mechanisms such as adsorption neutralization and adsorption bridging, achieving the goal of purifying water quality. In drinking water treatment, it can efficiently remove turbidity and suspended solids, improving water quality. Meanwhile, in the industrial field, polyaluminium chloride has also shown great potential and is widely used in wastewater treatment in industries such as papermaking, printing and dyeing, chemical engineering, and electroplating, effectively removing pollutants such as heavy metal ions, chromaticity, and organic matter. In addition, it is also used in mining industry for ore washing, soil improvement, as well as multiple industries such as food, pharmaceuticals, and daily chemical products, demonstrating strong application potential and market value. This article will systematically explain the diverse uses of polyaluminium chloride from these fields.

1. Core applications in the field of water treatment

      The application of polyaluminium chloride in the field of water treatment is dominant. Its mechanism of action involves physical and chemical processes such as adsorption neutralization, adsorption bridging, compression of the double layer, and sediment trapping, which cause fine suspended particles and colloidal ions in water to destabilize and aggregate, forming large particle alum flowers and rapidly settling.

      1. Drinking water purification

      It is an efficient water purifier for drinking water treatment, which can effectively remove turbidity, color, and microorganisms from water. Its floc formation rate is fast, the effluent turbidity is low, and it has significant removal effects on heavy metal ions (such as arsenic and mercury) and radioactive pollutants. The content of harmful substances in drinking water grade polyaluminium chloride must be strictly controlled to ensure that the product meets the GB 15892-2020 standard for polyaluminium chloride used in drinking water, with arsenic content ≤ 0.0001% and lead content ≤ 0.0005%, to ensure water quality safety.

      2. Urban sewage treatment

      In urban sewage treatment, polyaluminium chloride accelerates the flocculation process, promotes the formation of flocs and precipitation of impurities in water, and achieves efficient separation of water and impurities. When combined with polyacrylamide (PAM), it has a better flocculation effect and can significantly reduce the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in wastewater. For example, in municipal sewage treatment plants, the dosage of polyaluminium chloride is usually 10-20mg/L, which can reduce the effluent COD from 300mg/L to below 50mg/L, meeting the Class A standard of the "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB 18918-2002).

      3. Industrial wastewater treatment

      Polyaluminium chloride can treat various industrial wastewater, including printing and dyeing wastewater, leather wastewater, fluorine-containing wastewater, heavy metal wastewater, and oily wastewater. It effectively removes color, suspended solids, and toxic substances from wastewater through electrical neutralization and bridging. For example, in the treatment of printing and dyeing wastewater, polyaluminium chloride can reduce the chromaticity of the wastewater from 1000 times to below 50 times, while removing 60% -80% of COD; In the treatment of oily wastewater, it can aggregate oil droplets into larger particles through net capture, which facilitates subsequent separation.

2. Multi functional applications in the industrial field

      The application in the industrial field is not limited to water treatment, but also extends to multiple industries such as mining, papermaking, petroleum extraction, and textile printing and dyeing, playing a role in mineral separation, retention and filtration assistance, and oil displacement and water plugging.

      1. Mining industry

      During the ore washing process, polyaluminium chloride is used as a mineral separation agent, which can effectively separate water from gangue and facilitate the reuse of water. Meanwhile, when combined with polyacrylamide, it can dehydrate the generated sludge, reduce its moisture content, and improve resource recovery efficiency. For example, in iron ore washing, the dosage of polyaluminium chloride is usually 50-100mg/L, which can increase the grade of concentrate by 2% -3% and reduce the moisture content of tailings by 10% -15%.

      2. Paper industry

      Polyaluminium chloride is mainly used as a neutral sizing precipitant, retention aid, and filter aid in the papermaking industry. It can improve the precipitation efficiency of impurities in pulp, enhance paper quality, strength, and smoothness. For example, in the production of cultural paper, adding 0.5% -1% polyaluminium chloride can increase the tensile strength of the paper by 10% -15%, while reducing the amount of sizing agent by 20% -30%, achieving a dual benefit of economy and environmental protection.

      3. Oil extraction

      It is the main material for the treatment of oil extraction wastewater, and can also be used as an oil displacement agent, water plugging adjustment agent, and drilling fluid adjustment agent. It removes suspended solids and oils from wastewater through flocculation, reducing the cost of wastewater treatment; During the oil displacement process, it can change the wettability of the rock surface and improve the oil recovery rate. For example, in low-permeability reservoirs, using polyaluminium chloride as a water plugging agent can reduce water content by 5% -10% and significantly increase production.

      4. Textile printing and dyeing industry

      Textile printing and dyeing wastewater has the characteristics of large water volume, deep color, and high content of organic pollutants, making it one of the more difficult types to treat in industrial wastewater. Polyaluminium chloride forms large particle alum flowers and rapidly settles dye molecules and suspended solids in wastewater through electrical neutralization and bridging. For example, in the treatment of reactive dye wastewater, the dosage of polyaluminium chloride is usually 200-300mg/L, which can reduce the chromaticity of the wastewater from 2000 times to below 100 times, while removing 70% -80% of COD.

3. Environmental Remediation and Agricultural Applications

      The application of polyaluminium chloride in environmental remediation and agriculture is gradually receiving attention. It plays an ecological protection role by improving soil structure and purifying water bodies.

      1. Soil remediation

      Soil crust has the properties of high surface density, small pores, and low saturated hydraulic conductivity, which can hinder soil moisture infiltration, increase surface runoff, and hinder seed germination. Polyaluminium chloride can increase soil moisture content, inhibit soil crust formation, and increase water infiltration. For example, in soil improvement in arid areas, applying 0.1% -0.5% polyaluminium chloride can increase soil infiltration rate by 20% -30% and promote plant growth.

      2. Aquaculture

      In aquaculture, polyaluminium chloride can effectively remove organic matter from water and improve water quality. When there is an excessive amount of organic matter in the water, it can be precipitated through flocculation, and then oxidation bottom modifiers or microbial agents can be added to accelerate the energy flow and material circulation of the pond. For example, in fish ponds, the dosage of polyaluminium chloride is usually 1-2mg/L, which can increase water transparency by 30% -50% and reduce ammonia nitrogen content by 40% -60%.

4. Expanding applications in emerging fields

      With the advancement of technology, the application fields of polyaluminium chloride continue to expand, covering multiple industries such as food, pharmaceuticals, daily chemical products, and precision casting.

      1. Food industry

      Food grade polyaluminium chloride is a high-end product in water purification flocculants, which can be used to make beverage products such as fruit vinegar, fruit juice, and protein drinks. It plays a stabilizing, catalytic, and flocculation role in the saccharification process, improving food quality and taste. For example, in juice clarification, adding 0.05% -0.1% food grade polyaluminium chloride can increase the transparency of juice to over 90% and remove over 90% of suspended solids.

      2. Pharmaceutical industry

      Polyaluminium chloride can be used as a drug adsorbent in the pharmaceutical industry to adsorb harmful substances in the blood (such as urea, eosinophils, and Escherichia coli), expand the scope of drug application, and improve treatment efficacy. For example, in hemodialysis, polyaluminium chloride can be used as a flocculant to remove microorganisms and endotoxins from the dialysate, ensuring dialysis safety.

      3. Daily chemical industry

      Food grade polyaluminium chloride is also used for flocculation and sedimentation of wastewater in daily chemical production, and can be used as a raw material or additive in the cosmetics and beauty industries. Its non-toxic and harmless characteristics meet the safety requirements of daily chemical products. For example, in shampoo production, polyaluminium chloride can be used as a suspension agent to improve product stability.

      4. Precision casting

      In precision casting, polyaluminium chloride can be used as a curing agent for the mold shell to improve its strength and surface quality. It reacts with ethyl silicate hydrolysate to form a stable silicon aluminum composite gel, improving the crack resistance and air permeability of the shell mold. For example, in the casting of aircraft engine blades, adding 1% -2% polyaluminium chloride can increase the ambient temperature strength of the shell by 30% -50% and reduce the scrap rate.

      Polyaluminium chloride has become an indispensable key material in water treatment, industrial applications, environmental remediation, and emerging fields due to its efficient flocculation performance, wide range of applications, and economic advantages. With the improvement of environmental protection requirements and technological progress, polyaluminium chloride is developing towards low energy consumption, high functionality, and green direction, and will play an important role in more fields in the future.