Application of inorganic polymer aluminum salt flocculant

The treatment effect and the research direction of the inorganic polymer aluminum salt flocculant.

Raw material Process route Product characteristics Coal gangue acid-soluble one-step crude liquid or solid 丨 Zhang Chunyan (1968―), female, Jidong people of Heilongjiang Province, Daqing waste aluminum ash or bauxite + acid-soluble two-step crude liquid or The engineer and bachelor of Solidification Company's research institute mainly engaged in the pollution control of petrochemical enterprises and the development of industry. As a result, the use of water resources is gradually increasing. The water shortage problem that ensues is also becoming increasingly prominent. After wastewater treatment, it is reused as a solution to water. A major means of resources. Flocculation sedimentation method is the most commonly used method in water treatment process. Flocculating agent precipitation method has quick effect and low cost, and can provide guarantee for subsequent biological treatment.

Flocculation sedimentation method commonly used flocculants for inorganic polymer flocculant, the amount of the total amount of flocculants accounted for more than 70%. The most studied inorganic polymer flocculants are aluminum salt and iron salt flocculants.

Iron-salt flocculant has good flocculation effect, but due to its strong corrosion to the equipment, it limits its application in water treatment. At present, the most widely used polymer flocculant in water treatment is inorganic polymer aluminum salt flocculant.

1 Polymerization of aluminum and aluminum salts A coagulation and flocculation of colloidal particles in water is the result of a combination of chemical adsorption, neutralization and destabilization of aluminum hydrolyzed products, adsorption bridging, or adherent volume scanning. It is generally believed that the main influencing factors of the agglomeration process are the dosage of the pharmaceutical, pH, and the surface area and concentration of the particulates.

1.1 Polyaluminum Chloride The commonly used polyaluminum chloride production raw materials are: elemental aluminum (such as aluminum ingots, aluminum shavings, aluminum ash, etc.), aluminum-containing compounds (such as kaolin, bauxite, gangue, etc.) and pure aluminum compounds ( Such as aluminum hydroxide, aluminum chloride, etc.) In recent years, due to the continuous rise in the price of industrial sodium hydroxide, resulting in high costs, there has been a calcium aluminate powder as raw material production process. The production raw materials, routes and product characteristics of the polymerized aluminum are shown in Table 1. Table 1 Production of Polymerized Aluminum Raw Material Routes and Product Characteristics Continuation Table Aluminum Slag + Calcium Aluminate Powder Acid-Pressed Two-Step Process Crude Liquid or Solid Calcium Aluminate Powder Acid-soluble two-step crude liquid or solid metal aluminum or aluminum sulphate soluble and alkali-refined refined liquid or solid sodium hydroxide gel acid press-solution one-step or two-step refining liquid or solid polyaluminum chloride for processing In the case of petrochemical wastewater, its flocculating effect is better than that of traditional flocculants such as aluminum sulfate, ferrous sulfate, ferric chloride, or even poly-ferric. When the effluent turbidity reaches the same level, the amount of flocculant used is saved compared to that of conventional flocculants. 1/3 ~ 1/2 cost savings of more than 40%, and its high turbidity rate, little impact on the original water pH, corrosion of water treatment equipment, a wide range of uses, can be used for high turbidity water, low temperature, low turbidity water, colored The flocculants of industrial wastewater treatment such as water and petrochemical wastewater, but due to the limited content of residual aluminum in the treated water, its application is subject to certain restrictions.

1.2 Polymerization of Ferric Chloride Aluminum Polymerization Ferric chloride aluminum is produced from aluminum lanthanum salt and iron salt as a raw material, polymerized, filtered and dried.

Compared with ferric chloride and polyaluminum chloride, polyaluminum ferric chloride has the characteristics of rapid settling and large floc formation, and the effluent color is better than that of ferric chloride. The effect of reducing turbidity in the range of pH=7.08.0 is good. Printing and dyeing wastewater has obvious effects, but the disadvantage is relatively large amount.

1.3 Polymerization of Ferric Chloride Aluminum Ferric Chloride Ferric chloride aluminum chloride is produced by oxidizing polymerization with ferrous sulfate as the raw material under the action of a catalyst, which is passed through air and chlorine to adjust the chloride ion content of the product.

The development trend of inorganic polymer aluminum salt flocculants is to add aluminum sulfate from a single type. Diluted with water to an inspectable fraction of Li Zhizhi inorganic polymer A aluminum salt flocculant composite effect of swarovski varieties. The treatment results of polyferric chloride aluminum sulfate on domestic sewage, natural river water, printing and dyeing wastewater, and oily wastewater indicate that the aggregated aluminum sulfate ferric chloride flocculate has a large specific gravity, a rapid sedimentation rate, and is easy to filter. The dewatering rate is high, but its The processing process is complicated.

1.4 Polymerization of aluminum sulfate Wang Shicai used aluminum sulfate and calcium hydroxide as raw materials to produce polyaluminum sulfate at a certain temperature and tested its flocculating performance. The results show that the polyaluminum sulfate has better flocculation effect than aluminum sulfate at the same dosage. Polymeric aluminum sulfate pH is applicable from 5 to 9 and can be used for flocculation of drinking water, industrial water, and most wastewater. In the treatment of natural river water, the residual turbidity is low, and the decolorization effect is obvious; in the treatment of fluoride-containing wastewater, the F-mass concentration is lower than 10×10 6 mg/L, and a suitable stabilizer (tartaric acid sodium tartrate) 2 inorganic composite 2.1 has been found. Polymeric Aluminum Silicate Polymer Aluminum Silicate is a complex inorganic cationic polymer flocculant. Its development began abroad in the late 1980s, and it began in the early 1990s. The flocculant is made by properly introducing aluminum ions on the basis of polysilicic acid. The flocculant can simultaneously undergo electrostatic neutralization, adsorption and bridging, and net capture in the coagulation process of the colloid, resulting in a good flocculation effect.

The main raw material routes for the preparation of polyaluminum silicate at home and abroad are: (1) Prepared with ore, waste slag, fly ash, etc. as raw materials; (2) The introduction of aluminum salt into polysilicic acid solution; (3) Use of silicon Sodium, sodium aluminate, and aluminum sulfate are used as raw materials. With ore, waste slag, fly ash and other raw materials as raw materials, the resulting product in the effective component mass fraction is generally less than 10% product aggregation effect is better than aluminum sulfate, product storage period is short, the time is too long will appear adhesive Condensed and lost function. The aluminum salt was introduced into the polysilicic acid solution for preparation, and the resulting product was less stable. In 1991, Handy built a 27kt/a production facility in Laprairie, Quebec, Canada, using sodium silicate, sodium aluminate, and aluminum sulfate as raw materials, followed by facilities in the United States and Japan. The degree of alkalinization of polyaluminum silicate is 25% to 66%, and the content of AhO3 in liquid products is 7% to 14%, and that of a solid product is 24%. 2.2 Polymeric Silicate Aluminium Sulfate Polymeric Silicic Acid Aluminum Sulfate is a Cationic Novel Inorganic Material High-molecular polymers, known as sulphur-silicon polyaluminum or polyaluminum silicate silicates, are silica-aluminum complexes formed by introducing aluminum sulfate into polysilicic acid or by introducing polysilicic acid into polymeric aluminum sulfate. . The preparation method comprises the steps of taking a certain amount of sodium silicate, dissolving sulfuric acid with deionized water to adjust the pH, and mixing and aging for 2 hours to obtain the polymeric aluminum silicate sulfate. Wang Deying et al used sodium silicate and aluminum sulfate as raw materials, and used sulfuric acid to adjust the pH to obtain a polysilicon aluminum sulfate flocculant. The product has a wide pH use range, and has the best flocculation effect at pH 7-10. Wang Ping et al used sodium silicate and aluminum sulfate as raw materials to adjust the pH with sulfuric acid to prepare a polysilicon aluminum sulfate flocculant, and tested the treatment effects on low temperature and low turbidity water, domestic sewage, coal washing wastewater and oily wastewater, and their turbidity removal was tested. The efficiency can reach above 95%, and the CQD and chroma are significantly reduced. Yu Zhaokun used the method of introducing aluminum chloride and aluminum sulfate into polysilicic acid to obtain polysilicon aluminum chloride and polysilicon aluminum sulfate respectively, and the flocculation effect was good. Evergreen developed polysilicon aluminum sulfate preparation method: take a certain amount of water glass diluted to a certain concentration, and then use sulfuric acid to adjust the pH, control the polymerization reaction time, when the polymerization is completed, add quantitative aluminum sulfate, stirring to dissolve Then, the pH was adjusted with sulfuric acid to obtain polysilicon aluminum sulfate, which was dried and made into a finished product. Fushun's Liu Lin and others used sodium silicate, sulfuric acid and aluminum sulfate as raw materials to prepare polysilicate aluminum sulphate, and investigated its flocculating effect, demonstrating that its flocculation performance was superior to polyaluminum chloride.

2.3 Polymeric iron aluminum silicates Sun Jianhui et al. used sodium silicate, aluminum chloride, and ferric sulfate as raw materials, and adopted methods of introducing aluminum salts and iron salts into polysilicic acid solutions to prepare different molar ratios of Al/Fe/SiO2. Compared to the polymerized iron-aluminum silicate flocculant, and studied its flocculation performance. The results showed that in the range of pH 6~9, it had strong turbidity removal ability for papermaking wastewater, printing and dyeing wastewater, tannery wastewater and river water, and the optimal flocculating pH and effect were different due to the different Al/Fe/SiO2 molar ratio. . Researchers at Harbin Institute of Technology conducted research on polyaluminum iron silicate. The results showed that the polymerized iron aluminum silicate has excellent coagulation properties, and its amount is small. It is suitable for a wide range of pH, and rapid formation of pods is required. The short settling time is a promising inorganic polymer flocculant.

2.4 Polyaluminum Chloride Polyphosphorus Chloride is based on the effect of phosphate on the polymerization of polymeric aluminum. The introduction of an appropriate amount of phosphate in the polymeric aluminum causes a new type of high charge of the polyaluminophosphate through the polymerization of phosphate. Polyphosphate intermediate complex with phosphate. According to reports, the use of aluminum polyphosphate to treat oily wastewater, when the dosage is 5mg/L, the removal rate of turbidity and oil content respectively reach more than 90%, the removal rate of CQD is more than 80%; the solubility is low for low turbidity The polluted river water of natural humus has a de-turbidity rate of more than 90%, and has a good effect of removing color; the removal rate of Cr6+ in the wool dyeing factory is over 90%, and the amount of added CrCl is less than that of polyaluminum chloride. , Settlement is fast.

3 development trend breed development. The inorganic composite type is mainly used for the research and development of high-concentration polyaluminum silicon or silica-alumina varieties, and the inorganic and organic composites are mainly composites of polymeric aluminum and porous activated mineral adsorbents. The difficulty in the development of composite varieties lies mainly in their chemical stability, increased efficacy, and reduced costs. The specificity of flocculants is mainly applied to the treatment of wastewater with high acidity, alkalinity, high chroma, and refractory organics.