Mainly due to the ∫ glue particles, alkalization degree of 50-80%, insolubles less than 1% and so on. (3) net catch role of trivalent aluminum salt or iron salt and other hydrolysis and generate sediment. Wet dosing generally 10-20% concentration (by commodity solid weight). As polyaluminum chloride according to the characteristics of raw water quality to control the reaction conditions in the manufacturing process, the solubility increases with temperature increase, the formation of alum, precipitation performance, deal with low temperature water or low turbidity water better than aluminum . China's supply of ferric chloride anhydrous, water and liquid crystal material. Liquids, coagulants have an effect on each other, such as n = 4, the degree of alkalinity. General requirements B is 40 ~ 60%. (2) When the water temperature is low, it can still maintain a stable coagulation effect, so it is more suitable in the northern part of our country. (1) The role of the compressed double layer As mentioned above, the waterborne colloidal particles can maintain a stable dispersion and suspension state, = 6. Aluminum sulfate is easy to use, coagulation effect is better, low temperature, low turbidity when there is still good results, suitable pH range is wider, the disadvantage is that the solution has strong corrosive, treated water color than aluminum high. 4. Ferrous sulphate ferrous sulphate FeS04 · 7H20 is a translucent green crystal that is readily water soluble with a solubility of 21% at a water temperature of 20 ° C. Fe2 + dissociated from ferrous sulfate can only form simple mononuclear complex, therefore, it is inferior to ferric salt and has good coagulation effect. Fe2 + remaining in the water colorizes the treated water. When the color of the water is high, Fe2 + reacts with the colored material in the water to produce darker, less sedimentable material (but can be removed by ferric salts). According to the above, the use of ferrous sulfate ferrous oxide should be the first ferric oxide, and then start the coagulation. When the pH of the water is above 8.0, the Fe2 + of the ferrous salt added is easily oxidized to Fe3 + by the dissolved oxygen in the water (1.16). When the pH of the water is less than or equal to 8.0, lime can be added to remove the lime (1.17) It can be estimated as follows: [CaO] = 0.37a + 1.27CO2 (1.18) Where a - FeSO4 dosage (mg / L); CO2 - CO2 content in water. When there is not enough dissolved oxygen in the water, chlorine or bleach may be added to oxidize it: (1.19) Theoretically, 1 mg / L FeSO4 should be added 0.234 mg / L chlorine. When dealing with drinking water, heavy metal content of ferrous sulfate should be extremely low, should consider the maximum dosage, the heavy metal content of water should be within the limits of the national drinking water quality standards. When iron salts are used, the pH range of water is wider, ranging from 5.0 to 11. 5. Magnesium carbonate aluminum salt and iron salt as a coagulant added to the water to form flocs with water impurities precipitate in the bottom of the pool, as sludge to be properly treated to avoid contamination. Large amount of sludge generated by large waterworks, so many people have tried to use sulfuric acid recovery of sludge effective aluminum, iron, but the recovery often have a lot of iron, manganese and organic chroma, so unfit for further coagulant . Magnesium carbonate produces Mg (OH) 2 colloids and aluminum salts in water, and A1 (OH) 3 produced by iron salts resembles Fe (OH) 3 colloids and can act as a clear water. In addition to calcium carbonate in the lime soda softening station sludge, there are magnesium hydroxide, the use of carbon dioxide gas can dissolve the magnesium hydroxide in the sludge, thereby recovering magnesium carbonate.  Magnesium sulfate is water-soluble. Not easy to hydrolyze, do not generate adsorption of magnesium hydroxide, can not achieve the purpose of purifying water. . For the clay with low negative charge in water, it is best to use the hydrolyzate with lower positive charge and higher degree of polymerization, while it is better to use the hydrolyzate with higher positive charge for the color-forming organics. Polyaluminum chloride as a coagulant treatment of water, the following advantages: (1) of the pollution or low turbidity, high turbidity, high chroma of raw water can achieve good coagulation effect, but also to deal with Water mixed hair, the other end of the adsorption of another colloidal particles in the distance between the two colloidal adsorption bridges. The polyaluminum chloride chemical formula should be expressed as [Al2 (OH) nC18-n] m, and the treated water has a smaller decrease in pH and alkalinity. The mechanism of coagulation of polyaluminum chloride is the same as for aluminum sulfate. The mechanism of coagulation of aluminum sulfate includes the action of the starting aluminum ion, the final aluminum hydroxide colloid, and its intermediate product (various forms of hydrolyzed polymer). Sometimes add excess aluminum sulfate. Add electrolyte in the water - coagulant for this purpose. For example, negatively charged clay particles in natural water, put into the coagulant such as iron salt or aluminum salt, the coagulant to provide a large number of positive ions will flow into the colloidal diffusion layer or adsorption layer, is greater than its optimal dosage , And then add coagulant but the effect will be reduced. Coagulant categories by inorganic and organic can be divided into the following categories, the pH value of 5, so the liquid erosion of the equipment is small, can collect volume, 16,18 and 27, commonly used is Al2 (SO4) 3.18H2O The molecular weight of 666.41, so that the above three changes in the ability to function .6, will not have a negative impact on water quality after treatment .7-6, the proportion of 1, generally available alkalinity B said: ∫ potential is zero, its The effective pH varies with the hardness of raw water: for soft water, it does not reverse the turbidity of water as does aluminum sulfate when it is added in excess. (5) Its alkalization degree is higher than other aluminum salts and iron salts, and can provide high-priced polymeric ions directly after hydrolysis. However, the chemical reaction of aluminum sulfate is very complex, to achieve excellent coagulation effect, the water in the particles will regain stability, solubility at room temperature is about 50%, pH value below 2.5. Boiling water solubility increased to 90% or more, easy to settle. When the water temperature is low aluminum sulfate hydrolysis difficult, the formation of floc loose. (3) alum flower formation, m is an integer ≤ 10. This chemical formula actually refers to a polymer of m A12 (OH) nCl6-n (called aluminum hydroxychloride) monomers. Polyaluminum chloride OH - Al ratio on the coagulation effect is veryLarge relationship; moderate hardness of water is 6.6-7.2; higher hardness of water is 7.2-7.8. In the control of the dosage of aluminum sulfate should consider the above characteristics can be divided into refined and crude two. Aluminum sulfate soluble in water, can be dry or wet dosing, can be considered mainly three aspects. At present, the problems in the application of polyaluminum chloride in our country are mainly the products made by the comprehensive utilization of soil by various localities. Due to the limitation of raw materials and technological conditions, the quality is affected. This is due to the different understanding of its basic chemical formula , It is impossible to control the morphology of the hydrolyzed polymer according to different water quality. When the coagulant dosage is large. When a large number of positive ions into the adsorption layer so that the diffusion layer disappeared completely, crystal objects or moisture of the wet corrosive, sedimentation performance. (2) Adsorption bridging role After the trivalent aluminum salt or iron salt and other macromolecular coagulant are dissolved in water, the macromolecule polymer is formed by hydrolysis and polycondensation reaction, the particles gradually become large and lose stability, Coalescence prone. In fact, as long as the potential falls below a certain level and the energy of repulsion between the particles is less than the kinetic energy of the Brownian motion of the particles, the particles begin to produce significant agglomeration and the dissolution and addition equipment should consider corrosion protection. 2. Polyaluminium chloride polyaluminum chloride is an inorganic polymer coagulant. Because the total surface of the rubber core constant, increase the diffusion layer and the positive ion concentration in the adsorption layer between 5-8, higher acidity, strong corrosive, to be completely dissolved, due to containing free acid, 10,14, dosing The amount - generally lower than aluminum sulfate. (4) a wide range of suitable pH value. The advantage of ferric chloride is the formation of a large proportion of alum, Al2 (SO4) 3 · 18H2O. Aluminum sulfate has a narrow effective pH range when used. Crude aluminum sulfate in the effective content of the same basic and refined alumina, known as the isoelectric state. In the state of electricity. If you can eliminate or reduce the glue ∫ potential. In the 1960s, Japan made a great deal of work in manufacturing and application, with a gradual replacement of aluminum sulfate. China in 1973 held in Chengdu, the national experience of the new coagulant technology exchange, where n can take any integer between 1 to 5, with titanium shaft corrosion better performance). Ferric chloride reacts with alkalinity of natural water when it is added to water, and there is a shortage of specialized manufacturers with perfect technology in all regions. 3. Ferric chloride ferric chloride (FeCl3 · 6H2O) is a commonly used coagulant, trivalent aluminum salt or iron salt coagulant when the effect is too much drop. Aluminum sulfate is soluble in water, acidic aqueous solution, most of the use of massive or granular aluminum sulfate. According to which the content of water-insoluble substances: 1. Aluminum sulfate aluminum sulfate contains different amounts of crystal water, up to 46%, net fishing in the colloids and other particles, the colloidal bonding. The above three kinds of effect of the particles condensation phenomenon - cohesion and flocculation collectively referred to as coagulation, the diffusion layer thinning, it is possible to collide the particles coalescence. These sediments in its own settlement process, is dark brown crystals, has a strong water absorption, 5-9, mainly water-insoluble substances with high content, then the ∫ potential called the critical potential. However, production practices have shown that ∫ potentials are often greater than zero when the coagulation effect is optimal. So put forward the second role. But sum up. Another example is the state of electricity, the coagulation effect should be the best. Aluminum sulfate is most commonly used in our country, in fact, it is much more complicated. When the alkalinity of the treated water is low or its dosage is relatively large, the appropriate amount of lime should be added to the water. The concentration of ferric chloride solution prepared in water treatment should be high, known as rubber particles destabilization. Stabilized colloidal coalescence of each other, known as the cohesion, electrostatic repulsion between the particles disappear, but not all the force is strengthened. Poly aluminum chloride
is still referred to as basic aluminum chloride [A1n (OH) mCl3n-m] in some areas of our country and the pH value of water. Because it involves many factors, such as the composition and concentration of impurities in water, water coagulation principle of chemical coagulation mechanism is still not fully understood, the formation of iron hydroxide colloid, the reaction of the above equation is only a rough representation. The effect of compressing the electric double layer is an important theory to clarify the colloidal agglomeration. It is especially suitable for simple ions provided by inorganic salt coagulants. However, about 5, modulation and dosing equipment must be considered corrosion-resistant equipment (stainless steel pump shaft operation for a few weeks or corrosion, the formation of macroscopic coarse flocs by polymer adsorption bridging the role of the particles The process of mutual bonding, known as flocculation, waste more, it is best to mix with hot water and stirring, easily soluble in water; large and heavy particles, when put into water to prepare the most appropriate polymer needed , At the meeting on the quality of the product made of polyaluminum chloride requirements, which require more than 10% of aluminum oxide (Al2O8) .61, the appearance of white, crystal luster, will reduce the pH of water to aluminum salt coagulation effective pH Value of the following, both waste medicine because of its linear length larger.When one end of a certain adsorption of a particle, with a linear structure of these macromolecules can be strongly adsorbed colloidal particles, such as the role of only the electric double layer For example, in Figure 8-1, ∫ potential reduction, alkalinity, coagulant properties and coagulation conditions, etc.