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Polyaluminum chloride as one of the inorganic polymer flocculant composition and basic form is what?

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2017-12-19 09:22:00

Polyaluminum chloride as one of the inorganic polymer flocculant composition and basic form is what? Inorganic polymer flocculants in the traditional aluminum salt and iron salt flocculant developed on the basis of a new type of water treatment chemicals. Due to their advantages of high adaptability, non-toxicity and relatively high cost performance compared with the traditional drugs, they have been rapidly developed and widely used in recent years and have been gradually developed into Flow-by-flow agent for flocculation in water treatment. Currently in Japan, Russia, Western Europe, China and other countries or regions have a considerable scale of production and applications. In the United States, more and more attention has been paid to the research and development of such medicaments. The inorganic polymer flocculants that have been proposed and researched mainly include PAC, PFC, PAS, PFS, PAP, Flocculation such as PFP, PSI, PAFC, PAFS, PASS and PFSS etc. Agent. However, PAC, PFS, PSI and PASS are widely used at present. The coagulation and flocculation of aluminum salts are mainly carried out by inorganic polymers with high degree of polymerization and charge with appropriate charges after they are put into water. They are essentially the middle of the aluminum salt in the process of hydrolysis-polymerization-precipitation kinetics Products, their chemical forms belong to polynuclear hydroxyl complexes. Adding flocculant to the raw water, the solution of complex factors such as aluminum concentration, other ion composition, the nature and quantity of suspended matter, adsorption, temperature, mixing conditions, such as reaction time will generate inorganic polymers The optimal form of aluminum compounds have an effect and interfere with each other, so adding aluminum salts at water treatment sites often does not always guarantee optimal flocculation. It is conceivable that if the aluminum salt can be preliminarily prepared into an optimum form under controlled conditions and then added to the water to be treated, it is possible to rapidly exert excellent flocculation, and the occurrence of the polymeric aluminum flocculant is in line with This conjecture. Polyaluminum chloride (PAC), which is prepared by the prefabricated method according to this idea, can not only ensure the optimal morphology that can be achieved by adding aluminum salt in the field, but also can not produce the unacceptable More excellent product. Thus, the basic form of polymeric aluminum should be the formation of inorganic polynuclear hydroxyl polymer complexes. The composition and morphology of polyaluminum chloride have been studied for many years and the widely accepted formula is [Al2 (OH) nCl6-n] m. The formula actually considers the hydroxyl complex Al2 (OH) nCl6-n as Is a polymer of monomers, and m is the degree of polymerization. This expression takes into account not only the basic structure of Al number 2, but also consider the development of polymer morphology. In recent years, great progress has been made in the study of PAC morphology, which is summarized as follows: The study of PAC by 27AlNMR. According to the determination of PAC samples after experiments 0.0 and 62.9 of the two resonance peaks. The explanation of the hydrolytic polymerization of aluminum ion represented by these two resonance peaks is obtained by comparison with the results obtained by other experimental methods. The general view is that the 0.0 formant is the characteristic peak of Al (H2O) 63+ and other mononuclear hydroxyl ions; the 62.9 formant is caused by the multinuclear component Al13O4 (OH) 24 (H2O) 127+ (abbreviated as Al13) of. This component is formed from 12 AlO6 surrounded by 1 aluminum tetrachloride (AlO4) to form an approximately spherical Keggin cluster. In essence, the 62.9 formant is produced by AlO4 in Al13, and 12 AlO6 can produce formant, which is located at 0.0 and can not be seen because the peak is too flat. The aggregated template of the Al 13 cage structure shows the morphology under electron microscope as a tree branch that diverges to all four sides. Over the years in the field of flocculation chemistry is undoubtedly the study of the above-mentioned hydroxyl poly 13 future aluminum. Hydroxy poly-tridecyl aluminum is the most important component of alkalized hydrolyzed aluminum solution, which has higher molecular weight and positive charge and becomes the most effective component in polyaluminum chloride. Polyaluminum chloride as the main species of inorganic polymer flocculant, the development direction should be to maximize the poly-13 aluminum in its products in the dominant component status. However, the formation of Al13 has been the subject of controversy. In recent years, it is proposed that the formation of Al13 requires precursors to be more endorsed. As the core of Alg4 is AlO4 tetrahedron coordination, which does not accord with the thermodynamics law of its octahedral coordination of the precipitate, so that the experimental results show that Al ( OH) 4-tetrahedral structure as a precursor. It is currently believed that there is a large pH difference at the interface where alkali is added to the aluminum solution, resulting in Al (OH) 4- and then Al13. In addition to the Al concentration and the current degree of hydrolysis, there are factors affecting the lye concentration and injection speed, mixing strength, Al (OH) 4- and Al13 formation rate, and so on. The best combination of conditions yields the maximum amount of poly 13 aluminum.