application of polyacrylamide in water treatment(二)


The advantage of organic polymer flocculant PAM is that it has higher molecular weight, better product stability, stronger adsorption and bridging ability than inorganic polymer flocculant, multiple functional groups, good flocculation effect, wide application range, less dosage and less The advantages of low sludge volume and good filterability of the formed floc have been more and more widely used. Sewage of different natures adopts different treatment processes according to different pollutants and required discharge standards. At present, the common process of PAM in sewage treatment is: wastewater → pretreatment → coagulation → post-treatment. The pre-treatment process usually includes adsorption, filtration, etc. The post-treatment process can adopt oxidation, biological treatment, air floatation, etc. according to the nature of the sewage. PAM has great potential for wastewater treatment, especially for some suspension systems that are extremely difficult to treat.
    The PH value has a great influence on the Xu Ning effect of wastewater treatment, because: (1) he can change the electrical properties of the fixed surface and the thickness of the electric double layer, thereby affecting the adsorption of PAM on solid objects; (2) he Can change the shape of the flocculant molecular chain. NPAM has better flocculation effect in acidic and neutral media; it is often inferior to HPAM in alkaline media. PAM mainly relies on the adsorption of amide groups through hydrogen bonds with particles, and its action is quite rapid. Once the flocs encounter strong stirring, they are immediately broken up, which affects flocculation. Therefore, when choosing the dosing point, be sure to avoid strong stirring.
    The content of suspended matter in wastewater will directly affect the amount of flocculant and flocculation effect. An excessively large amount of solids will hinder the free settling of the flocs; an excessively small amount of solids will reduce the chance of collisions of particles and affect the formation of flocs. These will affect the flocculation effect and should be avoided as much as possible.
    The effect of temperature on the flocculation effect of wastewater is more complicated. As the temperature increases, the viscosity and density of the liquid decrease, which is beneficial to the sedimentation of flocs. However, when the temperature increases, it will affect the adsorption of PAM on the surface of the particles. Thermal convection also interferes with the aggregation and sinking of particles, often affecting the flocculation effect.
    In the next section we will start the treatment of metal-containing wastewater, so stay tuned!


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