Polyacrylamide use method and precautions

◆ Before the formal use of a type of polyacrylamide product, Water Treatment Chemicals, a small test should be carried out to determine the best dosage and conditions of use, when used as a flocculant, the general dosage is 0.1 ~ 0.5ppm.

◆ Polyacrylamide products must be dissolved into a solution before use, so that the polymer chain is fully extended for reserve use. Usually non-ionic and cationic products are diluted to about 0.1%, and the dissolution operation is carried out in a mixing tank such as plastic, ceramic or stainless steel. Because the PAM molecular chain in the solution is an irregular coil, in the preparation and dissolution, in part of the water wrapped in the coil, the coil and the volume is large and full, it is easy to intertwine and cross-linked between the coils, and there is a certain viscosity from the outside. If the centrifugal pump is used due to the high-speed rotation of the impeller, the structure of the macromolecular coil is deformed and a part is separated from the middle, the volume is changed, the cross-linking between the coils is destroyed, the viscosity is reduced, and the use effect is reduced.

◆ The molecular chain of PAM is subjected to shear force in solution, which will cause the molecular chain to break and degrade, affecting the performance, so the mixing time should be reduced as much as possible to reduce the mixing intensity when dissolving and diluting PAM; Reducing the mixing speed should generally be controlled at 50 ~ 250 RPM, not too fast. When using PAM solution, the dosing point should avoid strong mechanical stirring as much as possible; When transporting PAM solution, the pipeline should be thick, the variable head and branch pipe should be less, and the transport pump is best to use Monopump or diaphragm pump, rather than centrifugal pump.

◆ Dry powder PAM products should pay special attention to the operating procedure when dissolving, to prevent the particles from adhering to each other and causing the dissolution operation to fail. Methanol can be used for small scale tests. Ethanol and other organic agents wet to improve the dispersion of particles in water; Industrial applications, should be added to the container after 1/2 hour can be basically completely dissolved, instant products in 0.5 to 1 hour all dissolved, appropriate heating can accelerate the dissolution of the product, but should not exceed 60 ° C.

◆ When the inorganic flocculant is mixed with PAM, the inorganic flocculant and PAM should be dissolved in the two stirring equipment, otherwise it will cause the interaction between the two flocculants, and produce agglutination, affecting the effect; When using, attention should be paid to the order of feeding, generally speaking, when dealing with fine particles with particle size below 50um, add inorganic flocculant first, and then add PAM solution; When treating coarse particles with a diameter of more than 50um, PAM solution is first added for adsorption bridging, and then flocculant is added. When the user uses it, a small test should be carried out first to determine the order of adding.

As a general rule, the more favorable the solution conditions are for polymer molecular chain extension, the better the use effect. Therefore, cationic PAM is suitable for acidic media, anionic PAM is suitable for alkaline media, and non-ionic PAM is suitable for acidic or weakly alkaline media. Where conditions exist, the PAM solution is diluted to 0.01%-0.05% before use, which is conducive to the further extension of the molecular chain, thereby improving the use effect and saving the amount.

◆PAM products should not be stored in iron containers. Dry powder PAM can generally be stable for a long time, and the performance of PAM dissolved in water will decline with the increase of time, and the lower the concentration, the faster the performance decline. 0.05%-0.1% of non-ionic or anionic PAM solution can only be stored for about half a month, 0.1% of cationic PAM solution is extremely unstable, 1 to 2 days later, the performance began to decline, so PAM products should be ready to use as well.

◆ Due to the uneven arrangement of crystal lattice ions on the surface of mineral particles, excess charge is generated, which has a strong impact on PAM molecules, the bridging effect of PAM is difficult to play, only with a single particle, suspended in the slurry, if the appropriate adjustment of the PH value in the slurry to eliminate part of the excess charge, can increase the flocculation effect.

◆ The consumption of PAM is proportional to the surface area of solid particles, if the diameter of minerals and invisible fallout is very small, there is a large surface area, the amount of PAM required is also large.

◆ If the viscosity of the settling particles is very large, the surface is loose and charged, such as (iron oxide colloidal) acrylamide uniform distribution will be difficult, reducing the settling and flocculation effect.

◆ Toxicity of polyacrylamide:

PAM itself is not toxic, only when the amount is greater than 5000ppm, the absorption of nutrients into the animal's gastrointestinal mucosa is blocked and harmful.

The residual monomer acrylamide (Am) in PAM is toxic, the use of oil fields and urban sewage treatment and other products, the residual monomer is generally allowed to be about 1%, for Food Additives, such as drinking sucrose juice clarification, manufacturing paper that may be in contact with food, etc., the residual monomer content must be strictly controlled, generally below 0.05%.

In 1973, the Japanese Environmental Health Bureau stipulated that polymer flocculants should not be used in domestic water, and in 1975, the AM content of PAM in sewage treatment was 0.05%. Our country stipulates that the residual monomer amount of polyacrylamide used in food is also less than 0.5%.