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Difference and application of cationic, anionic and nonionic PAM


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Polyacrylamide (PAM) is a kind of linear water-soluble polymer, which is the most commonly used water treatment agent in our sewage treatment! In our practical application, PAM can be divided into cationic, anionic and non-ionic three types. How to choose these three types of PAM, we should start from the differences!

Structural differences

Cationic polyacrylamide (CPAM): it is a linear polymer compound, because it has a variety of active groups, it can form hydrogen bonds with many substances. It mainly flocculates colloids with negative charge.

Anionic polyacrylamide (APAM): is a water-soluble polymer, which is mainly used for flocculation, sedimentation and clarification of various industrial wastewater, such as wastewater treatment of iron and steel plant, electroplating plant, metallurgical industry, coal washing, sludge dewatering, etc. It can also be used for drinking water clarification and purification. Because its molecular chain contains a certain number of polar groups, it can bridge the particles by adsorbing the solid particles suspended in water, or coagulate the particles to form a large flocculate by charge neutralization, so it can accelerate the sedimentation of particles in suspension, and has a very obvious effect of accelerating solution clarification and promoting filtration.

Nonionic polyacrylamide (NPAM): it is a kind of high molecular polymer or polyelectrolyte. Its molecular chain contains a certain amount of polar genes, which can adsorb the suspended solid particles in water and bridge the particles to form a large flocculate. It can accelerate the sedimentation of particles in suspension, accelerate the clarification of solution and promote filtration. Because the molecular chain contains amide group or ion gene, its remarkable characteristic is high hydrophilicity, which can be dissolved in water in various proportions. Polyacrylamide aqueous solution has good tolerance to electrolytes, such as amine chloride, sodium sulfate, etc., which are not sensitive, and is also compatible with surfactants.

Use difference

  1. Application of nonionic polyacrylamide

Sewage treatment agent: when the suspended sewage is acidic, it is more appropriate to use non-ionic polyacrylamide as flocculant. This is PAM adsorption bridging role, so that suspended particles produce flocculation precipitation, to achieve the purpose of purifying sewage. It can also be used in the purification of tap water, especially in combination with inorganic flocculant.

Textile industry auxiliaries: chemical materials can be prepared by adding some chemicals for textile sizing.

Sand control and sand fixation: dissolve the non-ionic polyacrylamide into 0.3% concentration, add the crosslinking agent, and spray it on the desert, which can play the role of sand control and sand fixation.

Soil humectant: used as the basic material of soil humectant and various modified polyacrylamide.

  1. Application of cationic polyacrylamide

Sludge dewatering: according to the nature of the sewage, the corresponding brand of the product can be selected, which can effectively carry out gravity sludge dewatering before the sludge enters the pressure filtration. During dewatering, it produces large floccules, does not stick to the filter cloth, does not disperse during pressure filtration, uses less, has high dewatering efficiency, and the moisture content of mud cake is below 80%.

Treatment of wastewater and organic wastewater: This product presents positive electricity in acidic or alkaline medium, so it is very effective to flocculate, precipitate and clarify the wastewater with negative charge of suspended particles in wastewater, such as wastewater from alcohol factory, brewery, monosodium glutamate factory, sugar factory, meat and food factory, beverage factory, textile printing and dyeing factory, etc, The effect of cationic polyacrylamide is several times or tens of times higher than that of anionic polyacrylamide, nonionic polyacrylamide or inorganic salt, because this kind of wastewater generally has negative charge.

Flocculant for water treatment in waterworks: the product has the characteristics of small dosage, good effect and low cost, and it has better effect when combined with inorganic flocculant.

Oilfield chemicals: such as clay anti swelling agent, thickening agent for oilfield acidizing, etc.

Papermaking auxiliary: Cationic PAM paper strengthening agent is a kind of water-soluble cationic polymer containing carbamoyl group, which has the functions of strengthening, retention and drainage, and can effectively improve the strength of paper. At the same time, the product is also a highly effective dispersant.

  1. Application of anionic polyacrylamide

Industrial wastewater treatment: for suspended particles, relatively high concentration, particles with positive charge, pH value of water is neutral or alkaline, iron and steel plant wastewater, electroplating plant wastewater, metallurgical wastewater, coal washing wastewater and other sewage treatment, the effect is the best.

Drinking water treatment: the water source of many Waterworks in China comes from rivers, with high sediment and mineral content and relatively turbid. Although it is filtered by sedimentation, it still can not meet the requirements, so flocculant needs to be added. The dosage is 1 / 50 of inorganic flocculant, but the effect is several times of inorganic flocculant, It is better to use inorganic flocculant and cationic polyacrylamide together for river water with serious organic pollution.

Recovery of starch distiller’s grains: at present, the waste water of many starch factories contains a lot of starch. Now, anionic polyacrylamide is added to flocculate and precipitate starch particles, and then the precipitate is pressed into cake shape by filter press, which can be used as feed. The alcohol of alcohol factory can also be dehydrated by anionic polyacrylamide and recycled by pressure filtration.

How to distinguish three kinds of PAM?

  1. Use pH value to judge

First of all, the polyacrylamide agent that is being used and has good effect is configured into an appropriate proportion of aqueous solution, and the pH test paper is prepared. The pH of different ionic polyacrylamide agents will be different, and the polyacrylamide production process will also affect the pH. this can be consulted with the regular polyacrylamide manufacturers.

  1. The mixed exclusion method was used to judge

Friends who have basic chemistry will know that in chemistry, anions and cations react together. We can make a simple judgment from this point.

  1. It can be judged by the sewage treatment in the laboratory

First of all, we need to understand the water quality characteristics of the sewage to be treated. Anionic polyacrylamide has good flocculation effect on the sewage with high alkaline or inorganic content or more negative charges; Cationic polyacrylamide flocculants are mainly used to flocculate the wastewater with high acid or organic content or more positive charges. Simple judgment is made by the effect of the medicine.