Detailed introduction of polyacrylamide(PAM)
Polyacrylamide is a water-soluble linear high molecular polymer formed by free radical polymerization of acrylamide (AM) monomer. At the same time, it is also a polymer water
treatment flocculant, which can absorb suspended particles in water, act as a bridge between particles, make fine particles form relatively large flocs, and accelerate the speed of sedimentation.
Features of dry powder polyacrylamide
Classification of polyacrylamide
Mainly divided into two forms: dry powder and colloid
According to ionic characteristics: it can be divided into four types: anionic polyacrylamide,cationic polyacrylamide, nonionic polyacrylamide, and zwitterionic polyacrylamide.
According to its average molecular weight: it can be divided into three categories: low molecular weight (<1 million), medium molecular weight (2 million to 4 million) and high molecular weight (>7 million). According to its structure, it can be divided into non-ionic,anionic and cationic.
Product Features
Features of dry powder polyacrylamide
Mainly divided into two forms: dry powder and colloid
According to ionic characteristics: it can be divided into four types: anionic polyacrylamide,cationic polyacrylamide, nonionic polyacrylamide, and zwitterionic polyacrylamide.
According to its average molecular weight: it can be divided into three categories: low molecular weight (<1 million), medium molecular weight (2 million to 4 million) and high molecular weight (>7 million). According to its structure, it can be divided into non-ionic,anionic and cationic.
Features of emulsion polyacrylamide
Cross-linked structure, strong flocculation ability, wide range of PH adaptability
Flocculation speed, flocculation firmness, and low moisture content between flocculations
The solid recovery rate is high, and the content of floating matter in the supernatant is low
The dissolution is extremely fast, and the solution preparation only takes 30-60 minutes
For dehydration, it can increase the degree of mud biscuit by 2-5%, which is beyond the reach of conventional dry powder products.
Product Features
The principle of flocculation: when PAM is used as a flocculant, it is related to the surface properties of the flocs, the special potential, the year, the turbidity and the pH value of the suspension. The reason is that the addition of PAM with opposite surface charge can reduce the kinetic potential and cause aggregation.
Adsorption bridging: PAM molecular chains are fixed on the surfaces of different particles,and polymer bridges are formed between the particles, and the particles form aggregates and settle.
Surface adsorption: various adsorptions of polar group particles on PAM molecules.
Reinforcing effect: PAM molecular chains and dispersed phase implicate the dispersed phase together through various mechanical, physical, chemical and other actions to form a network, thereby playing a reinforcing role.
| Item Model | Anionic | Cationic | Non-Ionic | Zwitterionic |
| Exterior | White granule or powder | White particle | White particle | Color particles |
Molecular weight (ten thousand) | 300—2200 | 500-1200 | 200—1500 | 500—1200 |
| Solid content% | ≥88 | ≥88 | ≥88 | ≥88 |
Ionic degree or degree of hydrolysis% | Hydrolysis degree 10-80 | Ionic degree 5-80 | Hydrolysis degree 0-5 | Ionic degree 5-50 |
Residual monomer % | ≤ 0.2 | ≤ 0.2 | ≤ 0.2 | ≤ 0.2 |
| scope of use | The ph of the water is neutral or alkaline | Belt machine centrifugal filter press | The ph of the water is neutral or alkaline | Belt machine centrifugal filter press |
The use characteristics of polyacrylamide
Flocculation: PAM can make the suspended solids pass through and act as a bridge for adsorption and flocculation.
Adhesiveness: It can play an adhesive role through mechanical, physical, and chemical effects.
Resistance reduction: PAM can effectively reduce the frictional resistance of the fluid,adding a small amount of PAM to water can reduce the resistance by 50-80%.
Thickening: PAM has a thickening effect under both neutral and acidic conditions. When the pH value is above 10, PAM is easy to hydrolyze and forms a semi-network structure, and the thickening will be more obvious.
Polyacrylamide use
Application in domestic sewage
In the treatment of domestic sewage, polyacrylamide can promote the rapid coagulation and sedimentation of suspended particles to achieve the effect of separation and clarification by means of electrical neutralization and its own adsorption bridging effect. It is mainly used in the front stage flocculation and sedimentation of the sewage treatment plant and the rear-stage sludge dewatering.
Application in industrial wastewater
When polyacrylamide is added to the water in which the turbid particles are suspended, the suspended particles can be quickly coagulated and settled by the neutralization of electricity and the adsorption and bridging effect of the polymer itself, so as to achieve the effect of separation and clarification. Improve operating efficiency and reduce operating costs.
Application in water treatment in the field of papermaking
Polyacrylamide is widely used as retention aid, drainage aid, dispersant, etc. in the field of papermaking. Its function is to improve the quality of paper, improve the dehydration performance of pulp, increase the retention rate of fine fibers and fillers, reduce the consumption of raw materials and the pollution to the environment. The effect of using it in papermaking depends on its average molecular weight, ionic properties, ionic strength and the activity of other copolymers. Non-ionic PAM is mainly used to improve the filterability of pulp, increase the strength of dry paper, and improve the retention rate of fibers and fillers; anionic copolymers are mainly used as dry-wet strengthening agents and resident agents for paper; cationic copolymers are mainly used It is used for papermaking wastewater treatment and filter aid, and it also has a good effect on improving the retention rate of fillers. In addition, PAM is also used in papermaking wastewater treatment and fiber recovery.
Application in water treatment of textile printing and dyeing industry
As a sizing agent and finishing agent for fabric post-treatment, polyacrylamide can form a soft, wrinkle-resistant, and mold resistant protective layer. Utilizing its strong hygroscopicity, it can reduce the thread break rate when spinning spun yarn; it can also prevent static electricity and flame retardancy of the fabric. When used as printing and dyeing auxiliaries,it can enhance the adhesion fastness and vividness of products; it can also be used as a
non-silicon polymer stabilizer for bleaching; in addition, it can also be used for efficient purification of textile printing and dyeing wastewater.
Application in electronics and electroplating wastewater treatment
The common treatment process is to first adjust the pH value of the wastewater to 2-3 with sulfuric acid in the first reaction tank, then add a reducing agent, and then use NaOH or Ca(OH)2 to adjust the pH value to 7 8 in the next reaction tank to generate Cr (OH)3 precipitates, add coagulant, make Cr(OH)3 precipitate and remove.
Application in water treatment of coal industry
Coal washing wastewater, coal slime water from coal preparation plants, and ground washing wastewater from coal-fired power plants are all mixtures of water and fine coal powder. The repulsion between charges keeps these particles in a dispersed state in water, which is affected by gravity and Brownian motion; due to the interaction between solid particle interfaces in coal slime water, the properties of coal washing wastewater are quite complicated, not only have the properties of a suspension, but also It has colloidal properties. In order to make the slime water settle quickly in the thickening tank, ensure the production of qualified washing water and filter press slime, and make the production run efficiently and economically, it is necessary to select a suitable flocculant to strengthen the treatment of slime water. A series of polymer flocculation dehydrating agents developed for coal slime dehydration in coal washing plants have high dehydration efficiency and are easy to use.
Application in wastewater treatment of alcohol plants
How is polyacrylamide applied? In general, polyacrylamide is mainly used in the post-stage sludge dewatering process. In general, cationic polyacrylamide is selected in this case.What kind of ionic cationic polyacrylamide is selected and what raw materials are used in the production of alcohol? ?What kind of wastewater treatment process? It is related to the pH value of the sludge. It is generally recommended to do laboratory beaker experiment selection for specific conditions.
Application in food wastewater treatment
The traditional method is physical sedimentation and biochemical fermentation. In the biochemical treatment process, polymer flocculants are used for sludge dehydration. The polymer flocculant used in this section is generally a cationic polyacrylamide product with relatively high ionicity and molecular weight. However, the following aspects should still be paid attention to in the selection of polyacrylamide products:
Climate change (temperature) affects the selection of flocculants
Select the molecular weight of the flocculant according to the floc size required by the treatment process.
The charge value of the flocculant must be screened through experiments
The strength of the floc can be improved by increasing the molecular weight of the flocculant
The flocculant must be fully mixed and dissolved with the sludge before treatment.
The selection of flocculant must fully consider the requirements of process and equipment
Usage and Precautions
Features of dry powder polyacrylamide
Dissolved water: It is recommended to use low-hardness water with a neutral PH value.Use groundwater. Water with too many dissolved inorganic substances or metal ions will easily reduce product performance.
Dissolution time: Dry powder products can be used for optimal performance after dissolving for 1 hour (it is recommended that non-ionic dry powder products be dissolved for more than 2 hours). It is recommended to use up the dissolved solution on the same day, and it is best not to exceed 24 hours, otherwise the polyacrylamide solution will degrade rapidly, which will seriously affect the use effect.
Dissolution concentration: the general dissolution concentration of cationic products is 0.2% (0.1%-0.5% is feasible); the dissolution concentration of anionic and non-ionic products is 0.1% (0.05%-0.3% is feasible).
The dissolving operation should be carried out in tanks made of plastic, ceramics, stainless steel, etc. The stirring speed should not be too high, generally 200 rpm, and the time should not be less than 1 hour. To accelerate dissolution, the highest temperature in the pharmaceutical industry should be less than 60°C. Avoid using high-shear rotor pumps such as centrifugal pumps when transferring diluted solutions, and use low-shear pumps such as screw pumps.
Sufficient dissolution: When dissolving this product, care should be taken, especially the flow rate of the automatic dosing device should not be too fast to prevent polyacrylamide agglomeration, fish-eye phenomenon, and unnecessary trouble caused by pipeline blockage.
Product dosage
Treatment water volume Dosage amount
= Treatment water volume m³/h*Dosage volume g/m³
Dry sludge volume
= treated water volume * ((1-sludge moisture content)/(1-mud cake moisture content))
Unit consumption per ton of water
= dosing amount (Ton) * drug unit price (Y/Ton) / treated water volume m³
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