Polyacrylamide, known as a Baiye auxiliary agent, is widely used in many industries. Its main efficacy is to use it as a flocculant, precipitator, and sludge dehydrating agent in the sewage treatment process; In fact, in addition to being used as a sewage flocculant, polyacrylamide is also widely used in the manufacturing field, as a thickener in the fragrance and construction industries; Used as flotation agent and clarifying agent in the field of coal washing and beneficiation; Textile sizing as sizing agent and finishing agent; In the paper industry, it is used as a dispersant, retention and drainage aid for paper making; Protein extraction agent; Gelatin clarifier, paint mist coagulant, and other fields.
Polyacrylamide (anionic, cationic, non-ionic, lotion)
Polyacrylamide is a water-soluble polymer, and solid polyacrylamide must be dissolved in tap water before being used to form a colloidal liquid. The process of preparing solid polyacrylamide is actually the maturation process of polyacrylamide, which can expand its molecular chain and effectively exert its strong coagulation effect. It is not easy to fully dissolve, and the following precautions should be noted during the dissolution process:
1. It must be dissolved with clean water (such as tap water).
The recommended concentration for dissolution is 0.1% to 0.3%.
3. When dissolving, slowly and evenly add polyacrylamide to the stirred aqueous phase, with a low stirring speed (the linear speed at the end of the stirring blade is controlled below 8 meters/second), to prevent the shear reduction force of polyacrylamide from decreasing, and if the material is added too quickly, it will also form clusters and form fish eyes.
The water temperature shall not exceed 60 ℃.
5. Do not dissolve the solution with iron to prevent degradation.
Attention to the above points can more effectively play the role of polyacrylamide.
Secondly, polyacrylamide has become increasingly widely used in the field of environmental protection, especially in industrial and domestic wastewater, and has been applied in municipal wastewater treatment plants, industrial wastewater treatment plants, papermaking industry, food approval industry, textile industry, brewing industry, petrochemical industry, leather manufacturing industry wastewater, and oilfield wastewater treatment.
Polyacrylamide (anionic, cationic, non-ionic, lotion)
Polyacrylamide can be divided into four types according to its ionic properties: nonionic, anionic, cationic, and amphoteric.Tairan chemical has developed various types of polyacrylamide products for various needs, meeting the needs of customers. In the face of the chaotic specification system in the market, it is indeed difficult to choose the preferred polyacrylamide model for its own sewage system. This article introduces some common issues regarding the selection of polyacrylamides for sewage and sludge treatment.
1、 Understand the source of sludge.
Sludge is an inevitable product in wastewater treatment. First, it is necessary to understand the source, nature, composition, and solid content of sludge. According to the main components contained in sludge, sludge can be divided into organic sludge and inorganic sludge.
Generally speaking, cationic polyacrylamide is used to treat organic sludge, while anionic polyacrylamide is used to treat inorganic sludge. When the alkalinity is strong, cationic polyacrylamide is not easy to use, but when the acidity is strong, anionic polyacrylamide should not be used. When the solid content of sludge is high, the use of polyacrylamide is usually large.
2、 Selection of ionic degree of polyacrylamide.
For sludge requiring dehydration, small experiments can be conducted to screen coagulants with different ionic degrees, select appropriate polyacrylamide, and achieve good coagulant effect, reduce dosage, and save costs. The key to selecting an ionomer is:
(1) The size of the flocculent mass.
Size of flocculent group: If the flocculent group is too small, it will affect the drainage speed. If the flocculent group is too small, it will bind a lot of water and reduce the degree of mud biscuit. Selecting the molecular weight of polyacrylamide can adjust the size of the cotton ball.
(2) Flocculation strength (water content)
Flocculation strength: Flocculation should be stable and not broken under shear. Increasing the molecular weight of polyacrylamide or selecting a suitable molecular structure can help improve the stability of the flocs.
(3) Mixing of polyacrylamide and sludge:
Polyacrylamide should fully react with sludge at a certain position in the dehydration equipment to play a flocculation role. Therefore, the viscosity of the polyacrylamide solution should be appropriate, and it should be able to fully mix with the sludge under existing equipment conditions, and the mixture of the two should be uniform, which is a key factor for success. The viscosity of polyacrylamide solution is related to its molecular weight and preparation concentration.
(4) Dissolution of polyacrylamide:
Good dissolution can fully exert the flocculation effect. The dissolution process of polyacrylamide is actually the ripening process of polyacrylamide. Sometimes it is necessary to accelerate the dissolution rate, and it can be considered to increase the concentration of polyacrylamide solution.
Therefore, selecting a good product requires a laboratory cup experiment decision.
3、 Molecular weight selection of polyacrylamide.
Polyacrylamide molecular weight refers to the length of the molecular chain in the molecule. Polyacrylamide molecular weight ranges from 5 million to 18 million. Generally speaking, the higher the molecular weight of the polyacrylamide product, the greater the viscosity. However, when used, the higher the molecular weight of the product, the better the use effect
Polyacrylamide is a high molecular coagulant, and its products are divided into three types based on average molecular weight: low molecular weight (< 1 million), medium molecular weight (> 2-4 million), and high molecular weight (> 7 million).
Polyacrylamide is a water-soluble organic polymer with molecular weights ranging from millions to tens of millions, used in wastewater treatment. In China, there are nonionic polyacrylamide (abbreviated as NPAM, molecular weight 8-15 million), anionic polyacrylamide (abbreviated as APAM, molecular weight 8-20 million), and cationic polyacrylamide (abbreviated as CPAM, molecular weight 8-12 million, ionic degree 10% - 80%).
When used solely as a coagulant aid, the higher the molecular weight, the closer the flocs are, and the less medication is required. However, the molecular weight of anionic polyacrylamide is recommended not to exceed 20 million.
If it comes to sludge dewatering. When using a belt filter press, the molecular weight should not be too high. If the molecular weight is too high, it may cause clogging of the filter cloth, affecting the dehydration effect; For example, if you use a centrifugal filter press, the molecular weight requirement should be higher because the centrifugal filter press requires that the flocs be able to withstand shearing as much as possible, so it is necessary to select products with relatively high molecular weight.
It can be seen that the selection of molecular weight and ionic degree is different. Before selecting polyacrylamide, carry out a selection test and a mechanical operation test. The data obtained are correct, and the preferred polyacrylamide has a high cost performance ratio.
4、 Regarding the storage of polyacrylamide.
Many sewage treatment plants, especially in the southern region, often encounter moisture absorption and caking due to the humid climate in some sewage plants due to long stacking or untightened packaging openings. For the caking of polyacrylamide flocculants, many people have questions about whether they have failed and whether they can be reused. In fact, in this case, as long as you can dissolve it, the aqueous solution has viscosity, and there is no failure, However, the agglomerated polyacrylamide is difficult to dissolve, which actually means that it is ineffective.
