Cationic polyacrylamide and anionic polyacrylamide differ significantly in their applications.
It carries a positive charge in acidic or alkaline media. Its molecular weight is typically lower than that of anionic or non-ionic polyacrylamide, and its wastewater purification performance is achieved primarily through charge neutralization. The main function of this type of flocculant is to flocculate negatively charged wastewater; it also serves to reduce turbidity and remove color. In the wastewater treatment of distilleries, premium beverage plants, sugar refineries, meat processing plants, general beverage factories, textile printing and dyeing mills, and similar facilities, cationic polyacrylamide demonstrates an efficacy that is several-or even tens-of times higher than that of anionic polyacrylamide, non-ionic polyacrylamide, or inorganic salts, as the wastewater from these sources typically carries a negative charge.
Cationic polyacrylamide is suitable for use with specialized sludge dewatering machinery, such as high-speed centrifuges, belt filter presses, and plate-and-frame filter presses. It is characterized by rapid flocculation, excellent flocculation results, resistance to compression and shear forces, strong floc cohesion, and easy detachment from filter cloths. Consequently, it achieves high dewatering rates, results in filter cakes with low moisture content, and requires minimal dosage, thereby significantly reducing operational costs for users. It can also be utilized to separate and purify suspended solids and turbidity from liquids such as hydrochloric acid and medium-concentration sulfuric acid. As a result, this product is widely employed for sludge dewatering in wastewater treatment plants, breweries, food processing facilities, tanneries, paper mills, petrochemical plants, metallurgical operations, and the chemical industry.
1. Wastewater Treatment: Primary Applications
When treating wastewater using inorganic coagulants and flocculants-such as aluminum salts or iron salts-if the volume of water to be treated exceeds the capacity of the clarification tank, or if other factors cause the flocculants in the water to settle too slowly (resulting in floc carryover), the addition of just 0.1–0.2 ppm of polyacrylamide (PAM) as a coagulation aid can significantly enhance the sedimentation effect. Furthermore, the Chemical Oxygen Demand (COD) and color indices of the treated water will also show marked improvement. It is important to note that the specific inorganic coagulants and flocculants used in conjunction with this product should be selected to ensure compatibility with its characteristics.
2. Sludge Concentration
The application of 0.3–2 ppm of additives can reduce the sludge-to-water ratio within biochemical tanks and sludge thickening tanks, thereby enhancing the utilization efficiency of these facilities. Sludge concentration levels can be increased from the range of 3–10 g/L to 30–100 g/L. This significantly reduces the volume of sludge requiring processing in subsequent dewatering stages, thereby boosting the operational efficiency of both sludge dewatering equipment and personnel.
3. Sludge Dewatering
All types of thickened sludge require dewatering using polyacrylamide (PAM). During the sludge dewatering process, both the required dosage of PAM and the resulting dewatering efficiency are contingent upon the specific type of sludge being treated; consequently, it is essential to conduct testing and selection procedures to identify the most suitable PAM product for each specific application.
Anionic Polyacrylamide
1. Primarily used as a flocculant: This product is suitable for treating wastewater containing suspended particulate matter-specifically coarse particles, high-concentration solids, and positively charged particles-as well as wastewater with a neutral or alkaline pH. Due to the presence of polar groups within its molecular chains, anionic polyacrylamide can adsorb suspended solid particles present in the water, thereby forming large flocculation bridges between the particles. Consequently, it accelerates the sedimentation of particles within suspensions, delivers a highly pronounced clarifying effect on the liquid phase, and facilitates filtration processes. This product is applicable across a wide range of water treatment sectors, including chemical wastewater treatment, industrial liquid waste disposal, municipal sewage treatment, public water supply systems, purification of high-turbidity water, sedimentation processes, coal washing, mineral processing, metallurgy, steel manufacturing, zinc and aluminum processing, and the electronics industry.
2. Applications in the Petroleum Industry: Widely utilized in oil exploration and extraction operations, including the preparation of drilling fluids (muds), the treatment of waste drilling muds, the prevention of fluid channeling, friction reduction, and the enhancement of oil recovery rates (tertiary oil recovery).
3. Used as a textile sizing agent: It offers excellent sizing stability, minimizes size shedding, reduces fabric breakage rates during processing, and results in a clean, high-quality fabric finish. 4. For the papermaking industry, the primary objective is to increase the retention rate of fillers, pigments, and similar materials, thereby minimizing raw material loss and environmental pollution. Secondly, it aims to enhance paper strength (encompassing both dry and wet strength). Furthermore, the use of polyacrylamide can improve the paper's tear resistance and porosity, thereby enhancing its visual and printing properties; it is also suitable for use in food and tea packaging papers.
