Degradation, Transfer of Polyacrylamide Floculents and Aquatic Ecosystem Impacts
08-01-2026
1. Introduction
Polyacrylamide (PAM) is a linear water-soluble polymer formed by the polymerization of acrylamide monomers. As a high-efficiency flocculant, PAM has the advantages of strong flocculation ability, wide application range, and low dosage. It is widely used in urban sewage treatment, industrial wastewater treatment, drinking water purification, mineral processing, papermaking, and other fields . In the process of application, PAM floculants can effectively aggregate suspended solids in water, accelerate the sedimentation of suspended particles, and thus improve the efficiency of solid-liquid separation.
2. Degradation Mechanisms of Polyacrylamide Floculents
The degradation of PAM floculents in the environment is a complex process involving physical, chemical, and biological factors. The main degradation mechanisms include physical degradation, chemical degradation, and biological degradation.
2.1 Physical Degradation
Physical degradation refers to the breakage of PAM molecular chains due to physical factors such as shear force, ultraviolet radiation, and temperature changes. In the process of water treatment and transportation, PAM floculants are often subjected to strong shear forces, which can cause the breakage of molecular chains and reduce the molecular weight of PAM . Ultraviolet radiation is another important factor causing physical degradation of PAM. Ultraviolet rays can break the covalent bonds in PAM molecular chains, leading to the degradation of PAM. In addition, temperature changes can also affect the stability of PAM molecular chains. High temperatures can increase the kinetic energy of molecules, accelerate the movement of molecular chains, and thus increase the probability of molecular chain breakage.
2.2 Chemical Degradation
Chemical degradation refers to the chemical reaction between PAM and other substances in the environment, resulting in the breakage of molecular chains or the change of chemical structure. The main chemical degradation reactions of PAM include hydrolysis, oxidation, and reduction. Hydrolysis is the most common chemical degradation reaction of PAM. In the presence of water, the amide groups in PAM molecular chains can be hydrolyzed into carboxyl groups, resulting in the change of the charge properties and flocculation performance of PAM . Oxidation degradation is another important chemical degradation reaction of PAM. Oxidants such as oxygen, ozone, and hydrogen peroxide in the environment can oxidize the carbon-carbon bonds in PAM molecular chains, leading to the breakage of molecular chains. Reduction degradation is relatively rare, and it mainly occurs in the presence of strong reducing agents.
2.3 Biological Degradation
Biological degradation refers to the degradation of PAM by microorganisms in the environment. Microorganisms such as bacteria, fungi, and algae can secrete enzymes that decompose PAM, breaking down PAM molecular chains into small molecular substances. The biological degradation of PAM is a slow process, and its degradation rate is affected by many factors such as the type and concentration of microorganisms, environmental temperature, pH value, and nutrient conditions . At present, the research on the biological degradation of PAM is still in the preliminary stage, and the types of microorganisms that can effectively degrade PAM and their degradation mechanisms need to be further studied.
3. Transfer Processes of Polyacrylamide Floculents and Their Degradation Products
After entering the environment, PAM floculants and their degradation products will undergo a series of transfer processes, including migration in water bodies, adsorption and desorption in sediments, and migration and transformation in soil. These transfer processes directly affect the distribution and environmental risks of PAM floculants and their degradation products.
3.1 Migration in Water Bodies
PAM floculants and their degradation products can migrate in water bodies with the flow of water. The migration rate and distance are affected by many factors such as the molecular weight of PAM, the concentration of suspended solids in water, and the flow rate of water. In general, the smaller the molecular weight of PAM, the faster the migration rate in water bodies. The presence of suspended solids in water can adsorb PAM floculants and their degradation products, reducing their migration rate. In addition, the flow rate of water is also an important factor affecting the migration of PAM floculants and their degradation products. The higher the flow rate of water, the farther the migration distance.
3.2 Adsorption and Desorption in Sediments
Sediments are an important sink for PAM floculants and their degradation products in water bodies. PAM floculants and their degradation products can be adsorbed on the surface of sediments through physical adsorption, chemical adsorption, and ion exchange. The adsorption capacity of sediments for PAM floculants and their degradation products is affected by many factors such as the composition and structure of sediments, the pH value of water, and the concentration of PAM. Under certain conditions, the adsorbed PAM floculants and their degradation products can be desorbed from the sediments and re-enter the water bodies, causing secondary pollution.
3.3 Migration and Transformation in Soil
When PAM floculants and their degradation products enter the soil with sludge disposal or irrigation, they will undergo migration and transformation in the soil. The migration of PAM floculants and their degradation products in the soil is mainly affected by the soil texture, soil moisture content, and the adsorption capacity of soil colloids. In addition, PAM floculants and their degradation products can also undergo transformation reactions such as hydrolysis and oxidation in the soil, which affect their environmental behavior and ecological risks.
4. Research Gaps and Future Research Directions
Although great progress has been made in the research on the degradation, transfer, and aquatic ecosystem impacts of PAM floculents, there are still some research gaps that need to be further studied.
First, the current research on the degradation mechanisms of PAM floculants is mainly focused on a single degradation pathway, and the combined effects of multiple degradation pathways are not fully considered. In the actual environment, PAM floculants are affected by multiple physical, chemical, and biological factors at the same time, and the degradation process is more complex. Therefore, it is necessary to strengthen the research on the combined effects of multiple degradation pathways and reveal the comprehensive degradation mechanisms of PAM floculants in the environment.
Second, the research on the transfer processes of PAM floculants and their degradation products in the environment is mainly focused on the laboratory scale, and the research on the field scale is relatively lacking. The transfer processes of PAM floculants and their degradation products in the actual environment are affected by many factors such as hydrological conditions, geological conditions, and ecological conditions. Therefore, it is necessary to carry out field monitoring and research, and reveal the transfer rules of PAM floculants and their degradation products in the actual environment.
Third, the current research on the impacts of PAM floculants and their degradation products on aquatic ecosystems is mainly focused on the individual and population levels of aquatic organisms, and the research on the community and ecosystem levels is relatively lacking. The impacts of PAM floculants and their degradation products on aquatic ecosystems are comprehensive and systematic, and it is necessary to study from the community and ecosystem levels to fully understand the ecological risks of PAM floculants.
In the future, the research in this field should focus on the following directions: (1) Strengthen the research on the combined effects of multiple degradation pathways of PAM floculants and reveal the comprehensive degradation mechanisms in the environment. (2) Carry out field monitoring and research on the transfer processes of PAM floculants and their degradation products, and reveal the transfer rules in the actual environment. (3) Strengthen the research on the impacts of PAM floculants and their degradation products on aquatic ecosystems from the community and ecosystem levels, and fully understand the ecological risks. (4) Establish a comprehensive risk assessment system for PAM floculants and develop effective source control and process optimization technologies to ensure the safe application of PAM floculants and the protection of aquatic ecosystems.
Let's look forward to further research on PAM together - Shenyang Jiufang Technology Co., Ltd