Polyacrylamide is widely employed in numerous sewage treatment plants. However, does polyacrylamide deteriorate when stored for extended periods or exposed to moisture? Many remain unaware of the criteria for determining polyacrylamide degradation. They mistakenly equate clumping with deterioration and subsequent ineffectiveness. This is not the case. In cases where polyacrylamide has clumped or become damp, provided you can dissolve the granules in water, the resulting solution will exhibit viscosity. This indicates the product remains effective. Should an uninformed individual discard the polyacrylamide at this stage, it would constitute a waste of resources. The shelf life varies significantly between different polyacrylamide types, largely due to their chemical structures. Categorically, anionic polyacrylamide generally possesses a longer effective period. Cationic polyacrylamide has a shelf life of one year, as stipulated by national regulations. Any product exceeding this period is considered past its expiry date. The degradation of polyacrylamide can be identified through two primary indicators: reduced viscosity and diminished flocculation efficacy.
What factors contribute to the degradation of polyacrylamide? Let us examine these collectively. Incomplete or uneven dissolution of polyacrylamide compromises its efficacy. Powdered polyacrylamide may be stored for over two years in a dry, cool environment. Once dissolved, polyacrylamide solutions have limited shelf life: non-ionic and anionic polymer solutions last no longer than one week, while cationic polyacrylamide solutions remain viable for no more than one day. Iron ions act as catalysts for the chemical degradation of all polyacrylamides. Therefore, during the preparation, transfer, and storage of polyacrylamide solutions, iron ion contamination must be minimised. Equipment in contact with the solution should ideally be constructed from stainless steel, plastic, fibreglass, or carbon steel coated with resin. Failure to do so will diminish the efficacy of the polyacrylamide.
To minimise costs and enhance economic efficiency, how can we prevent polyacrylamide from losing efficacy during use? Firstly, adhere to the principle of preparing polyacrylamide solutions immediately before use. Prolonged storage of pre-prepared solutions readily leads to degradation. Secondly, water temperature is critically important during solution preparation. When dissolving polyacrylamide, temperatures must not exceed 60°C. Excessive heat causes degradation, compromising performance. Beyond temperature, the quality of water used for dilution also significantly impacts efficacy. Clean tap water should be selected for preparing polyacrylamide solutions to optimise its performance.
