The coagulation effect of polyferric sulfate at low temperature and low turbidity is better than other coagulants, and its habitual scale for pH value is also very wide, reaching 4 ~ 11. However, the coagulation process of polyferric sulfate still has its best coagulation conditions, that is, it will still be affected by the pH value of wastewater, waste water temperature and organic pollutant concentration.
When the concentration of organic matter in sewage, process and discharge specification are relatively fixed, we can judge the quality of polymerized ferric sulfate from the role of wastewater treatment. Assuming that the quality of polymerized ferric sulfate is fixed, we can judge the change of temperature concave convex to the coagulation of polymerized ferric sulfate through the change of water quality temperature.
After the test, we can conclude that the dissolution rate of polyferric sulfate accelerates with the rise of water temperature. When the wastewater temperature reaches about 70 ℃, polyferric sulfate forms a saturated solution, and the concentration of ferric ion is higher than 11% ~ 13%. The higher the reaction concentration of ferric ion, the faster the coagulation reaction speed. Of course, when the temperature continues to rise, the influence of salinity will affect the polymerization and reduce the coagulation performance.
With the decrease of temperature (below 20 ℃), polyferric sulfate will inhibit the hydrolysis of polyferric sulfate, weaken the Brownian motion between trace molecules in water, and reduce the adsorption viscosity of colloid, resulting in the weakening of the sedimentation rate of flocs composed of suspended particles adsorbed by polynuclear complexes. The solubility of polyferric sulfate will decrease with the decrease of temperature, resulting in poor coagulation. When the temperature is as low as about 2 ℃, the hydrolysis speed of polyferric sulfate will be particularly slow. Therefore, in the winter water treatment process in the north, thermal insulation methods and indoor thermal insulation are selected for the feeding demand of polyferric sulfate to ensure its coagulation effect.