pH effects on Z-potential, particle size distribution and turbidity of polyelectrolyte solution Zetag 9014

The main applications of organic polyelectrolytes in potable water production are in flocculation, and in the dewatering of waste water treatment plant sludges. The water production processes are usually followed by sedimentation and filtration or centrifugation. Although with only slightly contaminated waters the sedimentation step may be omitted. The structure of the cationic polymer ZETAG 9014® under the influence of changes in pH of the medium was studied in an aqueous solution. Cationic polymer type ZETAG 9014® is structured under the influence of pH changes. Turbidimetry and Z-potentiometry methods were used to estimate the changes in the Z- potential, the particle size distribution (PSD), and the turbidity of 0.3 N cationic polyelectrolyte ZETAG 9014 solution, depending on the pH change over a wide range. Hydrochloric, nitric, sulfuric, phosphoric and acetic acids and the following bases - NaOH, KOH, NH4OH and Ca(OH)₂ were used as reagents by means of which the pH values were changed. As a criterion for the estimation of PSD the value – K was introduced, which characterizes the ratio of the standard deviation of the average particle size to the average particle size. In an alkaline medium, the cationic polyelectrolyte Zetag 9014 is relatively more stable. The zero charge point depends on the type of cation. The lowest pH value at which the zero charge on the surface is set is observed when NH₄OH is used, and the highest value is observed when Ca(OH)₂ is used. A sharp increase in the turbidity of the solution of the cationic polyelectrolyte Zetag 9014 is observed near the zero charge points. At low pH values there is an obvious tendency to decrease of the average particle size and narrowing of the PSD and, conversely, at higher pH values, the average particle size increases, and the PSD expands