Precipitation of cetyl (hexadecyl) pyridineum chloride using mono and divalent oxyanions

Experimental investigations have been carried out to observe the performance of precipitation behavior of potassium permanganate (KMnO4) and potassium dichromate (K2Cr2O7) in cetyl (hexadecyl) pyridineum chloride (CPC) solution. As in the case of Al3+-dodecylbenzenesulfonate systems [P. Somasundaran, K.P. Anathapadmanabhan, M.S. Celik, Langmuir 4 (1988) 1061-1063], the precipitation is found to be caused by interaction of CPC micelles with oxyanions. The counter oxyanions have a strong tendency to bind themselves to the surface of cationic CPC micelles. This lowered the free oxyanion concentration in solution. Therefore, to start precipitation, higher oxyanion concentration is required for higher CPC concentration. The effects of temperature, concentrations of both counter ions and CPC on the precipitation have been studied in detail. It has been observed that at CPC to KMnO4 concentration ratio of 1.0 (concentration of CPC and KMnO4 is 400 ppm), the percentage precipitation of CPC is around 99.3 at 30 °C. The percent precipitation of CPC decreases to about 94% when temperature increases to 70 °C at the same condition. The extent of CPC precipitation increases at the same experimental condition when K2Cr2O7 is used instead of KMnO4.