An Experimental Study of the Effect of Temperature on Effective Charge Numbers and Diffusion Coefficients of Lignosulfonate.

Abstract

The counterion and ionic strength of the solution were varied as a function of temp. in a study that investigated the loss of charge on LS at elevated temp. (ca. 40 C). A method based on a convective diffusion process in a porous membrane was used to measure effective charge numbers and diffusion coefficients. The findings suggest that the loss of charge at ca. 40 C is independent of the counterion but dependent on ionic strength. The lower the Derbye length, i.e., the greater the ion strength, the lower the temp. at which the mol. becomes neutral. No evidence of aggregation of LS mol. was observed. It is concluded that the loss of charge at ca. 40 C occurs only when the mol. is a compact sphere, which suggests that the phenomenon is caused by changes in structured water near the surface of the macromolecule. (1 fig., 24 ref., 6 tab.)