Surface charge density of silica suspended in water-acetone mixtures

The net proton surface charge density of silica suspended in water-acetone mixtures was studied by potentiometric titration. LiCl and NaCl were used a s background electrolytes at concentrations of 10(-1), 10(-2), and 10(-3) m ol L-1. The results showed that acetone lowers the net proton surface charg e density of silica and that the greater the decrease, the greater the acet one concentration. The surface charge density of silica also is very sensit ive to the nature of the background electrolyte, LiCl producing much lower surface charge densities than NaCl. The concept of free energy of transfer (Delta G(t)(0)) of an electrolyte between two different solvents was applie d to explain the results in a qualitative manner. (C) 1999 Academic Press.