Gravimetric monitoring of nonionic surfactant adsorption from nonaqueous media onto quartz crystal microbalance electrodes and colloidal silica

Abstract

The adsorption from benzene of a series of monodisperse poly(ethylene glycol) monododecyl ethers (C12En, n = 3, 5, and 8) and a polydisperse nonyl phenol ethoxylate with an average ethylene oxide chain length of 5 (N5) onto gold and silicon dioxide surfaces has been investigated in situ using quartz crystal microgravimetry (QCM). The frequency shifts caused by surfactant adsorption onto the QCM electrodes, as a function of the equilibrium surfactant concentration, cannot be described by Langmuir adsorption. The introduction of a concentration-dependent term to the frequency shift revealed a frequency dependence on surfactant concentration. This suggests contributions from the bulk solution p..