Adsorption of Nonionic Surfactants and Polyacrylate on Talc

摘要

The aim of the work was to understand the adsorption mechanism of nonionic blockcopolymers of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) on talc, and the competitive adsorption of the surfactant and polyacrylate (PAA). The influence of temperature, Ca(2+)-ions and chain length of surfactant on the adsorption isotherms were studied using the serum replacement technique. The solution behavior of the block copolymers in aqueous solution, such as micellization and clouding, was also investigated. PEO-PPO-PEO adsorbed fairly well onto bare talc surfaces. The adsorption isotherms were described by a Langmuir type equation. The specific adsorption increased as the number of hydrophilic PEO or hydrophobic PPO units decreased, but also when the temperature increased, especially if the surfactant was rather hydrophobic (PEO/PPO<1). The surfactants adsorb mainly due to hydrophobic interactions of the PPO chain. The free energies of adsorption were quite low.