Real Time Study of Detergent Concentration Influence on Solid Fatty Acid Film Removal Processes
Résumé
Cleaning in an aqueous solution is a complex mechanism which depends on several parameters. The quartz crystal microbalance (QCM) technique was used to investigate the detachment, using an anionic and a nonionic detergents, of stearic acid (C18H36O2) films deposited on gold-coated quartz surfaces. The cleaning mechanism was observed in real time by measuring the frequency of a quartz crystal during the fatty acid film removal. These observations reveal two successive phenomena: firstly, adsorption and absorption of water and detergent on the stearic acid layer and, secondly, the detachment of the fatty acid layer. A relationship between removal time and detergent concentration was highlighted: fatty acid removal time decreases as detergent concentration increases until an asymptotic value is reached. Initial contamination greatly influences cleaning duration. Increased sample contamination actually leads to increased removal time. However, no real correlation between the two parameters can be established. As a result, optimal parameters can be determined for each detergent, thus the QCM technique appears to be of great interest in monitoring and optimising cleaning protocol.