Abstract
The ultimate objective of this work was to form microemulsions with motor oil at low salinity for detergency application. Three surfactants of alkyl diphenyl oxide disulfonate (ADPODS, Dowfax 8390), bis (2-ethylhexyl) sulfosuccinic acid sodium salt (AOT) and sorbitan monooleate (Span 80) were used to obtain a proper balance between hydrophobicity and hydrophilicity in order to form microemulsions with motor oil. The mixed surfactant system of 1.5 wt% Dowfax 8390, 5 wt% AOT and 5wt% Span 80 was found to exhibit a Winsor Type III microemulsion (middle phase) at a very low salinity of 2.83%. With this selected formulation, detergency performance increased with increasing active surfactant concentration and the maximum oily soil removal was found at around 0.1% active surfactant on all three types of fabrics (pure cotton, polyester/cotton (65/35) blend and pure polyester). Moreover, for any given active surfactant concentration, % detergency and % oil removal on pure cotton was slightly higher than those on the other two types of fabrics and the lowest % detergency was found on the pure polyester. Interestingly, increasing amount of rinsing water was found to affect insignificantly the oil removal efficiency. In addition, the detergency performance was optimized with twice rinse steps.
