Microemulsion formation and detergency with oily soil

Abstract

The ultimate objective of this work was to form microemulsions with different oils at low salinity for the detergency process. In this study, three surfactants-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 at low salinity. Under a microemulsion-based formulation, the motor oil removal increased with increasing total surfactant concentration and the maximum oily soil removal was around 0.1% total surfactant concentration for all three types of fabrics-pure cotton, polyester/cotton (65/35), blend and pure polyester). Detergency was found to improve with increasing hydrophilicity of the fabric with cotton being the cleanest after washing and polyester the most difficult to clean. An interesting characteristic of microemulsion-based formulations is that a substantial fraction of oil removal was found to occur in the rinse step. In this work, the low oil removal in the wash step was found to result from the ultralow oil/water interfacial tension and the surfactant loss due to the surfactant adsorption onto the fabric surface. From the results, the number of rinses and the volume of water per rinse can profoundly affect detergency in these systems, and it was found that the higher the amount of rinse water, the lower the residual surfactant on the fabric surface. In this study, the effects of water hardness and builder on both the phase diagrams of aqueous microemulsions with motor oil and the laundry detergency of oil removal from a polyester/cotton blend was investigated. Water hardness and builder were found to insignificantly affect the microemulsion phase diagram with motor oil. A mixed surfactant system of 0.1% C₁₄-₁₅(PO ) ₃S0₄Na (Alfotera) and 5% C₁₂-₁₄H₂₅-₂₉O(E0) ₅H (Tergitol) at 4% salinity was used to study the effects of water hardness; the addition of any studied builder-sodium tripolyphosphate (STPP) or ethylenediaminetetraacetic acid (EDTA) - showed approximately the same effect on oil removal. From the detergency results, the total oil removal decreased with increasing water hardness while the interfacial tension (IFT) increased. When hard water was used in laundering, the total oil removal was improved at a certain level, even though an excess amount of STPP or EDTA was added in the selected formulation.