Alcohol‐free diphenyl oxide disulfonate middle‐phase microemulsion systems

Abstract

Diphenyl oxide disulfonate (DPDS) surfactants were successfully used to formulate Winsor Type III middlephase microemulsion systems with tetrachloroethylene (PCE) and decane. To our knowledge this is the first time that monochain DPDS surfactant phenyloxide monohexadecyl disulfonate surfactant (C16MADS) and commercially available DOWFAX 8390 were found to form middle-phase microemulsion systems with oils. Hydrophobic dioctyl sodium sulfosuccinate (Aerosol OT) was also used as a cosurfactant to lower the systems' hydropholic-liphophilic balance. Two organic acids (hydrophobic octanoic acid and hydrophilic L-tartaric acid) were used in place of the alcohol to formulate middle-phase microemulsion. The middle-phase microemulsion systems dramatically increased organic solubility when compared to micellar DPDS surfactant systems. Winsor Type I systems near the Type I-III boundary produced "super" solubilization for hydrophobic oils. Findings from this study enable us to improve DPDS solubilization enhancement of hydrophobic compounds.Properly formulated surfactant systems can greatly facilitate contaminant extraction from the geologic subsurface (1-11). Surfactant micelles increase contaminant solubility by micellar-enhanced contaminant solubility. Surfactants can also mobilize subsurface contaminants by forming middle-phase microemulsions (1).Twin-head diphenyl oxide disulfonate (DPDS) surfactants are desirable for environmental application because of high water solubility, low subsurface sorption and precipitation potential, and strong electrolyte resistance (i.e., their robustness). Numerous laboratory studies and several field tests have demonstrated the robust nature of these surfactants (12,13). Their classification as indirect food-grade additives is also advantageous when considering subsurface injection. However, the relatively low solubilization enhancement of DPDS surfactants limits their usefulness for hydrophobic nonaqueous phase liquids (NAPL) (13).The low solubilization capacity of DPDS surfactants can be attributed to their relatively high hydrophilicity. As very hydrophilic surfactants, they have high critical micelle concentration (CMC) values and the charge distribution is higher in their aggregates. This highly hydrophilic nature also makes it difficult for DPDS surfactants to form middlephase microemulsions with highly hydrophobic NAPL (14).Increasing the DPDS surfactants' solubilization capacity will increase their competitiveness with other surfactants, especially when considering their robust nature (e.g., low sorption, low viscosity, and high electrolyte resistance). In a previous study (13), we investigated several approaches for enhancing the solubilization potential of DPDS. We first tried to increase the compound's partitioning into micelles by adjusting micelle size and hydrophobicity. We attempted this by lengthening the hydrocarbon chain of the surfactant and by mixing DPDS surfactants with hydrophobic nonionic surfactants like alkyl phenyl ethoxylates. We next tried formulating middle-p...

Formulating middle‐phase microemulsions using mixed anionic and cationic surfactant systems

“…These systems not only failed to form middle-phase microemulsions for Y < 0.67 but also failed to form a Type II system in this same region. These results reflect the extremely hydrophilic nature of SHDPDS (17,30,31). While the SHD-PDS is too hydrophilic to form a middle-phase microemulsion in anionic-rich surfactant systems, middle-phase microemulsions occurred for all three oils on the cationic-rich side (Y ≥ 0.67), as reflected by IFT values less than 0.1 mN/m in Figures.…”

“…Since downward migration is a significant concern for dense oils (16,17), a highly efficient Type I microemulsion (where oil solubilization is high in the aqueous phase, but IFT values are higher than in a Type III system) is preferred for solubilizing these dense NAPL-an approach known as supersolubilization (16). Generally surfactant systems that exhibit the highest oil/water solubilization and lowest IFT in a Type III microemulsion system also show the highest solubilization in the supersolubilization region in a Type I system.…”

Surfactant-enhanced remediation of organic contaminated soil and water

“…In microemulsion, reduction in the micelle curvature allow increased oil solubilization in the core of these "swollen" micelles [199]. Solubilization capacity of these swollen micelles can be higher up to 1 or 2 orders magnitude than the regular micelle solubilization [200][201][202]. Supersolubilization is becoming more attractive in many applications like hard surface cleaners, detergency, surfactant enhanced remediation of oil contaminated sites etc.…”

Synthesis, Surface and Interfacial Properties of Dodecyl Diphenyl Oxide Disulfonate with Different Counterions

“…Due to the disulfonated structure of the ADPODS, precipitation in hard water is not observed as with common monosulfonated surfactants such as sodium dodecyl benzene sulfonate (SDBS) [1]. Many papers have reported on the physiochemical properties of sodium alkyl diphenyl oxide disulfonate, but few on the magnesium or calcium salts of these surfactants [2][3][4][5][6][7][8].…”