Synthesis and Surface Properties of Photoresponsive Gemini Surfactants: Implication for Remediating PAHs-Contaminated Groundwater

Abstract

The efficient utility of surfactants remains a daunting task for groundwater remediation. In this study, we have synthesized a conventional p h o t o r e s p o n s i v e s u r f a c t a n t 4 -[ 4 -[ ( 4 -b u t y l p h e n y l ) a z o ] p h e n o x y ]butyldimethylethylammonium bromide (AzoPB) and a gemini photoresponsive surfactant N 1 ,N 2 -bis [4-[4-[(4-butylphenyl)azo]phenoxy]butyl]-N 1 ,N 2 -tetramethylethane-1,2-diammonium bromide (AzoPBT) for solubilizing PAHs in groundwater. The two surfactants' photosensitivity, surface properties, and solubilization/release ability for phenanthrene (Phe) and acenaphthylene (Ace) were studied in detail. Under UV-light irradiation for 15−20 s, the two surfactants can be converted from trans to cis, while cis-to-trans isomerization can be achieved under visible-light irradiation for 1 min. Compared to AzoPB, AzoPBT exhibited strong surface properties such as lower critical micelle concentration (0.52 mM), surface tension (γ, 28.94 mN•m −1 ), minimum area (A min , 1.72 × 10 −8 nm 2 ), and higher maximum adsorption (Γ max , 96.55 mol•m −2 ). The solubility of Phe and Ace in the AzoPBT aqueous solution (12.84 and 14.27 mg/L) was much higher than that in the AzoPB aqueous solution (7.51 and 8.77 mg/L) and gradually increased as the surfactant concentration increased in both aqueous solutions. Compared to AzoPB, gemini surfactant AzoPBT exhibited stronger solubilization ability. After four cycles of cis−trans isomerization conversion, AzoPBT could still reduce the hydrophobicity of Phe in natural groundwater, although the solubility of Phe decreased slightly. Additionally, the release capacity of AzoPBT was significantly higher than that of AzoPB during the cyclic solubilization-release process. The results indicated that gemini photoresponsive surfactants should be preferable to conventional photoresponsive surfactants for groundwater remediation due to their higher solubilization and release efficiency for Phe in the cyclic solubilization and release process, which can improve repair efficiency, minimize secondary pollution, and reduce remediation costs.

Switchable Pickering Emulsions Stabilized via Synergistic Nanoparticles–Superamphiphiles Effects and Rapid Response to CO2/N2

“…Such emulsions can be switched between demulsification and emulsification by applying a variety of triggers, including by changing the pH, − inducing redox reactions, − light irradiation, − applying magnetic field, − changing temperature, , and bubbling carbon dioxide/nitrogen gas (CO 2 /N 2 ). − However, surfactants responsive to oxidants/reductants or acids/bases often lead to environmental pollution. In contrast, CO 2 /N 2 -responsive surfactants offer a mild trigger condition that is nontoxic and cost-effective.…”

Properties and Aggregation Behavior of Gemini Surfactants for Heavy Oil Recovery in High Temperature and Salinity Conditions

“…Gemini surfactants have attracted increasing attention due to their unique structure, high surface/interface activity, better wettability, lower critical micelle concentration, and unusual rheological behaviors. − It is due to these characteristics that Gemini surfactants have gained potential applications in many fields, including EOR. − Mpelwa et al prepared the new Gemini surfactants EGSs, and they found that the surfactants could reduce the interfacial tension (IFT) to ultralow values (10 –3 mN/m) at a low concentration of 0.5 wt %, and core flooding experiments showed that the EGS1 could result in at least 12.3% of additional oil recovery after water flooding in the reservoir with high salinity. Liu et al synthesized a series of Gemini surfactants BA-n for the oilfield with high salinity.…”