Absorption and recovery of n-hexane in aqueous solutions of fluorocarbon surfactants

n-Hexane is widely used in industrial production as an organic solvent. As an industrial exhaust gas, the contribution of n-hexane to air pollution and damage to human health are attracting increasing attention. In the present study, aqueous solutions of two fluorocarbon surfactants（FSN100 and FSO100） were investigated for their properties of solubilization and dynamic absorption of n-hexane, as well as their capacity for regeneration and n-hexane recovery by thermal distillation. The results show that the two fluorocarbon surfactants enhance dissolution and absorption of n-hexane, and their effectiveness is closely related to their concentrations in solution. For low concentration solutions（0.01%–0.30%）, the partition coefficient decreases dramatically and the saturation capacity increases significantly with increasing concentration, but the changes for both are more modest when the concentration is over 0.30%. The FSO100 solution presents a smaller partition coefficient and a greater saturation capacity than the FSN100 solution at the same concentration,indicating a stronger solubilization for n-hexane. Thermal distillation is a feasible method to recover n-hexane from these absorption solutions, and to regenerate them. With 90 sec heating at 80–85°C, the recovery of n-hexane ranges between 81% and 85%, and the regenerated absorption solution maintains its original performance during reuse. This study provides basic information on two fluorocarbon surfactants for application in the treatment of industrial n-hexane waste gases.

Fluorinated Surfactants and Fluorinated Polymer Materials(Ⅳ): Strategy for Solving PFOS Problems

Fluorinated alkyl substances are irreplaceable in many fields because of the special properties of fluorocarbon chains.Many efforts have been made to solve the historic problems of PFOS.In this paper,several strategies were discussed,including the possibilities in the methods of degradation,separation,recycling use,and reducing the using concentration.The most reliable one is to obtain replacement products of PFOS.Several kinds of replacement products were introduced and their feasibility of application was also discussed.

Effects of Hydroxyl Groups in Organic Ammonium Counterions on the Properties of Fluorinated Surfactants

The surface tension, foaming and viscosity for C7F15COO^-N^＋H（C2H4OH）χ（C2Hs）3-x and C8F17SO3- N^＋H（C2H4OH）χ（C2H5）3-χ （x = 0, 1, 2, 3） were measured to systematically study the effects of hydroxyl groups in organic ammonium counterions on the properties of perfluorooctanoates and perfluorooctanesulfonates. The results showed that the critical micelle concentration （cmc） and the surface tension at cmc （γcmc） were both increased with the increase of number of hydroxyl groups （χ） in the two series. The perfluorooctanesulfonate had smaller cmc but higher γ=cmc than perfluorooctanoate with the same counterion. The minimum molecular area of surface adsorption （Amin） of C8F17zSO3^-N^＋H（C2H4OH）χ（C2H5）3-χ were 0.64, 0.57, 0.63 and 0.72 nm^2 while the Amin values of C7F15COO^-N^＋H（C2H4OH）χ（C2H5）3-χ were 0.61, 0.62, 0.61 and 0.71 nm^2 when χ = 0, 1, 2 and 3, respectively. For the investigated systems of surfactants, the results of foam expansion ratio agreed with those of surface activity, while the 25% drainage time were consistent with the results of viscosity.

Study of Oil-Bearing Drill Cuttings Cleaning and De-Oiling Treatment Method for Shale Gas Reservoirs

Due to its extensive use in shale gas exploration and development,oil-based drilling fluids generate large amounts of oil-bearing drill cuttings during the drilling process.The large amount of oil-bearing drill cuttings generated during the drilling process can lead to serious secondary contamination.In this study,a wetting agent FSC-6 with good hydrophobic and oleophobic properties was synthesized to construct an efficient oil removal system.For the first time,the mechanism of this system was analyzed by using the theory of adhesion function,interfacial tension and wettability.At the same time,a combined acoustic-chemical treatment process was applied to the wastewater and slag generated after the cleaning of the oil-bearing drill cuttings.The experimental results show that the application of this pollution-free technology can effectively solve the environmental pollution and resource recovery problems of oil-bearing drill cuttings.It meets the standard of drilling chips with oil content less than 2%in SY/T7422-2018“Oil-based drilling fluid drilling chips treatment system for oil and gas drilling equipment”.

Experimental investigation on the spread of aqueous foam over ethanol surface

The presence of ethanol has an adverse effect on foam spreading,and ethanol fire is difficult to extinguish with aqueous fire-fighting foams.Thus,it is necessary to explore the foam formulation suitable for ethanol fuels and study the spreading behavior of foam over ethanol surface.In the current work,stable foams based on hydrocarbon surfactant(SDS),fluorocarbon surfactant(FC1157),and polymers(XG)were prepared by using the compressed-air foam system.The spreading behaviors of foam on polar ethanol and non-polar heptane surface were observed and compared.Furthermore,the effects of stabilizer concentrations,foam flow rates and expansion ratios on foam spreading performance were investigated,respectively.The results indicate that aqueous SDS foam can spread on the heptane layer continuously,but it is difficult to cover the ethanol surface.The addition of XG and FC1157 can synergistically improve the spreading performance of aqueous foam over ethanol.Depending on stabilizer concentrations,there are remarkable differences in foam spreading behaviors.Besides,different foam application parameters including expansion ratios and foam flow rates significantly affect the foam spreading rate,despite the same foam formulation.The research methods and results guide the optimal design of foam formulations as well as the practical application of aqueous foam for ethanol fire extinguishment.

p-Sulfonatocalix[4]arene-induced amphiphilic aggregation of fluorocarbon surfactant

Sulfonatocalix[4]arene lowers the critical aggregation concentration of fluorocarbon surfactant pronouncedly by a factor of ca.100 to form binary amphiphilic aggregates on the basis of host-guest complexation,which was identified by1H NMR spectroscopy,fluorescence spectroscopy,optical transmittance spectroscopy,dynamic laser scattering,high-resolution transmission electron microscopy,scanning electron microscopy,and surface tension experiments.Moreover,the resulting aggregates can respond to external stimuli,including temperature and inclusion of competitor guest.Therefore,the present system may have potential applications in drug delivery systems.

Strong synergistic effect of cationic hydrocarbon surfactant and novel nonionic tri-block short-chain fluorocarbon surfactant mixtures on surface activity, wettability and solubilization

Mixing hydrocarbon surfactants with fluorocarbon surfactants is still an important strategy to improve the economic benefits and performances of fluorocarbon surfactants and expand their range of application.Herein,we prepared a novel kind of hydrocarbon-fluorocarbon surfactant mixtures via mixing a cationic surfactant,cetyltrimethylammonium bromide(CTAB),with a tri-block nonionic short-chain fluorocarbon surfactant(F_(9)EG_(13)F_(9))in aqueous solution.The results showed that adding a small CTAB amount to F_(9)EG_(13)F_(9)(the molar fraction of CTAB in the mixture(x_(1))was 0.2)could greatly reduce its critical micelle concentrations(cmc)from 0.408mmol/L to 0.191 mmol/L.At this x_(1),the contact angle of the mixture was the minimum(57.7°)at 100 s on polytetrafluoroethylene film,which was even lower than that of F_(9)EG_(13)F_(9).Besides,CTAB/F_(9)EG_(13)F_(9) mixtures possessed better colloidal stability and solubilization ability toward hydrophobic dye(SudanІ)than F_(9)EG_(13)F_(9).The outstanding performances of binary surfactant mixtures benefited from the non-ideal mixing and strong synergistic effect evidence that CTAB/F_(9)EG_(13)F_(9) surfactant mixtures could be used in practical applications instead of individual F_(9)EG_(13)F_(9),thereby reducing the used cost of F_(9)EG_(13)F_(9).