Synthesis and application of non- bioaccumulable fluorinated surfactants: a review

Due to negative effects of conventional fluorinated surfactants with long perfluorocarbon chain(C_(x)F_(2x+1),x≥7)like perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),these conventional long perfluorocarbon chain surfactants have been restricted in many industrial applications.Nowadays,their potential non-bioaccumulable alternatives have been developed to meet the requirements of environmental sustainable development.In this paper,the recent advances of potential non-bioaccumulable fluorinated surfactants with different fluorocarbon chain structures,including the short perfluorocarbon chain,the branched fluorocarbon chain,and the fluorocarbon chain with weak points,are reviewed from the aspects of synthesis processes,properties,and structure-activity relationships.And their applications in emulsion polymerization of fluorinated olefins,handling membrane proteins,and leather manufacture also are summarized.Furthermore,the challenges embedded in the current non-bioaccumulable fluorinated surfactants are also highlighted and discussed with the hope to provide a valuable reference for the prosperous development of fluorinated surfactants.

Efficient promotion of methane hydrate formation and elimination of foam generation using fluorinated surfactants

Methane hydrate preparation is an effective method to store and transport methane.In promoters to facilitate methane hydrate formation,homogeneous surfactant solutions,sodium dodecyl sulfate(SDS)in particular,are more favorable than heterogeneous particles,thanks to their faster reaction rate,more storage capacity,and higher stability.Foaming,however,could not be avoided during hydrate dissociation with the presence of SDS.This paper investigated the ability of five fluorinated surfactants:potassium perfluorobutane sulfonate(PBS),potassium perfluorohexyl sulfonate(PHS),potassium perfluorooctane sulfonate(POS),ammonium perfluorooctane sulfonate(AOS),and tetraethylammonium perfluorooctyl sulfonate(TOS)to promote methane hydrate formation.It was found that both PBS and PHS achieve a storage capacity of 150(V/V,the volume of methane that can be stored by one volume of water)within 30 min,more than that of SDS.Cationic ions and the carbon chain length were then discussed on their effects during the formation.It was concluded that PBS,PHS,and POS produced no foam during hydrate dissociation,making them promising promoters in large-scale application.

Effect of a synthesized anionic fluorinated surfactant on wettability alteration for chemical treatment of near-wellbore zone in carbonate gas condensate reservoirs

The pressure drop during production in the near-wellbore zone of gas condensate reservoirs causes condensate formation in this area.Condensate blockage in this area causes an additional pressure drop that weakens the effective parameters of production,such as permeability.Reservoir rock wettability alteration to gas-wet through chemical treatment is one of the solutions to produce these condensates and eliminate condensate blockage in the area.In this study,an anionic fluorinated surfactant was synthesized and used for chemical treatment and carbonate rock wettability alteration.The synthesized surfactant was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.Then,using surface tension tests,its critical micelle concentration(CMC)was determined.Contact angle experiments on chemically treated sections with surfactant solutions and spontaneous imbibition were performed to investigate the wettability alteration.Surfactant adsorption on porous media was calculated using flooding.Finally,the surfactant foamability was investigated using a Ross-Miles foam generator.According to the results,the synthesized surfactant has suitable thermal stability for use in gas condensate reservoirs.A CMC of 3500 ppm was obtained for the surfactant based on the surface tension experiments.Contact angle experiments show the ability of the surfactant to chemical treatment and wettability alteration of carbonate rocks to gas-wet so that at the constant concentration of CMC and at 373 K,the contact angles at treatment times of 30,60,120 and 240 min were obtained 87.94°,93.50°,99.79°and 106.03°,respectively.However,this ability varies at different surfactant concentrations and temperatures.The foamability test also shows the suitable stability of the foam generated by the surfactant,and a foam half-life time of 13 min was obtained for the surfactant at CMC.

Synthesis and combined properties of novel fluorinated cationic surfactants derived from hexafluoropropylene dimer

Three novel fluorinated cationic surfactants were prepared by adopting perfluoro-2-methy1-2-pentene as raw substrate. The as-obtained fluorinated cationic surfactants exhibited excellent surface properties, all of them can reduce the surface tension of water to below 20.00mN/m at the critical micelle concentrations （CMC）. The incorporation of SDS, AOS, APG or LAB into 2-（4-（3,3,4,4,5,5,5-heptafluoro- 2,2-bis（trifluoromethyl）pentyl）benzamido）-N,N-dimethylethana-mine oxide 4a could generate much lower CMC and surface tension value at the CMC than individual 4a. Especially, the surface tension values of that combined APG/4a can be reduced to 17.31 mN/m. The excellent surface activities and their remarkable compatibility to various types of hydrocarbon surfactants make them as sustainable alternatives to PFOA （perfluorooctanoic acid, C7F15CO2H） and PFOS （perfluorooctane sulphonate, C8F17SO3X, with X = K, Na, H）.

Synthesis and Surface Activity Study of a Novel Branched Fluorinated Anion Surfactant with CF_(3)CF_(2)CF_(2)C(CF_(3))_(2) Group

A novel branched fluorinated anion surfactant 4-(3,3,4,4,5,5,5-heptafluoro-2,2-bis-trifluoromethyl-pentyl)-benzene lithium phosphonate was successfully synthesized via a four-step route using perfluoro-2-methyl-2-pentene as starting material.The surface activity was investigated.The result showed that the cmc value of the surfactant in water is about 1.5×10^(−2) mol/L at 298 K and the surface tension of the aqueous solution is 19.2 mN/m at the cmc.

Strategies for synthesizing non-bioaccumulable alternatives to PFOA and PFOS

This minireview describes the strategies for synthesis of fluorinated surfactants potentially non- bioaccumulable. Various strategies have been focused on （Ⅰ） reducing the length of the perfluorocarbon chain, （Ⅱ） introducing hereto atoms into the fluorocarbon chain, （Ⅲ） introducing branch （herein and after branch means the fluoro-carbon chain section is not straight）. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above strategies led to various highly fluorinated （perfluorinated or not perfluorinated） surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid （PFOA） and perfluorooctane sulphonate （PFOS）.