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Short‐chain fluorocarbon surfactants grafted with alcohol, carboxyl and ester functional groups were prepared by quaternization with short‐chain perfluorobutyl sulfonyl fluoride as raw material. The structures of surfactants were characterized by infrared spectroscopy, nuclear magnetic resonance and mass spectrum. The surface activity, micelle formation process and micelle aggregation behavior of surfactants were studied by surface tensiometer, dynamic light scattering particle size analyzer and fluorescent spectrophotometer. The results show that the critical micelle concentration (CMC) of surfactants are 19.3, 7.8 and 2.2 mmol L−1, and the surface tension of the surfactant solution at CMC are as low as 17.3, 19.2 and 18.5 mN m−1, respectively. The standard Gibbs free energy (ΔGm0 ${\Delta G_{\rm{m}}^0 }$) values of surfactants are negative, and the absolute values of ΔGm0 ${\Delta G_{\rm{m}}^0 }$ are less than the standard Gibbs adsorption energy (ΔGa0 ${\Delta G_{\rm{a}}^{\rm{0}} }$), illustrating that the adsorption process is easier than the micelle formation process. In addition, the size distribution of the aggregates is much larger than that of spherical micelles, showing that the surfactant self‐assembled into larger aggregates in solution. The grafted hydrophilic functional groups show a significant effect on the performance of surfactants. The ester‐based surfactant has a lower CMC value, which has the advantages of small dosage, good economy and excellent application value. [ABSTRACT FROM AUTHOR]

Surface properties of three fluorocarbon surfactants with different carbon chain lengths were studied at low pressures of 94.6, 74.1 and 61.0 kPa, respectively. The results showed that the saturation adsorption capacity and the critical micelle concentration (CMC) decreased, while the average molecular area (AS) and the surface tension at CMC (γCMC) of fluorocarbon surfactants increased with decreasing pressure. The surface tension (γ) decreased with the decrease of pressure when the concentration of fluorocarbon surfactants was low. However, γ tended to be stable and increased with the drop of pressure when the concentration of surfactants was close or reach to CMC. In addition, the foaming and spreading performance of fluorocarbon surfactants decrease with the decrease of pressure, and the combination of fluorocarbon and hydrocarbon surfactants is beneficial to the improvement of performance (mixed systems: foam expansion E>6, 25% drainage time t25%>241 s, 1/2 defoaming time t1/2>851 s, spreading amount Vs>223 μL, spreading time ts<2 s). Further fire extinguishing experiment found that the influence of low pressure environment on fuel combustion characteristics is the key factor to determine fire extinguishing performance, while the influence of aqueous film‐forming foam (AFFF) performance is small. And AFFF based on the environmental‐friendly surfactant C4F9SO2NH(CH2)2N+(CH3)2CH2BrCH2OH (FC‐4) is an effective fire extinguishing agent under low pressure. [ABSTRACT FROM AUTHOR]

Aqueous film‐forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long‐chain fluorinated surfactants have been banned by most countries because of their persistence, bio‐accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short‐chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short‐chain fluorosurfactant‐based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn‐back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn‐back time is more than 15.18 min. The results imply a potential application prospect of the short‐chain fluorinated surfactants in AFFFs. [ABSTRACT FROM AUTHOR]

A novel short fluorocarbon chain cationic surfactant has been synthesized to reduce the bioaccumulation of traditional fluorocarbon surfactants and maintain excellent surface properties simultaneously. The structure, surface activity, and micelle formation of surfactants have been investigated by surface tension, conductivity, dynamic light scattering, steady‐state fluorescence, Fourier transform infrared spectroscopy, and Nuclear magnetic resonance. The novel surfactant (yield more than 81%) exhibited good surface activity, the critical micelle concentration and surface tension were below 2.35 mmol L−1 and 20.54 mN m−1 in the range of temperature from 288 to 303 K, respectively. The surface tension decreased to 17.45 mN m−1 with an increase in temperature. The thermodynamic parameters (ΔGm0, ΔHm0 and ΔSm0) of micellization for surfactants were evaluated, which implying the micellization process was contributed primarily by the entropy driving. In addition, the aggregation behavior of surfactants was also studied in detail, which demonstrated a small micelle aggregation number of 9.40 and large size distribution of 164–342 nm. [ABSTRACT FROM AUTHOR]

In order to purify phosphoric acid, the suspension melt crystallization process was studied. The suspension crystallization experiments were carried out with 80, 84 and 88 wt% phosphoric acid melt at the cooling rates of 0.05, 0.1 and 0.2 K/min, respectively. Sweating experiments were executed for various crystals obtained in suspension crystallization step. The purification effects of the sweating parameters including sweating time, initial inclusion amount and initial impurity content were studied. The inclusion fraction increases with the increase in cooling rate. The inclusion fraction of the crystals which were formed with feed concentration of 84 wt% phosphoric acid melt is lowest among the three feed concentrations. Different impurities have different purification performances during sweating. High inclusion amount and low impurity concentration favor the purification of H3PO4·0.5H2O crystals during sweating. [ABSTRACT FROM AUTHOR]