Surface and bulk properties of surfactants used in fire-fighting

Abstract

All FC surfactants in this study generate very low surface tensions (< 20 mN m) which are comparable, and in some cases, lower than fully-fluorinated surfactant analogues. The complementary techniques (tensiometry and NR) allowed direct comparison to be made with NaPFO in terms of adsorption parameters such as surface excess and area per molecule. Surface tension data for these technical grade FC surfactants were not amenable to reliable interpretation using the Gibbs adsorption equation, however NR provided reliable results. SANS has highlighted how changes in surfactant head group structure can affect bulk properties. This work therefore provides fresh insight into the structure property relationships of some industrially relevant FC surfactants, highlighting properties which are essential for development of more environmentally friendly replacements.

Impact of a Hydrocarbon Surfactant on the Retention and Transport of Perfluorooctanoic Acid in Saturated and Unsaturated Porous Media

“…Lastly, the sorption of SDS by the sand has been characterized in our prior study. 38 Unlabeled PFOA (95% purity, CAS # 335-67-1) and SDS (99% purity, CAS # 151-21-3) were purchased from Sigma-Aldrich Co. 13 C 4 -PFOA was obtained from Wellington Laboratories Inc. Pentafluorobenzoic acid (98% purity, CAS # 602-94-8), which is neither a PFAS nor a surfactant, was obtained from Macklin Inc. (China). It was used as the nonreactive tracer (NRT) for all experiments.…”

“…Per- and poly-fluoroalkyl substances (PFAS) have become an emerging concern due to their high toxicity, long-term persistence, and worldwide distribution in various environmental media including atmosphere, water, soil, sediment, wastewater, biosolids, and even remote areas such as polar glaciers. − Sites where aqueous film-forming foam (AFFF) has been used, such as firefighter training areas and crash sites, have been identified as major source zones where PFAS concentrations in soil and groundwater are comparatively high. − AFFF is a mixture of both fluorocarbon surfactants (i.e., PFAS) and hydrocarbon surfactants that has been used to extinguish fires involving hydrocarbon fuels since the 1960s. ,− Many PFAS, such as perfluorooctanoic acid (PFOA), perfluoropentanoic acid, and perfluorooctane sulfonate (PFOS), have been detected in soil and groundwater where AFFF was used. ,,,− Nine classes of hydrocarbon surfactants have been identified in AFFFs, such as octylphenol polyethoxylates, linear alcohol ethoxylates, alkyl sulfates, and alkyl ether sulfates . It is therefore quite possible that hydrocarbon surfactants and PFAS may co-occur at some AFFF-contaminated sites.…”

Synthesis and Performance Analysis of New Hybrid Polymer Gel Based on Carboxymethyl Cellulose for Preventing Spontaneous Coal Combustion

“…In Figure 10(a), (b), and (c), the middle three curves show the FTIR spectra of the raw materials” sodium silicate, citric acid, and polyaluminum chloride. Figure 10(a), (b), and (c) show that the peak value of −OH was from 3439 to 3488 cm −1 , and the absorption peak between 1581 and 1730 cm −1 changed from the single peak of the matrix to the double peak of product in the reaction process from matrix to product, which indicates that new substances appeared and new chemical reactions occurred [23] …”

“…Figure 10(a), (b), and (c) show that the peak value of À OH was from 3439 to 3488 cm À 1 , and the absorption peak between 1581 and 1730 cm À 1 changed from the single peak of the matrix to the double peak of product in the reaction process from matrix to product, which indicates that new substances appeared and new chemical reactions occurred. [23] shows that for the SA-Al 3 + /WG cross-linked gel, the peak at 3477 cm À 1 was from the tensile vibration of À OH, the peak at 2336 cm À 1 was from the tensile vibration of CÀ H, and a new absorption peak appeared near 1084 cm À 1 , which was mainly due to hydrogen bonding between the molecules. [24] The peaks at 1649 and 1592 cm À 1 were asymmetric tensile vibration absorption peaks of À COONa, and the peak at 1611 cm À 1 was a common tensile vibration peak.…”

Studying surfactants adsorption on heterogeneous substrates

“…Neutron reflectivity, 5 neutron scattering 6 and ellipsometry 7 can probe the conformation of adsorbed surfactants. Ellipsometry and neutron reflectivity have been combined, 8 showing patchy or fully formed surfactant bilayers. Other techniques include NMR 9 and quartz crystal microbalance with dissipation (QCM-D).…”