Facile identification of fluorosurfactant category in aqueous film-forming foam concentrates via optimized^(19)F NMR

Aqueous film-forming foams(AFFFs)are the primary source of toxic perfluoroalkyl and polyfluoroalkyl substances(PFAS)in wastewater.Thus,it is urgent to develop a facile and fast method for identifying fluorosurfactants in commercially available AFFFs.In this work,fluorine nuclear magnetic resonance(^(19)F NMR)spectroscopy was optimized to measure AFFFs directly with the extra addition of 5%D_(2)O as the locking reagent,and high-quality spectra could be acquired within 4 min(0.1%fluorosurfactant content).Recovery experiments demonstrated that the use of different AFFFs had no marked influence on the quantitative analysis of fluorosurfactants.Such method works with low-field NMR spectroscopy(1.4 T)as well.Two-dimensional(2D)^(19)F COSY NMR was used to make signal assignments for different fluorosurfactant derivatives.The optimized ^(19)F NMR could quantify the commercially available fluorosurfactants in different AFFFs,identify them being in either the perfluorooctane sulfonate(PFOS)or fluorotelomer sulfonic acid(FTS)categories,and distinguish the head-group of PFOS and FTS derivatives,which exhibits great potentials in the developments of relevant commercial detections.

Study of the relationship between the local geometric structure and the stability of La_(0.6)Sr_(0.4)MnO_(3-δ) and La_(0.6)Sr_(0.4)FeO_(3-δ)electrodes

Sr-substituted ABO_3 perovskite oxides such as La_(0.6) Sr_(0.4 )Mn_(O3-δ)(LSM) and La_(0.6) Sr_(0.4) FeO_(3-δ)(LSF) are widely used as oxygen electrode materials in solid oxide cells. The substituted Sr is not adequately stable under the operating conditions, because of the surface segregation of Sr. Herein, we focused on investigating the relationship between the local geometric structure due to Sr substitution and stability of LSM and LSF. We characterized the local geometric structure of Sr atoms via X-ray absorption spectroscopy. A greater Debye-Waller factor and a longer bond length of both the second and third Sr-O shells were observed in LSF, which demonstrates that LSF has a higher local structural disorder and that Sr in LSF requires less energy to segregate. After 20 h of heat treatment in the presence of a Fe-Cr alloy interconnect, the Sr/La molar ratio on LSF was observed to be much larger than that on LSM. This result unequivocally suggests that Sr in LSF is not as stable as in LSM, and the reaction between Sr and Cr accelerates the Sr surface segregation in LSF.

Electroplating titanium film on 316L stainless steel in LiCl–KCl–Ti^x+(2

To improve the anti-corrosion properties of 316 L stainless steel,titanium(Ti)metal films were electroplated on it using Li Cl–KCl molten salts as the electrolyte,and low-valence Tix+(2<x<3)as the solute.The solute was produced by the reaction of Ti4+and Ti0 via mixing K2TiF6,and Ti metal(sponge Ti)in the melts.Anti-corrosion test has shown significant enhancement in the stability of the Ti-coated 316 L due to the presence of Ti film.However,the anti-corrosion properties did not enhance with an increase in the thickness of the Ti layers owing to a possible defect in the thicker Ti layers.

A perspective on hydrogen production via high temperature steam electrolysis

High temperature （700-900 ℃） steam electrolysis （HTSE） based on solid oxide electrolysis cells （SOECs） has been val- ued as an efficient and clean path for large scale hydrogen production with nearly zero carbon emissions, compared with the traditional paths of steam methane reforming or coal gasi- fication.