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Pasadena, CA, United States

Campbell T.,Linde Robinson Laboratories | Hoffmann M.R.,Linde Robinson Laboratories
Separation and Purification Technology | Year: 2015

Perfluorosulfonates and carboxylates, C4 to C8 surfactants, are sonolytically degraded primarily at the vapor-water interface of cavitation bubbles. The observed pseudo first-order rate constants for the elimination of the perfluorosurfactants indicate that rates should be proportional to the degree of interfacial bubble-water partitioning. In fact, the sonochemical degradation rates of the more soluble and less hydrophobic perfluorobutane sulfonate, PFBS, and perfluorobutanoate, PFBA, were found to be slower than longer chain analogs due to their greater water solubility compared to the C8 counter parts. The observed degradation rate constants are found to increase with increasing power density. Enhanced degradation rates were observed for the C8 surfactants, PFOS (∼12%) and PFOA (∼23%) under simultaneous irradiation at 20 kHz and 202 kHz at a power combined power density of 250 W L-1. © 2015 Published by Elsevier B.V. Source


Balcerski W.C.,Linde Robinson Laboratories | Ryu S.Y.,Linde Robinson Laboratories | Hoffmann M.R.,Linde Robinson Laboratories
Separation and Purification Technology | Year: 2015

Niobium oxides (KNbO3, K4Nb6O17) were combined with nano-particulate CdS and Ni to form composite photocatalysts that are able to produce H2 gas from water/ethanol solutions under visible light illumination. Ni doping was shown to affect the Nb-O bonding states, and to compete with Cd for ion exchange sites, although the Ni/CdS-doped catalysts still were found to have higher photo-catalytic activity than composite potassium niobates with nanoparticle CdS deposits alone. XPS studies showed the loss of excess Cd2+, but not sulfur, during the course of the photoreaction for the KNbO3 support matrix, but significant loss of both Cd and S for the K4Nb6O17 support. © 2015 Published by Elsevier B.V. Source

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