Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr(III) passivation baths

Conversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and electrochemical impedance spectroscopy measurements at open circuit potential conditions in 3.5 g/L NaCl solutions. The main objective was to assess the benefits brought by EPT using electrochemical methods. Cr (III) passivation baths regenerated using the EPT process have been compared to the bath used in a local industry as well as to fresh and spent baths. According to the results, the samples passivated in the EPT regenerated bath showed a significant improvement in their electrochemical behaviour compared to the samples passivated in the spent baths. This study concluded the suitability of EPT for regenerating Cr (III) passivation baths

Vocabulario forestal [galego-español-inglés]

Deputación de Lugo. Vicepresidencia Primeir

Perfluorinated alkyl substances (PFASs) in northern Spain municipal solid waste landfill leachates

Landfill leachates have been recognized as significant secondary sources of poly- and perfluoroalkyl substances (PFASs). This study presents data on the occurrence and concentration of 11 perfluoroalkyl carboxylates (PFCAs) and 5 perfluoroalkyl sulfonates (PFSAs) in leachates from 4 municipal solid waste landfill sites located across northern Spain. To the best of our knowledge, this is the first report of the presence of PFASs in Spanish landfill leachates. Two of the landfill sites applied on-site treatment using membrane bioreactors (MBR), and its effect on PFASs occurrence is also reported. Total PFASs (∑PFASs) in raw leachates reached 1378.9 ng/L, while in treated samples ∑PFASs was approximately two-fold (3162.3 ng/L). PFCAs accounted for the majority of the detected PFASs and perfluorooctanoic acid (PFOA) was the dominant compound in raw leachates (42.6%), followed by shorter chain PFHxA (30.1%), PFPeA and PFBA. The age of the sites might explain the PFASs pattern found in raw leachates as all of them were stabilized leachates. However, PFASs profile was different in treated samples where the most abundant compound was PFHxA (26.5%), followed by linear perfluorobutane sulfonate (L-PFBS) (18.7%) and PFOA (17.7%). The overall increase of the PFASs content as well as the change in the PFASs profile after the MBR treatment, could be explained by the possible degradation of PFASs precursors such as fluorotelomer alcohols or fluorotelomer sulfonates. Using the volume of leachates generated in the landfill sites, that served 1.8 million people, the discharge of 16 ∑PFASs contained in the landfill leachates was estimated as 1209 g/year.The authors thank financial support from the Spanish Ministry of Economy and Competitiveness (Project CTM2013-44081-R)

Nanofiltration separation of polyvalent and monovalent anions in desalination brines

This work, as part of a global membrane process for the recovery of alkali and acids from reverse osmosis (RO) desalination brines, focuses on the nanofiltration (NF) separation of polyvalent and monovalent anions, more specifically sulfate and chloride. This pretreatment stage plays a key role in the whole recovery process. Working with model brines simulating the concentration of RO concentrates, 0.2–1.2 M chloride concentration and 0.1 M sulfate concentration, the experimental performance and modeling of the NF separation is reported. The study has been carried out with the NF270 (Dow Filmtec) membrane. The effect of operating pressure (500–2000 kPa), ionic strength (0.4–1.3 M) and chloride initial concentration (0.2–1.2 M) on the membrane separation capacity has been investigated. Finally, the Donnan Steric Pore Model (DSPM) together with experimentally determined parameters, effective pore radius (rp), thickness of the membrane effective layer (d) and effective membrane charge density (Xd), was proved accurate enough to satisfactorily describe the experimental results. In this work we provide for the first time the analysis of partitioning effects and transport mechanism in the NF separation of sulfate and chloride anions in concentrations that simulate those found in RO desalination brines.This work has been financially supported by projects CTQ2008-0690, ENE2010-15585 and CTM2011-23912 (co-financed by ERDF Funds).The authors would like to acknowledge SADYT, S.A. for providing assistance for this work

Board Composition, Political Connections and Performance in State-Owned Enterprises

This paper analyses the effects of board composition on the behaviour of a sample of 114 Italian local public utilities, for which information about 1630 directors during 1994-2004 has been collected. This period is particularly interesting because of the legal changes that forced many firms to alter their juridical form and allowed the entrance of private investors. We investigate whether board size and/or board composition do affect decisions about employment and how they ultimately impact on performance. Our main findings indicate that politically connected directors dominate boards of directors in Italian public utilities, exerting a positive and significant effect on employment, and impacting negatively on performance

Board Composition, Political Connections and Performance in State-Owned Enterprises

This paper analyses the effects of board composition on the behaviour and performance of a sample of 114 Italian local public utilities, for which information about 1630 directors during 1994-2004 has been collected. This period is particularly interesting because of the legal changes that forced many firms to alter their juridical form and allowed the entrance of private investors. We investigate whether board size and/or board composition do affect decisions about employment and how they ultimately impact on performance. Our main findings indicate that politically connected directors, representing the state or the local municipality, dominate boards of directors in the Italian public utilities in the period under investigation. Politically connected directors exert a positive and significant effect on employment, while they impact negatively on performance

Board Composition, Political Connections and Performance in State-Owned Enterprises

This paper analyses the effects of board composition on the behaviour and performance of a sample of 114 Italian local public utilities, for which information about 1630 directors during 1994-2004 has been collected. This period is particularly interesting because of the legal changes that forced many firms to alter their juridical form and allowed the entrance of private investors. We investigate whether board size and/or board composition do affect decisions about employment and how they ultimately impact on performance. Our main findings indicate that politically connected directors, representing the state or the local municipality, dominate boards of directors in the Italian public utilities in the period under investigation. Politically connected directors exert a positive and significant effect on employment, while they impact negatively on performance