Chronopotentiometric study of the transport of phosphoric acid anions through an anion-exchange membrane under different pH values

[EN] Phosphate is the main cause of eutrophication in many water bodies. Its presence in waters is associated to the fact that is not completely removed in conventional wastewater treatment plants. On the other side, phosphate rocks are a non-renewable resource and considered as a critical raw material. A membrane separation process, able to recover phosphate from wastewater, is a promising process to avoid pollution and to reuse phosphate. This paper investigates the transport of salts of phosphoric acid through an anion-exchange membrane (AEM) by means of chronopotentiograms and polarization curves (CVCs). The presence of multiple transition times in the chronopotentiograms and the corresponding limiting current densities in the CVCs indicate a change in the species being transported in the membrane/diffusion boundary layer system, due to the hydrolysis reactions that take place when the concentration polarization is reached. Under the experimental conditions tested, coupled convection (gravitational and elctroconvection) occurs when a certain threshold in the membrane voltage drop is surpassed independently of the electrolyte concentration. However, at high pH values, only one transition time in the chronopotentiograms, due to the transfer of OH- ions with greater concentration and mobility. This fact is reflected in the CVCs by the large plateaus obtained, which hinders the occurrence of coupled convection phenomena, and consequently, water splitting can be considered as the main mechanism responsible for the overlimiting regime.The authors wish to thank the financial support from FINEP, FAPERGS, CAPES and CNPq (Brazil), from the BRICS-STI/CNPq (BRICS STI Framework Programme), from the European Union through the Erasmus Mundus Program (EBW +) and from the CYTED (Network 318RT0551).Gally, C.; García Gabaldón, M.; Ortega Navarro, EM.; Bernardes, A.; Pérez-Herranz, V. (2020). 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The role of the anode material and water matrix in the electrochemical oxidation of norfloxacin

[EN] The roles of the anode material, boron-doped diamond (BDD), with different boron (B) and substrate Silicon (Si) or Niobium (Nb) content, and one dimensionally stable anode (DSA (R)), were evaluated in the oxidation of norfloxacin (NOR) by electrochemical advanced oxidation process (EAOP). The effect of other components in real wastewater on the performance of EAOP was also studied. The anode materials were characterized by cyclic voltammetry, regarding diamond quality, electro-generation of oxidants and NOR oxidation mechanism (direct and/or indirect). The results showed that the anode material influences on the NOR oxidation pathway, due to distinct characteristics of the substrate and the coating. Apparently, low difference in diamond-sp(3)/sp(2)-carbon ratio (Si/BDD100 x Si/BDD2500) does not leads to significant differences in the EAOP. On the other hand, the variation in the sp(3)/sp(2) ratio seems to be higher when Si/BDD2500 and Nb/BDD2500 are compared, which would explain the best current efficiency result for Si substrate. However, the Nb substrate presented a similar current efficiency and a 60% lower energy consumption. Dissolved organic matter (DOM) present in the real wastewater affect the EAOP-Nb/BDD due to HO center dot and persulfate ions scavenged. However, when supporting electrolyte was added to a real wastewater spiked with NOR, the NOR decay reaches similar values found to the synthetic one. Due to the energy saving and mechanical properties, Nb substrate presents some technological advantages in relation to Si, which can facilitate the application to industrial levels. (C) 2018 Published by Elsevier Ltd.The authors thanks CNPq, CAPES, Cyted, FAPERGS and Finep for the financial support.Da Silva, SW.; Ortega Navarro, EM.; Rodrigues, M.; Bernardes, A.; Pérez-Herranz, V. (2018). The role of the anode material and water matrix in the electrochemical oxidation of norfloxacin. Chemosphere. 210:615-623. https://doi.org/10.1016/j.chemosphere.2018.07.057S61562321

Influence of the co-ions on the transport of sulfate through anion exchange membranes

[EN] The increasing demand for clean industrial processes has intensified the use of electrodialysis (ED) in the treatment of metal containing effluents from plating processes. Nickel rinsewater is a multicomponent solution that can be treated by ED in order to recover chemicals and reuse water. The investigation of the different phenomena involved in the transport of anions through anion-exchange membranes in this wastewater has been performed in different synthetic solutions by chronopotentiometry. Parameters like the limiting current density (i(lim)), the plateau length (Delta U-m), the resistance of the ohmic region (R-ohm) and the resistance of the overlimiting region (R-3) were also determined. Even though an anion exchange membrane (AEM), the limiting current density was affected by the proton leakage phenomena, indicated that the proton H+ has a greater effect than the other co-ions (Ni2+, Mg2+ and Na+). Ohmic resistances were reduced and plateau lengths were increased in the presence of protons. For salts solutions (without acid) the highest diffusion coefficients and lowest co-ion hydrated radii gave the highest plateau lengths and i(lim), but the lowest R-ohm.This study was financially supported by Erasmus Brazilian Windows Plus (EBW+), CAPES, CNPq, BNDES, FINEP, SCIT and FAPERGS.Benvenuti, T.; García Gabaldón, M.; Ortega Navarro, EM.; Rodrigues, M.; Bernardes, A.; Pérez-Herranz, V.; Zoppas-Ferreira, J. (2017). Influence of the co-ions on the transport of sulfate through anion exchange membranes. Journal of Membrane Science. 542:320-328. doi:10.1016/j.memsci.2017.08.021S32032854

Sulfuric acid recovery from acid mine drainage by means of electrodialysis

In the present work the recovery of sulfuric acid from acid mine drainage by means of 3-compartment electrodialysis (ED) is evaluated. An effective recovery of sulfuric acid free from Fe(III) species was obtained in the anodic compartment as a result of the co-ion exclusion mechanism in the membranes. The difference in the pH and pSO42 − values between the membrane phase and the external electrolyte promotes the dissociation of complex species inside the membranes. This phenomenon impedes the transport of Fe(III) and sulfates in the form of complex ions toward the anodic and cathodic compartment, respectively. The current efficiency values of the anion-exchange membrane at different current densities were approximately constant with time. However, the increase in the recovery of acid decreases as the current increases. This result is explained by the shift in the equilibrium at the membrane/solution interface as more SO42 − ions cross the anionic membrane and, by the enhancement of the dissociation of water when the limiting current density is exceeded. The main limitation of the process is related to an abrupt increase in the cell voltage due to the formation of precipitates at the surface of the cation-exchange membrane.This work was supported by Ministerio de Economia y Competitividad (Spain) with the project number CTQ2012-37450-C02-01/PPQ. M.C. Marti-Calatayud is grateful to the Universitat Politecnica de Valencia for a postgraduate grant (Ref.: 2010-12). D.C. Buzzi wants to express her gratitude to CAPES (Brazil) for a postgraduate grant (Proc. BEX 8747/11-3).Martí Calatayud, MC.; Cardoso Buzzi, D.; García Gabaldón, M.; Ortega Navarro, EM.; Bernardes, A.; Suarez Tenorio, JA.; Pérez Herranz, V. (2014). Sulfuric acid recovery from acid mine drainage by means of electrodialysis. Desalination. 343:120-127. https://doi.org/10.1016/j.desal.2013.11.03112012734

REMOVED: Nanofiltration for the Treatment of Coke Plant Ammoniacal Wastewaters

This article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been removed at the request of the Executive Publisher.This article has been removed because it was published without the permission of the author(s)

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters