Loading carbonaceous materials with silver for the treatment of chloro-organic compounds in aqueous phase

Many electrochemical technologies, either based on novel concepts (such as microbial fuel cells), experimental setups (such as photoelectrochemical or solar photoelectro-Fenton reactors) or materials (mainly focused on the use of large O2-overpotential anodes like BDD) have been devised in recent years for water remediation. Special attention has been paid to highly toxic, biorefractory organic pollutants such as the chlorinated hydrocarbons, which conjugate toxicity with chemical stability, bioaccumulation and long-range diffusivity [1]. Electroreduction at silver cathodes becomes an interesting alternative to degrade chloro-organic compounds, but it may lead to the accumulation of reaction by-products, even upon coupling with electro-oxidation at BDD [2]. On the other hand, some Fenton-based processes have proven very effective for the destruction of organic matter due to the action of •OH formed when cathodically electrogenerated H2O2 reacts with added Fe2+ [3]. Based on this, we have envisaged a potential strategy for the enhanced removal of chloro-organic pollutants and their by-products: electro-Fenton process in the bulk upon H2O2 electrogeneration at a carbonaceous cathode, which can simultaneously act as the substrate for electroreduction at loaded Ag nanoparticles. To achieve this goal, a highly efficient material for H2O2 production, i.e., a gas diffusion electrode (GDE), has been chosen for Ag-loading experiments. Several authors have reported the preparation of Ag-loaded carbonaceous materials based on a simple electroless deposition (ELD) process from Ag+ solutions. Some of them have addressed the full preparation of GDEs with Ag catalysts [4,5]. Here, we report the use of a commercial GDE as a suitable substrate to obtain conveniently dispersed Ag nanoparticles. The effect of several ELD parameters (e.g., nature of reductant, mode of application and deposition time) on the surface morphology has been mainly studied by SEM-EDX. Bulk electrolyses in 50 mM Na2SO4 at various pH were subsequently performed with the best materials to assess their ability to electrogenerate H2O2. For comparison, carbon paper was used as an alternative substrate. An important objective of the research was to find the optimum conditions to load the substrate so as to keep the balance between covered and uncovered area, in order to favor both H2O2 production and pollutant electroreduction. The performances of these electrodes for the electrogeneration of H2O2 and the abatement of chloro-organic pollutants is currently being investigated. [1] S. Rondinini, A. Vertova, in Electrochemistry for the environment, 2010, pp. 279–306. [2] O. Scialdone, A. Galia, L. Gurreri, S. Randazzo, Electrochim. Acta 55 (2010) 701–708. [3] E. Brillas, I. Sirés, M.A. Oturan, Chem. Rev. 109 (2009) 6570–6631. [4] E. Gülzow, N. Wagner, M. Schulze, Fuel Cells 3 (2003) 67–72. [5] S. Rondinini, G. Aricci, Z. Krpetic, C. Locatelli, A. Minguzzi, F. Porta, A. Vertova, Fuel Cells 3 (2009) 253–263

Valorization of bottom ash from municipal solid waste incineration: recovery of copper by electrowinning

Postprint (published version

Optimization of electrocatalytic H2O2 production at pilot plant scale for solar-assisted water treatment

This manuscript summarizes the successful start-up and operation of a hybrid eco-engineered water treatmentsystem, at pilot scale. The pilot unit, with 100L capacity, has been devised for the efficient electrocatalyticproduction of H2O2at an air-diffusion cathode, triggering the formation of%OH from Fenton's reaction withadded Fe2+catalyst. These radicals, in combination with those formed at a powerful boron-doped diamond(BDD) anode in an undivided cell, are used to degrade a mixture of model pesticides. The capability of the plantto produce H2O2on site was initially optimized using an experimental design based on central composite design(CCD) coupled with response surface methodology (RSM). This aimed to evaluate the effect of key processparameters like current density (j) and solution pH. The influence of electrolyte concentration as well as liquidand air flow rates on H2O2electrogeneration and current efficiency at optimizedjand pH was also assessed. Thebest operation conditions resulted in H2O2mass production rate of 64.9mgmin−1, 89.3% of current efficiencyand 0.4kWh m-3of energy consumption at short electrolysis time. Performance tests at optimum conditions werecarried out with 75L of a mixture of pesticides (pyrimethanil and methomyl) as a first step towards the elim-ination of organic contaminants by solar photoelectro-Fenton (SPEF) process. The combined action of homo-geneous (%OH) and heterogeneous (BDD(%OH)) catalysis along with photocatalysis (UV photons collected at asolar CPC photoreactor) allowed the removal of more than 50% of both pesticides in 5min, confirming the fastregeneration of Fe2+catalyst through cathodic reduction and photo-Fenton reaction

Effect of Thermal Treatment on Nickel-Cobalt Electrocatalysts for Glycerol Oxidation

Nickel-cobalt electrocatalysts with atomic ratios of 2 : 1 and 1 : 2 were synthesized on nickel foam (NF) substrates by cathodic electrodeposition, further evaluating the performance of the pristine and thermally-treated materials as anodes for glycerol oxidation in alkaline medium. The electrodes were characterized by cyclic and linear sweep voltammetry at alkaline pH, showing an indirect oxidation of glycerol mediated by the metal oxyhydroxides. Under the selected conditions, a favourable potential window of 0.2 V upon comparison of water and glycerol oxidation was found. In addition, the increase in nickel content and the thermal treatment enhanced the anode polarization. After galvanostatic electrolysis at 10 mA cm−2, the products were analysed by HPLC, formate ion being the primary product, with a faradaic efficiency (FE) higher than 70 % in most cases. Both the FE to formate and the glycerol conversion were substantially enhanced using the thermally-treated anodes, whereas the effect of the Ni/Co ratio on these two parameters did not follow a clear trend

Inactivation of microbiota from urban wastewater by single and sequential electrocoagulation and electro-Fenton treatments

This work aims at comparing the ability of two kinds of electrochemical technologies, namely electrocoagulation (EC) and electro-Fenton (EF), to disinfect primary and secondary effluents from municipal wastewater treatment plants. Heterotrophic bacteria, Escherichia coli, enterococci, Clostridium perfringens spores, somatic coliphages and eukaryotes (amoebae, flagellates, ciliates and metazoa) were tested as indicator microorganisms. EC with an Fe/Fe cell at 200 A m-2 and natural pH allowed > 5 log unit removal of E. coli and final concentration below 1 bacteria mL-1 of coliphages and eukaryotes from both effluents in ca. 60 min, whereas heterotrophic bacteria, enterococci and spores were more resistant. A larger removal was obtained for the primary effluent, probably because the flocs remove higher amount of total organic carbon (TOC), entrapping more easily the microbiota. EF with a boron-doped diamond (BDD) anode and an air-diffusion cathode that produces H2O2 on site was first performed at pH 3.0, with large or even total inactivation of microorganisms within 30 min. A more effective microorganism removal was attained as compared to EC thanks to ¿OH formed from Fenton's reaction. A quicker disinfection was observed for the secondary effluent owing to its lower TOC content, allowing the attack of greater quantities of electrogenerated oxidants on microorganisms. Wastewater disinfection by EF was also feasible at natural pH (~7), showing similar abatement of active microorganisms as a result of the synergistic action of generated oxidants like active chlorine and coagulation with iron hydroxides. A sequential EC/EF treatment (30 min each) was more effective for a combined decontamination and disinfection of urban wastewater

Mahogunin Ring Finger 1 Is Required for Genomic Stability and Modulates the Malignant Phenotype of Melanoma Cells.

The mouse mahoganoid mutation abrogating Mahogunin Ring Finger-1 (MGRN1) E3 ubiquitin ligase expression causes hyperpigmentation, congenital heart defects and neurodegeneration. To study the pathophysiology of MGRN1 loss, we compared Mgrn1-knockout melanocytes with genetically matched controls and melan-md1 (mahoganoid) melanocytes. MGRN1 knockout induced a more differentiated and adherent phenotype, decreased motility, increased the percentage of cells in the S phase of the cell cycle and promoted genomic instability, as shown by stronger γH2AX labelling, increased burden of DNA breaks and higher abundance of aneuploid cells. Lack of MGRN1 expression decreased the ability of melanocytes to cope with DNA breaks generated by oxidizing agents or hydroxyurea-induced replicative stress, suggesting a contribution of genomic instability to the mahoganoid phenotype. MGRN1 knockout in B16-F10 melanoma cells also augmented pigmentation, increased cell adhesion to collagen, impaired 2D and 3D motility and caused genomic instability. Tumors formed by Mgrn1-KO B16-F10 cells had lower mitotic indices, fewer Ki67-positive cells and showed a trend towards smaller size. In short-term lung colonization assays Mgrn1-KO cells showed impaired colonization potential. Moreover, lower expression of MGRN1 is significantly associated with better survival of human melanoma patients. Therefore, MGRN1 might be an important phenotypic determinant of melanoma cells

Electrochemical oxidation of meglumine in a pharmaceutical formulation using a nanocomposite anode

The electrocatalytic oxidation of meglumine and gadoterate meglumine (Gd-DOTA) on a TiO2-Ni(SO4)0.3(OH)1.4 composite anode was investigated in alkaline medium (5 M KOH) using cyclic voltammetry and chronoamperometry. The composite was prepared by hydrothermal method and the morphology and structure of the produced nanoparticles were studied by scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy, BET surface area analysis and Fourier transform infrared spectroscopy. The characterization revealed the formation of Ni(SO4)0.3(OH)1.4 nanobelts dispersed on TiO2 nanoaggregates. The composite was coated onto a porous graphite rod, showing good adherence without requiring any binder (according to their anodic and cathodic charges). The supported composite was electrocatalytic, allowing the oxidation of meglumine, either as pure reagent or contained in gadoterate meglumine solutions. Electrochemical methods allowed determining the kinetic parameters, such as the electron transfer coefficient α, the total number of electrons n and the standard heterogeneous rate constant k0 for the reaction of meglumine. The chronoamperometric tests informed about the good stability of the composite anode upon meglumine oxidation at +0.6 V for 10 h. The electrochemical oxidation of meglumine in a commercial pharmaceutical formulation (Dotarem®) was corroborated via ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry

Electrochemical degradation of beta-blockers. Studies on single and multicomponent aqueous solutions.

International audienc

Electro-Fenton process and related electrochemical technologies based on Fenton's reaction chemistry.

International audienc