Electrolytic removal of metals using a flow-through cell with a reticulated vitreous carbon cathode

The aim of the present study was to establish an electrolytic method for the removal of metals from wastewater using a three dimensional, reticulated vitreous carbon cathode. During the development of the experimental set up, particular attention was paid to the electrolyte flow rate and to the cathode porosity. The electrolytic cell employed potential values in such a way that the metals reduction reaction occurred under mass transport control. These potentials were determined by hydrodynamic voltammetry on a vitreous carbon rotating disc electrode. The cell proved to be efficient in removing copper, zinc and lead and it was able to reduce the levels of these metals from 50 mg/L to 0.1 mg/L.O objetivo do presente trabalho foi estabelecer um processo eletrolítico para remover metais de efluentes aquosos usando um catodo tridimensional de carbono vítreo reticulado. Durante o desenvolvimento do trabalho foi estudado a influência do fluxo do eletrólito e da porosidade do eletrodo. A célula eletrolítica utilizou potenciais tais que a reação de redução ocorreu sob controle de transporte de massa. A célula demonstrou eficiência na remoção de chumbo, zinco e cobre, reduzindo a concentração desses metais de 50 mg.L-1 a 0,1 mg.L-1 em 20 min de recirculação da solução.48749

Construction and application of an electrochemical sensor for paracetamol determination based on iron tetrapyridinoporphyrazine as a biomimetic catalyst of P450 enzyme

This work describes the construction and application of a biomimetic sensor for paracetamol determination in different samples . The sensor was prepared by modifying a glassy carbon electrode surface with a Nafion® membrane doped with FeTPyPz. The best performance of the sensor in 0.1 mol L-1 acetate buffer was at pH 3.6. Under these conditions, an oxidation potential of paracetamol was observed at 445 mV vs. Ag|AgCl. The sensor presented a linear response range between 4.0 and 420 µmol L-1, a sensitivity of 46.015 mA L mol-1 cm-2, quantification and detection limits of 4.0 µmol L-1 and 1.2 µmol L-1, respectively. A detailed investigation about its electrochemical behavior and selectivity was carried out. The results suggested that FeTPyPz presents catalytic properties similar to P450 enzyme for paracetamol oxidation. Finally, the sensor was applied for paracetamol determination in commercial drugs and for the monitoring of its degradation in an electrochemical batch reactor effluent.Descreve-se a construção e aplicação de um sensor biomimético para determinação de paracetamol em diversos tipos de amostras. O sensor foi construído modificando a superfície de um eletrodo de carbono vítreo com membrana de Nafion® dopada com tetrapiridinoporfirazina de ferro (FeTPyPz). Esse sensor apresentou melhor desempenho em tampão acetato 0,1 mol L-1 e pH 3,6. Nessas condições o potencial de oxidação do paracetamol foi de 445 mV vs. Ag|AgCl. O sensor apresentou uma faixa de resposta linear entre 4,0 e 420 µmol L-1, sensibilidade de 46,015 mA L mol-1 cm-2, limite de quantificação de 4,0 µmol L-1 e limite de detecção de 1,2 µmol L-1. Estudos eletroquímicos e de seletividade demonstraram a propriedade catalítica da FeTPyPz como sendo similares a da enzima P450 na oxidação do paracetamol. O sensor foi usado na determinação de paracetamol em formulações comerciais e no acompanhamento de sua degradação eletroquímica em efluentes provenientes de um reator em escala piloto.734743Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

CCAT2, a novel noncoding RNA mapping to 8q24, underlies metastatic progression and chromosomal instability in colon cancer

The functional roles of SNPs within the 8q24 gene desert in the cancer phenotype are not yet well understood. Here, we report that CCAT2, a novel long noncoding RNA transcript (lncRNA) encompassing the rs6983267 SNP, is highly overexpressed in microsatellite-stable colorectal cancer and promotes tumor growth, metastasis, and chromosomal instability. We demonstrate that MYC, miR-17-5p, and miR-20a are up-regulated by CCAT2 through TCF7L2-mediated transcriptional regulation. We further identify the physical interaction between CCAT2 and TCF7L2 resulting in an enhancement of WNT signaling activity. We show that CCAT2 is itself a WNT downstream target, which suggests the existence of a feedback loop. Finally, we demonstrate that the SNP status affects CCAT2 expression and the risk allele G produces more CCAT2 transcript. Our results support a new mechanism of MYC and WNT regulation by the novel lncRNA CCAT2 in colorectal cancer pathogenesis, and provide an alternative explanation of the SNP-conferred cancer risk

Electrochemical degradation of Reactive Blue 19 dye by combining boron doped diamond and reticulated vitreous carbon electrodes

Reactive Blue 19 (RB-19) dye has low fixation efficiency, a long half-life and high toxicity. It is easily loss during the cleaning of textiles and can remain in the environment for long time causing serious environmental problems if not removed. This study reports the degradation of RB-19 by: 1) the electrochemical direct degradation with Boron-Doped Diamond (BDD) electrodes and 2) a combined processes using BDD and Reticulated Vitreous Carbon (RVC) electrodes that generates H2O2. The direct degradation uses different current densities and concentrations. High currents densities, longer electrolysis time and low volumetric flow rates, favour RB-19 degradation removing total colour and 100 % TOC at 5 and 60 min respectively. At 41 mA cm-2 current density and 20 dm3 h-1 volumetric flow rate, the energy consumption to degrade 20 mg dm-3 of RB-19 was 279 kWh kg-1. The TOC removal of RB-19 dye combining BDD and RVC at a current density of 41 mA cm-2 was below 72% during 90 min and the energy consumption increased to 612 kWh kg-1. The higher energy consumption obtained during the combined process suggested that the direct degradation process at low volumetric flow rates is more efficient than the combined process

The Role of Mediated Oxidation on the Electro-irradiated Treatment of Amoxicillin and Ampicillin Polluted Wastewater

In this work, the electrolysis, photoelectrolysis and sonoelectrolysis with diamond electrodes of amoxicillin (AMX) and ampicillin (AMP) solutions were studied in the context of the search for technologies capable of removing antibiotics from liquid wastes. Single-irradiation processes (sonolysis and photolysis) were also evaluated for comparison. Results showed that AMX and AMP are completely degraded and mineralized by electrolysis in both chloride and sulfate media, although the efficiency is higher in the presence of chloride. The effect of the current density on mineralization efficiency is not relevant and this may be related to the role of mediated oxidation. Irradiation by ultraviolet light or ultrasound (US) waves does not produce a synergistic effect on the mineralization of AMX and AMP solutions. This indicates that the massive formation of radicals during the combined processes can favor their recombination to form stable and less reactive species

Electrochemical degradation of RB-5 dye by anodic oxidation, electro-Fenton and by combining anodic oxidation–electro-Fenton in a filter-press flow cell

This paper reports the removal of a recalcitrant and toxic dye, Reactive Black 5 (RB-5) by threemethods; 1) anodic oxidation (AO) on Boron-Doped Diamond (BDD), 2) by electro-Fenton (EF) process where hydrogen peroxide was produced by oxygen reduction on reticulated vitreous carbon (RVC) electrodes and 3) by the combination of AO–EF. The BDD and RVC electrodes were fitted in a filter-press flow cell in recycle batch mode of operation. The experimental set-up for the AO and EF processes consisted of two electrolyte compartments separated by a Nafion membrane with the dye contained in the anolyte and the catholyte, respectively. The combined AO–EF process used only one electrolyte compartment. The colour and total organic carbon (TOC) removal were more efficientwhen the AO and EF processes were used separately than the combined process, AO–EF. The influence of current density and initial concentration of ferrous ions were examined. The lowest energy efficiency (208 kWh kg?1) with the EF process was found when ?0.4 V vs. Ag/AgCl was applied to a RVC electrode and the concentration of Fe2+ was 1.0 × 10?4 mol dm?3 achieving total colour and 74% of TOC removals in less than 90 min electrolysis. All proposed processeswere able to promote high percentages of TOC removal following a pseudo-first order kinetic oxidation. The BDD electrode was the most effective material to remove RB-5 dye within 7.5 min and presented the highest apparent rate constant (0.835 min?1) with 82% TOC removal within 30 min at an energy consumption of 291 kWh kg?1 and 41.1 mA cm?2 current density. In the case of the combined process AO–EF the electrodegradation rate of RB-5 was at least three times lower, apparent rate constant (0.269 min?1), and 32% of TOC was removed with a high EC (682 kWh kg?1). Therefore oxidation process applied separately was more efficien

Insertion of nanostructured titanates into the pores of an anodised TiO2 nanotube array by mechanically stimulated electrophoretic deposition

TiO2 nanotube (TiO2NT) surfaces can achieve a high area surface and enhanced electrocatalytic properties. One of the key challenges is the insertion of nanostructured titanates deeply into the pores of TiO2NT. We describe the electrophoretic deposition (EPD) of two different titanates - nanosheets (TiNSs) and nanotubes (TiNTs) into the pores of TiO2NT to produce controlled hierarchical surfaces. A sufficiently high applied cell potential and mechanical stimulation of the surface are important to incorporate TiNSs and TiNTs inside the pores of TiO2NTs. The electrodes show improved hydrophobicity after deposition of titanates. The beneficial effect of a counter electrode equipped with a brush to avoid the accumulation of a thick outer layer on TiO2NTs is highlighted

Electrolytic removal of metals using a flow-through cell with a reticulated vitreous carbon cathode

The aim of the present study was to establish an electrolytic method for the removal of metals from wastewater using a three dimensional, reticulated vitreous carbon cathode. During the development of the experimental set up, particular attention was paid to the electrolyte flow rate and to the cathode porosity. The electrolytic cell employed potential values in such a way that the metals reduction reaction occurred under mass transport control. These potentials were determined by hydrodynamic voltammetry on a vitreous carbon rotating disc electrode. The cell proved to be efficient in removing copper, zinc and lead and it was able to reduce the levels of these metals from 50 mg/L to 0.1 mg/L

The oxygen reduction reaction on palladium with low metal loadings:The effects of chlorides on the stability and activity towards hydrogen peroxide

Hydrogen peroxide is considered one of the most important commodity chemicals worldwide but its main production method, the anthraquinone process, poses serious logistical, environmental and safety challenges. Electrocatalytic synthesis through the reduction of molecular oxygen is a promising H2O2 production route. However, the reduction of molecular oxygen is kinetically hindered and stable electrocatalysts with a high activity and selectivity towards the 2-electron transfer reaction are needed. In this work, we evaluated the influence of chloride on catalysts with low palladium loadings on the ORR selectivity towards H2O2. We report the factors and dynamics that influence H2O2 production and highlight synthesis strategies to obtain close to 100% selectivity. By probing the electrode surface after various degradation cycles, we evaluate the role of adsorbing species and the catalysts oxidation states on the hydrogen peroxide selectivity. We systematically modified the catalyst synthesis using different Pd-precursors that were reduced and supported on high surface area graphene nanoribbons. Identical location transmission electron microscopy was used to probe catalyst dynamics during reaction and the activities and selectivities were measured by a rotating ring disk electrode. We probe the potential boundary conditions that lead to catalyst degradation during accelerated stress tests and potentiostatic polarisation and demonstrate how the catalytically active surface can be revived after degradation. The obtained insights can be used as guideline for the development of active, selective and stable catalysts with low noble metal loadings.</p