Effect of chloride on the one step electrochemical treatment of an industrial textile wastewater with tin dioxide anodes. The case of trichromy procion HEXL.

The resulting solutions from the cotton fabrics dyeing using the trichromy Procion HEXL, with NaCl as electrolyte, were electrochemically treated. These dyes have two azo groups as chromophores and two monochlorotriazinic groups as reactive groups in their structure. The combined oxidation/reduction at 125 mA cm-2 in a filter-press cell without compartment separation was carried out using an anode of Ti/SnO2-Sb-Pt and a cathode of stainless steel. This procedure has been effective in previous experiments using sulphate as electrolyte. A significant decrease in total organic carbon (TOC), chemical oxygen demand (COD), and total nitrogen (TN) was obtained. Moreover, the process took place efficiently. The average oxidation state (AOS) and the carbon oxidation state (COS) data confirmed the presence of stable oxidized intermediates in the electrolysed solution. The chromatography and the UV-Visible spectrophotometry assays indicated that full decolourisation is obtained at a loaded charge of around 0.81 Ah L-1 which is associated with an electrical energy per order (EEO) of 1.20 kWh m-3.

Peripheral dose around a mobile linac for intraoperative radiotherapy: radiation protection aspects.

The aim of this work is to analyse the scattered radiation produced by the mobile accelerator Mobetron 1000. To do so, detailed Monte Carlo simulations using two different codes, Penelope2008 and Geant4, were performed. Measurements were also done. To quantify the attenuation due to the internal structures, present in the accelerator head, on the scattered radiation produced, some of the main structural shielding in the Mobetron 1000 has been incorporated into the geometry simulation. Results are compared with measurements. Some discrepancies between the calculated and measured dose values were found. These differences can be traced back to the importance of the radiation component due to low energy scattered electrons. This encouraged us to perform additional calculations to separate the role played by this component. Ambient dose equivalent, H*(10), outside of the operating room (OR) has been evaluated using Geant4. H*(10) has been measured inside and outside the OR, being its values compatible with those reported in the literature once the low energy electron component is removed. With respect to the role played by neutrons, estimations of neutron H*(10) using Geant4 together with H*(10) measurements has been performed for the case of the 12 MeV electron beam. The values obtained agree with the experimental values existing in the literature, being much smaller than those registered in conventional accelerators. This study is a useful tool for the clinical user to investigate the radiation protection issues arising with the use of these accelerators in ORs without structural shielding. These results will also enable to better fix the maximum number of treatments that could be performed while insuring adequate radiological protection of workers and public in the hospital.

On the behavior of reduced graphene oxide based electrodes coated with dispersed platinum by alternate current methods in the electrochemical degradation of reactive dyes.

The electrochemical behavior of different carbon-based electrodes with and without nanoparticles of platinum electrochemically dispersed on their surface has been studied. Among others, reduced graphene oxide based electrodes was used to determine the best conditions for the decolorization/degradation of the reactive dye C.I. Reactive Orange 4 in sulfuric medium. Firstly, the electrochemical behavior was evaluated by cyclic voltammetry. Secondly, different electrolyses were performed using two cell configurations: cell with anodic and cathodic compartments separated (divided configuration) and without any separation (undivided configuration). The best results were obtained when reduced graphene oxide based anodes were used. The degree of decolorization was monitored by spectroscopic methods and high performance liquid chromatography. It was found that all of them followed pseudo-first order kinetics. When reduced graphene oxide-based electrodes coated with dispersed platinum by alternate current methods electrodes were used, the lowest energy consumption and the higher decolorization kinetics rate were obtained. Scanning Electronic Microscopy was used to observe the morphological surface differences.

Graphene-based materials for the electrochemical determination of hazardous ions.

The use of graphene in the field of electrochemical sensors is increasing due to two main properties that make graphene and derivatives appealing for this purpose: their conductivity and high surface area. In addition, graphene materials can be easily functionalized with nanoparticles (Au, Pt, etc.) or organic molecules (DNA, polymers, etc.) producing synergies that allow higher sensitivity, lower limit of detection as well as increased selectivity. The present review focuses on the most important works published related to graphene-based electrochemical sensors for the determination of hazardous ions (such as As(III), Cd2+, Pb2+, Hg2+, Cr(VI), Cu2+, Ag+, etc.). The review presents examples of the use of graphene-based electrodes for this purpose as well as important parameters of the sensors such as: limit of detection, linear range, sensitivity, main interferences, stability, and reproducibility. The application of these graphene-based electrodes in real samples (water or food matrices) is indicated, as well. There is room for improvement of these type of sensors and more effort should be devoted to the use of doped graphene (doped for instance with N, B, S, Se, etc.) since electrochemically active sites originated by doping facilitate charge transfer, adsorption and activation of analytes, and fixation of functional moieties/molecules. This will allow the sensitivity and the selectivity of the electrodes to be increased when combined with other materials (nanoparticles/organic molecules).

Study of the electrochemical oxidation and reduction of C.I. Reactive Orange 4 in sodium sulphate alkaline solutions.

Synthetic solutions of hydrolysed C.I. Reactive Orange 4, a monoazo textile dye commercially named Procion Orange MX-2R (PMX2R) and colour index number C.I. 18260, was exposed to electrochemical treatment under galvanostatic conditions and Na2SO4 as electrolyte. The influence of the electrochemical process as well as the applied current density was evaluated. Ti/SnO2-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively, and the intermediates generated on the cathode during electrochemical reduction were investigated. Aliquots of the solutions treated were analysed by UV-visible and FTIR-ATR spectroscopy confirming the presence of aromatic structures in solution when an electro-reduction was carried out. Electro-oxidation degraded both the azo group and aromatic structures. HPLC measures revealed that all processes followed pseudo-first order kinetics and decolourisation rates showed a considerable dependency on the applied current density. CV experiments and XPS analyses were carried out to study the behaviour of both PMX2R and intermediates and to analyse the state of the cathode after the electrochemical reduction, respectively. It was observed the presence of a main intermediate in solution after an electrochemical reduction whose chemical structure is similar to 2-amino-1,5-naphthalenedisulphonic acid. Moreover, the analysis of the cathode surface after electrochemical reduction reveals the presence of a coating layer with organic nature.

Influence of electrochemical reduction and oxidation processes on the decolourisation and degradation of C.I. Reactive Orange 4 solutions.

The electrochemical treatment of wastewaters from textile industry is a promising treatment technique for substances which are resistant to biodegradation. This paper presents the results of the electrochemical decolourisation and degradation of C.I. Reactive Orange 4 synthetic solutions (commercially known as Procion Orange MX2R). Electrolyses were carried out under galvanostatic conditions in a divided or undivided electrolytic cell. Therefore, oxidation, reduction or oxido-reduction experiences were tested. Ti/SnO(2)-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively. Degradation of the dye was followed by TOC, total nitrogen, COD and BOD(5) analyses. TOC removal after an oxidation process was higher than after oxido-reduction while COD removal after this last process was about 90%. Besides, the biodegradability of final samples after oxido-reduction process was studied and an improvement was observed. UV-Visible spectra revealed the presence of aromatic structures in solution when an electro-reduction was carried out while oxido-reduction process degraded both azo group and aromatic structures. HPLC analyses indicated the presence of a main intermediate after the reduction process with a chemical structure closely similar to 2-amine-1, 5-naphthalenedisulfonic acid. The lowest decolourisation rate corresponded to electrochemical oxidation. In these experiences a higher number of intermediates were generated as HPLC analysis demonstrated. The decolourisation process for the three electrochemical processes studied presented a pseudo-first order kinetics.