3RD INTL. SYMP. ON ELECTROCHEMISTRY FOR SUSTAINABLE DEVELOPMENT

Treatment and adequate disposal of slaughterhouse wastewater (SWW) is a worldwide economy and public health necessity. SW contains elevated amounts of organic matter and salts. Typical parametrical analyses include pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorous (TP), total organic carbon (TOC) and total suspended solids (TSS) [2]. After preliminary treatment, the electrochemical processes such anodic oxidation (AO) and electrocoagulation (EC) have been considered an alternative technology for the treatment of SWW.
In this study, a real beef slaughterhouse wastewater presented the following characteristics: TOC (1150 mg L–1), COD (4320 mg L–1), TP (25 mg L–1), TN (72.28 mg L–1), TSS (1433 mg L–1) at pH 7.18 and conductivity of 2.79 mS cm–1. Bright red color was observed at 416 nm (1.24 A.U.) and the presence of coliform bacteria was confirmed (> 1600 MPN). AO and EC tests were carried out in a single open cell compartment in batch operation mode with constant stirring to ensure mass transport of the oxidant specie towards/from the anode to the bulk. AO was assessed using two different dimensionally stable anodes (DSA) type anodes: i) Ti/IrO2/Ta2O5 coating (DSA-O2) ii) Ti/Ru0,3Ti0,7O2 (DSA-Cl2). AISI 304 stainless steel plate was used as cathode. EC was evaluated using iron and aluminum electrodes (anode and cathode).
The best operating conditions were found at current density of 20 mA cm–2 without supporting electrolyte. TOC, COD and TP removal efficiency were 79.77% and 78.62 %; 89.22% and 79.4%; 96.0% and 64% using DSA-Cl2 (Ti/Ru0,3Ti0,7O2) and DSA-O2 (Ti/IrO2/Ta2O5), respectively. Moreover, a complete discoloration and disinfection were achieved.
Electrochemical oxidation test at best operating conditions gave energy consumption and specific energy consumption values for TOC, COD and TP using DSA-Cl2 and DSA-O2 of 24.5- and 26.5-kW h m–3-, 27.1- and 28.9-kW h kgTOC–1-, 7.14- and 6.88-kW h kgCOD–1 and, 1531.25- and 1104.17-kW h kgTP–1, respectively.

Many practical systems at micro- and nanoscale can be represented as arrays of active sites distributed randomly [1]. As shown previously these systems can be efficiently addressed theoretically by using Voronoi diagrams [2, 3] which allows facile tessellation of the system into the unit cells around each active sites. The overall current flowing in the system can then be evaluated by modelling diffusion-reaction processes inside every unit cell and summing the contributions from individual active sites. Although this approach is tempting by its simplicity and efficiency [3] one should bear in mind that Voronoi diagram representing the unit cells by polygonal prisms remains approximation and as each approximation remains valid only under certain conditions. In this work [4] we show that even for the case of diffusion limited electron transfer (ET) the actual shapes of the unit cells are more complicated and depend on the local configuration of the neighbouring active sites. This was exemplified on the small patches of the random arrays with band-like and disk-like active sites via simulations and in the case of band-like active sites confirmed by analytical derivations.
Importantly, by comparing the total array current obtained by employing Voronoi tessellation and simulation of the system without any approximations we found that they agree well (relative error ca. 5% or less). At the same time, the individual contributions from the active sites are reproduced with a much larger relative error [4]. The latter suggests that in the case of kinetic control or reaction mechanisms that are more complicated than simple ET the diffusion-reaction competition between the active sites may become even stronger eventually leading to significant deviations from the total current predicted on the basis of the Voronoi approximation. This is currently investigated in our team.

For four decades, the development of biointerfaces has been the subject of increasing research efforts in the field of analytical chemistry and energy conversion. In particular, the functionalization of electrodes by biomaterials based on electrogenerated polymers, carbon nanotubes and / or nano-objects, is widely used for the design of biosensors and biofuel cells [1-3].
Some new approaches for developing nanostructured biomaterials based on functionalized tungsten disulfide nanotubes, glyconanoparticles and compressions of carbon nanotubes will be illustrated with enzymes as a biosensing element. Composite bioelectrodes by compression of enzymes and carbon nanotube mixtures and modification of the resulting disks by polypyrrole or polynorbornene films as well as the effect of the enzyme nature on the compression, will be reported. Moreover, WS2 nanotubes functionalized with carboxylic acid functions were used for the elaboration of enzyme electrode for monitoring dopamine. The development of glyconanoparticles resulting from the self-assembly of block copolymers composed of polystyrene and cyclodextrin as an inclusion site will be also reported. These glyconanoparticles allow a post-functionalization by hydrophobic molecules through host-guest interactions. They were used in solution or immobilized for fixing redox mediators or enzymes modified by adamantane groups. This innovative approach will be applied to the elaboration of solubilized enzymatic fuel cell or biosensors [4].

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