François Zaviska

A high charge efficiency electrode by self-assembling sulphonated reduced graphene oxide onto carbon fibre: towards enhanced capacitive deionization

Sulphonated reduced graphene oxide (SRGO) is self-assembled onto carbon fibre cloth (CFC) by electrophoresis deposition as a composite (CFC–SRGO) electrode for high-performance capacitive deionization (CDI). The resulting CFC–SRGO composite shows a cross-linked nanotubular structure and the individual carbon fibre is fully encapsulated by SRGO nano-sheets, forming a cylindrical-shell microstructure. The electrosorption performance of the CFC–SRGO composite electrode is determined by carrying out a batch-mode electrosorption experiment, showing a great improvement in charge efficiency of more than twice that of a bare CFC electrode. Remarkably, this result is comparable with that of membrane enhanced capacitive deionization. Further, the low exponential decay constant of the CFC–SRGO composite electrode derived from the electrosorption kinetics demonstrates that the deposited SRGO favors a decrease in the internal electrode resistivity and therefore improves the ion electrosorption rate which contributed to the enhanced charge efficiency significantly. Another possible reason accounting for the high charge efficiency of the CFC–SRGO electrode is that the functionalized SRGO is analogous to a cation-exchange membrane which can block the co-ions during electrosorption. In addition, the electrosorption isotherm of the CFC–SRGO film follows Langmuir adsorption, indicating the monolayer adsorption mechanism. Meanwhile, the thermodynamic analyses imply that the electrosorption of salt ions onto the CFC–SRGO electrode is driven by a physisorption process.

Experimental design methodology applied to electrochemical oxidation of the herbicide atrazine using Ti/IrO2 and Ti/SnO2 circular anode electrodes

The degradation of the herbicide atrazine in aqueous medium (initial concentration of 100 μg l(-1)) has been studied by electrooxidation process using Ti/IrO(2) and Ti/SnO(2) circular anode electrodes. The performance of the electrolytic cell resulted from its capability of reacting on the pollutants by using indirect effect of electrical current where active chlorine is electrochemically generated. A factorial experimental design was firstly used for determining the influent parameters on the herbicide atrazine degradation. The current intensity and treatment time were the main influent parameters on the degradation rate. Using a 2(4) factorial matrix, the best performance for atrazine degradation (removal of 95%) was obtained by selecting Ti/IrO(2) anode operated at a current intensity of 2.0 A during 40 min of treatment time in the presence of 1.0 g Na Cl l(-1). Then, the optimal experimental parameters for atrazine degradation have been investigated by using a Central Composite methodology. Under the optimal conditions determined by this method, electrooxidation can economically be applied to oxidise atrazine (73% of degradation for a total cost of 0.057 US

Effect of nitrate ions on the efficiency of sonophotochemical phenol degradation.

m(-3)) while using Ti/IrO(2) anode operated at a current intensity of 1.4A during 22 min of treatment time in the presence of 1.0 g NaCl l(-1).

Optimization of Copper Removal from ACQ-, CA-, and MCQ-Treated Wood Using an Experimental Design Methodology

A sonophotochemical oxidation process has been used for the treatment of an aqueous solution of phenol. The aim of this work is to evaluate the effect of nitrate ions on hydroxyl radical production and on phenol oxidation. It has been demonstrated that ultrasound can produce NOx (nitrate and nitrite), with a production rate of 2.2 μM min(-1). The photolysis of nitrate can significantly improve the hydroxyl radical production. The apparent rate constant for hydroxyl radical production increased from 0.0015 min(-1) to 0.0073 min(-1) while increasing initial nitrate concentration from 0 to 0.5mM. The concentration of hydroxyl radical was directly proportional to the initial nitrate concentration. Using US/UV process, the apparent reaction rate constant of phenol degradation in the presence of nitrate reached 0.020 min(-1), which was relatively lower than the value obtained (0.027 min(-1)) in the absence of nitrate. It appeared that, nitrate ions can inhibit the sonochemical degradation of organic compounds such as phenol.

Electrochemical Oxidation of Chlortetracycline Using Ti/IrO2 and Ti/PbO2 Anode Electrodes: Application of Experimental Design Methodology

AbstractThe development of appropriate disposal options for copper-based treated wood waste has been encouraged owing to stringent regulations regarding solid-waste landfilling or burning. Previous studies identified an efficient chemical process for removing metals from wood treated with chromated copper arsenate (CCA), alkaline copper quaternary (ACQ), copper azole (CA), and micronized copper quaternary (MCQ). The objective of this research was to identify optimal leaching parameters for removing copper from ACQ-, CA-, and MCQ-treated wood in terms of efficiency and operating costs. A 24 Box-Behnken design was used for determining influential parameters (sulfuric acid concentration, temperature, retention time, and number of leaching steps) on the copper removal and for identifying optimal leaching conditions. The results obtained showed that sulfuric acid concentration and number of leaching steps were the main influential parameters on copper solubilization from alternatively treated wood. The values ...

Effectiveness of a hybrid process combining electro-coagulation and electro-oxidation for the treatment of domestic wastewaters using response surface methodology

AbstractThe degradation of chlortetracycline hydrochloride in aqueous medium (initial concentration of 10  mg/L) has been studied by electrooxidation process using Ti/PbO2 and Ti/IrO2 anode electrodes. The performance of the electrolytic cell resulted from its capability of reacting on pollutants by using both effects of electrolysis. Indeed, the organic pollutants can be destroyed at the electrode surface where hydroxyl radicals are generated (direct effect), and they can be simultaneously oxidized in solution by means of active chlorine (indirect effect). Different operating parameters, such as current density, reaction time, and temperature, were investigated. The optimal experimental parameters for chlortetracycline degradation have been investigated by using a central composite design (CCD) methodology. It has been demonstrated that under the optimal conditions determined by this method, electrooxidation can economically be applied to oxidize chlortetracycline (96% of degradation for a total cost of ...

Selective recovery of metals in leachate from chromated copper arsenate treated wastes using electrochemical technology and chemical precipitation

The performance of a two-stage process combining electro-coagulation (EC) and electro-oxidation (EO) was studied for the treatment of domestic wastewater (DWW) loaded with organic matter. The process was firstly evaluated in terms of its capability of simultaneously producing an oxidant and a coagulant agents using aluminum (Al) (or iron (Fe)) as bipolar and sacrificial electrodes, whereas graphite (Gr) electrodes were used as monopolar electrodes. Relatively high concentrations of chlorine (9.6 mg/min A) and Al (20—40 mg Al/L) or Fe (40–60 mg Fe/L) were produced. Subsequently, the factorial and central composite design methodologies were successively employed to define the optimal operating conditions for total chemical oxygen demand (COD) removal from DWW. Current intensity and treatment time were found to be very meaningful for chemical oxygen demand removal. The effect of these two main factors was around 90% on the investigated response, whereas the type of sacrificial electrode and the other interaction effects represent only 10%. The treatment using aluminum electrode and a current intensity imposed of 0.7 A during 39 min was found to be the optimal conditions in terms of cost/effectiveness. Under these conditions, 78% of COD removal can be obtained for a total cost of 0.78 US

Experimental design methodology applied to electrochemical oxidation of carbamazepine using Ti/PbO2 and Ti/BDD electrodes.

/m3.