The environment pollution, in particular that of the aquatic environment, by wastewater is a reality because it is discharged for the most part without treatment. The presence of pharmaceutical pollutants such as paracetamol in these waters can constitute a risk to human health. The objective of this work is to study the electrochemical oxidation of paracetamol using cyclic voltammetry on the boron doped diamond (BDD) anode and boron doped diamond modified by gold particles (Au-BDD) anode. The Au-BDD electrode was obtained by modifying the surface of BDD with gold particles. This was done by electrodeposition (chronoamperometry) in 0.5 M HAuCl4 and 0.1 M H2SO4 using a three pulse nucleation and growth process. Physical characterization with Scanning Electron Microscopy coupled with Dispersive Energy spectroscopy has shown that the Au-BDD surface presents asperities with the presence of microparticles and nanoparticles. The electrochemical characterization made in three electrolytic solutions (H2SO4, NaOH and KClO4) showed that Au-BDD has a high electroactivity domain than that of BDD. The study of the Benzoquinone-hydroquinone redox couple has shown a quasi-reversible character of these two anodes. It also revealed that Au-BDD has a more accentuated metallic character than BDD. The voltammetric measurements made it possible to show that the paracetamol oxidation is limited by the transport of material on each anode. This oxidation is characterized by the presence of an anodic peak in the support electrolytes stability domain. The paracetamol oxidation is rapid on Au-BDD than on BDD in the various medium explored, thus showing that Au-BDD is more efficient than BDD for the paracetamol oxidation by electrochemical means.

Lead, even in low concentrations, can be dangerous and toxic to humans and their environment. Due to the toxicity of this metal, an electroanalytical method has been developed for the direct quantitative determination of Pb2+. The Pb2+ detection was performed using Differential Pulse Anodic Stripping Voltammetry. The quantification of Pb2+ by these electrochemical methods was carried out on a boron-doped diamondmicro electrode in HNO3 medium (0.01 M). This work made it possible to efficiently detect lead with a detection limit equal to 0.052 μM and a quantification limit equal to 0.173 μM. This method made it possible to selectively detect and quantify the Pb2+ in the presence of other metals such as Cd2+ and Cu2+. In the presence of other metals, a recovery rate of 94.53% was observed. This value is close to the recovery rate obtained (98.6%) when the Pb2+ is alone in electrolyte.

This study investigated the electrochemical behavior of iohexol in its commercial formulation omnipaque on a boron-doped diamond electrode using cyclic voltammetry and chronoamperometry. The dependence of the anodic peak current density vs. iohexol concentration is linear and can be applied to the determination of the substrate concentration in environmental samples and pharmaceuticals. The iohexol electrooxidation on boron-doped diamond electrode is diffusion-controlled process and proceed via two ways: a direct electron transfers at the surface of boron-doped diamond electrode and an indirect oxidation mediated by in situ oxidative species. The iohexol electrooxidation in pH range from 2 to 6 includes exchange of 4 electrons and 1 proton, at pH superior to 6 it includes an exchanged of 2 electrons and 1 proton. The values of activation energy, anodic transfer coefficient, heterogenous rate constant, diffusion coefficient and the catalytic rate constant were 14.164 kJ mol-1, 0.428, 1.06 s-1, 4.47 cm2 s-1 and 3.61 M-1 s-1 respectively. It appears from those results that, on our electrode, for the high potential scan rates, few actives sites mainly those located at the electrode surface are involved in the iohexol oxidation process. As the potential scan rate decreases, more actives sites are involved in the process.

This study showed that the oxidation of rhodamine B by the Fenton process is a very fast method because the reaction takes place within the first 20 minutes. The mixture of Fe2+ and H2O2 produces hydroxide radicals responsible for the degradation of rhodamine B. The study of pH influence on the rhodamine B oxidation reveals that for maximum oxidation of rhodamine B, the pH must be less than or equal to 2. For pH > 2, there is a decrease in rhodamine B oxidation. This is due to side reactions that occur if the concentration of Fe2+ is high. This reduces the amount of oxidized rhodamine B. We note that the oxidation of rhodamine B is faster for low concentrations than for high concentrations of rhodamine B. According to our results, for a maximum oxidation of 5 mg / L of rhodamine, it takes 8.4.10−4 mg / L of Fe2+, 3.10−3 M of H2O2 and pH = 2. This work also showed that the presence of inorganic ions strongly slows down the rate of degradation of rhodamine in the following order: Cl− ˂ NO3− ˂ SO42− ˂ PO43−.

The platinum anode modified by metal oxides electrodes degrades Abidjan wastewater which contains a high concentration of Cl-. During this degradation process, the organic polluants are oxidized, O2 and Cl2 are produced. The purpose of this study is to contribute to the understanding of these reaction mechanisms by studying the kinetics of O2 and Cl2 evolution at neutral pH on Pt. The study was performed by interpreting the voltammograms and Tafel slopes obtained. The voltammetric measurements were carried out using an Autolab Potentiostat from ECHOCHEMIE (PGSTAT 20) connected by interface to a computer. Pt electrode was prepared on titanium (Ti) substrate by thermal decomposition techniques at 400°C. The characterization of the surface of the prepared electrode by scanning electron microscopy and X-ray photoelectron spectrometry showed the presence of platinum on its surface. The results obtained show that the OH· are adsorbed on the active sites of Pt. Then they react to form PtO. Then by reaction between the surface oxygen and PtO, O2 is produced and the active sites are regenerated. In the presence of low Cl- concentration, there is a competition between the Cl2 and O2 evolution reactions. However, Cl2 only is produced for high Cl- concentrations. The kinetics of the evolution reaction of chlorine increases with the concentration of Cl- and remains constant for concentrations greater than 0.5 M. This study also showed that the chlorine reduction reaction produced in solution is a diffusion-controlled reaction for low scan rates.