Highly porous seeding-free boron-doped ultrananocrystalline diamond used as high-performance anode for electrochemical removal of carbaryl from water.

Boron-doped diamond (BDD) electrodes are regarded as the most promising catalytic materials that are highly efficient and suitable for application in advanced electrochemical oxidation processes targeted at the removal of recalcitrant contaminants in different water matrices. Improving the synthesis of these electrodes through the enhancement of their morphology, structure and stability has become the goal of the material scientists. The present work reports the use of an ultranano-diamond electrode with a highly porous structure (B-UNCDWS/TDNT/Ti) for the treatment of water containing carbaryl. The application of the proposed electrode at current density of 75 mA cm-2 led to the complete removal of the pollutant (carbaryl) from the synthetic medium in 30 min of electrolysis with an electric energy per order of 4.01 kWh m-3 order-1. The results obtained from the time-course analysis of the carboxylic acids and nitrogen-based ions present in the solution showed that the concentrations of nitrogen-based ions were within the established maximum levels for human consumption. Under optimal operating conditions, the proposed electrode was successfully employed for the complete removal of carbaryl in real water. Thus, the findings of this study show that the unique, easy-to-prepare BDD-based electrode proposed in this study is a highly efficient tool which has excellent application potential for the removal of recalcitrant pollutants in water.

Electrochemical oxidation of ciprofloxacin in different aqueous matrices using synthesized boron-doped micro and nano-diamond anodes.

The present work investigates the electrocatalytic performance of two different morphologies of boron doped-diamond film electrode (microcrystalline diamond - MCD, and nanocrystalline diamond - NCD) used in electrochemical oxidation for the removal of the antibiotic ciprofloxacin (CIP). A thorough study was conducted regarding the formation of the MCD and NCD films through the adjustment of methane in CH4/H2 gas mixture, and the two films were compared in terms of crystalline structure, apparent doping level, and electrochemical properties. The physicochemical results showed that the NCD film had higher sp2 carbon content and greater doping level; this contributed to improvements in its surface roughness, as well as its specific capacitance and charge transfer, which consequently enhanced its electrocatalytic activity in comparison with the MCD. The results obtained from CIP removal and mineralization assays performed in sulfate medium also showed that the NCD was more efficient than the MCD under all the current densities investigated. The effects of CIP concentration and the evolution of the final by-products, including short-chain carboxylic acids and inorganic ions, were also investigated. The electrochemical performance of the NCD was evaluated in different aqueous matrices, including chloride medium, real wastewater and simulated urine. The application of the NCD led to complete or almost complete CIP degradation, regardless of the medium employed. The kinetic constant rates obtained under the different media investigated were as follows: synthetic urine (0.0416 min-1 - R2 = 0.991) < real wastewater (0.0923 min-1 R2 = 0.997) < synthetic matrix containing chloride (0.1992 min-1 - R2 = 0.995); this shows that the pollutant degradation was affected by the type of aqueous matrix and the oxidants that were electrogenerated in situ. The results obtained from the analysis of electrical energy per order (EE/O) showed that the treatment of simulated urine spkiked with required the highest energy consumption, followed by the real effluent and synthetic matrix containing chloride. The present study proves the viability of electrocatalytic nanostructured materials to the treatment of antibiotics in complex matrices.

Lead detection using micro/nanocrystalline boron-doped diamond by square-wave anodic stripping voltammetry.

Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 µg L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio.