Ultrasound potentialities on the determination of the pesticide carbaryl using diamond electrodes

The potentiality of the use of ultrasound radiation in association with a boron-doped diamond electrode was evaluated on the voltammetric determination of the pesticide carbaryl. Improvements in the sensitivity, limit of detection and reproducibility of the measurements were observed due to both, the enhancement of mass transport and the cleaning of the electrode surface provided by ultrasound. Satisfactory recovery levels for carbaryl in pure water (96-98%) and pineapple juice (89-92%) for quiescent and sonovoltammetric methodologies were obtained. These methodologies can be alternative tools for the analyses of pesticides in fruit samples, mainly the insonated condition that improve the analytical performance and dispense intermediary cleanings of the electrode surface.CNPqFapes

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.CNPqFAPES

Biodegradability improvement of clopyralid wastes through electrolysis using different diamond anodes

The use of boron-doped (BDDs) anodes for efficient removal of complex organic molecules, such as organochlorine compounds, is well stated in the literature. However, the role of the different characteristics of this anode on the transformation of these type of contaminants into more biodegradable molecules is a topic of interest that need to be clarified when aimed an efficient combination of an electrochemical system as a previous step to biological treatment. In this work, improvement in the biodegradability of synthetic wastes polluted with clopyralid, as an organochlorine model compound, is studied after electrolysis with different BDDs in the presence of the two most common supporting electrolytes (containing sulfate or chloride ions). For that, clopyralid removal, mineralization, aromatics intermediates, short-chain carboxylic acids, and inorganic ions were monitored. Improved results were found in sulfate media for BDD with 200 ppm, capable of removing 88.7% of contaminants and 85% of TOC, resulting in an improvement in biodegradability of almost 7-fold compared to the initial sample. These findings point out that lower doping levels are preferable when coupling studied technologies

Photoelectrolysis of clopyralid wastes with a novel laser-prepared MMO-RuO2TiO2 anode

This paper studies the applicability of a novel laser-prepared mixed metal oxide (MMO-RuO2TiO2) anode in the photoelectrochemical degradation of clopyralid, a toxic and biorefractory herbicide. Results are compared to those obtained using the well-known boron-doped diamond (BDD) anode and demonstrate that, although the electrolysis with diamond is more effective than that obtained with the new electrode, the irradiation of UVC light makes the novel MMO material more effective in chloride media. It was explained in terms of the homolysis of hypochlorous acid/hypochlorite to form chloride and hydroxyl radicals. Photoelectrochemical degradation with MMO produced a marked synergistic effect in TOC removal, especially in the presence of chloride ions. On the contrary, for the BDD anode, at the tested conditions, antagonisms were found in both sulfate and chloride media. These important synergisms allows finding conditions in which the novel anode can be competitive with the BDD

Understanding the electrolytic generation of sulfate and chlorine oxidative species with different boron-doped diamond anodes

The electrochemical generation of several oxidative species was studied at the surfaces of five commercial boron-doped diamond anodes with different doping levels (100–8000 ppm). These insights can open the possibility of tailoring anodes for a more efficient application in environmental remediation processes. All materials evaluated were characterized by linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, contact angle, and scanning electron microscopy, as well as by bulk electrolysis. As a result, it was confirmed that the boron doping level influences the physical and electrochemical properties of the electrodes, indicating distinct behavior of the electrodes on the production of chlorine and sulfate oxidative species. The higher the boron doping, the lower is the crystallite size, and the higher is the conductivity, the hydrophilic behavior, and the electron-transfer activity. Voltammetric characterization demonstrates that low boron doping favors the formation of hydroxyl radicals, while high doping levels favor the direct electrochemical oxidation of sulfate or chloride. Moreover, when operating at high overpotentials in bulk electrolysis (typical conditions in environmental applications), the formation of chlorine and sulfate oxidative species is favored at low boron doping levels. This behavior is attributed to the very efficient mediated formation of these oxidants from the hydroxyl radicals, whose production is promoted with these electrodes at those conditions. It means that only operating at much softer conditions, the unique direct generation of hydroxyl oxidant occurs, opening a way for the potential prevention of perchlorate formation during disinfection by using highly boron-doped diamond anodes

Testing the role of electrode materials on the electro-Fenton and photoelectro-Fenton degradation of clopyralid

This work studies the effect of the anode and cathode materials on the degradation of the herbicide clopyralid. Different electrochemical advanced oxidation processes (EAOPs), including electrochemical oxidation with electrogenerated hydrogen peroxide (EO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF) were carried out. The first experiments were focused on the effect of the cathode, where the use of the hydrophobic carbon felt modified by the deposition of carbon black & PTFE mixture (MCF) improves the H2O2 production in comparison to a conventional carbon felt (CF), regardless of the anode material employed. On the other hand, a laser-made Ti/Ru0.3Ti0.7O2 mixed metal oxide (MMO) and a commercial boron-doped diamond (BDD) were compared as anodes. Results obtained point out that the MMO anode promotes the accumulation of this oxidant (H2O2) in bulk. Once characterized by the production of hydrogen peroxide, the second part of this study focused on the degradation of clopyralid with the MCF cathode with different EAOPs. Results demonstrate that clopyralid fastly degrades in the sequence EO-H2O2 < EF < PEF, and almost complete mineralization occurs for EF and PEF employing MMO or BDD as the anode. Synergy effect study shows that irradiation of 9 W UVC produces a positive synergistic effect of 81.7% and 41.55% (for the PEF-MMO and PEF-BDD, respectively), ascribed to the additional removal of aromatic intermediates by the UVC and the activation of H2O2. At the end of the treatment, mineralization of the herbicide was attained at 1.22 kW h (g−1 TOC). Finally, considering the lower cost of the prepared MMO, these findings demonstrate the potentiality of using modified carbon felt combined with the laser-made Ti/Ru0.3Ti0.7O2 anode for the treatment of polluted waters

Influence of the doping level of boron-doped diamond anodes on the removal of penicillin G from urine matrixes

The objective of this study is to understand the influence of the characteristics of boron-doped diamond anodes on the degradation of Penicillin G contained in urine. Therefore, five commercial BDD anodes with different boron doping levels (100 ppm - 8000 ppm) were studied. These electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and electrolysis. The boron doping was found to correlate well with the electrochemical properties of the electrodes, and results indicate a different behavior in drug degradation. The improvement in the toxicity and the reduction of the antibiotic effect of urine were the most innovative inputs monitored. For this, the concentration of Penicillin G, the toxicity toward Vibrio fisheri, and the antibiotic effect in Enterococcus faecalis were monitored. The best results were found for the BDD with a boron content of 200 ppm, capable of removing 100% of the antibiotic, reducing toxicity by 90%, and eradicating the antibiotic effect. These results indicate that low doping levels are more efficient for urine removal by anodic oxidation

Improving biodegradability of clopyralid wastes by photoelectrolysis: The role of the anode material

In this work, the removal of the non-readily biodegradable herbicide clopyralid by electrochemical (EC) and photoelectrochemical (PhEC) oxidation with different anode materials were conducted looking to improve not only its oxidation but also its biodegradability. First, in order to find out optimal conditions, it was carried out EC and PhEC degradations in chloride medium, at current densities ranging from 30 to 100 mA cm−2 during 1 h (0.8–2.7 A h L−1), using as anodes MMO-RuO2TiO2, MMO-RuO2IrO2, MMO-IrO2Ta2O5 and boron-doped diamond (BDD). Results show better efficiencies on clopyralid removal for MMO-RuO2IrO2 and BDD anodes at lower current densities. Then, the influence of all anodes on clopyralid transformation was evaluated, extending the electrolysis and photoelectrolysis for 8 h applying 30 mA cm−2 (6.4 A h cm−3). At these conditions, better outcomes are observed for PhEC degradation, where complete pollutant removal is attained for BDD anode and 88.7% for MMO-RuO2IrO2, while COD removal is 47.7% for MMO and 43.1% for BDD anode. Then, short-term biodegradability tests, conducted for EC and PhEC processes, pointed out that MMO-RuO2TiO2 is the most promising anode material, being capable of improving biodegradability in 48.2% and 53% for EC and PhEC degradation, respectively. The toxicity of treated solutions using MMO-RuO2TiO2 and BDD anodes in both EC and PhEC degradation were compared, employing the inhibitory effect in the bioluminescence of marine bacteria Vibrio Fisheri. Toxicity assessments show that toxicity significantly reduces by using the MMO-RuO2TiO2 in NaCl and Na2SO4 medium for both processes. Finally, this study demonstrates that photoelectrolysis with MMO anodes was the most effective strategy in order to increase biodegradability in chloride media, as well as to reduce the toxicity of the treated waste

New laser-based method for the synthesis of stable and active Ti/SnO2–Sb anodes

The main drawback impairing the application of highly electrocatalytic SnO2–Sb anodes in the removal of recalcitrant pollutants from wastewater is their short service life. Here, we report the synthesis of Ti/SnO2–Sb anodes with improved stability through a CO2 laser as the primary heating source. The influence of different calcination temperatures (400, 500, 600 °C), and varied composition of the solvent in the precursor solution, on the stability and activity of the anodes, were investigated. Notably, the use of the CO2 laser heating method at 600 °C improves the service life up to 5-fold as compared to the conventionally prepared anodes. The laser-made Ti/SnO2–Sb anode calcined at 600 °C exhibits the best electrocatalytic performance with the fastest color removal rates in the oxidation of methylene blue dye. Therefore, for the first time, Ti/SnO2–Sb anodes with superior properties were produced by a fast method employing CO2 laser, envisaging its future applications in wastewater treatment

Enhancement of wastewater treatment using novel laser-made Ti/SnO2–Sb anodes with improved electrocatalytic properties

In this study, a novel Ti/SnO2–Sb anode, improved using a laser heating manufacturing procedure, was applied in wastewater treatment. For comparison purposes, similar anodes were manufactured using the conventional furnace heating procedure. Electrochemical characterizations in the background electrolyte confirmed that the novel material has improved electric conductivity, as compared to the furnace-made one and, hence, it may lead to much lower operating costs in real applications. The electrocatalytic properties of the novel anode in comparison with the conventional were evaluated using a standard and well-known reaction: the phenol oxidation. Different operational conditions were evaluated. Concentrations of phenol were monitored by HPLC and analysis of organic matter by TOC analyzer. The best condition of phenol removal was associated with a relatively low energy consumption of 0.80 kWh (gTOC)−1 and specific electrical energy consumption of 0.81 kWh m−3 order−1. Interestingly, the phenol is not completely removed after 60 min of treatment using the furnace-made anode under the same operating conditions in which was fully depleted with the new electrode. Moreover, chlorinated by-products remained in the final solution with the conventional electrode and were exhausted with the novel one. Finally, after an extensive comparison with literature about the oxidation of phenol, the Ti/SnO2–Sb produced by laser-manufacturing procedure presented the best phenol removal as compared with both non-active and active anodes