Electrochemical incineration of sulfanilic acid at a boron-doped diamond anode

Electrochemical Oxidation of Anastrozole over a BDD Electrode: Role of Operating Parameters and Water Matrix

The electrochemical oxidation (EO) of the breast-cancer drug anastrozole (ANZ) is studied in this work. The role of various operating parameters, such as current density (6.25 and 12.5 mA cm−2), pH (3–10), ANZ concentration (0.5–2 mg L−1), nature of supporting electrolytes, water composition, and water matrix, have been evaluated. ANZ removal of 82.4% was achieved at 1 mg L−1 initial concentration after 90 min of reaction at 6.25 mA cm−2 and 0.1 M Na2SO4. The degradation follows pseudo-first-order kinetics with the apparent rate constant, kapp, equal to 0.022 min−1. The kapp increases with increasing current density and decreasing solution pH. The addition of chloride in the range 0–250 mg L−1 positively affects the removal of ANZ. However, chloride concentrations above 250 mg L−1 have a detrimental effect. The presence of bicarbonate or organic matter has a slightly negative but not significant effect on the process. The EO of ANZ is compared to its degradation by solar photo-Fenton, and a preliminary economic analysis is also performed.

Biofouling suppresses effluent toxicity in an electrochemical filtration system for remediation of sulfanilic acid-contaminated water

Electrochemical filtration system (EFS) has received broad interest due to its high efficiency for organic contaminants removal. However, the porous nature of electrodes and flow-through operation mode make it susceptible to potential fouling. In this work, we systematically investigated the impacts of biofouling on sulfanilic acid (SA) removal and effluent toxicity in an EFS. Results showed that the degradation efficiency of SA slightly deteriorated from 92.3% to 81.1% at 4.0 V due to the electrode fouling. Surprisingly, after the occurrence of fouling, the toxicity (in terms of luminescent bacteria inhibition) of the EFS effluent decreased from 72.3% to 40.2%, and cytotoxicity assay exhibited similar tendency. Scanning electron microscopy and confocal laser scanning microscopy analyses revealed that biofouling occurred on the porous cathode, and live microorganisms were the dominant contributors, which are expected to play an important role in toxicity suppression. The relative abundance of Flavobacterium genus, related to the degradation of p-nitrophenol (an aromatic intermediate product of SA), increased on the membrane cathode after fouling. The analysis of degradation pathway confirmed the synergetic effects of electrochemical oxidation and biodegradation in removal of SA and its intermediate products in a bio-fouled EFS, accounting for the decrease of the effluent toxicity. Results of our study, for the first time, highlight the critical role of biofouling in detoxication using EFS for the treatment of contaminated water.

Photo-electrooxidation treatment of Acetaminophen in aqueous solution using BDD-Fe and BDD-Cu systems

In this study, acetaminophen (ACT) in aqueous solution was treated with electrooxidation and photo-electrooxidation processes (PEO). An electrochemical cell was used for the treatment of different concentrations of ACT (10, 50 and 80 mg L^-1). A 2³ factorial design was proposed, and the variables studied were current intensity 0.5 A (45.45 mA cm^-2) and 1.0 A (90.91 mA cm^-2), electrode configuration (anode:BDD, cathode:Fe or Cu) and presence/absence of UV light; NaCl 0.043 M (2.5 g L^-1) was used as supporting electrolyte, the initial pH was 5.5, and the treatment time was 3 h. The aqueous solutions were characterized before and after the treatment using infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), chemical oxygen demand (COD), total organic carbon (TOC), total carbon (TC), and fluorescence spectroscopy. The optimal operating conditions using an initial ACT concentration of 80 mg L^-1 were 1.0 A, BDD-Fe configuration and UV light (254 nm). The removal efficiencies were 100% of ACT and 82.75% of TOC after 15 min of treatment. At concentrations of 50 and 10 mg L^-1, 77.16% and 50.29% of TOC were removed after 10 and 5 min of treatment, respectively. Finally, the kinetic study showed an increase in the rate constants when the UV light was applied.

Chemical removal of m-cresol: a critical review

m-Cresol containing wastewater has generally become a globally environmental issue due to its refractory and high toxicity towards plants, animals and human being. The development of m-cresol related industries increases the risk of excessive m-cresol discharge, making high efficiency methods to treat m-cresol an urgent topic in both economic and environmental aspects. This review focuses on the chemical treatment methods of m-cresol wastewater, including chemical adsorption, photocatalytic degradation, electrocatalytic degradation and catalytic wet oxidation. The efficiency, cost and process optimization of different methods are discussed in detail. Chemical adsorption is convenient but has relatively low efficiency. Photocatalytic degradation is an easily operated technology with high efficiency, but the selection of catalyst is too limited and the cost of light source is relatively high. Electrocatalytic degradation is time-saving but energy-intensive, and operational difficulty brings a barrier to industrialization. Catalytic wet oxidation (CWO) is highly effective and easily modified, but the performance and stability of catalysts are still very moderate. Following this, the selection and application of different methods regarding the requirement of actual environment are analyzed. Finally, a perspective on the opportunities and development for efficient m-cresol removal method is given.

Ultrathin Diamond Nanofilms-Development, Challenges, and Applications

Diamond is a highly attractive material for ample applications in material science, engineering, chemistry, and biology because of its favorable properties. The advent of conductive diamond coatings and the steady demand for miniaturization in a plethora of economic and scientific fields resulted in the impetus for interdisciplinary research to develop intricate deposition techniques for thin (≤1000 nm) and ultra-thin (≤100 nm) diamond films on non-diamond substrates. By virtue of the lowered thickness, diamond coatings feature high optical transparency in UV-IR range. Combined with their semi-conductivity and mechanical robustness, they are promising candidates for solar cells, optical devices, transparent electrodes, and photochemical applications. In this review, the difficulty of (ultra-thin) diamond film development and production, introduction of important stepping stones for thin diamond synthesis, and summarization of the main nucleation procedures for diamond film synthesis are elucidated. Thereafter, applications of thin diamond coatings are highlighted with a focus on applications relying on ultrathin diamond coatings, and the excellent properties of the diamond exploited in said applications are discussed, thus guiding the reader and enabling the reader to quickly get acquainted with the research field of ultrathin diamond coatings.

Electrochemical oxidation of butyl paraben on boron doped diamond in environmental matrices and comparison with sulfate radical-AOP

The electrochemical oxidation (EO) of butyl paraben (BP) over boron-doped diamond (BDD) anode was studied in this work. Emphasis was put on degradation performance in various actual water matrices, including secondary treated wastewater (WW), bottled water (BW), surface water (SW), ultrapure water (UW), and ultrapure water spiked with humic acid (HA). Experiments were performed utilizing 0.1 M Na₂SO₄ as the electrolyte. Interestingly, matrix complexity was found to favor BP degradation, i.e. in the order WW ~ BW > SW > UW, thus implying some kind of synergy between the water matrix constituents, the reactive oxygen species (ROS) and the anode surface. The occurrence of chloride in water matrices favors reaction presumably due to the formation of chlorine-based oxidative species, and this can partially offset the need to work at increased current densities in the case of chlorine-free electrolytes. No pH effect in the range 3-8 on degradation was recorded. EO oxidation was also compared with a sulfate radical process using carbon black as activator of sodium persulfate. The matrix effect was, in this case, detrimental (i.e. UW > BW > WW), pinpointing the different behavior of different processes in similar environments.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.

Conductive diamond: synthesis, properties, and electrochemical applications

This review summarizes systematically the growth, properties, and electrochemical applications of conductive diamond.

Study on the degradation mechanism and pathway of benzene dye intermediate 4-methoxy-2-nitroaniline via multiple methods in Fenton oxidation process

Benzene dye intermediate (BDI) 4-methoxy-2-nitroaniline (4M2NA) wastewater has caused significant environmental concern due to its strong toxicity and potential carcinogenic effects. Reports concerning the degradation of 4M2NA by advanced oxidation process are limited. In this study, 4M2NA degradation by Fenton oxidation has been studied to obtain more insights into the reaction mechanism involved in the oxidation of 4M2NA. Results showed that when the 4M2NA (100 mg L-1) was completely decomposed, the TOC removal efficiency was only 30.70-31.54%, suggesting that some by-products highly recalcitrant to the Fenton oxidation were produced. UV-Vis spectra analysis based on Gauss peak fitting, HPLC analysis combined with two-dimensional correlation spectroscopy and GC-MS detection were carried out to clarify the degradation mechanism and pathway of 4M2NA. A total of nineteen reaction intermediates were identified and two possible degradation pathways were illustrated. Theoretical TOC calculated based on the concentration of oxalic acid, acetic acid, formic acid, and 4M2NA in the degradation process was nearly 94.41-97.11% of the measured TOC, indicating that the oxalic acid, acetic acid and formic acid were the main products. Finally, the predominant degradation pathway was proposed. These results could provide significant information to better understand the degradation mechanism of 4M2NA.

Boron-doped diamond electrooxidation of ethyl paraben: The effect of electrolyte on by-products distribution and mechanisms

Ethyl paraben (EP), a representative emerging pollutant of the parabens family, was subject to electrochemical oxidation over a boron-doped diamond (BDD) anode. Experiments were carried out in a single-compartment cell at 10-70 mA cm^-2 current density, 200-600 μg L^-1 EP concentration, initial solution pH 3-9 and 0.1 M electrolyte concentration. The degradation rate is favored at increased current densities and in the presence of NaCl as the supporting electrolyte, while the pH effect is inconsiderable. For instance, the first order rate constant for the degradation of 200 μg L^-1 EP at 30 mA cm^-2 was 0.25, 0.1 and 0.07 min^-1 with NaCl, Na₂SO₄ and HClO₄, respectively. Degradation in secondary treated wastewater was faster than in pure water presumably due to the action of chloride ions present in the effluent. Liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) was employed to determine major transformation by-products (TBPs). The route of EP degradation with Na₂SO₄ involves hydroxylation and demethylation reactions, signifying the role of electrogenerated hydroxyl radicals in the process. Twenty one TBPs were identified with NaCl as the electrolyte, including several chlorinated and non-chlorinated dimers and trimers; these findings suggest that indirect oxidation mediated by chlorine radicals and other chlorine active species also takes place. In this view, the role of the supporting electrolyte is crucial since it can influence both reaction kinetics and pathways.

Electrochemical mineralization pathway of quinoline by boron-doped diamond anodes

Boron-doped diamond anodes were selected for quinoline mineralization, and the resulting intermediates, phenylpropyl aldehyde, phenylpropionic acid, and nonanal were identified and followed during quinoline oxidation by gas chromatography-mass spectrometry and high-performance liquid chromatography. The evolutions of formic acid, acetic acid, oxalic acid, NO2(-), NO3(-), and NH4(+) were quantified. A new reaction pathway for quinoline mineralization by boron-doped diamond anodes has been proposed, where the pyridine ring in quinoline is cleaved by a hydroxyl radical giving phenylpropyl aldehyde and NH4(+). Phenylpropyl aldehyde is quickly oxidized into phenylpropionic acid, and the benzene ring is cleaved giving nonanal. This is further oxidized to formic acid, acetic acid, and oxalic acid. Finally, these organic intermediates are mineralized to CO2 and H2O. NH4(+) is also oxidized to NO2(-) and on to NO3(-). The results will help to gain basic reference for clearing intermediates and their toxicity.

Single and Coupled Electrochemical Processes and Reactors for the Abatement of Organic Water Pollutants: A Critical Review

Traditional physicochemical and biological techniques, as well as advanced oxidation processes (AOPs), are often inadequate, ineffective, or expensive for industrial water reclamation. Within this context, the electrochemical technologies have found a niche where they can become dominant in the near future, especially for the abatement of biorefractory substances. In this critical review, some of the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants are discussed in detail with the following goals: (1) to present the fundamental aspects of the selected processes; (2) to discuss the effect of both the main operating parameters and the reactor design on their performance; (3) to critically evaluate their advantages and disadvantages; and (4) to forecast the prospect of their utilization on an applicable scale by identifying the key points to be further investigated. The review is focused on the direct electrochemical oxidation, the indirect electrochemical oxidation mediated by electrogenerated active chlorine, and the coupling between anodic and cathodic processes. The last part of the review is devoted to the critical assessment of the reactors that can be used to put these technologies into practice.

Effluent characteristics of advanced treatment for biotreated coking wastewater by electrochemical technology using BDD anodes

Effluent of biotreated coking wastewater comprises hundreds of organic and inorganic pollutants and has the characteristics of high toxicity and difficult biodegradation; thus, its chemical oxygen demand cannot meet drainage standards in China. A boron-doped diamond anode was selected for advanced treatment of biotreated coking wastewater, and considering the efficiency of the removal of total organic carbon and energy consumption, optimal conditions were obtained as current density of 75 mA cm(-2), electrolysis time of 1.5 h, and an electrode gap of 1.0 cm in an orthogonal test. Effluent characteristics were investigated at different electrolysis times. The ratio of the 5-day biochemical oxygen demand (BOD5) to the chemical oxygen demand increased from an initial value of 0.05 to 0.65 at 90 min. Fluorescence spectra were used to evaluate the evolution of refractory organics. Two fluorescence peaks for raw wastewater, corresponding to an aromatic protein-like substance II and humic acid-like substance, weakened at 30 and at 90 min, only the former was detected. The specific oxygen uptake rate was used to assess effluent toxicity, and an obvious inhibition effect was found at 15 min; then, it was significantly faded at 30 and 45 min. The BOD5/NO3 (-)-N ratio increased from an initial value of 0.48 to 1.25 at 45 min and then gradually dropped to 0.69 at 90 min. According to the above effluent characteristics, it is strongly suggested that electrochemical technology using boron-doped diamond anodes is combined with biological denitrification technology for the advanced treatment of biotreated coking wastewater.

Effective heterogeneous electro-Fenton process of m-cresol with iron loaded actived carbon

The degradation of m-cresol (MC) has been investigated by heterogeneous electro-Fenton process using iron loaded activated carbon (Fe-AC) as heterogeneous electro-Fenton catalyst.

Mineralization of Quinoline by BDD Anodes: Variable Effects and Its Effluent Characteristics

BDD anodes were selected for quinoline mineralization and influence of operating parameters, such as current density, initial quinoline concentration, supporting electrolyte, and initial pH was investigated. Based on the consideration of quinoline removal efficiency and average current efficiency, at initial quinoline concentration of 50 mg L−1and pH of 7, the optimal condition was confirmed as current density of 75 mA cm−2, electrolysis time of 1.5 h, and Na2SO4concentration of 0.05 mol L−1by orthogonal test. At different electrolysis time, its effluent characteristics were focused on. The biodegradability (the ratio between BOD5and COD) was enhanced from initial 0.02 to 0.57 at 90 min. The specific oxygen uptake rate was used to assess effluent toxicity, and the value gradually reduced with decreasing effluent organic concentration with mean value of 5.51, 4.19, and 2.20 mgO2 g−1MLSS at electrolysis time of 15, 30, and 45 min, respectively. Compared with control sample (prepared with glucose), the effluent of quinoline mineralization showed obvious inhibition effect on microorganisms at electrolysis time of 15 min, and then it was significantly faded at 30 min and 45 min.