Highly porous seeding-free boron-doped ultrananocrystalline diamond used as high-performance anode for electrochemical removal of carbaryl from water
Graphical abstract
Introduction
Anodic oxidation (AO) is one of the major electrochemically-driven technologies which have been widely applied for the remediation of recalcitrant organic substances - including dyes, personal care and pharmaceutical products, and pesticides, usually present in water bodies (Sirés and Brillas, 2012; Sirés et al., 2014; Baddouh et al., 2018; Garcia-Segura et al., 2018b; Martínez-Huitle and Panizza, 2018; dos Santos et al., 2021b). AO is considered an environmentally friendly technique as the process does not require the use of chemicals and oxidants are electrogenerated in situ. Several studies have shown that the electrocatalytic properties of the anode material are among the main factors that determine the efficiency of the AO process (Panizza and Cerisola, 2009; Sirés et al., 2014; Moreira et al., 2017; dos Santos et al., 2019, 2021a). In this context, boron-doped diamond (BDD) anode is regarded as the best material for application in AO due to its excellent properties including high stability, inert surface, and large O2 overpotential window (Kapałka et al., 2009). The large O2 overpotential window of BDD anode helps generate a huge amount of oxidant species such as physiosorbed hydroxyl radicals (M(OH), Eq. (1) which can attack organic pollutants (R) non-selectively, turning them into non-hazardous products or even leading them to complete combustion, as shown in Eq. (2) below (do Vale-Júnior et al., 2019; Brillas, 2021; Karim et al., 2021; Mostafa et al., 2021).M + H2O → M(OH) + H+ + e−aM(OH) + R → mCO2 + nH2O + xH+ + ye−
The properties of BDD can be enhanced considerably by varying the concentration of boron, film thickness, and sp2/sp3 ratio, as well as the electrode morphology and porosity (Baluchová et al., 2019; Mei et al., 2019). As pointed out in the literature, one can promote the contact between the electrolyte and the electrode by increasing the electrochemical surface area through the adjustment of the film porosity from macro to nano-porous depending on both the porosity of the substrate and specific post-growth treatment on the diamond surface. So far, a number of studies reported in the literature have employed the seeding substrate pre-treatment mechanism to boost the diamond growth through the application of the chemical vapor deposition technique (Wei et al., 2009; Szunerits et al., 2015; Yang et al., 2016). This pre-treatment mechanism involves the use of diamond powder to improve diamond growth since diamond is unable to grow naturally on non-diamond substrates. Due to the fast deposition kinetics, this seeding substrate pre-treatment procedure, which boosts the diamond growth, favors the formation of agglomerated structures; on the other hand, the fast deposition kinetics makes it harder to obtain structures with nano or ultranano-porosity which are more suitable and efficient for improving the efficiency of the AO process (May and Mankelevich, 2008; Luong et al., 2009; Macpherson, 2015).
As an alternative to the typical BDD synthesis method, in a previous study (Vernasqui et al., 2022), our research group proposed the use of an innovative boron-doped ultrananocrystalline diamond grown on titanium dioxide nanotube without the seeding substrate pre-treatment procedure (B-UNCDWS/TDNT/Ti). The use of titanium dioxide nanotubes (TDNT) allows spontaneous diamond growth under slower deposition kinetics compared to the seeding process, and this enables one to have higher control of deposition and the ability to produce extremely thin films, in addition to maintaining the porosity of the substrate material. This approach represents a major step forward in the synthesis of BDD and helps explore the unique properties of BDD when it comes to the treatment of recalcitrant pollutants. Thus, this study evaluates the efficiency of the innovative B-UNCDWS/TDNT/Ti electrode when applied for the removal of carbaryl (CBR) pesticide in both synthetic and real media under the AO process. Carbaryl is a broad-spectrum N-methyl carbamate insecticide applied worldwide for the control of pests during the production of crops (cotton, corn, soybean, nut, fruits, and vegetables) and for the protection of lawns, home gardens and other ornamental plants (Koshlukova and Reed, 2014).
CBR ranks second among the insecticides that are commonly detected in surface water (Nair et al., 2022). CBR can dissolve in water, migrate through soil, and find its way into groundwater, contaminating it (Wu et al., 2019). People are mostly exposed to CBR through the intake of food and water or other liquids. Depending on the individual and the dose of CBR ingested into the body, the person may experience a variety of symptoms which range from weakness to reduced heart and lung function. In view of that, it is essential to develop techniques that are capable of removing this type of contaminant from food and water so as to prevent excessive human exposure to this pollutant and the occurrence of severe health problems in humans. To analyze the efficiency and viability of the proposed anode in terms of CBR degradation, different current densities were tested, and the best operating conditions were applied for the analysis of real drinking water with a view to evaluating the potential of the technique in real applications. The presence of different oxidants in the system was evaluated using scavenger compounds. Energetic figures of merit were calculated, and the evolution of intermediates produced during the treatment process was also thoroughly monitored. For comparison purposes, the study also provides comprehensive data related to the physical and electroanalytical characterization of the proposed B-UNCDWS/TDNT/Ti anode.
Section snippets
Chemical reagents
Carbaryl (CBR) pesticide (99% purity, Sigma-Aldrich) was used as a model pollutant. Analytical grade potassium sulfate – acquired from Neon, was used as supporting electrolyte; methanol (MeOH) and tert-butanol (TBH), both acquired from Sigma Aldrich, were used as scavengers; and acetonitrile – obtained from Merck, was used as mobile phase for the conduct of high-performance liquid chromatography (HPLC) analysis. All reagents were used directly without extra purification. Ultrapure water from a
Morphological, physical, and electrochemical characterizations of the B-UNCDWS/TDNT/Ti
Fig. 1a-d shows the remarkable homogeneous morphology of the UNCDWS/TDNT/Ti with different growth planes obtained after chemical vapor deposition on TDNT in different magnifications. As can be observed, the entire surface of the electrode is covered by a thin layer, and one will notice the presence of a diamond film in the pore walls which helps maintain the porosity of the electrode surface. Furthermore, one can see clusters of ballas diamond which are distributed on the sample surface. In the
Conclusions
The present work reported the synthesis of B-UNCDWS/TDNT/Ti electrodes with extremely thin diamond films using an innovative methodology without seeding substrate pre-treatment and their successful application for the treatment of water containing recalcitrant compounds. The material proposed in this study was found to possess suitable electrochemical properties, including highly porous ultranano-structures, improved specific capacitance (274 μF cm−2) and high onset potential for water
Author statement
L. G. Vernasqui: Methodology, Investigation, Writing - original draft. A. J. dos Santos: Investigation, Conceptualization, Methodology, Writing - original draft, Writing - review & editing. G. V. Fortunato: Investigation, Conceptualization, Methodology, Writing - original draft, Writing - review & editing. M. S. Kronka: Investigation, Writing - review & editing. H. L. Barazorda-Ccahuanac: Conceptualization, Writing - original draft. A. S. Fajardo: Conceptualization, Writing - original draft,
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors acknowledge the financial support provided by the following Brazilian research funding agencies: Brazilian National Council for Scientific and Technological Development - CNPq (grant #465571/2014-0 and #303943/2021–1), São Paulo Research Foundation - FAPESP (grants #2014/50945–4, #2017/23464–3, #2017/10118–0, #2019/04421–7, #2019/20634–0, #2019/00592–1 and #2021/07615–7) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES – Finance Code 001) in support of this
References (46)
- et al.
Impedance characteristics of the diamond/carbon fiber electrodes for electrical double-layer capacitor
Diam. Relat. Mater.
(2008) - et al.
Electrochemical decolorization of Rhodamine B dye: influence of anode material, chloride concentration and current density
J. Environ. Chem. Eng.
(2018) - et al.
Porous boron doped diamond for dopamine sensing: effect of boron doping level on morphology and electrochemical performance
Electrochim. Acta
(2019) Recent development of electrochemical advanced oxidation of herbicides. A review on its application to wastewater treatment and soil remediation
J. Clean. Prod.
(2021)- et al.
Electrochemical incineration of diclofenac in neutral aqueous medium by anodic oxidation using Pt and boron-doped diamond anodes
Chemosphere
(2010) - et al.
Application of electrochemical advanced oxidation to bisphenol A degradation in water. Effect of sulfate and chloride ions
Chemosphere
(2018) - et al.
Electrochemical oxidation of carbaryl on platinum and boron-doped diamond anodes using electro-Fenton technology
Separ. Purif. Technol.
(2015) - et al.
Deep ultra-violet Raman imaging of CVD boron-doped and non-doped diamond films
Diam. Relat. Mater.
(2008) - et al.
Effect of electrochemically-driven technologies on the treatment of endocrine disruptors in synthetic and real urban wastewater
Electrochim. Acta
(2021) - et al.
Electrochemical oxidation of ciprofloxacin in different aqueous matrices using synthesized boron-doped micro and nano-diamond anodes
Environ. Res.
(2022)
A ceramic electrode of ZrO2-Y2O3 for the generation of oxidant species in anodic oxidation. Assessment of the treatment of Acid Blue 29 dye in sulfate and chloride media
Separ. Purif. Technol.
Recent advances in electrochemical water technologies for the treatment of antibiotics: a short review
Curr. Opin. Electrochem.
Carbon materials for the electrochemical storage of energy in capacitors
Carbon N. Y.
Electrocatalytic reduction of nitrate: fundamentals to full-scale water treatment applications
Appl. Catal. B Environ.
Electrochemical oxidation remediation of real wastewater effluents — a review
Process Saf. Environ. Protect.
The importance of electrode material in environmental electrochemistry
Electrochim. Acta
Boron-doped diamond electrodes for the mineralization of organic pollutants in the real wastewater
Curr. Opin. Electrochem.
Carbaryl
Electrical energy per order and current efficiency for electrochemical oxidation of p-chlorobenzoic acid with boron-doped diamond anode
Chemosphere
Electrochemical oxidation of organic pollutants for wastewater treatment
Curr. Opin. Electrochem.
3D macroporous boron-doped diamond electrode with interconnected liquid flow channels: a high-efficiency electrochemical degradation of RB-19 dye wastewater under low current
Appl. Catal. B Environ.
Electrochemical advanced oxidation processes: a review on their application to synthetic and real wastewaters
Appl. Catal. B Environ.
Unraveling the role of electrolytes during electrochemical oxidation by differential electrochemical mass spectrometry
Electrochim. Acta
Cited by (9)
Electrochemical oxidation of surfactants as an essential step to enable greywater reuse
2024, Environmental Technology and InnovationElectrochemical degradation of ciprofloxacin from water: Modeling and prediction using ANN and LSSVM
2023, Physics and Chemistry of the EarthDegradation of real lindane wastes using advanced oxidation technologies based on electrogenerated hydrogen peroxide
2023, Process Safety and Environmental ProtectionNew electrochemical reactor design for emergent pollutants removal by electrochemical oxidation
2023, Electrochimica Acta