Anodic oxidation of diuron using Co3O4/graphite composite electrode at low applied current

Cobalt etched graphite felt electrode for enhanced removal of organic pollutant in aqueous solution with a solid polymer electrolyte

In this study, cobalt etched graphite felt electrodes were produced using a simple etching technique. It was used in combination with a solid polymer electrolyte (SPE) for the degradation of the target contaminant Orange II by Electro-Fenton (EF) technique in low conductivity water. In this method, 94% of Orange II in low conductivity water was removed in 90 min. The characterization analysis substantiates the hypothesis that the electrodes produced exhibit a three-dimensional porous structure, augmented defect concentration, and enhanced electron transfer capability. In addition, the potential reaction mechanism was inferred from the radical quenching experiments, and hydroxyl radicals (·OH) were deemed the main reactive substances. The combination of cobalt etched graphite felt electrodes with SPE demonstrates remarkable efficacy in the treatment of organic wastewater characterized by low electrical conductivity.

Tetracycline removal from aqueous solution by electrooxidation using ruthenium-coated graphite anode

This paper reports the electrochemical oxidation treatment of 80 mL of acidic aqueous solutions with 0.2 mM of the drug tetracycline in 25 mM Na₂SO₄ using a lab-scale electrochemical cell. The performance of tetracycline removal with Ru-coated graphite by the chemical bath deposition (CBD) and raw graphite anode has been demonstrated. The effects of operating parameters were tested such as pH, applied current, supporting electrolyte concentration, and initial tetracycline concentration. The best tetracycline degradation was obtained with Ru-coated graphite anode due to its higher oxidation power, which allowed the complete degradation of refractory compounds. The modified surface structure of the Ru-coated graphite anode was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray (EDX). The EO process with Ru-coated graphite anode allowed 93.8% tetracycline abatement after 100 min of electrolysis at an applied current of 100 mA. In all cases, tetracycline decay obeyed pseudo-first-order kinetics. The tetracycline removal performance of graphite electrodes with nano coating on graphite has offered a performing alternative. A Comparative study revealed that electrolysis with Ru-coated graphite acted as a better electrode material than raw graphite for the catalytic reaction.

Effect of Persulfate Activation by Electrogenerated H2O2 and Anodic Oxidation on the Color Removal of Dye Solutions at Pt and BDD Anodes

In this study, tartrazine solutions were oxidized using innovative electrochemical advanced oxidation processes (EAOPs) that combined persulfate (PS) activation with electrogenerated H₂O₂, cathodic reduction and anodic oxidation at Pt and BDD anodes, and graphite cathode in an undivided stirred reactor. For the Pt anode, SO₄·^- was generated from a reduction reaction at the cathode and a reaction between the PS and electrogenerated H₂O₂. For the BDD anode, SO₄·^- was generated from a reduction reaction at the cathode, an oxidation reaction at the anode, and a reaction between PS and electrogenerated H₂O₂. Among these activation methods, the activation efficiency of PS by electrogenerated H₂O₂ is much better than other methods. The effects of PS concentration up to 36 mM, applied current density between 6 to 15 mA cm^-2, and temperatures between 25 to 45 °C were investigated. For the electro-Fenton process with Pt anode (Pt-H₂O₂/PS process), the best result for oxidizing 250 mg L^-1 tartrazine solution was obtained with 37.5 mM Na₂SO₄ + 9.0 mM Na₂S₂O₈, applied current density at 12 mA cm^-2 and 45 °C, acquiring total color removal after 30 min reaction. For the electro-Fenton process with BDD anode (BDD-H₂O₂/PS process), the best result for oxidizing 250 mg L^-1 tartrazine solution was obtained with 25 mM Na₂SO₄ + 18 mM Na₂S₂O₈, applied current density at 12 mA cm^-2 and 45 °C, yielding 100% color removal after 30 min reaction. The main oxidizing agents are SO₄·^- and OH· in the anodic oxidation process with PS and the electro-Fenton process with PS. It is concluded that the additions of PS tremendously improve the oxidation power of electro-Fenton processes with PS, especially the Pt-H₂O₂/PS process.

Electrocatalytic oxidation of antidiabetic drug metformin adsorbed on intercalated MXene

Two-dimensional (2D) Ti₃C₂T_x transition metal carbide (MXene) nanosheets intercalated with sodium ions (SI-Ti₃C₂T_x MXene) were used in the adsorption and electrochemical regeneration process for removal of the antidiabetic drug metformin (MF) as a model emerging pollutant. After MF adsorption, SI-Ti₃C₂T_x MXene oxidized the MF on its surface through its electrocatalytic activity at very low current density and cell potential. For complete oxidation the optimum parameters were 0.525 C g^-1, 0.005 mA cm^-2, and pH 6 in absence of NaCl or 26.25 C g^-1 and 0.5 mA cm^-2 in the presence of 2.5 w/v% NaCl. The overall regeneration of SI-Ti₃C₂T_x is governed by a combined mechanism, i.e., desorption followed by degradation. The degradation mechanism, such as direct electron transfer or indirect oxidation, depends on the applied operating conditions. Thus, the investigation suggests that these 2D sheets are good nanoadsorbents as well as good electrocatalysts and proves their usefulness in practical water-treatment applications.

Fabrication of MOF-derivated CuOx-C electrode for electrochemical degradation of ceftazidime from aqueous solution

Antibiotic contamination has already been one of hazards to aquatic environment due to the abuse of antibiotics. Metal-organic frameworks (MOFs) are known as a kind of promising porous material for solving the environmental deterioration. In this article, the physicochemical and electrochemical properties of a series of porous copper oxide carbon materials (CuOx-C) synthesized by carbonizing Cu-BTC were compared. Due to the suitable carbonization temperature, CuOx-C-550 N, whose geometric structure was similar to Cu-BTC, possessed a multiscale pore structure containing many mesopores and partial macropores in accordance with the pore size distribution curves. More copper/copper oxides were introduced toimproving the electrochemical ability, evidence by XRD, XPS, CV and EIS characterization. Moreover, the degradation of ceftazidime (CAZ) through anodic oxidation was discussed. In AO/CuOx-C-550 N system, the effects of current, solution pH, initial CAZ concentration and Na₂SO₄ concentration were analyzed. CAZ removal rate reached 100% within 20 min under the optimal condition and a good electrocatalytic ability with 90% CAZ removal after 20 runs indicated a good electrochemical stability of CuOx-C-550 N. Furthermore, the degradation mechanism and pathway of CAZ were proposed. The Cu(II)/Cu(I) oxidation-reduction couples on the anodic surface contribute to the efficiently selective degradation of cephalosporins for CuOx-C-550 N. Overall, this study shows a good method to design and prepare a new MOF derivative for the remediation of aquatic contamination.

Anodic oxidation of ciprofloxacin using different graphite felt anodes: Kinetics and degradation pathways

Ciprofloxacin (CIP) is ubiquitous in the environment which poses a certain threat to human and ecology. In this investigation, the physical and electrochemical properties of graphite felt (GF) anodes which affected the anodic oxidation (AO) performance, and the CIP removal effect of GF were evaluated. The GFs were used as anodes for detection of ·OH with coumarin (COU) as molecule probe and removal of CIP in a 150 mL electrolytic cell with Pt cathode (AO-GF/Pt system). The results showed that hydrophilic GF (B-GF) owned higher sp³/sp² and more oxygen-containing and nitrogen-containing functional groups than the hydrophobic GF (A-GF). Moreover, B-GF possessed higher oxygen evolution potential (1.12 V), more active sites and stronger ·OH generation capacity. Above mentioned caused that B-GF exhibited more superior properties for CIP removal. The best efficiencies (96.95%, 99.83%) were obtained in the AO-B-GF/Pt system at 6.25 mAcm^-2 after 10 min (k₁, 0.356 min^-1) and 60 min (k₂, 0.224 min^-1), respectively. Furthermore, nine degradation pathways of CIP in AO-B-GF/Pt system were summarized as the cleavage of the piperazine ring, cyclopropyl group, quinolone ring and F atom by ·OH. It provides new insights into the removal and degradation pathways of CIP with GF in AO system.

Thermal decomposition based fabrication of dimensionally stable Ti/SnO2-RuO2 anode for highly efficient electrocatalytic degradation of alizarin cyanin green

In this work, Ti/SnO₂-RuO₂ dimensionally stable anode has been successfully fabricated via thermal decomposition method and further used for highly efficient electrocatalytic degradation of alizarin cyanin green (ACG) dye wastewater. The morphology, crystal structure and composition of Ti/SnO₂-RuO₂ electrode are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF), respectively. The result of accelerated life test suggests that as-prepared Ti/SnO₂-RuO₂ anode exhibits excellent electrochemical stability. Some parameters, such as reaction temperature, initial pH, electrode spacing and current density, have been investigated in detail to optimize the degradation condition of ACG. The results show that the decolorization efficiency and chemical oxygen demand removal efficiency of ACG reach up to 80.4% and 51.3% after only 40 min, respectively, under the optimal condition (reaction temperature 25 °C, pH 5, electrode spacing 1.0 cm and current density 3 mA cm^-2). Furthermore, the kinetics analysis reveals that the process of electrocatalytic degradation of ACG follows the law of quasi-first-order kinetics. The excellent electrochemical activity demonstrates that the Ti/SnO₂-RuO₂ electrode presents a favorable application prospect in the electrochemical treatment of anthraquinone dye wastewater.