Lauryl benzene sulfonic acid sodium-carbon nanotube-modified PbO2 electrode for the degradation of 4-chlorophenol

Photo-electrochemical activation of persulfate for the simultaneous degradation of microplastics and personal care products

The recent widespread use of microplastics (MPs), especially in pharmaceuticals and personal care products (PPCPs), has caused significant water pollution. This study presents a UV/electrically co-facilitated activated persulfate (PS) system to co-degrade a typical microplastic polyvinyl chloride (PVC) and an organic sunscreen p-aminobenzoic acid (PABA). We investigated the effect of various reaction conditions on the degradation. PVC and PABA degradation was 37% and 99.22%, respectively. Furthermore, we observed alterations in the surface topography and chemical characteristics of PVC throughout degradation. The possible degradation pathways of PVC and PABA were proposed by analyzing the intermediate products and the free radicals generated. This study reveals the co-promoting effect of multiple mechanisms in the activation by ultraviolet light and electricity.

Robust PbO2 modified by co-deposition of ZrO2 nanoparticles for efficient degradation of ceftriaxone sodium

In recent years, PbO2 electrodes have received widespread attention due to their high oxygen evolution reaction (OER) activity. However, due to the brittle nature of the plating layer, it is easy to cause the active layer to fall off. Pb2+ will leach out with the electrochemical process causing secondary pollution. The starting point of this study is established to improve the stability and adhesion of the electrode coating. Electrochemical oxidation technology has the characteristics of high treatment efficiency, wide range of applications, and non-polluting environment. In this study, conventional PbO2 electrodes were modified by using co-deposition of ZrO2 nanoparticles. In addition, α-PbO2 was added to increase the stability of the electrodes. At a high current density of 1 A/cm2, the accelerated life of the pure PbO2 electrode is 648 h, the accelerated life of the PbO2-ZrO2 electrode is 1.37 times that of the pure PbO2, and the electrode with an added α-PbO2 layer is 1.69 times that of the pure PbO2 electrode. The amount of dissolved Pb2+ was only 29% of that of pure PbO2. The electrochemical performance of the electrode is evaluated by studying the degradation effect of ceftriaxone sodium (CXM). The addition of ZrO2 nanoparticles alters the particle size and deposition content of PbO2, leading to a unique crystal structure distinct from pure PbO2. Compared to conventional PbO2 electrodes, the PbO2-ZrO2 can remove chemical oxygen demand (COD) and pollutants more efficiently, removing for 59% increased by 38.47%. Therefore, PbO2-ZrO2 is of great value in the field of electrochemical degradation of industrial pollutants.

Fabrication of nanofibrous PbO2 electrode embedded with Pt for decomposition of organic chelating agents

A new fabrication method of nanofibrous metal oxide electrode comprising Pt nanofiber (Pt-NF) covered with PbO2 on a Ti substrate was proposed. Pt-NF was obtained by performing sputtering deposition of Pt on the surface of electrospun poly(vinyl alcohol) (PVA) nanofiber on a Ti substrate, in which PVA was then removed by calcination (Ti/Pt-NF). Subsequently, by introducing PbO2 to the Ti/Pt-NF using the electrodeposition method, a nanofibrous Ti/Pt-NF/PbO2 electrode was finally obtained. Because the Ti substrate was covered by nanofibrous Pt, it had no environmental exposure and thus, was not oxidized during calcination. The crystal structure of the PbO2 mainly consisted of β-form rather than α-form; the β-form was suitable for electrochemical decomposition and remained stable even after 20 h of use. The nanofibrous Ti/Pt-NF/PbO2 electrodes showed 10% lower anode potential, 1.6 times higher current density at water decomposition potential, lower electrical resistance in the ion charge transfer resistance, and 2.27 times higher electrochemically active surface area than those of a planar-type Ti/Pt/PbO2 electrode, and demonstrated excellent electrochemical performance. As a result, compared with the planar electrode, the Ti/Pt-NF/PbO2 electrode showed more effective electrochemical decomposition toward nitrilotriacetic acid (80%) and ethylenediaminetetraacetic acid (83%), which are commonly used as chelating agents in nuclear decontamination.

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.

Electrochemical oxidation of ceftazidime with graphite/CNT-Ce/PbO2-Ce anode: Parameter optimization, toxicity analysis and degradation pathway

In this work, the electrochemical degradation of antibiotic ceftazidime has been studied using a novel rare earth metal Ce and carbon nanotubes codoped PbO₂ electrode. A competitively high oxygen evolution potential (2.4 V) and enhanced catalytic surface area were obtained, evidence by LSV and CV electrochemical characterization. The G/CNT-Ce/PbO₂-Ce electrode possessed a more compact structure and a smaller grain size than the other PbO₂ and Ce-PbO₂ electrodes, exhibiting a prolonged service lifetime, evidence by accelerated lifespan test and recycling degradation experiment. As electrolysis time reached 120 min, the removal efficiency of ceftazidime and TOC arrived at 100.0% and 54.2% respectively in 0.05 M Na₂SO₄ solution containing 50 mg⋅L^-1 ceftazidime. The effect of applied current density, pH value, initial ceftazidime concentration and chloride contents on the degradation performance were systematically evaluated. The results demonstrated that electrochemical oxidation of ceftazidime over the G/CNT-Ce/PbO₂-Ce electrode was highly effective, and the mineralization rate was greatly improved, compared with pristine PbO₂ electrode. Considering the toxicity was increased after 30 min electrolysis, the intermediates were quantitatively investigated through HPLC-MS, GC-MS and IC technology. According to the identified products, a reaction mechanism has been proposed and pyridine and aminothiazole were detected with concentration from approximately 1 to 3 mg⋅L^-1, which were regarded as toxic byproducts during electrooxidation. Further electrocatalyzing by ring cleavage reaction and complete mineralization to CO₂, NO₃^- and NH₄⁺ was proposed, which demonstrated the G/CNT-Ce/PbO₂-Ce electrode exhibited high efficiency for ceftazidime removal in mild conditions.

Fabrication of boron-doped diamond films electrode for efficient electrocatalytic degradation of cresols

The choice of anode materials has a significant influence on the electrocatalytic degradation of organics. Accordingly, the electrocatalytic activity of several active anodes (Ti/Ru-Ir, Ti/Ir-Ta, Ti/Pt) and non-active anodes (Ti/PbO₂, Ti/SnO₂, Si/BDD (boron-doped diamond)) was compared by electrocatalytic degradation of m-cresol. The results indicated Si/BDD electrode had the strongest mineralization ability and the lowest energy consumption. And the order of the activity of m-cresol degradation was as follows: Si/BDD > Ti/SnO₂>Ti/PbO₂>Ti/Pt > Ti/Ir-Ta > Ti/Ru-Ir. Also their intermediate products were compared. The effects of experimental parameters on electrocatalytic degradation of m-cresol with Si/BDD electrode showed m-cresol conversion was affected slightly by the electrode spacing and electrolyte concentration, but affected greatly by the temperature and current density. And smaller electrode spacing and current density, higher electrolyte concentration and temperature were beneficial to reduce energy consumption. Their degradation processes were all accord with the pseudo-first-order reaction kinetics completely. In addition, the results of electrocatalytic degradation of m, o, p-cresol indicated there was almost no significant difference on conversion rate between cresols isomers with the current density of 30 mA cm^-2. However, the influence of group position was shown when the current density was reduced to 10 mA cm^-2 and cresols conversion followed the sequence of m-cresol ≈ o-cresol > p-cresol.

Hydroxyl multi-walled carbon nanotube-modified nanocrystalline PbO2 anode for removal of pyridine from wastewater

We prepared a hydroxyl multi-wall carbon nanotube-modified nanocrystalline PbO₂ anode (MWCNTs-OH-PbO₂) featuring high oxygen evolution potential, large effective area, and excellent electrocatalytic performance. The oxygen evolution potential and effective area of the MWCNTs-OH-PbO₂ electrode were 1.5 and 3.7-fold higher than the traditional PbO₂ electrode. Electrochemical degradation of pyridine in aqueous solution was investigated by using the MWCNTs-OH-PbO₂ anode. Based on pyridine decay rate (93.8%), total organic carbon reduction (84.6%), and energy consumption (78.8WhL^-1order^-1) under the optimal conditions, the MWCNTs-OH-PbO₂ electrode modified with MWCNTs-OH concentration of 1.0gL^-1 exhibited higher electrochemical oxidation ability than the traditional PbO₂ electrode. The intermediate, hydroxypyridine, was found at the first stage of electrolysis. The primary mineralization product, NO₃^-, was detected in aqueous solution after electrolysis. A possible electrochemical mineralization mechanism including two potential routes, i.e., via formation of small organic molecules by ring cleavage reaction and direct mineralization to CO₂ and NO₃^-, was proposed. The results demonstrated that the MWCNTs-OH-PbO₂ electrode exhibited high efficiency for pyridine mineralization in aqueous solution under mild conditions.

Preparation and characterization of PbO2 electrodes modified with polyvinyl alcohol (PVA)

Novel PbO₂ electrodes were successfully synthesized with polyvinyl alcohol (PVA) modification through electro-deposition technology.

Preparation and characterization of titanium-based PbO2electrodes modified by ethylene glycol

The present work focused on studying the effect of ethylene glycol (EG) modification on the electrochemical properties of lead dioxide electrodes prepared by the electrochemical deposition method.

Fabrication and characterization of a novel PbO2 electrode with a CNT interlayer

A novel PbO₂ electrode (marked as CNT–PbO₂) with a carbon nanotube (CNT) interlayer was prepared by electrophoretic deposition and electro-deposition.

Electrocatalytic degradation of ibuprofen in aqueous solution by a cobalt-doped modified lead dioxide electrode: influencing factors and energy demand

PbO₂ electrode modified with Co exhibited higher electrochemical oxidation. The effects of HA, FA, OA and CA were investigated.

Fabrication and characterization of PbO2 electrode modified with [Fe(CN)6](3-) and its application on electrochemical degradation of alkali lignin

PbO2 electrode modified by [Fe(CN)6](3-) (marked as FeCN-PbO2) was prepared by electro-deposition method and used for the electrochemical degradation of alkali lignin (AL). The surface morphology and the structure of the electrodes were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. The stability and electrochemical activity of FeCN-PbO2 electrode were characterized by accelerated life test, linear sweep voltammetry, electrochemical impedance spectrum (EIS) and AL degradation. The results showed that [Fe(CN)6](3-) increased the average grain size of PbO2 and formed a compact surface coating. The service lifetime of FeCN-PbO2 electrode was 287.25 h, which was longer than that of the unmodified PbO2 electrode (100.5h). The FeCN-PbO2 electrode showed higher active surface area and higher oxygen evolution potential than that of the unmodified PbO2 electrode. In electrochemical degradation tests, the apparent kinetics coefficient of FeCN-PbO2 electrode was 0.00609 min(-1), which was higher than that of unmodified PbO2 electrode (0.00419 min(-1)). The effects of experimental parameters, such as applied current density, initial AL concentration, initial pH value and solution temperature, on electrochemical degradation of AL by FeCN-PbO2 electrode were evaluated.

Novel three-dimensional macroporous PbO2 foam electrode for efficient electrocatalytic decolorization of dyes

3D macroporous PbO₂ foam electrode possesses a binder-free and highly-porous architecture, and ensures a high efficiency for degrading organic contaminants.

Solar photocatalytic degradation of chlorophenols mixture (4-CP and 2,4-DCP): Mechanism and kinetic modelling

The solar-photocatalytic degradation mechanisms and kinetics of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) using TiO2 have been investigated both individually and combined. The individual solar-photocatalytic degradation of both phenolic compounds showed that the reaction rates follow pseudo-first-order reaction. During the individual photocatalytic degradation of both 4-CP and 2,4-DCP under the same condition of TiO2 (0.5 g L(-1)) and light intensities (1000 mW cm(-2)) different intermediates were detected, three compounds associated with 4-CP (hydroquinone (HQ), phenol (Ph) and 4-chlorocatechol (4-cCat)) and two compounds associated with 2,4-DCP (4-CP and Ph). The photocatalytic degradation of the combined mixture (4-CP and 2,4-DCP) was also investigated at the same conditions and different 2,4-DCP initial concentrations. The results showed that the degradation rate of 4-CP decreases when the 2,4-DCP concentration increases. Furthermore, the intermediates detected were similar to that found in the individual degradation but with high Ph concentration. Therefore, a possible reaction mechanism for degradation of this combined mixture was proposed. Moreover, a modified Langmuir-Hinshelwood (L-H) kinetic model considering all detected intermediates was developed. A good agreement between experimental and estimated results was achieved. This model can be useful for scaling-up purposes more accurately as its considering the intermediates formed, which has a significant effect on degrading the main pollutants (4-CP and 2,4-DCP).