Xiang Hu

Preparation and electrochemical properties of SnO2-Sb-Ni-Ce oxide anode for phenol oxidation

A novel Ni-Ce co-doped SnO2-Sb anode with macroporous titanium sheet as substrate (mp-Ti/SnO2-Sb-Ni-Ce anode) was prepared by modified sol–gel method. The surface morphology, the crystal structure, and the valence of the dopants were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. In addition, cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and accelerated life test were also carried out to study the electrochemical properties and stability of the anodes. The results indicated that mp-Ti/SnO2-Sb-Ni-Ce anode possessed a compact and uniform surface and a longer service life than other modified SnO2 anodes. Electrocatalytic oxidation of phenol was studied in a constant current density of 10xa0mAxa0cm−2 at 25xa0°C to evaluate the application potential of the electrode. Effects of current density and initial pH value on phenol degradation were studied. The co-doping of Ni-Ce significantly enhanced the degradation of phenol and the total organic carbon (TOC) removal on the anode, which might be attributed to the improved generation of reactive oxygen species (ROS) in the solution and the indirect oxidation.

Modification of a Pd-loaded electrode with a carbon nanotubes–polypyrrole interlayer and its dechlorination performance for 2,3-dichlorophenol

A novel Pd loaded Ti electrode was prepared with a carbon nanotubes and polypyrrole interlayer modification, referred to as a Pd/CNTs–PPy/Ti electrode. Pretreated CNTs were deposited on the substrate uniformly by electrophoretic deposition technique. Modification by the CNTs–PPy interlayer made the Pd particles smaller and well-distributed. Pulsed-current electrodeposition technique led to more compact Pd particles. The hydrogen adsorption current value increased 55.3% and the electrochemical active surface area (EASA) increased 58.7% compared to the electrode without modification. The prepared Pd/CNTs–PPy/Ti electrode was employed in dechlorination of 2,3-dichlorophenol (2,3-DCP) in aqueous solution. The potential impact factors on the electrocatalytic dechlorination were studied, including dechlorination current, initial pH value of catholyte, reaction temperature and common ions in aqueous solution. Complete dechlorination could be achieved within 70 min under the selected conditions i.e., current of 5 mA, and an initial pH of 2.5 at ambient temperature. The common ions in aqueous solution, such as NO3−, CO32−, HCO3−, Mg2+, K+ and Ca2+, had no obvious effect on the electrocatalytic dechlorination within the scope of this investigation. The prepared Pd/CNTs–PPy/Ti electrode exhibited promising dechlorination potential with higher electrochemical activity.

Electrocatalytic activity of Ce-PbO2/C anode for acid red B reduction in aqueous solution

Graphite–lead dioxide electrodes doped with rare earth Cerium (Ce-PbO2/C electrodes) were prepared by electrodeposition. The scanning electron microscope results showed that the microstructure and crystal orientation of electrode surface were changed by Cerium doping. CeO2 was detected from modified electrodes by X-ray diffraction analysis. The cyclic voltammetry spectra indicated that the oxidation peak potential of cerium-doped electrode was smaller than pure PbO2 electrode. Effects of the novel electrode on acid red B degradation were evaluated systematically under different parameters, including applied voltage, initial pH, supporting electrolyte concentration, electrode spacing, and influent concentration. The results indicated that chemical oxygen demand, decolorization, and ammonia nitrogen removal rate of Ce-PbO2/C electrodes reached 90.17, 99.98, and 97.23xa0%, respectively, after 60-min electrolysis at initial 1000xa0mgxa0L−1 acid red B concentration. The possible mechanism of acid red B degradation over Ce-PbO2/C electrodes was monitored by gas chromatography-mass spectrometer.

Dechlorination of pentachlorophenol (PCP) in aqueous solution on novel Pd-loaded electrode modified with PPy-SDBS composite film

Pentachlorophenol (PCP) is a persistent pollutant and a suspected human carcinogen. It can be found in the air, water, and soil and enters the environment through evaporation from treated wood surfaces, industrial spills, and disposal at uncontrolled hazardous waste sites. Ecotoxicity of PCP necessitates the development of rapid and reliable remediation techniques. Electrocatalytic hydrogenolysis (ECH) has been proven as a promising method for detoxification of halogenated wastes, due to its rapid reaction rate, low apparatus cost, mild reaction conditions, and absence of secondary contaminants. Challenge for the application of ECH is to prepare a Pd-coated cathode with high stability, high catalytic activity, and low Pd loading level. In this work, Pd/polypyrrole–sodium dodecyl benzene sulfonate/meshed Ti (Pd/PPy–SDBS/Ti) electrode was prepared and was characterized by cyclic voltammetry, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma-atomic emission spectrometry. Electrochemically reductive dechlorination of PCP on the Pd/PPy–SDBS/Ti electrode in aqueous solution was investigated. Pd microparticles were uniformly dispersed on PPy–SDBS film which was previously electrodeposited on the meshed Ti supporting electrode. The loading of Pd on the electrode was 0.72xa0mgxa0cm−2. Electrocatalytic dechlorination of PCP was performed in a two-compartment cell separated by cation-exchange membrane. The PCP removal on the Pd/PPy–SDBS/Ti electrode could reach 100xa0% within 70xa0min with dechlorination current 3xa0mA when PCP initial concentration was 10xa0mgxa0L−1 and initial pH was 2.4. Conversion of PCP on the Pd/PPy–SDBS/Ti electrode followed pseudo-first-order kinetics, and the apparent activation energy was 13.0xa0kJxa0mol−1. The removal of PCP still kept 100xa0% after 70xa0min dechlorination when the Pd/PPy–SDBS/Ti cathode was reused ten times. The electrode exhibited promising dechlorination potential with high electrocatalytic activity, good stability, and low cost.

Electrochemical dechlorination of 2,4-dichlorophenol in aqueous solution on palladium-loaded meshed titanium electrode.

Electrochemical dechlorination of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was investigated on palladium-loaded meshed titanium (Pd/Ti) electrode at ambient temperature. Pd/Ti electrode was prepared with an electrodepositing method. Scanning Electron Microscope (SEM) micrographs show that Pd microparticles uniformly disperse on the meshed Ti supporting electrode with spheroidal structure. Dechlorination experimental results indicate that, in aqueous solution, with the current efficiency of 24.3%, the removal efficiency of 100 mg/L 2,4-DCP on Pd/Ti electrode was 93.2% under the conditions of the dechlorination current of 5 mA and dechlorination time of 90 min. The effect of initial 2,4-DCP concentration was also investigated.

Electrocatalytic dechlorination of 2,3,5-trichlorophenol on palladium/carbon nanotubes-nafion film/titanium mesh electrode

Palladium/carbon nanotubes-nafion film-modified titanium mesh electrode (Pd/CNTs-nafion film/Ti electrode) was prepared and used for catalytic dechlorination of 2,3,5-trichlorophenol (2,3,5-TCP). The influences of factors, such as Pd2+ concentration, plating solution pH, and electrodeposition time and current, on the preparation of the electrode were studied by cyclic voltammetry (CV) to establish the optimal electrode preparation conditions. Additionally, the CV results highlighted that the addition of the CNTs-nafion film could enhance the electrochemical performance of the electrode. The Pd/CNTs-nafion film/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The electrode exhibited good stability and high catalytic dechlorination capacity on 2,3,5-TCP―100xa0mgxa0L−1 2,3,5-TCP was completely dechlorinated within 100xa0min at a dechlorination current of 5xa0mA and an initial solution pH of 2.3. High-performance liquid chromatography (HPLC) was used to detect the chlorinated phenolic intermediates, and the results revealed that the final products were mainly phenol. The kinetics studies revealed that the dechlorination of 2,3,5-TCP followed two-stage mixed order kinetics, and a possible degradation pathway for 2,3,5-TCP was proposed.

Degradation of diuron by heterogeneous electro-Fenton using modified magnetic activated carbon as the catalyst

In this work, polytetrafluoroethylene coating was firstly conducted to make stable and effective magnetic-activated carbon as a heterogeneous electro-Fenton catalyst for diuron oxidation. The catalysts were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In addition, the effects of operating parameters such as catalyst dosage, current intensity, substrate concentration and pH on the degradation of diuron were investigated. The removal efficiency of diuron was more than 95% within 120 min oxidation under the conditions of I = 100 mA, pH = 6.7 ± 0.2, catalyst loading 3 g L−1 and diuron concentration 10 mg L−1. Moreover, the catalyst durability test demonstrated that the modification of 5% PTFE on the catalyst indeed has a significant beneficial effect on the useful life of the catalyst. We compared the performance of catalysts with or without PTFE modification in consecutive experiments; the modified catalysts exhibited remarkable advantages in that the diuron removal efficiency was stable with relatively low iron leaching (<0.1 mg L−1) during ten consecutive degradation experiments, which proved the durability and reusability of the modified catalyst. This work demonstrates that such a heterogeneous EF using stable magnetic activated carbon catalyst with PTFE modification is promising for organic wastewater treatment in initial neutral pH conditions; at the same time, these good properties of the modified catalyst increase the possibility of practical application.

Preparation and application of magnetic superhydrophobic polydivinylbenzene nanofibers for oil adsorption in wastewater

Superhydrophobic materials have an excellent performance in oil adsorption. In this study, a novel magnetic polydivinylbenzene (PDVB) nanofiber was synthesized by the method of cation polymerization to adsorb oil from water. The magnetic PDVB was hollow nanofiber with Fe3O4 nanoparticles embedded in its structure. The synthesis condition was optimized that the ratio of divinylbenzene (DVB) to boron fluoride ethyl ether (BFEE) was 10:1 (v/v), and the Fe3O4 dosage was 0.175xa0g/g of DVB. The material showed an excellent oil adsorption performance in wastewater, and the oil concentration could be reduced from 2000 to 92.2xa0mg/L within 5xa0min. The magnetic PDVB had relatively high adsorption capacity (12xa0g/g) for oil, which could be attributed to its super hydrophobicity and one-dimensional nanostructure with high crosslinking degree. The isotherm study indicated that the magnetic PDVB adsorbed oil was an asymmetric or multilayer adsorption process. The material could be regenerated by simple squeeze and maintain its adsorption capacity after it has been used for 10 recycles. In real coking wastewater, the magnetic PDVB kept a good oil adsorption performance without the interference of various pollutants, indicating a wide prospect in practical use.

Comparative Degradation of Atrazine by Anodic Oxidation at Graphite and Platinum Electrodes and Insights into Electrochemical Behavior of Graphite Anode

AbstractAnodic oxidation capacities of graphite and platinum (Pt) electrodes were investigated for the degradation of the herbicide atrazine in synthetic aqueous medium. The electro-oxidation of atrazine under various supporting electrolytes and applied currents was conducted in an undivided reactor with different electrode materials. The electrochemical behavior between anode material and supporting electrolyte was investigated by means of cyclic voltammetry. Graphite anode exhibited good oxidation capacity for degradation of 10xa0mgxa0L−1 atrazine in near-neutral pH condition, achieving over 90% removal efficiency in all cases within 60xa0min. Atrazine removal efficiency of 100% was obtained with graphite anode in 60xa0min of reaction time at applied current 60xa0mA, NaCl concentration 0.05xa0molxa0L−1, and initial pHxa06.8; nevertheless, less than 60% of removal was achieved with Pt anode under the same conditions. Five times consecutive runs demonstrated that the atrazine removal efficiency was obviously increased with the positive polarized graphite anode. Positive polarization of graphite anode during anodic oxidation process functionalizes the surface, generating oxygen-containing functional groups; these functional groups played a catalytic role during the oxidation of substrates. An oxidation pathway was proposed in which atrazine was virtually destroyed by chemisorbed reactive oxygen at the graphite anode.n Graphical AbstractAnodic oxidation capacities of graphite and platinum (Pt) anodes were investigated for the degradation of atrazine. Experimental results show that graphite anode was more powerful than Pt to destroy atrazine in all cases. Oxygen-containing functional groups generated from positive polarization of graphite played catalytic roles during the oxidation process.