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It is of great significance to establish an effective method for removing Cr(VI) from wastewater. Herein, Fe-doped g-C3N4 (namely Fe-g-C3N4-2) was synthesized and then employed as photocatalyst to conduct the test of Cr(VI) reduction. Notably, the embedding of Fe ion in g-C3N4 can offer the Fe2+/Fe3+ redox couples, so reducing the interfacial resistance of charge transfer and suppressing the recombination of photogenerated electrons and holes. The impurity energy levels will form in g-C3N4 after the introduction of Fe ion, thereby boosting the light absorption capacity of catalyst. Thus, Fe-g-C3N4-2 showed good performance in photocatalytic Cr(VI) reduction, and the reduction efficiency of Cr(VI) can reach 39.9% within 40 min. Different with many previous studies, current work unexpectedly found that the addition of p-benzoquinone (BQ) can promote the Cr(VI) reduction, and the reduction efficiency of Cr(VI) over Fe-g-C3N4-2 was as high as 93.2% in the presence of BQ (1.5 mM). Further analyses showed that BQ can be reduced to hydroquinone (HQ) by photogenerated electrons, and UV light can also directly induce BQ to generate HQ by using H2O as the hydrogen donor. The HQ with reducing ability can accelerate the Cr(VI) reduction. In short, current work shared some novel insights into photocatalytic Cr(VI) reduction in the presence of BQ. Future research should consider possible reactions between photogenerated electrons and BQ. For the UV-induced photocatalysis, the suitability of BQ as the scavenger of O2â¢â must be given carefully consideration.
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Benzoquinonas , Cromo , Ferro , Oxirredução , Benzoquinonas/química , Cromo/química , Catálise , Ferro/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/efeitos da radiação , Processos Fotoquímicos , Compostos de Nitrogênio/química , Compostos de Nitrogênio/efeitos da radiação , GrafiteRESUMO
SnS2 nanosheets combined with multi-walled carbon nanotubes (MWNTs) were made into sponge electrodes which were used for CO2 reduction reaction (CO2RR) in dielectric barrier discharges (DBD) system. The amounts of formate and formaldehyde produced by CO2 reduction with SnS2/MWNTs/sponge electrode were 299.52 and 31.62 µmol h-1, which were higher than that of MWNTs/sponge electrodes. The addition of pollutants had different degrees of inhibitory effect on CO2 reduction, among which addition of bisphenol A (BPA) had the smallest effect that the degradation rate of BPA was 94.37% and the C1 products remained 204.43 µmol after 60 min discharge. The mechanism of CO2RR was studied by quencher experiment, and the main contribution order of the active substance in DBD system for CO2RR is: H+>e->·OH>·O2-. It was found that the degradation process of pollutants consumed H+ and e- in solution, thereby inhibiting CO2RR. Generally, the SnS2/MWNTs/sponge electrode provided a reference for the design of catalysts for CO2 reduction and pollutant degradation in plasma gas-liquid system.
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Poluentes Ambientais , Nanotubos de Carbono , Dióxido de Carbono , EletrodosRESUMO
Photocatalytic technique is regarded as the cleanest approach for producing H2O2. Herein, two kinds of novel polyimide COFs decorated with CQDs (namely, MPa-COFs/CQDs and MNd-COFs/CQDs) were constructed by using the one-pot hydrothermal method. Due to the electron donor role of CQDs, the recombination of photoinduced electrons and holes was suppressed after the combination of polyimide COFs with CQDs. Importantly, the introduction of CQDs not only boosted the absorbing ability of polyimide COFs toward visible light but also reduced the impedance and improved the charge transfer efficiency. After CQDs were embedded into polyimide COFs, the surface hydrophilicity of catalysts was significantly improved, which provided convenience for the water oxidation reaction. Benefiting from the electron donor-acceptor interaction between polyimide COFs and CQDs, a step-by-step two-electron oxygen reduction reaction over polyimide COFs was enhanced. More interestingly, the embedding of CQDs can create a direct two-electron water oxidation reaction pathway, which played an important role in photocatalytic H2O2 generation. Meanwhile, H+ generated from water oxidation can also be used for the reduction of oxygen to form H2O2. Under the synergistic effects of water oxidation and oxygen reduction, as-prepared MPa-COFs/CQDs-2 displayed excellent performance in photocatalytic H2O2 generation, and its yield was as high as 540 µmol/g within 60 min. In short, the current work shared an effective strategy to improve the performance of polyimide COFs in photocatalytic H2O2 production.
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Photocatalytic oxygen reduction is regarded as the cleanest approach for the production of hydrogen peroxide (H2O2). Herein, oxygen-modified graphite carbon nitride (g-C3N4) with nitrogen-defect (namely g-C3N4-ND4-OM3) was synthesized by a feasible method. Owing to the existence of nitrogen vacancy and oxygen-containing functional group, the absorption bands derived from n â π* and π â π* electronic transitions were enhanced, thereby enlarging the visible light response range of catalysts. Interestingly, nitrogen-defect can capture electron and effectively suppress the recombination of photoinduced electrons and holes. More importantly, the introduction of oxygen-containing functional groups can improve the hydrophilicity of g-C3N4, which was beneficial for the adsorption of dissolved oxygen. The electrostatic potential distributions of g-C3N4-based photocatalyst structural unit were also changed after introducing nitrogen vacancy and oxygen-containing functional group, and the electron-donating ability of g-C3N4 was improved. As a result, the evolution rate of H2O2 catalyzed by g-C3N4-ND4-OM3 was as high as 146.96 µmol/g/L under visible light irradiation. The photocatalytic H2O2 generation was completed through the direct 2-e- oxygen reduction. In short, current work will share novel insights into photocatalytic H2O2 generation over g-C3N4-based catalyst.
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A novel CeO2/Co3O4-Fe2O3@CC electrode derived from CeCo-MOFs was developed for detecting the endocrine disruptor bisphenol A (BPA). Firstly, bimetallic CeCo-MOFs were prepared by hydrothermal method, and obtained material was calcined to form metal oxides after doping Fe element. The results suggested that hydrophilic carbon cloth (CC) modified with CeO2/Co3O4-Fe2O3 had good conductivity and high electrocatalytic activity. By the analyses of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the introduction of Fe increased the current response and conductivity of the sensor, greatly increasing the effective active area of the electrode. Significantly, electrochemical test proves that the prepared CeO2/Co3O4-Fe2O3@CC had excellent electrochemical response to BPA with a low detection limit of 8.7 nM, an excellent sensitivity of 20.489 µA/µM·cm2, a linear range of 0.5-30 µM, and strong selectivity. In addition, the CeO2/Co3O4-Fe2O3@CC sensor had a high recovery rate for the detection of BPA in real tap water, lake water, soil eluent, seawater, and PET bottle samples, which showed its potential in practical applications. To sum up, the CeO2/Co3O4-Fe2O3@CC sensor prepared in this work had excellent sensing performance, good stability and selectivity for BPA, which can be well used for the detection of BPA.
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Carbono , Nanocompostos , Carbono/química , Nanocompostos/química , Água , Técnicas Eletroquímicas/métodosRESUMO
It is of great significance to regulate rationally the activation mechanism of persulfate for promoting the development of sulfate radical-based advanced oxidation processes in wastewater treatment. Herein, carbon coated porous Co3O4 with hollow structure was synthesized. Notably, the formation of porous hollow structure improved specific surface area of Co3O4 and offered more redox couples of Co2+/Co3+, thereby reducing electron transfer resistance. Thus, the generation of reactive oxygen species and the role of high-valent transition metal complexes (namely Co3O4Co4+) were improved. The formation of carbon layer on the Co3O4 surface can avoid the release of Co ion during reaction process. Benefiting from the role of carbon layer in electron transport, catalyst-mediated the direct electron transfer from pollutant to PMS was boosted. Radical and nonradical pathways worked in coordination each other and realized the rapid removal of various organic pollutants in the presence of a little PMS. In short, current work revealed that modulating rationally the microstructure of catalyst was an efficient strategy for achieving controllable regulation of PMS activation process. More significantly, whether the direct electron transfer process can occur or not depended on both catalyst structure and electronic density of pollutants.
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The degradation of phenylic contaminants (phenol, hydroquinone, nitrobenzene, p-nitrophenol) containing Cr(VI) has been investigated in a dielectric barrier discharge (DBD) system using a ZnCo2O4 composite catalyst. The ZnCo2O4 nanowires combined with multi-walled carbon nanotubes (MWNTs) on a sponge substrate in the discharge system can induce a decrease in the corona inception voltage and discharge becomes more stable resulting in an improvement in the energy utilization efficiency. With the synergistic degradation of phenylic species containing Cr(VI), the total elimination efficiency was further improved. The active substances (H2O2 and O3) were detected in the discharged solution, and some of them were consumed in the phenylic system. The effects of ·OH, O2·- and e- were also verified using free radical trapping experiments in which ·OH exhibited the main oxidation effect for the degradation of phenylic pollutants, and e-, H2O2 and H· affect the reduction of Cr(VI). The intermediate products were determined in order to analyze the degradation process of phenylic pollutants by the ZnCo2O4 composite catalyst in combination with the DBD system. The electron transfer process in the ZnCo2O4 composite catalyst during discharge was analyzed. Finally, the biotoxicity of the phenylic pollutants before and after degradation was compared.
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Poluentes Ambientais , Nanotubos de Carbono , Poluentes Químicos da Água , Peróxido de Hidrogênio , Nanotubos de Carbono/química , Fenóis , Cromo/química , Oxirredução , Poluentes Químicos da Água/análiseRESUMO
Carbon quantum dots (CQDs) have been supported on WO3/TiO2-NRs using a hydrothermal method and a novel CQDs/WO3/TiO2-NRs composite formed via dielectric barrier discharge. The composite electrodes were characterized using morphology, structural, optical and electrochemical analysis. The CQDs were successfully prepared on the composite electrode with the highest photocurrent density reaching 2.51 mA·cm-2 under UV-visible light irradiation (100 mW·cm-2) and an applied voltage of 0.6 V vs. Ag/AgCl. The CQDs/WO3/TiO2-NRs electrode exhibited a good degradation effect toward bisphenol A (BPA) (75.66 %) combined with the production of hydrogen (0.89 mmol) in Na2SO4 system after 2 h of the photoelectrocatalytic (PEC) reaction and the BPA degradation rate reached 100 % after 7 min of reaction in both simulated and real seawater. The CQDs/WO3/TiO2-NRs exhibited excellent stability and efficient PEC performance in which the CQDs acted as electron reservoirs to capture and promote charge separation. Our analysis of intermediates of BPA degradation indicated the possible degradation pathways that mainly formed BPA polymers in the Na2SO4 system or chlorinated compounds in the high chloride salt system.
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Poor water stability and difficult separation severely limited the application of Co-based catalysts in persulfate activation. Herein, for the first time, the calcium alginate-immobilized Co-g-C3N4-2 composite microspheres were prepared by a feasible method. Notably, embedding Co ion into g-C3N4 can improve its specific surface area and electrochemical activities. More significantly, as-prepared Co-g-C3N4-2 microsphere presented excellent catalytic performance in PMS activation for the degradation of TC. For the activation mechanisms of PMS over Co-g-C3N4-2 microspheres, the calcium alginate microspheres could mediate the direct electron transfer between TC and PMS, while both radical and nonradical pathways were involved in the activation of PMS over Co-g-C3N4-2. Meanwhile, SO4â¢-, OHâ¢, O2â¢- and 1O2 were major reactive oxygen species formed in the Co-g-C3N4-2 microsphere/PMS system. Proposed Co-g-C3N4-2 microsphere/PMS system still exhibited great degradation ability towards TC over a wide pH range, and co-existing anions had weak influence on TC degradation over Co-g-C3N4-2 microsphere/PMS system. Moreover, the construction of Co-g-C3N4-2 microspheres not only avoided the release of metal ion from catalyst, but also provided convenience for the recovery of catalyst. In short, current work shared some novel insights into the application of heterogeneous catalysis in persulfate activation for wastewater treatment.
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Poluentes Ambientais , Alginatos , Microesferas , Peróxidos , Espécies Reativas de Oxigênio , ÁguaRESUMO
Nowadays effective treatment of high concentration organic wastewater is still a formidable task facing human beings. Herein, for the first time, a well-defined ZIF-67-derived NiCo2O4 nanosheet array was successfully prepared by a feasible method. In comparison with ordinary NiCo2O4 nanosphere, the formation of nanosheet structure could offer more opportunities to exposure internal active sites of NiCo2O4, thereby resulting in smaller interface resistance and higher charge transfer efficiency. As expected, ZIF-67-derived NiCo2O4 nanosheet array displayed great performance in peroxymonosulfate (PMS) activation. More importantly, recyclable redox couples of Co3+/Co2+ and Ni3+/Ni2+ endowed the stable catalytic activity of NiCo2O4 nanosheet. Interestingly, developed NiCo2O4-1/PMS oxidation system could achieve the effective degradation of antibiotics with high concentration in a short time. Both radical and nonradical pathways were involved into PMS activation, wherein SO4-, OH, O2- and 1O2 were major reactive oxygen species. The formation paths of reactive oxygen species and effects of inorganic anions were also investigated. Electrochemical analyses revealed that NiCo2O4-1 with nanosheet structure mediated the electron transfer between PMS and tetracycline (TC), which played a vital role in TC degradation. Furthermore, developed NiCo2O4-1/PMS oxidation system displayed great removal ability towards TC in actual water samples, and degradation products were low toxicity or no toxicity. In short, current work not only developed an effective oxidation system for completing the rapid degradation of antibiotic with high concentration, but also shared some novel insights into the activation mechanism of SR-AOPs.
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Poluentes Ambientais , Águas Residuárias , Antibacterianos , Humanos , Peróxidos/química , Espécies Reativas de Oxigênio , Tetraciclina , Águas Residuárias/química , ÁguaRESUMO
Efficient removal of toxic hexavalent chromium (Cr(VI)) under alkaline conditions is still a challenge due to the relatively low reactivity of CrO42-. This study proposed a new sulfite/iodide/UV process to remove Cr(VI). The removal of Cr(VI) followed pseudo-zero-order kinetics at alkaline pHs, and was enhanced by sulfite and iodide with synergy. Compared with sulfite/UV, iodide in sulfite/iodide/UV showed about 40 times higher concentration-normalized enhancement for Cr(VI) removal, and reduced the requirement of sulfite ([S(IV)]0/[Cr(VI)]0 of about 2.1:1) by more than 90%. The Cr(VI) removal was accelerated by decreasing pH and by increasing temperature, and was slightly influenced by dissolved oxygen, carbonate, and humic acid. The process was still effective in real surface water and industrial wastewater. Mechanism and pathways of Cr(VI) removal were revealed by quenching experiments, competition kinetic analysis, product identification and quantification, and mass and electron balance. Both eaq- and SO3â¢- were responsible for Cr(VI) removal, making contributions of about 75% and 25%, respectively. When eaq- mainly reacted with Cr(VI), SO3â¢- participated in reduction of Cr(V) and Cr(IV) intermediates, with Cr(III), S2O62-, and SO42- as the final products. A model was developed to predict removal kinetics of Cr(VI), and well interpreted the roles of S(IV) and iodide in the process. This study sheds light on mechanism of Cr(VI) removal at alkaline pHs by kinetic modeling, and thus advances the applicability of this promising process for water decontamination.
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Iodetos , Poluentes Químicos da Água , Adsorção , Cromo/análise , Concentração de Íons de Hidrogênio , Cinética , Oxirredução , Sulfitos , Raios Ultravioleta , Água , Poluentes Químicos da Água/análiseRESUMO
Electrochemistry is considered to be one of the most efficient and environment-friendly methods for removing highly toxic Cr (â ¥). In this study, a 3D self-supported MoS2-Co-P/nickel foam (NF) electrode was prepared via a calcination-hydrothermal process to remove the Cr (â ¥) in aqueous medium. Scanning electron microscope (SEM) analysis indicated that the pine-needle-like Co2P nanoneedle and flower-like MoS2 nanosheets were successfully loaded on the three-dimensional (3D) framework of NF, which provided abundant active sites. The electrode modified by Co, P and MoS2 exhibited high removal efficiency of Cr (â ¥) (96.9%) at pH 3.0, current of 0.128 mA and voltage of 2.5 V. Co, P and MoS2 have the synergistic promotion on the catalytic performance of electrodes, and the reduction efficiency of Cr (â ¥) was greatly improved by 127.5 times relative to pure NF. The enhanced removal of Cr (â ¥) was related to the coupling effect of adsorption and electrocatalytic reduction. The mechanism study indicated that electron (e-) is the active species of Cr (â ¥) reduction. The Cr (â ¥) removal rate was maintained at 90 ± 1% after five successive cycle experiments, demonstrating good stability and potential industrial applications of MoS2-Co-P/NF.
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Molibdênio , Níquel , Adsorção , Cromo , Eletrodos , Molibdênio/química , Níquel/químicaRESUMO
A Zn0.5Cd0.5S (ZCS) solid solution was prepared using a hydrothermal method, in which CoP nanowires were added as a co-catalyst and co-deposited with multiwalled carbon nanotubes (MWNTs) on sponge to prepare a series of ZCS/CoP/MWNTs/sponge electrodes. The microstructures of catalysts were analyzed to confirm ZCS and CoP were successfully loaded in MWNTs/sponge. The CO2 reduction products (formate and formaldehyde) produced via dielectric barrier discharge (DBD) using the different catalysts proved that the introduction of the CoP nanowires co-catalyst can enhance the catalytic activity of ZCS/MWNTs/sponge in the DBD system. Using 10% CoP and a ZCS/CoP concentration of 2.5 g·L-1, the resulting ZCS/CoP/MWNTs/sponge catalyst exhibited the best catalytic of CO2 reduction ability toward formate (7894.6 µmol·L-1) and formaldehyde (308.5 µmol·L-1) after 60 min of discharge, respectively. The proposed DBD catalytic mechanism for the reduction of CO2 was analyzed according to the Tafel slope, density functional theory calculations, photocurrent density and plasma reaction process. Furthermore, the application of the DBD catalytic technology for CO2 capture and reduction was shown to be efficient in a seawater system, and as such, it could be useful for marine CO2 storage and conversion.
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Bimetallic oxides with spinel structure show great prospects in the photocatalysis owing to many active sites. Herein, a novel 500NiCo2O4@CdS-5%Ag composite was fabricated via a feasible strategy. Interestingly, the combination with NiCo2O4 could significantly enhance the absorption ability of CdS for visible light. Benefiting from the formation of heterojunction structure between NiCo2O4 and CdS, the recombination of photogenerated electrons and holes was remarkably restrained. As an effective mediator, deposition of Ag could further promote the transfer of photogenerated charge carriers, thereby accelerating the reaction rate. Meanwhile, light absorption capacity of composite was also improved, owing to the surface plasmon resonance effect of metallic Ag. More importantly, 500NiCo2O4@CdS-5%Ag composite with great stability displayed an excellent performance in the photocatalytic degradation of OFX, and its highest removal efficiency was as high as 99.14%. Possible degradation pathways of OFX were given, and most of OFX could be degraded into CO2, H2O and other by-products with no toxicity. Significantly, the separation and transfer of photogenerated charge carriers followed indirect Z-scheme heterojunction mechanism. The O2-, OH and 1O2 were main active species in photocatalytic reaction system. All in all, current work inspired some new ideas for designing novel photocatalytic system in wastewater treatment.
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Poluentes Ambientais , Catálise , Luz , ÓxidosRESUMO
Dielectric barrier discharge (DBD) plasma applied as surface treatment technology was employed for the modification of Ag2O and graphitic carbon nitride (g-C3N4) powders. Subsequently, the pretreated powders were sequentially loaded onto TiO2 nanorods (TiO2-NRs) via electro-deposition, followed by calcination at N2 atmosphere. The results indicated that at the optimal plasma discharge time of 5 min for modification of g-C3N4 and Ag2O, photocurrent density of ternary composite was 6 times to bare TiO2-NRs under UV-visible light irradiation. Phenol was degraded by using DBD plasma-modified g-C3N4/Ag2O/TiO2-NRs electrode to analyze the photoelectrocatalytic performance. The removal rate of phenol for g-C3N4-5/Ag2O-5/TiO2-NRs electrode was about 3.07 times to that for TiO2-NRs electrode. During active species scavengers' analysis, superoxide radicals and hydroxyl radicals were the main oxidation active species for pollutants degradation. A possible electron-hole separation and transfer mechanism of ternary composite with high photoelectrocatalytic performance was proposed.
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Nanotubos , Prata , Catálise , TitânioRESUMO
A new electrochemically-modified BiVO4-MoS2-Co3O4 (represented as E-BiVO4-MoS2-Co3O4) thin film electrode was successfully synthesized for environmental application. MoS2 and Co3O4 were grown on the surface of BiVO4 to obtain BiVO4-MoS2-Co3O4. E-BiVO4-MoS2-Co3O4 film was achieved by further electrochemical treatment of BiVO4-MoS2-Co3O4. The as-prepared E-BiVO4-MoS2-Co3O4 exhibited significantly enhanced photoelectrocatalytic activity. The photocurrent density of E-BiVO4-MoS2-Co3O4 thin film is 6.6 times that of BiVO4 under visible light irradiation. The degradation efficiency of E-BiVO4-MoS2-Co3O4 for bisphenol A pollutant was 81.56% in photoelectrochemical process. The pseudo-first order reaction rate constant of E-BiVO4-MoS2-Co3O4 film is 3.22 times higher than that of BiVO4. And its reaction rate constant in photoelectrocatalytic process is 14.5 times or 2 times that in photocatalytic or electrocatalytic process, respectively. The improved performance of E-BiVO4-MoS2-Co3O4 was attributed to the synergetic effects of the reduction of interfacial charge transfer resistance, the formation of oxygen vacancies and sub-stoichiometric metal oxides and higher separation efficiency of photogenerated electron-hole pairs. E-BiVO4-MoS2-Co3O4 is a promising composite material for pollutants removal.
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Bismuto , Vanadatos , Compostos Benzidrílicos , Molibdênio , FenóisRESUMO
In this study, a sponge modified by multi-walled carbon nanotubes (MWNTs) was used as sheet support for the adsorption of CuO@Cu and Ag nanowires to prepare a CuO@Cu/Ag/MWNTs/sponge electrode. Similar to their use in a dielectric barrier discharge (DBD) reactor, the MWNTs changed the conductivity and water absorptivity of the modified electrode, whereas the CuO@Cu and Ag nanowires significantly enhanced the tip effect to increase discharge. The optimal ratio of the Ag:CuO@Cu nanowires was 5:3â¯at a total adsorbed concentration of 0.8â¯gâ¯L-1. Compared with CuO@Cu and Ag nanowires were separately adsorbed on the MWNTs/sponge, and the CuO@Cu/Ag/MWNTs/sponges recorded higher current response, lower discharge inception voltage, and higher removal efficiency of phenol and 2,4,5-trichlorobiphenyl (PCB29) through their degradation. The removal efficiency reached 100% within 30â¯min of the reaction for the degradation of phenol and 65.1% within 60â¯min of the reaction for the degradation of PCB29 at an input voltage of 30â¯V. These results show that the CuO@Cu/Ag/MWNTs/sponge structure has significant potential for use in the DBD reactor to improve the discharge efficiency of the system and reduce energy consumption, and can be further extended to other types of plasma reactors.
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Cobre/química , Eletroquímica/instrumentação , Poluentes Ambientais/química , Poluentes Ambientais/isolamento & purificação , Nanotubos de Carbono/química , Prata/química , Adsorção , Impedância Elétrica , Eletrodos , Cinética , Nanofios/química , Água/químicaRESUMO
Plasmonic Bi0 modified BiOI-Bi2O3 composite (Bi/BiOI-Bi2O3) was prepared via in situ UV reduction method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) techniques were carried out to identify the formation of semimetal Bi0. The results indicated that the dot-like bismuth particles were originated from the partial reduction of lattice Bi3+ to Bi0 by accumulated conduction band electrons in BiOI-Bi2O3. The as-prepared ternary composite exhibited enhanced visible-light-response, decreased charge transfer impedance and higher charge carrier density relative to unmodified BiOI-Bi2O3. Due to synergistic effect between plasmonic Bi0 and BiOI-Bi2O3 heterojunction, dramatically enhanced photocatalytic activity for phenol degradation can be achieved. After 3.5â¯h visible light irradiation, the value for phenol removal efficiency was ca. 60% and 100% on BiOI-Bi2O3 and Bi/BiOI-Bi2O3, respectively. The calculated zero-order rate constant on Bi/BiOI-Bi2O3 was 1.7 and 3.9 times that on BiOI-Bi2O3 and Bi2O3, respectively. In addition to phenol, organic dyes (zwitterionic RhB, cationic MB and anionic Org II) were also used as model pollutants. Pronounced photocatalytic degradation by Bi/BiOI-Bi2O3 can be observed, further confirming the importance of Bi0. Trapping experiments using different scavengers indicated that photogenerated holes were major active species during the degradation of phenol. Furthermore, good stability was also observed in 5 successive cyclic runs. This study opens a new strategy for in situ preparation of plasmonic Bi0 modified composite.
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A novel visible-light-active Cs3PMo12O40/Bi2O3 (CsPMo/Bi2O3) composite was prepared by a simple dissolution-precipitation method. The as-prepared samples were characterized by XRD, XPS, FT-IR, SEM, UV-Vis DRS, N2 adsorption-desorption isotherms and electrochemical analysis. The results revealed that Bi2O3 was successfully modified by trace CsPMo. After the addition of H3PMo12O40 acid (HPMo), the surface of Bi2O3 can be roughed. Subsequently, the presence of Cs2CO3 can neutralize the protons of HPMo forming CsPMo precipitate on Bi2O3. Comparing to naked Bi2O3 and CsPMo, the binary composite exhibited many beneficial characteristics in charge generation and separation, such as formation of p-n heterojunction, decreased band gap, enhanced photocurrent response and greatly reduced charge transfer resistance. The photocatalytic activities of the as-prepared samples were evaluated by the degradation of phenol under visible light. The calculated pseudo-first-order rate constants for phenol degradation were 2.7 and 14.8 times relative to that on Bi2O3 and CsPMo, respectively. Dramatically enhanced photocatalytic performance can be observed when the optimal CsPMo/Bi2O3 composite (2.5% CsPMo) was applied. The major active species involved in the degradation process are in the following order: superoxide radical (O2-) > hydroxyl radical (OH)â¯≈â¯hole (h+). Besides, the CsPMo/Bi2O3 composite also displayed good stability in cyclic experiments.
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A gas-liquid hybrid discharge system was applied to microcystin-LR (MC-LR) degradation. MC-LR degradation was completed after 1 min under a pulsed high voltage of 16 kV, gas-liquid interface gap of 10 mm and oxygen flow rate of 160 L/h. The Box-Behnken Design was proposed in Response Surface Methodology to evaluate the influence of pulsed high voltage, electrode distance and oxygen flow rate on MC-LR removal efficiency. Multiple regression analysis, focused on multivariable factors, was employed and a reduced cubic model was developed. The ANOVA analysis shows that the model is significant and the model prediction on MC-LR removal was also validated with experimental data. The optimum conditions for the process are obtained at pulsed voltage of 16 kV, gas-liquid interface gap of 10 mm and oxygen flow rate of 120 L/h with ta removal efficiency of MC-LR of 96.6%. The addition of catalysts (TiO2 or Fe2+) in the gas-liquid hybrid discharge system was found to enhance the removal of MC-LR. The intermediates of MC-LR degradation were analyzed by liquid chromatography/mass spectrometry. The degradation pathway proposed envisaged the oxidation of hydroxyl radicals and ozone, and attack of high-energy electrons on the unsaturated double bonds of Adda and Mdha, with MC-LR finally decomposing into small molecular products.