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Phenolic acids can reduce nitrogen utilization rate of poplar, which seriously restrict the productivity of poplar plantation. In this study, three phenolic acid concentrations (T0, T1, and T2) and three ratios of nitrogen forms (NHIncreasing the ratio of ammonia nitrogen fertilizer in soil can effectively reduce the toxic effect of phenolic acids on poplar and improve the photosynthetic productivity of poplar.

Anodic oxidation with boron-doped diamond (BDD) has been regarded as outstanding option for wastewater treatment. However, in the presence of halide, the extreme promise of the technology may be hampered by the formation of toxic halogenated by-products. While the behaviors of chloride are relatively understood, little is currently known about the role of bromide and its effect on the generation of brominated transformation by-products (BTPs). Herein, we reported for the first time the bromide-mediated electrochemical mineralization of bisphenol A with BDD anodes. Firstly, we employed statistical methodology to determine the impacts of the main operating variables on the mineralization performance, and the novel and peculiar roles of bromides during the electrolytic oxidations were identified. Next, LC/MS analysis was used to identify the reaction intermediates, and plenty of BTPs (including oligomers of complex structures) were thus detected. Detailed transformation mechanisms responsible for the BTPs were also proposed. Lastly, we used ECOSAR program to determine the ecological toxicity of all detected by-products, and the structure-toxicity relation involved was discussed. Overall, the above results are of particular interest to understand BTPs formation mechanism in electrochemical oxidation processes, which as well provide guidelines to minimize potential risks of BDD technology for phenolic wastewater treatment.

Flavin-mediated extracellular electron transfer was studied in two Gram-positive bacteria: Bacillus cereus strain DIF1 and Rhodococcus ruber strain DIF2. The electrochemical activities of these strains were confirmed using amperometric I–t curves and cyclic voltammetry (CV). Spent anodes with biofilms in fresh anolytes showed no redox peaks, while new anodes in the spent broth showed relative redox peaks using CV measurements, indicating the presence of a redox electron mediator secreted by bacteria. Adding riboflavins (RF) and flavin mononucleotide (FMN) improved the electron transfer of the microbial fuel cells inoculated with the two strains. The redox peaks indicated that flavins existed in the anolyte, and HPLC analysis showed that RF and FMN were secreted by the two bacterial strains. The concentration of RF increased until the bacteria grew to the log phase in microbial fuel cells. The concentration of RF decreased and that of FMN increased after the log phase. The two strains secreted FMN only in the microbial fuel cell. These results confirmed that the electrochemical activity mediated by flavins and FMN is essential in the extracellular electron transfer process in the strains DIF1 and DIF2.

Using boron-doped diamond (BDD) anodes to degrade bisphenol A (BPA) had been an active area of research interest within the past 20 years. A major concern about the process lie in the formation of toxic chlorinated aromatic by-products when chloride electrolytes were present in the reaction system. In this contribution, we highlighted the formation of complex poly-chlorinated oligomer by-products in electrochemical oxidation processes, which had often been overlooked in previous studies. Moreover, the distribution and complexity of the chlorinated oligomers were found to be strongly linked to the adopted initial chloride concentration. Formation of simple chlorinated by-products was ascribed to the electrophilic substitution reactions mediated by active chlorine species, while the oligomer by-products (including chlorinated dimers, trimers and tetramers) were generated through the coupling reactions between various chlorinated phenoxy radicals. The possible mechanisms describing the formation of these by-products were also proposed. The obtained results shed light on the possible risk of BDD technology in the treatment of phenolic wastewater containing chloride electrolytes.

The electrochemical incineration of diethylenetriaminepentaacetic acid (DTPA) with boron-doped diamond (BDD) anode had been initially performed under galvanostatic conditions. The main and interaction effects of four operating parameters (flow rate, applied current density, sulfate concentration and initial DTPA concentration) on mineralization performance were investigated. Under similar experimental conditions, Doehlert matrix (DM) and central composite rotatable design (CCRD) were used as statistical multivariate methods in the optimization of the anodic oxidation processes. A comparison between DM model and CCRD model revealed that the former was more accurate, possibly due to its higher operating level numbers employed (7 levels for two variables). Despite this, these two models resulted in quite similar optimum operating conditions. The maximum TOC removal percentages at 180 min were 76.2% and 73.8% for case of DM and CCRD, respectively. In addition, with the aid of quantum chemistry calculation and LC/MS analysis, a plausible degradation sequence of DTPA on BDD anode was also proposed.

In this work, a novel definitive screening design (DSD) was initially used to investigate the in situ chemical oxidation of acid orange-II (AO II) dye using a homogeneous cobalt-catalyzed peroxymonosulfate (Co2+/PMS) system. Experiments were performed in a batch reactor using a synthetic AO II solution containing cobalt ions, humic acid (HA) and five electrolyte salts (NaCl, NaNO3, NaHCO3, Na2SO4 and NaH2PO4). The effects of nine operating variables on AO II degradation: NaCl concentration (0–20 mM), NaH2PO4 concentration (0–20 mM), NaHCO3 concentration (0–20 mM), NaNO3 concentration (0–20 mM), Na2SO4 concentration (0–20 mM), HA concentration (0–40 mg L−1), PMS concentration (2–10 mM), AO II concentration (0–100 mg dm−3) and Co2+ concentration (0–1.36 mM), were investigated. Analysis of a DSD model revealed that only four variables were statistically significant. Besides, our results indicated that there were no significant interactive effects between the five anions employed. Thereafter, a central composite rotatable design (CCRD) was adopted to further optimize these significant variables. A CCRD model describing AO II conversion as a function of PMS concentration, NaCl concentration and Co2+ concentration was then constructed and used to explore the final optimal operating conditions. As a consequence, the combination of DSD and CCRD allowed reducing the number of experiments from over 600 to only 39. Lastly, a plausible reaction sequence concerning the oxidation of AO II in the Co2+/PMS/Cl− system was also proposed. The route of AO II oxidation involved hydroxylation and chlorination, signifying the roles of both sulfate radicals and active chlorine species.

Anode surface plays important role for extracellular electron transfer (EET) of exoelectrogenic microbes in microbial fuel cell (MFC). In this report, the electrochemical performance of a TiO2nanorod array modified carbon paper electrode (TiO2NRs/CP) is greatly improved by controlled chemical etching process. The etching process keeps the array morphology but yields obvious hollows on tops of TiO2nanorods. The etched electrode (TiO2NRs-HOT/CP) exhibits better hydrophilicity than carbon paper (CP) and TiO2NRs/CP electrode as seen from smaller contact angle (CA) and more attached microbes S.loihica PV-4. Meanwhile, the hollows allow higher local concentration of microbial self-secreted flavins that can act as electron mediators for interfacial electron transfer of PV-4 through in-direct pathway. Accordingly, PV-4 produces larger current density at TiO2NRs-HOT/CP electrode with maximum current density of 0.038 mA cm–2, which was much higher than that at CP electrode, and almost five times higher than that at un-etched TiO2NRs/CP electrode.

The performance of TiO2 nanosheets (TiO2-NSs) modified carbon paper anode (TiO2-NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO2-NSs to modulate its electronic properties. TiO2-NSs/CP is calcined in NH3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO2-NSs/CP, T represents temperature), in which 600-NTiO2-NSs/CP electrode show best performance with the maximum output power density increased by 196% and 50% compared to that from the bare CP and TiO2-NSs/CP electrodes respectively. The surface morphology, structure and electrochemical activity are characterized by FESEM, XRD, Raman, XPS, CVs and EIS. The results show that heating in NH3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential Em (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO2-NSs/CP anode is in accordance with that at TiO2-NSs/CP. However, 600-NTiO2-NSs/CP electrode had smaller charge transfer resistance, more positive flat-band potential and larger transient charge storage capacity than untreated electrode due to modulation of the electronic structure via N doping, which all are favorable to interfacial electron transfer from OMCs to underlying electrode. The method is simply and efficient, and could be extended to other nano-semiconductor modified electrodes for superior MFC anodes.

Detection of proteins in a wide concentration range from fg mL–1 to sub mg mL–1 is a challenge in the high throughput analysis of precision medicine. Herein, we proposed a biosensor consisting of core–shell surface-enhanced Raman scattering (SERS) nanotags as labels and photonic crystal beads (PCBs) as carriers for ultrasensitive detection of proteins. In practice, Raman dyes (RDs) were embedded in the interface of gold core and silver shell in the bimetal nanoparticles to form SERS nanotags. It was found that the sensitivity was significantly improved due to the enhanced Raman signal by the coupling of the core–shell structure and linear dynamic range (LDR) was extended owing to the high surface to volume ratio of PCBs as well. In addition, we also demonstrated that the biosensor exhibited fine stability and low background, which has great application potential in the detection of protein biomarkers.

Efficient and robust Earth-abundant catalysts for hydrogen evolution reaction (HER) is one of the key components for clean energy technologies aimed at reducing future carbon emissions. Here, an in-situ anion exchange approach to prepare hierarchical nanostructures consisting of ultrathin Cu2-xSe nanosheet is reported. With the aid of the selenylation process and the hierarchical ultrathin nanostructure, the nanostructured Cu2-xSe/Cu foam electrode achieved considerably enhanced HER performance with a large geometric current density of −100 mA cm−2 at a small overpotential of 313 mV and outstanding long-term operational stability. Significant improvement of electrocatalytic activity for Cu2-xSe catalyst could be attributed to the promoted mass diffusion/transfer properties, which results from its special structural feature. Meanwhile, the overpotential associated with the catalyst/substrate interface could be effectively eliminated due to the self-supported construction. We believe that this work will lead towards the further development of Cu-based chalcogenides for applications in electrocatalysis and energy conversion.

Taking Acid orange-II (AO II) as pollutant model, the relationship between anode material, supporting electrolyte and applied current density was quantitatively investigated with the aid of a statistical tool, factorial design methodology. Boron-doped diamond (BDD), mixed metal oxide (MMO) and platinum (Pt) used as anode materials were examined with Na 2 SO 4 and NaCl as supporting electrolytes. Analysis of result showed that AO II degradation efficiency was strongly linked to the anode-electrolyte-current interaction. The differing performances recorded in these anode/electrolyte systems could be explained in terms of oxygen evolution over-potential and electro-generated oxidants, and BDD/NaCl system outperformed other systems in terms of decolorization and mineralization efficiency. Further kinetic study indicated that the electrochemical degradation of AO II might follow different reaction orders, depending on the anode material and supporting electrolytes adopted. As a consequence, the new results recorded above were mainly consistent with the low electrolyte concentrations employed (1.0 ∼ 10.0 mM). Thus, we highlighted the importance of operating level selections in anodic oxidation processes, especially when different concentrations of supporting electrolytes were present in the reaction system.

Schwertmannite (SCH), a ferric oxyhydroxy sulfate mineral, had attracted extensive interests due to its excellent adsorption performance in decontamination processes. The present study initially explored the fractal properties of SCH by SEM imaging and nitrogen adsorption analysis. The two SCH samples under investigation were synthesized through chemical and biological routes, respectively. Our results revealed that biosynthesized SCH exhibited higher inner fractal dimension but lower surface fractal dimension than chemosynthesized SCH. These outcomes were in line with their differing adsorption capabilities toward humic acid and Cr(VI). As a result, the employment of fractal geometry had led to new dimension of understanding the structure-property relationship in SCH.

Extracellular electron transfer (EET) allows microorganisms to perform anaerobic respiration using insoluble electron acceptors, including minerals and electrodes. EET-based applications require efficient electron transfer between living and non-living systems. To improve EET efficiency, the TiO

In this contribution, the electrocatalytic abatement of bisphenol A (BPA) with boron-doped diamond (BDD) anode had been conducted in NaNO2 electrolytes. Central composite design was used as statistical multivariate method to optimize the operating parameters adopted (applied current density, flow rate, concentration of NaNO2 and initial pH). The results from response surface analysis indicated that pH was the most influential factor for TOC decay, and a maximum TOC decay of 63.7% was achieved under the optimized operating conditions (9.04 mA cm−2 of applied current density, 400 mL min−1 of flow rate, 10 mM of NaNO2, 4.0 of initial pH and 60 min of electrolysis time). Besides, LC/MS technique was applied to identify the main reaction intermediates, and plenty of nitrated oligomers were detected at the end of the degradation. These by-products were generated via the coaction of coupling reaction of nitrated phenol and electrophilic substitution mediated by nitrogen dioxide radicals. Moreover, our results showed that the degree of nitration depended heavily on the employed initial nitrite concentration. This was one of the very few investigations dealing with nitrophenolic by-products in nitrite medium, and thus the findings exhibited important implications for electrochemical degradation of BPA and its related phenolic pollutants.

Exploring the structure and composition of catalysts to realize fast electron transfer in electrochemical reaction is a challenging part for the development of highly efficient electrocatalysts. Herein, nitrogen-doped carbon nanotube with encapsulated cobalt nanoparticles is synthesized via co-pyrolysis of zeolitic imidazolate framework and assisted nitrogen/carbon precursors with high N/C ratio. These precursor-dependent materials are served as catalysts for determination of hydrogen peroxide (H2O2) and oxygen reduction reaction (ORR). Electrochemical measurement results suggest a strong relationship between N-doped types and electrochemical performance. The as-proposed ZU catalyst (urea as N-rich precursor) exhibits optimal electrocatalytic performance towards ORR and H2O2 detection. Furthermore, ZU also can be a potential cathode candidate for direct borohydride fuel cell (DBFC).The synthesis strategy offers a new clue in constructing effective non-noble-metal catalysts for electrochemical applications.

Here, the electrochemical degradation of 50 mg/dm 3 Acid Orange II dye over mixed metal oxide anode has been conducted in the presence of different supporting electrolytes (sulfate, chloride, and their mixture of different proportion). A factorial design methodology was adopted to evaluate the statistically important input variables, among treatment time (30–60 min), flow rate (300–600 ml/min), applied current density (2.58–5.16 mA/cm 2 ) and total concentration of supporting electrolytes (1.0–4.0 mM), on degradation performance; the latter was assessed in terms of color removal rate. The results obtained, demonstrated that the electrolytic oxidation was strongly favored by the presence of chlorides. In addition, the information obtained from electrochemical measurements and UV–vis spectra were used to better clarify the different roles of operating parameters recorded.

Electron transfer kinetics of Shewanella loihica PV-4 at the up-growing TiO2 nanosheet (TiO2-NS) modified carbon paper (CP) electrode was investigated. The effect of TiO2-NSs, which speeds up the interfacial electron transfer of outer membrane c-type cytochromes (OMCs), was revealed for the first time. TiO2-NSs with a polar surface modified hydrophobic CP into super-hydrophilic TiO2-NS/CP. The favorable interaction between PV-4 and TiO2-NSs not only enhanced microbial adhesion, but also altered the redox nature of OMCs. The mid-point potential of OMCs at TiO2-NS/CP was shifted to a more negative potential, indicating a higher thermodynamic driving force for the protein to release electrons. Moreover, electron transfer from OMCs to TiO2-NSs was also benefited from the positive shift of flat-band potential Vfb owing to reduced pH at the electrode/microorganism interface, as well as good electrical conductivity of TiO2-NSs. As a result, the electron transfer rate constant ket of OMCs at the TiO2-NS/CP anode was about three times faster than that at the CP anode. The accelerated electron transfer kinetics as well as 15% increase of biomass together accounted for a 97% increase of the maximum output power density in the MFC. The result expanded our knowledge about the role of a designed TiO2 nanostructure in microbial electron transfer that can be applied in other bio-electrochemical systems.

Self-healing materials are gradually being developed because they can restore structural properties and maintain their function after being damaged. Here, branched poly(ethyleneimine) (bPEI), poly(acrylic acid) (PAA), and microcapsules were used to fabricate a functional (bPEI/PAA)*30-microcapsule composite PEM film based on a layer-by-layer (LbL) self-assembly technique. As a proof of concept, the model molecules hydrophilic rhodamine B (RB) and hydrophobic roxithromycin (ROX) were loaded in (bPEI/PAA)*30-microcapsule composite PEM films, and tests with these self-healing films showed them to be endowed with the desired functional properties and hence showed the microcapsules to constitute a promising functional carrier candidate. The results indicated that the microcapsules can be assembled successfully on polyelectrolyte multilayer (PEM) films, and the as-prepared (bPEI/PAA)*30-microcapsule composite PEM film can not only be tailored with desired properties but also show an excellent self-healing ability. Based on our study, we expect more functional molecules to be grafted onto self-healing PEM films using microcapsules and expect functional self-healing PEM composite films to have great potential applications in the future.

Here, the fractal properties of buckypapers (BPs) have been initially studied by SEM imaging at different scales, as well as by low-pressure nitrogen adsorption analysis. The BPs under investigation are composed of either single-walled carbon nanotubes (SWNTs) or multi-walled carbon nanotubes (MWNTs). Fractal analysis of either film morphology or adsorption isotherm shows that the fractal dimension of SWNT-BPs is higher than that of the MWNT-BPs. As a result, such difference offers a new and important explanation for their differing adsorption capabilities during decontamination processes.

Taking phenol as a pollutant model, the role of chloride electrolytes during the anodic oxidations was investigated in a wide range of concentrations (0.1–1000 mM). Experiments were performed with an electrochemical cell containing a boron-doped diamond (BDD) anode and Pt cathode. The influence of the initial chloride concentration on the degradation performance was assessed by comparing both phenol and TOC removal efficiencies at various time intervals. The results revealed that the chloride ions played interesting and important roles during the electrolytic oxidations, and the reaction kinetics and by products might vary from case to case. Thus, we emphasize the importance of operating level selections in BDD technology, especially when high concentrations of chloride electrolytes are present in the bulk solutions.

Multiplex bioassays have drawn more and more attention for the development of novel analytical techniques. Herein, we used photonic crystal (PC) and surface enhanced Raman scattering (SERS) as two encoding elements in different modes for the dual encoding of multiplex bioassays. In practice, PC beads and SERS nanotags act as carriers and labels, respectively, for the multiplex detection of antigens in a sandwich format. Except for the amplified capacity by two encoding modes, we also demonstrated that fine stability, low background and high sensitivity were realized for the quantitative analysis of multiple analytes, which holds great promise in biomedical applications like protein biomarker analysis.

Extracellular electron transfer (EET) allows microorganisms to perform anaerobic respiration using insoluble electron acceptors, including minerals and electrodes. EET-based applications require efficient electron transfer between living and non-living systems. To improve EET efficiency, the TiO2@TiN nanocomposite was used to form hybrid biofilms with Shewanella loihica PV-4 (PV-4). Chronoamperometry showed that peak current was increased 4.6-fold via the addition of the TiO2@TiN nanocomposite. Different biofilms were further tested in a dual-chamber microbial fuel cell. The PV-4 biofilm resulted a maximum power density of 33.4 mW/m2, while the hybrid biofilm of the TiO2@TiN nanocomposite with PV-4 yielded a 92.8% increase of power density. Electrochemical impedance spectroscopy analyses showed a lower electron-transfer resistance in the hybrid biofilm. Biological measurements revealed that both flavin secretion and cytochrome c expression were increased when the TiO2@TiN nanocomposite presented. These results demonstrated that the TiO2@TiN nanocomposite could synergistically enhance the EET of PV-4 through altering its metabolism. Our findings provide a new strategy for optimizing biotic-abiotic interactions in bioelectrochemical systems.

Using boron-doped diamond (BDD) to mineralize recalcitrant organics has been one of the hottest areas of research interest in the field of water treatment. Here we report for the first time that, in the presence of nitrite ions (NO2-), the anodic oxidation of phenol with BDD electrode will lead to the formation of nitrated by-products of phenol. These by-products include 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 2,4,6-trinitrophenol, 2,3,4,6-tetranitrophenol, 2,3,4,5,6-pentanitrophenol, as well as a large number of dimers and trimers of nitrophenols. Increasing the concentration of NO2- will not only greatly affects the degradation and mineralization of phenol, but also enhances the formation of nitrophenols. The nitrated by-products are mainly generated via electrophilic substitution reactions mediated by nitrogen dioxide radicals and hydroxyl radicals, as well as via coupling reactions of phenol. In addition, it is found that several simple nitrophenols may also be formed in nitrate media. As a whole, formation of nitrated by-products is a novel phenomenon in anodic oxidation processes. Since nitrated aromatics are well known for their persistence in the environment, their formations in BDD anode cells should be carefully scrutinized before such technology is applied to groundwater remediation.

In the present study, the mineralization performance and pathway of uric acid (UA) on boron-doped diamond (BDD) anodes were investigated. The oxidation behavior of UA on BDD surface was firstly tested through cyclic voltammetry measurements. The individual and joint effects of four quantitative parameters (applied current density, NaHCO3 concentration, NaCl concentration and flow rate) on UA mineralization were then examined with Doehlert experimental design. The results acquired by statistical analysis revealed that NaCl concentration and applied current density displayed the most dominant roles on UA degradation, while the influences of NaHCO3 concentration and flow rate were statistically insignificant. As a result, the following optimal conditions were reached: applied current density of 7.80 mA cm−2, NaHCO3 concentration of 6.0 mM, NaCl concentration of 9.0 mM and flow rate of 600 mL min−1, which gave a TOC decay of 89.4%, a specific energy consumption of 125.36 KWh kg−1 TOC, a combustion current efficiency of 15.0% and an electrical energy per order of 35.79 KWh m−3 order−1 within 30 min of electrolysis. Further results from LC/MS analysis confirmed the ring rupture of UA during the electrolysis, due to the attack of hydroxyl radicals and active chlorine species. Accordingly, two plausible degradation pathways of UA in bicarbonate and chloride media on BDD anode were proposed respectively.

Bead-based assays have drawn more and more attention in biomedical fields. Herein, we proposed a novel approach to achieve multiplex analysis on a single porous hydrogel bead (PHB) with Raman dyes (RDs) encoded core-shell surface-enhanced Raman scattering (SERS) nanotags. Because of the amplified signal of RDs by core-shell metal structure of the nanotag and the high surface area to volume ratio (SVR) of the PHB, the sensitivity and linear dynamic range (LDR) of the as-proposed multiplex analysis method are significantly improved. We anticipate this approach to be widely used in the multiplex assays and biosensors.

Here, the electrochemical incineration of methyl green (MG), a toxic triarylmethane dye, had been initially performed using boron-doped diamond anode under galvanostatic conditions. The individual and interaction effects of four operating variables (flow rate, applied current density, sulfate concentration and initial MG concentration) on mineralization efficiency were investigated with the aid of Doehlert experimental design. Among the independent variables, sulfate concentration displayed the most interesting roles on MG degradation. Optimum MG degradation was achieved by applying a flow rate of 350 ml/min, applied current density of 7.75 mA/cm2, 5.0 mM Na2SO4, and initial MG concentration of 200 mg/dm3 at 120 min of electrolysis, being reduced color by 100% and TOC by 80.1%. In addition, the reaction intermediates were properly identified by LC/MS analysis and a plausible reaction sequence was proposed.

This study investigated the electrochemical incineration of nitrilotriacetic acid (NTA) at boron-doped diamond (BDD) and platinum (Pt) anodes. Trials were performed in the presence of sulfate electrolyte media under recirculation mode. The parameters that influence the degradation efficiency were investigated, including applied current density, flow rate, supporting electrolyte concentration and reaction time. To reduce the number of experiments, the system had been managed under chemometric technique named Doehlert matrix. As a consequence, the mineralization of NTA demonstrated similar behavior upon operating parameters on these two anodes. Further kinetic study indicated that the degradations followed pseudo-first-order reactions for both BDD and Pt anodes, and the reaction rate constant of the former was found to be higher than that of the latter. Such difference could be interpreted by results from fractal analysis. In addition, a reaction sequence for NTA mineralization considering all the detected intermediates was also proposed.

The electrochemical incineration of bromoamine acid (BAA), an intermediate of anthraquinone dyes, was conducted using cells containing boron-doped diamond (BDD) anode and Pt cathode under galvanostatic conditions. The effect of input variables, including applied current density (jappl), flow rate, sulfate concentration and initial BAA concentration ([BAA]0), on process performance was assessed implementing a Doehlert experimental design. The foregoing results obtained by response surface methodology led to the following optimal conditions for BAA degradation: jappl of 15.50 mA cm−2, flow rate of 550 ml min−1, sulfate concentration of 1.0 mM and [BAA]0 of 125 mg dm−3, which gave a decolorization rate of 100%, a mineralization rate of 85.29%, a specific energy consumption of 3623.57 kW h kg−1 TOC and a mineralization current efficiency of 10.1% at 120 min of electrolysis. Under the optimized conditions, BAA decays followed pseudo first-order kinetics. In addition, a possible degradation sequence involving all the detected intermediates was proposed for the anodic oxidation of BAA on BDD electrode. Our results had wide ranging implications for the soft and efficient treatment of BAA polluted wastewater.

A novel composite anode α-FeOOH–NWs/CP was fabricated by growth of α-FeOOH nanowhiskers (NWs) on the surface of carbon paper (CP) through facile hydrothermal reaction. The intercrossed α-FeOOH NWs were about 30–50 nm in diameter and 500–800 nm in length, formed open pores on the CP surface. The composite electrode markedly facilitated bacterial extracellular electron transfer in the cell containing the strain PV-4. The current density of 0.48 A/m2 on α-FeOOH–NWs/CP was 60% higher than that of 0.30 A/m2 on bare CP after 42 h cultivation of PV-4, which was attributed to better growth of PV-4 and lower charge transfer resistance. The result shows a feasible way to obtain an inexpensive anode with high biocompatibility and bio-electrocatalytic activity.

Taking bromophenol blue as pollutant model, the role of sulfate electrolytes during the anodic oxidations was investigated in a widerange of concentrations (0.1–500 mM). Trials were performed with an electrochemical cell containing boron-doped diamond anodeand stainless steel cathode. The impact of sulfate concentration on the degradation performance was assessed by comparing thecolor removal efficiencies at various time intervals. The results revealed a significant and peculiar influence of this parameter onthe degradation efficiency. Thus, we emphasize the importance of selection of operating levels in electrolytic oxidations, especiallywhen certain activators (from the cathode) may be formed in the treated solutions.© 2015 The Electrochemical Society. [DOI: 10.1149/2.0361508jes] All rights reserved.Manuscript submitted January 15, 2015; revised manuscript received April 20, 2015. Published May 8, 2015.

To improve the output power density of dye-fed microbial fuel cells (MFCs), which decreases with increasing dye concentration, a new strategy involving TiO2 photocatalysis pretreatment of high content dye wastewater was proposed and demonstrated in this study. 200 mg L−1 X-3B wastewater was treated using F-doped nano-TiO2 under visible light for 2.5 h and then mixed into the substrate, and the maximum output power density (PM) of MFC reached 392 mW m−2. As a comparison, PM was only 276 mW m−2 when untreated X-3B wastewater was used as the substrate. About 42% power density was retrieved from the MFC fed with high concentration X-3B wastewater via prior photocatalytic treatment. Moreover, the decolorization rate of X-3B was also enhanced from 42% to 56.5% when combined with the photocatalysis process. The increase of power density after photocatalysis of X-3B was attributed to less electron consumption by decomposed X-3B, extra electron donors and mediators from produced intermediates as well as increased bacterial diversity in the anode chamber. These results demonstrated TiO2 photocatalysis pretreatment as an effective and easy to implement technology for improving both the electricity harvest and pollutant elimination from wastewaters that contain concentrated hard-to-use biomass without specially acclimatizing or modifying MFC.

A unique vertically oriented TiO2 nanosheets (TiO2-NSs) layer was synthesized in situ on the surface of a carbon paper (CP) electrode via hydrothermal synthesis upon addition of a suitable amount of activated carbon powders in a reactor. Field emission scanning electron microscopy images showed that the nanosheets were about 2 μm in length, 200-600 nm in width and 15 nm in thickness. X-ray diffraction and Raman patterns verified TiO2-NSs crystallized in the anatase phase. The electrochemical activities of CP and TiO2-NSs/CP electrode have been investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The maximum power output density of a mixed consortia inoculated microbial fuel cell was increased by 63% upon using TiO2-NSs/CP as a bioanode compared with that using bare CP as a bioanode. The performance improvement could be ascribed to unique 3D open porous interface made of vertically oriented TiO2-NSs, which provides good biocompatibility, favorable mass transport process, large surface areas for adhension of bacteria and direct pathways for electron movement to the electrode.

Hydrogen peroxide (H2 O2 ) is a major messenger molecule in cellular signal transduction. Direct detection of H2 O2 in complex environments provides the capability to illuminate its various biological functions. With this in mind, a novel electrochemical approach is here proposed by integrating a series of CoO nanostructures on CuO backbone at electrode interfaces. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction, and X-ray photoelectron spectroscopy demonstrate successful formation of core-shell CuO-CoO hetero-nanostructures. Theoretical calculations further confirm energy-favorable adsorption of H2 O2 on surface sites of CuO-CoO heterostructures. Contributing to the efficient electron transfer path and enhanced capture of H2 O2 in the unique leaf-like CuO-CoO hierarchical 3D interface, an optimal biosensor-based CuO-CoO-2.5 h electrode exhibits an ultrahigh sensitivity (6349 µA m m-1 cm-2 ), excellent selectivity, and a wide detection range for H2 O2 , and is capable of monitoring endogenous H2 O2 derived from human lung carcinoma cells A549. The synergistic effects for enhanced H2 O2 adsorption in integrated CuO-CoO nanostructures and performance of the sensor suggest a potential for exploring pathological and physiological roles of reactive oxygen species like H2 O2 in biological systems.

Inspired by the rapid development of metal-organic-framework-derived materials in various applications, a facile synthetic strategy was developed for fabrication of 3D hierarchical nanoarchitectures. A surface-mounted metal-organic framework membrane was pyrolyzed at a range of temperatures to produce catalysts with excellent trifunctional electrocatalytic efficiencies for the oxygen reduction, hydrogen evolution, and oxygen evolution reactions.

In this research, the brominated oligomers formed during phenol degradation with boron-doped diamond (BDD) anode had been initially studied at three different concentrations of bromide (1, 10 and 100 mM). The results from LC/MS analysis indicated that, brominated monomer, dimer and trimer of phenols resulting from electrophilic substitution and coupling reactions were the important reaction by-products. Specifically, the trimer by-products were generated only in bromide-rich systems. The reaction mechanisms concerning oligomer formations were proposed in detail accordingly. The above results were in well accordance with those recorded in the degradation experiments. As a whole, bromides and chlorides demonstrated quite different effects toward phenol degradation, which deepened our understanding on the reactions involved in BDD anode cells.

This study investigated the degradation performance and mechanism of creatinine (a urine metabolite) with boron-doped diamond (BDD) anodes. Experiments were performed using a synthetic creatinine solution containing two supporting electrolytes (NaCl and Na2SO4). A three-level central composite design was adopted to optimize the degradation process, a mathematical model was thus constructed and used to explore the optimum operating conditions. A maximum mineralization percentage of 80% following with full creatinine removal had been achieved within 120 min of electrolysis, confirming the strong oxidation capability of BDD anodes. Moreover, the results obtained suggested that supporting electrolyte concentration should be listed as one of the most important parameters in BDD technology. Lastly, based on the results from quantum chemistry calculations and LC/MS analyses, two different reaction pathways which governed the electrocatalytic oxidation of creatinine irrespective of the supporting electrolytes were identified.

This study investigated the electrochemical incineration of bromophenol blue (BPB) at boron-doped diamond (BDD) anode. The individual and interaction effects of three control parameters (applied current density, flow rate and supporting electrolyte concentration) on process efficiency were estimated by central composite rotatable design. Among the independent variables, supporting electrolyte concentration displayed the most interesting roles on BPB degradation. The optimal conditions obtained by response surface methodology were: applied current density of 7.36 mA cm − 2 , 2.6 mM Na 2 SO 4 and flow rate of 568 ml min − 1 , which gave a decolorization rate of 91.7% and a mineralization rate of 47.3%, as well as an energy consumption of 3518.89 kWh kg − 1 TOC (7.0 kWh m − 3 ) and a mineralization current efficiency of 15.1% at 120 min of electrolysis. The results presented here demonstrated the high efficiency of BDD technology in mineralizing BPB under mild conditions, as well as the usefulness and capability of the experimental design strategy for successful investigation and modeling of the electrocatalytic processes.

1-naphthol (1-NAP) and 2-naphthol (2-NAP) are both hazardous pollutants which pose great threat to our living environment. In the current work, a comparative investigation on the electrochemical mineralization of 1-NAP and 2-NAP using boron-doped diamond (BDD) anode was presented. Experiments were carried out using synthetic 1-NAP or 2-NAP solutions containing Na2SO4 as supporting electrolyte. A two-level factorial design methodology was adopted to optimize the mineralization process, six mathematical models were thus constructed and used to explore the structure-property relation involved. The results obtained suggested that 1-NAP was easier and faster to break down than 2-NPA under the same oxidation conditions, which were in line with the outcome obtained from cyclic voltammetry, HPLC and TOC measurements. To understand the destruction mechanism, the electron structures of 1-NAP and 2-NAP were further examined by the quantum chemistry calculations with density functional theory. It was also found that the results from frontier orbital analysis could well explain the differing mineralization performances recorded in BDD anode cell. Finally, with the aid of LC/MS analysis, the oxidation pathways of 1-NAP or 2-NAP on BDD anodes were proposed.

Here, a novel three-level definitive screening design (DSD) was initially employed to investigate the electrochemical degradation of Chromotrope 2R (C2R) with boron-doped diamond (BDD) anodes. Experiments were performed using a synthetic C2R solution containing five supporting electrolytes (Na2SO4, NaCl, Na3PO4, NaNO3 and Na2CO3). The effects of nine quantitative parameters on C2R removal rate: initial C2R concentration (50-100 mg L-1), applied current density (1.29-3.87 mA cm-2), Na2SO4 concentration (0-10 mM), NaCl concentration (0-10 mM), Na3PO4 concentration (0-10 mM), NaNO3 concentration (0-10 mM), Na2CO3 concentration (0-10 mM), flow rate (300-500 mL min-1) and temperature (10-50 °C), were investigated. The model obtained was validated and used to select three most significant variables for further investigation. Interestingly, the differing roles of electrolytes during the electrolysis revealed the ion-selective nature of BDD anode system. A five-level central composite rotatable design (CCRD) was then employed to describe the C2R conversion as a function of applied current density, NaCl concentration and temperature. The results obtained confirmed the strong capability of DSD to separate and identify the significant variables in BDD technology. Moreover, the strategy (DSD plus CCRD) employed here enabled a significant reduction in the number of experiments (from over 500 to only 38) compared to traditional screening methods. The possible degradation mechanism of C2R in BDD anode cells was also proposed.

Electron transfer kinetics of Shewanella loihica PV-4 at the up-growing TiO

This work reported a comparative study on the electrochemical incineration of nitrilotriacetic acid (NTA) in the presence of different supporting electrolytes (Na2SO4 and NaCl). Galvanostatic electrolyses were conducted in an undivided electrochemical cell containing boron-doped diamond (BDD) anode and platinum cathode. Initial solution pH, flow rate, applied current density, and supporting electrolyte concentration were selected as variables, besides the mineralization efficiency of NTA that was selected as response. Central composite rotatable design and response surface methodology were employed here to examine the statistical significance of the selected variables, as well as to determine the optimal conditions of the degradation process. Under the same operating conditions, two regression models were thus constructed to illustrate the differing impact of supporting electrolytes in BDD anode cells. The kinetics for NTA degradation followed different reaction orders for the two scenarios (in the absence and presence of NaCl), indicating the complex interaction between hydroxyl radicals and active chlorine. Despite this, the experimental results demonstrated that effective mineralization of NTA might also be achieved in the presence of chlorides (of lower concentrations). Besides, in the case of chlorides, the average mass transfer coefficient of the system was found to be strongly dependent on the initial solution pH. Lastly, a plausible reaction sequence concerning the electrolytic oxidation of NTA in chloride media was also proposed.

The interfacing of polyoxometalates and reduced graphene oxide (rGO) can be considered to be an effective way to generate hybrid structures which colligates the advantages of both components. Here, a hybrid material (polyoxometalate-based metal–organic framework (POMOF)/rGO) integrating POMOF and rGO is obtained via a simple one-pot approach. The as-prepared materials are used as electrochemical active materials to detect dopamine for the first time. It is shown that the hybridization results in a superior catalytic activity for oxidation of dopamine owing to the synergistic effect between POMOF and rGO, as well as favorable interaction of DA with CC network of the composite. The promoted electron transfer, as well as abundant active sites, open channels, and aromatic planes in the hybrid material produce a wider linear detection range of 1 × 10−6 to 2 × 10−4 m with the lower detection limit of 80.4 × 10−9 m (S/N = 3). Moreover, the developed biosensor also exhibits favorable selectivity, reproducibility, and stability. As a non-noble metal catalyst constructing from function and structure-matched building blocks, the prepared POMOF/rGO hybrid material demonstrates its highly promising properties for dopamine detection and the result should promote the further development of POMOF-based sensors.