Bi2S3 nanorods grown on multiwalled carbon nanotubes as highly active catalysts for CO2 electroreduction to formate.

Bi-based materials are promising electrocatalysts for CO2 reduction but one of the key technological hurdles is the design of stable, active and affordable Bi-based catalysts over a wide potential range. Herein, Bi2S3/CNTs nanocomposites are constructed by anchoring bismuth sulfide (Bi2S3) nanorods onto the multiwalled carbon nanotubes (CNTs) and utilizing them in electrocatalytic CO2 reduction. CNTs, as a support, not only guarantee the conductivity and dispersibility of Bi2S3 nanorods but also improve the electrolyte infiltration and optimize the electronic structure of the Bi2S3. As expected, the Bi2S3/CNTs nanocomposite exhibits a faradaic efficiency for HCOO- (FEHCOO-) of 99.3% with a current density of -20.3 mA cm-2 at -0.91 V vs. RHE. The FEHCOO- is stably maintained at over > 91% in a wide potential window from -0.71 V to -1.31 V. Theoretical calculation analyses reveal that the strong interaction between Bi2S3 and CNTs is conductive to decreasing the energy barrier of *OCHO, stabilizing the intermediate *OCHO, and inhibiting the hydrogen evolution reaction. The current study provides an insightful understanding of the mechanism of the CO2 electroreduction reaction, and paves a new way for developing superior and affordable electrocatalysts.

Singlet oxygen-dominated electrocatalytic oxidation treatment for the high-salinity quaternary ammonium compound wastewater with Ti/(RuxIry)O2 anode.

The widespread application of quaternary ammonium compounds (QAC) has posed a serious hazard to the environment and human being, and high concentration of Cl- in QAC wastewater may further increase the difficulty of pollutants elimination. In this study, such a QAC wastewater under high salinity conditions was chosen as the target, the prepared Ti/(RuxIry)O2 anode exhibited favorable catalytic performance for the oxidation and mineralization of QAC under high salinity conditions. Increasing the Ru/Ir ratio of Ti-based electrode coating also slightly promoted the inner catalytic capacity. The combination of electron paramagnetic resonance (EPR) and quenching experiments indicates that 1O2 served as a main reactive specie in the Ti/(RuxIry)O2 electrooxidation system. The increase of pH could decrease the removal efficiency of QAC for the reduced 1O2 yield, and the rise of Cl- concentration could favor the QAC oxidation, and Cl- was a better electrolyte to promote the oxidation of organic contaminants when compared to Na2SO4 or Na2CO3. Additionally, the conversion pathway of the model pollutant was tentatively investigated, the results demonstrated that there were almost no halogenated final products residual by electrocatalytic oxidation with Ti/(RuxIry)O2 anode. This study not only elucidate the reaction mechanism of Ti/(RuxIry)O2 anode electrocatalytic oxidation of high salinity QAC wastewater, but also may provide an efficacious and eco-friendly method for the treatment of high salinity QAC wastewater.

Efficient sulfur cycling improved the performance of flowback water treatment in a microbial fuel cell.

The sulfate-reducing mediate microbial fuel cell (MFC) shows advantages in treating recalcitrant flowback water (FW) from shale gas extraction, but the stability under fluctuant concentrations of sulfate in FW remains unknown. Herein, we investigated the impact of fluctuant sulfate concentrations on the performance of FW treatment in MFCs. Sulfate concentration showed a significant role in the MFC treating FW, with a COD removal of 69.8 ± 9.7% and a peak power density of 2164 ± 396 mW/m3 under 247.5 mg/L sulfate, but only 39.1% and 1216 mW/m3 under 50 mg/L sulfate. The fluctuation of sulfate in a short time allowed to a stable performance, but a longtime intermittent decrease of feeding sulfate concentration significantly inhibited power generation to no more than 512 mW/m3. The sulfur cycling between sulfate and sulfide existed in the system, but the cycling rate became much lower after the longtime intermittent decrease, with resulting to the decreased power generation. Abundant sulfur-oxidizing bacteria (SOB) of Desulfuromonadaceae and Helicobacteraceae in the MFC stably feeding with 247.5 mg/L sulfate supported a high sulfur cycling rate. With the cooperation of abundant sulfate-reducing bacteria (SRB) of Desulfovibrionaceae (capable of producing electricity) on the anode and Desulfobacteraceae in anolyte, this sulfur cycling endowed the MFC with high sulfate tolerance and critically contributed to recalcitrant organics removal and power generation. However, much less SOB of Helicobacteraceae and Campylobacteraceae on the anode with high S0 accumulation on the surface after the longtime intermittent decrease of sulfate likely led to the low sulfur cycling rate. With also less SRB of Marinilabiaceae (capable of producing electricity) and Synergistaceae in the system, this low sulfur cycling rate thus hampered power generation. This research provides an important reference for the bioelectrochemical treatment of wastewater containing recalcitrant organics and sulfate.

Response mechanism of microbial community to the environmental stress caused by the different mercury concentration in soils.

Despite the toxicity of mercury for mammal has been widely studied in recent years, little is known on its impact on the soil microbiome. In this paper, the effects of mercury in soils microbial communities along a gradient of contamination from no to high concentration was assessed by the richness and diversity of microbial community using high throughput sequencing method. The richness of microbial community decreased gradually with the increase of culture time, while the low and medium concentration of mercury had little effect on the evenness of soil microbial community. Proteobacteria tolerated the mercury contamination, while Acidobacteria, Planctomycetes and Chloroflexi were sensitive to mercury pollution in phylum level. Omnitrophica and Ignavibacteriae microorganisms were very sensitive to mercury contamination and dead quickly when contaminated with mercury. Mercury contamination selected two mercury tolerance genuses which were Massilia and Burkholderia in genus level and at least 22 microorganisms such as Alkanindiges, Geothrix, Polycyclovorans and Sporichthya in genus which mainly from the Acidobacteria, Proteobacteria, Bacteroides, Chloroflexi and Omnitrophica phylum were sensitive to mercury. The bacteria tolerant to mercury in soil were Massilia and Burkholderia from Betaproteobacteria and Lysobacter, Luteimonas from Gammaproteobacteria, separately, they were Gram-negative bacteria with thin cell walls and complex ingredients that responded quickly to pollution stress.

Efficient Activation of Peroxymonosulfate by V-Doped Graphitic Carbon Nitride for Organic Contamination Remediation.

Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation have been developed as an ideal pathway for completely eradication of recalcitrant organic pollutants from water environment. Herein, the V-doped graphitic carbon nitride (g-C3N4) is rationally fabricated by one-step thermal polymerization method to activate PMS for contamination decontamination. The results demonstrate the V atoms are successfully integrated into the framework of g-C3N4, which can effectively improve light absorption intensity and enhance charge separation. The V-doped g-C3N4 displays superior catalytic performance for PMS activation. Moreover, the doping content has a great influence on the activation performances. The radical quenching experiments confirm •O2-, SO4•-, and h+ are the significant species in the catalytic reaction. This work would provide a feasible strategy to exploit efficient g-C3N4-based material for PMS activation.

Peroxymonosulfate Activation by Bi2WO6/BiOCl Heterojunction Nanocomposites under Visible Light for Bisphenol A Degradation.

The combination of peroxymonosulfate (PMS) activation and photocatalysis has proven to be effective for organic contaminants treatment. However, the construction of an efficient catalytic material is an important challenge. Herein, novel Bi2WO6/BiOCl heterojunction nanocomposites were successfully designed and fabricated using a facile and effective strategy for bisphenol A (BPA) photodegradation with PMS activation. The well-designed heterojunction with improvement of the contact area and interface microstructure was obtained through in situ growth of the Bi2WO6 on the surface of BiOCl. The Bi2WO6/BiOCl nanocomposites exhibit excellent catalytic performance in PMS activation for BPA degradation under visible light irradiation. A possible photocatalytic reaction mechanism was systematically revealed. The excellent catalytic performance is mainly attributed to the strong interaction between Bi2WO6 and BiOCl, resulting in an enhanced photoabsorption and a more efficient interfacial charge separation and transfer. This paper provides a novel strategy to design efficient catalytic materials for organic contaminants remediation with PMS activation.

The anodic potential shaped a cryptic sulfur cycling with forming thiosulfate in a microbial fuel cell treating hydraulic fracturing flowback water.

The flowback water (FW) from shale gas exploitation can be effectively treated by bioelectrochemical technology, but sulfide overproduction remains to be addressed. Herein, sulfate-reducing bacteria (SRB) meditated microbial fuel cells (MFCs) with anodic potential control were used. COD removal gradually increased to 67.4 ± 5.1% in electrode-potential-control (EPC) MFCs and 78.9 ± 2.4% in the MFC with open circuit (OC-MFC). However, in EPC MFCs sulfate removal stabilized at much lower levels (no more than 19.9 ± 1.9%) along with much lower sulfide concentrations, but in OC-MFC it increased and finally stabilized at 59.9 ± 0.1%. Partial sulfur reuse in EPC MFCs was indicated by the current production. Notably, thiosulfate was specially detected under low potentials and effectively oxidized in EPC MFCs, especially under -0.1 V vs. SHE, which probably related to the sulfur reuse. Metagenomics analysis showed that the anode with -0.1 and -0.2 V likely shunted electrons from cytochromes that used for reducing DsrC-S0 trisulfide and thus contributed to producing thiosulfate and decreasing sulfide production. Meanwhile, the anode with -0.1 V specially accumulated sulfur-oxidizing system (Sox) genes regarding thiosulfate and sulfite oxidation to sulfate, which concurred to the effective thiosulfate oxidation and also indicated the possible direct sulfite oxidation to sulfate during the sulfur cycling. But the anode of -0.2 V highly accumulated genes for thiosulfate and sulfite reduction. Both anodes also distinctly accumulated genes regarding thiosulfate oxidation to tetrathionate and sulfide oxidation to sulfur or polysulfide. Further, sulfur-oxidizing bacteria were specially enriched in EPC MFCs and likely contributed to thiosulfate and sulfite oxidation. Thus, we suggested that the higher electrode potential (e.g. -0.1 V) can shape a cryptic sulfur cycling, in which sulfate was first reduced to sulfite, and then reoxidized to sulfate by forming thiosulfate as an important intermediate or by direct sulfite oxidation. The results provide new sights on the bioelectrochemical treatment of wastewater containing complex organics and sulfate.

Facile Fabrication of Z-Scheme Bi2WO6/WO3 Composites for Efficient Photodegradation of Bisphenol A with Peroxymonosulfate Activation.

The rational fabrication of direct Z-scheme heterostructures photocatalysts is a pivotal strategy to boost the interfacial charge migration and separation. Herein, direct Z-scheme Bi2WO6/WO3 composites were rationally fabricated for the degradation of bisphenol A combined with the activation of peroxymonosulfate (PMS). The tight interface contact between Bi2WO6 and WO3 was successfully formed by the in situ epitaxial growth of ultrathin Bi2WO6 nanosheets at the surface of WO3 nanorods. The Bi2WO6/WO3 composite presented highly efficient catalytic performance toward degradation of BPA with PMS activation as compared to the WO3 and Bi2WO6. PMS can dramatically boost the photocatalytic activity of the composites. Moreover, the results of active radical scavenging experiments revealed that h+, •O2-, and •SO4- are critical active species in the photodegradation reaction. Finally, the photocatalytic mechanism for the degradation of BPA is also discussed in detail. The great improvement of photocatalytic performance should be ascribed to the effective formation of the direct Z-scheme heterojunctions between Bi2WO6 and WO3, resulting in improved light absorption, an efficient transfer and separation of photoinduced charge carriers, and a considerable amount of the electrons and holes with strong reduction and oxidation abilities. The study might provide new inspirations to design and construct heterostructured nanomaterials with outstanding photoactivity for environmental remediation.

Simultaneous removal of organic matter and iron from hydraulic fracturing flowback water through sulfur cycling in a microbial fuel cell.

The high volume of flowback water (FW) generated during shale gas exploitation is highly saline, and contains complex organics, iron, heavy metals, and sulfate, thereby posing a significant challenge for the environmental management of the unconventional natural gas industry. Herein, the treatment of FW in a sulfur-cycle-mediated microbial fuel cell (MFC) is reported. Simultaneous removal efficiency for chemical oxygen demand (COD) and total iron from a synthetic FW was achieved, at 72 ±â€¯7% and 90.6 ±â€¯8.7%, respectively, with power generation of 2667 ±â€¯529 mW/m3 in a closed-circuit MFC (CC-MFC). However, much lower iron removal (38.5 ±â€¯4.5%) occurred in the open-circuit MFC (OC-MFC), where the generated FeS fine did not precipitate because of sulfide supersaturation. Enrichment of both sulfur-oxidizing bacteria (SOB), namely Helicobacteraceae in the anolyte and the electricity-producing bacteria, namely Desulfuromonadales on the anode likely accelerated the sulfur cycle through the biological and bioelectrochemical oxidation of sulfide in the anodic chamber, and effectively increased the molar ratio of total iron to sulfide, thus alleviating sulfide supersaturation in the closed circuitry. Enrichment of SOB in the anolyte might be attributed to the formation of FeS electricity wire and likely contributed to the stable high power generation. Bacteroidetes, Firmicutes, Proteobacteria, and Chloroflexi enriched in the anodic chamber were responsible for degrading complex organics in the FW. The treatment of real FW in the sulfur-cycle-mediated MFC also achieved high efficiency. This research provides a promising approach for the treatment of wastewater containing organic matters, heavy metals, and sulfate by using a sulfur-cycle-mediated MFC.

Uniformity dispersive, anti-coking core@double-shell-structured Co@SiO2@C: Effect of graphitic carbon modified interior pore-walls on C5+ selectivity in Fischer-Tropsch synthesis.

Highly dispersed Co nanoparticles with proper interaction with mesoporous support are benefit for the suppression of self-aggregation, which enhances its Fischer-Tropsch synthesis (FTs) activity. However, construct such Co based supported catalysts with high activity and stability in FTs by conventional mesoporous support, especially the common used mesoporous SiO2, has proven challenging due to their undesirable hydrothermal stability and poor reducibility. Herein, we developed a unique core@double-shell Co@SiO2@C structure with optimized interface of the mesoporous catalyst by introducing graphitic carbon layer which can weaken the interaction between metallic Co and silica. Transmission electron microscopy (TEM) images, together with Nitrogen adsorption-desorption characterization result, proved the well-defined core@double-shell structure of graphitic carbon modified catalyst. The Co@SiO2@C-2 material produced after optimizing the calcination temperature to 600°C process large surface area and pore volume, and show higher CO conversion (62.2%) and C5+ selectivity (62.2%) than Co3O4@SiO2 in a period of 100h. The significant improvement in the FTS performance of Co@SiO2@C is not only attributed to a good synergistic effect by a combination of the Co dispersion and reducibility. The unique core@double-shell structure with graphitic carbon modified interior pore-walls also contributes to the formation of heavy hydrocarbon, as well as the protecting with the metallic Co particles away from oxidation and aggregation.

Efficient Photocatalytic Bilirubin Removal over the Biocompatible Core/Shell P25/g-C3N4 Heterojunctions with Metal-free Exposed Surfaces under Moderate Green Light Irradiation.

Highly-monodispersed g-C3N4/TiO2 hybrids with a core/shell structure were synthesized from a simple room temperature impregnation method, in which g-C3N4 was coated through self-assembly on the commercially available Degussa P25 TiO2 nanoparticles. Structural and surface characterizations showed that the presence of g-C3N4 notably affected the light absorption characteristics of TiO2. The g-C3N4/TiO2 heterojunctions with metal-free exposed surfaces were directly used as biocompatible photocatalysts for simulated jaundice phototherapy under low-power green-light irradiation. The photocatalytic activity and stability of g-C3N4/TiO2 were enhanced relative to pure P25 or g-C3N4, which could be ascribed to the effective Z-scheme separation of photo-induced charge carriers in g-C3N4/TiO2 heterojunction. The photoactivity was maximized in the 4 wt.% g-C3N4-coated P25, as the bilirubin removal rate under green light irradiation was more than 5-fold higher than that under the clinically-used blue light without any photocatalyst. This study approves the future applications of the photocatalyst-assisted bilirubin removal in jaundice treatment under moderate green light which is more tolerable by humans.