NO Removal Rate Research Articles

Creation of an internal electric field in SnO2@ZnS-ZnSn(OH)6 dual-type-II heterojunctions for efficient NO photo-oxidation

Well-designed heterojunction photocatalysts are promising high-performance materials, effective in inducing charge transfer to achieve a particular migration path and long-lasting carriers. However, the traditional binary heterojunction photocatalysts still show low-efficiency charge separation. Herein, we report a direct dual-type-II SnO2@ZnS-ZHS (ZHS = ZnSn(OH)6) ternary heterojunction, obtained by a facile in-situ face-to-face growth approach. Experimental results and density functional theory calculations reveal that the carrier dynamics of SnO2@ZnS-ZHS, with dual-type-II mechanisms, enables the photogenerated holes (h+) of SnO2 to migrate to the valence bands of ZHS and ZnS. This ensures that SnO2@ZnS-ZHS has twice as much oxidizing potential to produce enough hydroxyl radicals (·OH) to participate in NO oxidation reactions. With a unique dual-type-II ternary structure, SnO2@ZnS-ZHS shows the highest NO removal rate (44.5%) after 30 min, which is 23.5, 29.7 and 15.9 times higher than the values shown by the single components ZHS, SnO2 and ZnS, respectively. A reaction mechanism is proposed. The improved photocatalytic activity shows the advantages of the SnO2@ZnS-ZHS heterostructure as a promising candidate for ternary heterojunction design.

Synergistic effect of cyano defects and CaCO3 in graphitic carbon nitride nanosheets for efficient visible-light-driven photocatalytic NO removal.

Photo-oxidation with semiconductor photocatalysts provides a sustainable and green solution for NOx elimination. Nevertheless, the utilization of traditional photocatalysts in efficient and safe photocatalytic NOx removal is still a challenge due to the slow charge kinetic process and insufficient optical absorption. In this paper, we report a novel porous g-C3N4 nanosheet photocatalyst modified with cyano defects and CaCO3 (xCa-CN). The best performing sample (0.5Ca-CN) exhibits an enhanced photo-oxidation NO removal rate (51.18%) under visible light irradiation, largely surpassing the value of pristine g-C3N4 nanosheets (34.05%). Such an enhancement is mainly derived from an extended visible-light response, improved electron excitation and transfer, which are associated with the synergy of cyano defects and CaCO3, as evidenced by a series of spectroscopic analyses. More importantly, in-situ DRIFTS and density functional theory (DFT) results suggest that the introduction of cyano defects and CaCO3 enables control over NO adsorption and activation processes, making it possible to implement a preference pathway (NO → NO+ → NO3¯) and reduce the emission of toxic intermediate NO2. This work demonstrates the potential of integrating defect engineering and insulator modification to design highlyefficient g-C3N4-based photocatalysts for air purification.

Effect of oxygen vacancies on the photocatalytic activity of flower-like BiOBr microspheres towards NO oxidation and CO2 reduction

The presence of defects on semiconductor photocatalysts can change the electronic band structure and improve the catalytic activity. However, the synthesis of photocatalysts with defects is a challenging task, and the role of defects is still unclear. This work reports flower-like BiOBr microspheres prepared by a facile hydrothermal process in the presence of glycerol (GL), which induces the creation of oxygen vacancies (OVs). The obtained samples are denoted as BrGLx, where x is the amount of glycerol (0–150 mL) in the total (160 mL) volume of glycerol/water mixture. The photocatalytic performance of BrGLx photocatalysts is reported for NO oxidation and CO2 reduction. Comparing the pristine BiOBr sample (BrGL0) with the BrGL150 material, the NO removal rate increases from 10.6% to 48.2%, and the CH4 generation rate improves from 0 to 7.1 μmol·g−1·h−1, respectively, maintaining the same level of CO production. Combining the results of reaction kinetics, reactive oxygen species identification and in situ Fourier-transform infrared spectroscopy, the improved photoreactivity of BiOBr with OVs is attributed to the combined effects of enhanced substrate adsorption, enlarged light-response range and increased charge separation/migration. This work not only demonstrates the effect of OVs on the structure and photocatalytic performance/selectivity of BrGLx photocatalysts towards NO and CO2 conversion, but also provides new insights to tune and evaluate OVs.

Effect of hydraulic retention time on performance of autotrophic, heterotrophic, and split-mixotrophic denitrification systems supported by polycaprolactone/pyrite: Difference and potential explanation.

Biological denitrification is still the most important pathway to purifying nitrate-containing wastewater. In this study, pyrite (FeS2 ) and polycaprolactone (PCL) were used as electron donors to construct sole or combined denitrification systems, that is, pyrite-based autotrophic denitrification (PAD) system, PCL-supported heterotrophic denitrification (PHD) system, and split-mixotrophic denitrification system (combined PAD + PHD), all of which were operated under five different hydraulic retention times (HRTs) for 150 days. The results showed that the removal rates (RE) of nitrate (NO3 - -N) and inorganic phosphorus (PO4 3- -P) by PAD were 91% and 94%, respectively, but the effluent sulfate (SO4 2- ) concentration was as high as 168.2mg/L; the removal rate of NO3 - -N by PHD was higher than 99%, but the PO4 3- -P could not be removed ideally; the removal rates of NO3 - -N and PO4 3- -P by PAD + PHD were higher than 95% and 99%, respectively, and the effluent SO4 2- concentration was only 7.2mg/L. Through the analysis of the surface scanning electron microscope (SEM) images of the two kinds of media before and after use, it was found that the coupled mode of PAD + PHD was more favorable for biofilm formation than the sole PAD or PHD process, and the microorganisms in the PAD + PHD mode made more full use of electron donors. Moreover, the biomass of the PAD + PHD mode was lower than that of the PAD or PHD process, but the denitrification efficiency of the coupled mode was more efficient, indicating that the functional microorganisms in the PAD + PHD mode might have a certain synergistic effect. PRACTITIONER POINTS: Removal rates of NO3 -, PO4 3 -, and SO4 2 - by PAD were 91%, 94%, and -233%, respectively. Removal rate of NO3 - by PHD exceeded 99%, but PO4 3 - could not be removed ideally. Removal rates of NO3 -, PO4 3 -, and SO4 2 - by PAD + PHD were 95%, 99%, and 86%, respectively. The coupled mode was more favorable for biofilm formation than the sole PAD or PHD. The coupled mode had lower biomass but got more excellent denitrification efficiency.

Constructing the multilayer O-g-C3N4@W18O49 heterostructure for deeply photocatalytic oxidation NO

Suffering from inefficient separation and transfer of photogenerated carriers, the deeply photocatalytic oxidation of NO-to-NO3– over g-C3N4 is still a daunting challenge. Well-designed heterojunction photocatalysts have been proven to be effective in steering charge transfer for achieving a particular migration path and more active sites, which hold huge promise in further performance stimulation. Herein, in-situ face-to-face hydrothermal approach is developed to prepare a multilayer heterostructure O doping g-C3N4 (O-g-C3N4) with W18O49 (O-g-C3N4@W18O49). The experimental and theoretical results show that the unique multilayer heterostructure can improve the separation efficiency of carriers by changing the electron migration path. Moreover, doping O atoms are identified as the newly formed active centers to largely facilitate the activation of NO. Impressively, the O-g-C3N4@W18O49 photocatalyst thus exhibits largely improved photocatalytic NO removal rate (56.7 %, 0.1 g of sample) and high selectivity of NO to NO3– (98.3 %). It outperforms the reported photocatalysts materials in visible light. This study not only provides a facile strategy for experimentally screening advanced photocatalytic materials, but also paves the way for the deep oxidation of NO.

Boosting the photocatalytic hydrogen evolution and NO removal via synergistic effects of in-situ Pt NPs formation and titanium integration in Zr-Porphyrin MOFs

An efficient bifunctional porphyrin-based MOF is fabricated for photocatalytic hydrogen evolution and NO removal, in which the mixed Zr/Ti-oxo clusters are the metal nodes and uniformly distributed Pt nanoparticles (Pt NPs) are the co-catalysts. It is worth noting that the optimal Zr-MOF-s(Pt)(Zr/Ti)-R is obtained through replacing partial Zr(IV) with Ti(IV) in the original Zr-based porphyrin MOFs and in-situ generating confined Pt NPs with a relatively small size within the internal cavities. Compared with the majority of reported Zr-based porphyrin MOFs, the Zr-MOF-s(Pt)(Zr/Ti)-R exhibits an extremely high hydrogen evolution activity (2545.11 μmol·g−1·h−1) and NO removal rate (46.6 %) under visible light irradiation. The excellent photocatalytic performance should be ascribed to the reason that the mixed Zr/Ti-oxo cluster and the in-situ generated Pt NPs significantly promote the rate of charge transfer and separation. Moreover, the photocatalytic NO oxidation process was also monitored by in-situ DRIFTS, which indicates the Zr-MOF-s(Pt)(Zr/Ti)-R could realize the effective oxidation of NO and intermediates to the final product (NO3–). This work provides us with a practical route to further improve the photocatalytic performance by synergistically modifying the original metal clusters to adjust the ligand-to-metal charge transfer efficiency and in-situ introducing metal nanoparticles to form Schottky junctions.

Encapsulation of in-situ generated g-CNQDs with up-conversion effect in Zr/Ti-based porphyrin MOFs for efficient photocatalytic hydrogen production and NO removal

In this study, a highly efficient bifunctional porphyrin-based MOFs with uniformly in-situ generated g-C3N4 quantum dots (g-CNQDs) was fabricated for photocatalytic hydrogen evolution and NO removal, in which PtTCPP as the organic ligand and mixed Zr/Ti-oxo clusters as the metal nodes. Compared with most reported Zr-based porphyrin MOFs, the g-CNQDs@Zr-MOFs(Pt)(Zr/Ti) exhibited outstanding hydrogen evolution activity (14511.57 μmol g−1) and NO removal rate (31.9 %) under visible light irradiation. The obviously improved photocatalytic performance could be attributed to the significantly enhanced charge separation and transfer rates by the mixed Zr/Ti-oxo clusters via the rapid Ti3+/Ti4+ process. Moreover, the uniformly in-situ generated g-CNQDs via confinement effect in the cavity of MOFs could also improve the utilization of visible light especially through the up-conversion effect, and promote charge carriers separation. This work provides an idea for us to expand the scope of light utilization and promote charge transfer and separation rates of MOFs via functionalizing host MOFs matrix and coupling guest active species to improve photocatalytic performance further.

Active site exposure of sulfur-etched CeO2 nanorods for nitrogen oxide reduction

CeO2 is an extensively used catalyst in denitration reaction, however, weak acidity of CeO2 is not conducive for NO conversion. Traditional sulfur etching by impregnation results in a large amount of sulfate deposition. To address this limitation, washing with deionized water was added following traditional impregnation (S1.0-CeO2-wash catalyst). The washing process successfully reduced the sulfate deposition, optimized the pore structure of the S1.0-CeO2-wash catalyst. The NO removal rate of the S1.0-CeO2-wash sample reached approximately 90% at 250–350 °C. Additionally, the Ce4+ content on the surface of S1.0-CeO2-wash catalyst increased. Moreover, the action of the S1.0-CeO2-wash catalyst in the reaction was determined to follow both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms. This work provides a reference for the acid etching of other catalysts.

Cobalt clusters on g-C3N4 nanosheets for enhanced H2/H2O2 generation and NO removal

A one-step thermal polymerization method was developed to create homogeneous metallic cobalt (Co) clusters on graphitic carbon nitride (g-C3N4) nanosheets. The size (less than 3 nm) and distribution of Co clusters were controlled by a subsequent acid treatment. Because of the nanofluidic channels, efficient charge transfer, and enhanced light harvesting ability, optimized Co/g-C3N4 nanoarchitectonics by acid treatment revealed excellent photocatalytic activities. The visible-light photocatalytic H2 generation, H2O2 evolution and NO removal rate of the nanoarchitectonics were 82, 4, and 2 times of those of g-C3N4 nanosheets, respectively, suggesting that integrating transition metal clusters on g-C3N4 nanosheets is a novel strategy for NO removal and water splitting. Interestingly, Co/g-C3N4 nanoarchitectonics were further heat-treated at high temperature to create Co clusters decorated N-doped carbon nanosheets, in which ideal performance in hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction in alkaline solution were observed. This result supplied an efficient route to construct non-noble metal multifunctional catalysts.

Construction of oxygen vacancy on Bi12O17Cl2 nanosheets by heat-treatment in H2O vapor for photocatalytic NO oxidation

· Carbon doped Bi 12 O 17 C l2 nanosheets was synthesized by a facile hydrothermal reaction using sodium oleate as surfactant and carbon source. · Oxygen vacancies was in-situ introduced on the Bi 12 O 17 C l2 nanosheets by the reductive H 2 generated from the water gas reaction between water vapor and the doped carbon. · The introduction of OVs significantly improved the photocatalytic activity of Bi 12 O 17 C l2 nanosheets for NO removal. · The OVs on Bi 12 O 17 C l2 not only enhanced the photogenerated e − /h + separation efficiency but also facilitated the O 2 activation to produce more reactive oxygen species. Oxygen-vacancies (OVs) play significant roles in semiconductor-based photocatalysis, such as elevating light absorption property, photogenerated carries separation efficiency, molecular activation, and photocatalytic activity. However, heat-treatment of semiconductors in dangerous H 2 atmosphere is usually indispensable for OVs formation. In this work, C-doped Bi 12 O 17 C l2 nanosheets were facially heat-treated in H 2 O vapor (∼2.3 vol%) mixed with Ar at 300 °C to in-situ introduce OVs by the proposed reactions of C(s) + H 2 O(g) → CO(g) + H 2 (g) and H 2 (g) + O Lattice → H 2 O(g) + OV. The formation of OVs, which was confirmed by electron paramagnetic resonance (EPR), can narrow the band gap, and enhance the photogenerated e − /h + separation efficiency on Bi 12 O 17 C l2 . Moreover, OVs-rich Bi 12 O 17 C l2 nanosheets can facilitate molecular O 2 activation and produce more reactive oxygen species (ROS), especially 1 O 2 , which greatly improve the NO to NO 3 − conversion efficiency with NO removal rate of ∼63% and NO 3 − production selectivity of ∼92.6 %. The present work will bring new insights into the construction and roles of OVs in semiconductor-based photocatalysis.

NOx removal ability of photocatalytic cement-based materials with porous structure

The photocatalytic performance of photocatalytic cement-based materials (PCM) is significantly limited because the photocatalytic reaction is mainly focused on the surface of PCM. In the present research, a porous structure is designed to facilitate the transport of light and pollutants inside PCM, enhancing photocatalytic performance. The NO removal capacity of porous PCM is measured; the pore structure is characterized by total porosity and BET; the nano-TiO2 content and distribution are analyzed by SEM-EDS. Results showed that the photocatalytic performance of PCM is enhanced by the growth of total porosity. Specifically, the increase of total porosity from 26.5% to 61.4%, NO removal rate is promoted from 525 μmol m−2·h−1 to 1133 μmol m−2·h−1, with an increase by 115%. As the total porosity is increased, the specific surface area and mesopore volume of PCM is augmented simultaneously. The increase in the specific surface area can activate the photocatalytic activity of nano-TiO2 partially located inside the PCM, thereby heightening the photocatalytic reaction depth of the PCM. Moreover, the increase in the mesopore volume can enhance the adsorption capacity for pollutants, thereby promoting the full occurrence of photocatalytic reactions in PCM. Such results provide support to the design of PCM with high photocatalytic performance.

Catalytic Oxidation of NO by Ozone over Mn-Ce/Al2O3/TiO2 Catalyst

In this study, Mn-Ce/Al2O3/TiO2 catalyst prepared by impregnation method was used for synergistic O3 oxidation NO. The catalyst prepared by impregnating Al2O3/TiO2 at a Mn:Ce molar ratio of 4:1 showed the best catalytic activity. The catalyst performance showed that when the molar ratio of Mn:Ce was 4:1 and the volume ratio of O3:NO was 1:4, the removal rate of NO could reach 63%, which could increase the removal rate by 40% compared with that of NO oxidized by O3 alone. BET, XRD, and TEM characterization results showed that when the molar ratio of Mn:Ce was 4:1, the catalyst specific surface area, and pore capacity were the largest. A large amount of MnOx and CeOx were distributed on the catalyst surface. The XPS analysis showed that the oxidation-reduction and oxygen vacancy of Mn (IV)/Mn (III)/Mn (II) and Ce (IV)/Ce (III), had a synergistic effect on the decomposition of O3 into reactive oxygen species(O*), thus improving the catalytic capacity of Mn-Ce/Al2O3/TiO2 catalyst for O3. The O2-TPD analysis showed that the oxygen vacancies and oxygen species in the catalyst could be used as the active point of decomposition of O3 into O*. The experimental results show that the prepared catalyst can significantly improve the efficiency of ozone oxidation of NO and reduce the amount of ozone. The catalyst can be applied to ozone oxidation denitrification technology.

Density functional theory study on catalytic reduction of NO on semi-coke containing N and Fe: The effect of CO

NOx is a common air pollutant, and its removal research is imminent. In this paper, the semi-coke segment was used as the catalyst carrier to study the three important factors of nitrogen doping, iron doping and CO introduction, and the NO heterogeneous reduction was analyzed by the DFT calculation method. And at the range of 300 to 1000 K, the reaction kinetics was quantitatively analyzed by the conventional transition state theory (TST). Only one NO molecule was needed to finish the whole reaction path by doping the nitrogen, as suggested the nitrogen doping improved the NO removal rate at low NO concentrations. Through the analysis of the adsorption energy, it was found that the adsorption capacity of carbon active sites for NO and CO was significantly enhanced with iron doping. Among them, the appearance of FeO groups also reduced the activation energy of the stage reaction. In addition, the CO introduction significantly promoted the production of N2, CO2 and N2O, which was manifested in the reduction of activation energy of NO catalytic reaction and the increase of the N2 and N2O reaction rate constant. This theoretical research provided a theoretical foundation for the subsequent experimental research on NO removal.

In-situ formation of Au nanoparticles with surface plasmon resonance confined in the framework of Cu ions doped NH2-MIL-125(Ti) to enhance photocatalytic hydrogen production and NO removal

A novel bifunctional photocatalyst Au@NML-(Cu/Ti) was fabricated to improve the photocatalytic performance of hydrogen production and NO removal, in which the Cu ion was first doped into the titanium oxide clusters of NH2-MIL-125(Ti) (NML) via a convenient method, and uniformly dispersed gold nanoparticles with surface plasmon resonance effect in-situ generated under the constraint of NML-(Cu/Ti) framework. The introduction of copper ions reduced the band gap of NML and accelerated the charge separation rate. Moreover, the NML-(Cu/Ti) framework could prevent the Au nanoparticles agglomeration as far as possible via confinement effect to obtain highly dispersed gold nanoparticles in very small size, which can effectively improve the atom utilization efficiency for enhancing photocatalytic performance. The photocatalytic hydrogen production of Au@NML-(Cu/Ti) was 5193.4 μ mol·g−1, which was 11.8 times that of the original NML. Meanwhile, the NO removal rate of Au@NML-(Cu/Ti) was about 25.6% higher than that of the pristine NML. Moreover, the photocatalytic NO oxidation process was also monitored by in-situ DRIFTS, which indicates Au@NML-(Cu/Ti) could realize the effective oxidation of NO. These results showed that the synergistic combination of central metal cluster modification of MOFs with surface plasma resonance provided a feasible strategy for improving photocatalytic hydrogen production and NO removal.

Interaction mechanism between nitrogen conversion and the microbial community in the hydrodynamic heterogeneous interaction zone.

To study the inorganic nitrogen in the process of interaction of river and groundwater and the changes in the microbial community, a vertical simulation device was used to simulate groundwater recharge to river water (upwelling) and river water recharge to groundwater (downwelling). The inorganic nitrogen concentrations in the soil and water solution as well as the characteristics of the microbial community were assessed to determine the inorganic nitrogen transformation and microbial community response in the heterogeneous interaction zone under hydrodynamic action, and the interaction mechanism between nitrogen transformation and the microbial community in the interaction zone was revealed. The removal rates of NO3--N in the simulated solution reached 99.1% and 99.3% under the two fluid-groundwater conversion modes, and the prolonged hydraulic retention time (HRT) of the oxidization-reduction layer in the fine clay area and the high organic matter content made the inorganic nitrogen transformation process dominated by microorganisms more complete. The denitrification during upwelling, dominated by denitrifying bacteria in Sphingomonas, Pseudomonas, Bacillus, and Arthrobacter, was stronger than that during downwelling. Dissimilatory nitrate reduction to ammonium (DNRA), controlled by some aerobic bacteria in Pseudomonas, Bacillus, and Desulfovibrio, was more intense in downflow mode than upflow mode.

Biochar immobilized bacteria enhances nitrogen removal capability of tidal flow constructed wetlands.

To improve the nitrogen removal (NR) capability of tidal flow constructed wetlands (TFCWs) for treatment of saline wastewater, biochar, produced from Cyperus alternifolius, was used to adsorb and immobilize a salt tolerant aerobic denitrifying bacteria (Zobellella sp. A63), and then was added as a substrate into the systems. Under low (2:1) or high (6:1) C/N ratio, the removal of NO3--N and total nitrogen (TN) in the biochar immobilized bacteria (BIB) dosing system (TFCW3) was significantly higher (q < 0.05) than that in the untreated system (TFCW1) and the biochar dosing system (TFCW2). At low C/N ratio, the removal rates of NO3--N, TN and chemical oxygen demand (COD) of TFCW3 were 68.2%, 72.6% and 82.5%, respectively, 15-20% higher than TFCW1 and 5-10% higher than TFCW2. When C/N ratio was further increased to 6, the pollutant removal rate of each system was greatly improved, but the removal rate of TFCW3 for NO3--N/TN was still nearly 10% and 5% higher than TFCW1 and TFCW2, respectively. Microbial community analysis showed that aerobic denitrifying bacteria, sulfate reducing bacteria and sulfur-driven denitrifiers (DNSOB) played the most important role of NR in TFCWs. Moreover, biochar bacterial agent significantly increased the abundances of genes involved in NR. The total copy numbers of bacterial 16S rRNA, nirS, nirK, drsA and drsB genes in the TFCW3 were 1.1- to 3.76-fold higher than those in the TFCW1; Especially at low C/N ratio, the copy number of drsA and drsB in the upper layer of TFCW3 were 85.5 and 455 times that of TFCW1, respectively. Thus, BIB provide a more feasible and effective amendment for constructed wetlands to improve the N removal of the saline wastewater by enhancing the microbial NR capacity mainly via aerobic and sulfur autotrophic denitrification.

Low-temperature NH3-SCR reaction over 3D Cu/Fe-TiO2-rGO composite catalyst synthesized by photoreduction method

Nitrogen oxides is a typical atmospheric pollutant and selective catalytic reduction with NH3 is an efficient and commonly used solution to remove NO from power plants and factories. In this paper, the Cu/Fe-TiO2-rGO catalysts with 3D hierarchical dandelion-like TiO2 microspheres and reduced graphene oxide as carrier were prepared by photocatalytic reduction method. The catalyst possessed the improved NO removal rate due to the following advantages: firstly, graphene oxide improved the specific surface area of Cu/Fe-TiO2-rGO catalyst. In addition, the Fe species promoted NH3 desorption and increased the oxidation of Cu species leading to the improvement of the low temperature activity of the catalyst. In another aspect, the amount of graphene oxide used to prepare MOx/GO by common hydrothermal method is large. The catalyst synthesized by photoreduction method with less amount and higher dispersion degree of reduced graphene oxide possessed the best NO conversion rate over 97 % at 250 °C, and Cu and Fe species were simultaneously distributed on the surface of rGO and 3D TiO2 microspheres. What was more, a large number of Lewis acid sites and a small amount of Brönsted acid sites in the catalysts were detected, and Fe element improved the NO conversion of Cu0.4Fe0.6-TiO2-rGO sample by Langmuir–Hinshelwood mechanism.

Dual-quantum-dots heterostructure with confined active interface for promoted photocatalytic NO abatement

Constructing heterostructure is an effective way to fabricate advanced photocatalysts. However, the catalytic performance of typical common multi-dimensional bulk heterostructure still suffers from the limited active interface and inefficient carrier migration. Herein, we successfully synthesize the SnO2/Cs3Bi2I9 dual-quantum-dots nanoheterostructure (labeled as SCX, X = 1, 2, 3) for efficiently and stably photocatalytic NO removal under visible light irradiation. The NO removal rate of SC2 is almost 8 and 17 times higher than that of the single SnO2 and Cs3Bi2I9, respectively. Moreover, the SC2 photocatalyst shows only 3 % attenuation after five consecutive cycles, demonstrating good photocatalytic stability. Systematic experimental characterization and theoretical density functional theory calculations revealed that the high activity and stability of SCX originated from the efficient charge transfer at the confined interface between SnO2 and Cs3Bi2I9 quantum dots. This work provides a new perspective for constructing innovative dual-quantum-dots nanoheterostructure and assesses their potential in photocatalytic environmental applications.

SO2 Tolerance of Rice Hull Ash Based Fe-Cu Catalysts for Low-Temperature CO-SCR of NO

Rice husk ash (RHA) has potential as a supporter of catalysts. In this research, we studied the activity and SO2 tolerance of RHA-based Fe-Cu oxide in the reduction of NO by CO. Characterization methods were employed to study the properties of the catalysts and their SO2 tolerance. Activity and SO2 resistance were also tested at different temperatures. We recommend two catalysts with SO2 resistance ability: Fe0.67Cu0.33/RHA (the highest catalytic activity) and Fe0.8Cu0.2/RHA. The NO removal rate hardly changed with the addition of SO2 and was kept at about 100%. However, the CO conversion rate decreased with increasing SO2 at the lower reaction temperatures, which may be due to the formation of sulfites. Fortunately, the deactivation was reversible and can be reduced with an increase in the reaction temperature. The results of our research may help promote the application of CO-SCR.

Efficient degradation of inorganic nitrogen in mariculture wastewater by electrochemical methods

The effective treatment of inorganic nitrogen in mariculture wastewater is important to ensure the quality and yield of cultured organisms, and protect the marine environment. The concentration of inorganic nitrogen, i.e. NO3−-N, NO2−-N and NH4+-N, reaches to the first-level of Water Drainage Standard for Seawater Mariculture (SC/T 9103–2007) after electrochemical treatment with a double-chamber cell (Ti/RuO2-IrO2 anode and Ni cathode) in this study. The results showed that the reductions of NO3−-N and NO2−-N on Ni cathode are easier than Ti and Pt cathodes. The removal rate and products (NH4+-N and NO2−-N) selectivity in degradation of NO3−-N using Pt and Ni cathodes are much higher than Ti cathode. However, the energy consumption of Pt cathode is much higher than Ti and Ni cathodes. With the potential shifted to negative using Ni cathode, both the removal rate of NO3−-N and the selectivity of NH4+-N increase, while the selectivity of NO2−-N decreases. The lowest energy consumption of Ni cathode is achieved under the potential of NO3−-N reduction peak, i.e. −1.25 V. Most of NH4+-N is oxidized indirectly on Ti/RuO2-IrO2 anode through active chlorine, and 1.30 V is the optimum potential. NO2−-N is oxidized to NO3−-N on Ti/RuO2-IrO2 anode, which can be introduced into cathode chamber again for further electrolyzing. The final product is N2 for treatment of mariculture wastewater in the double-chamber cell with Ni cathode and Ti/RuO2-IrO2 anode.