NO Removal Research Articles

A superior Mn5CeTi5Ox catalysts for synergistic catalytic removal of chlorobenzene and NOx: Performance enhancement and mechanism studies

The transition metal titanium-doped Mn-Ce-Ox catalysts catalyst were employed to achieve synergetic removal of NO and CB at 180–220 °C. The Mn5CeTi5Ox catalyst with a molar ratio of Mn/Ce/Ti = 5:1:5 exhibits excellent activity, and the NOx and CB removal efficiencies reach 96 % and 89 % at 160–220 °C, respectively. The selectivity for N2 and CO2 are 93 % and 78 %, respectively. The N2-physisorption, NH3-TPD, H2-TPR and XPS results show that Ti doping makes the catalyst possess a mesoporous structure, suitable particle sizes, and excellent redox and Lewis site properties. All of these features contribute to the observed high NO and CB removal efficiency. The synergetic removal of CB and NO over Mn5CeTi5Ox results from the synergistic catalysis between the redox and the solid acid. On the one hand, in the synergistic removal process, CB and NH3 are competitively adsorbed on the catalyst surface, resulting in a decrease in the NH3-SCR activity. On the other hand, the removal of NO and CB has a synergetic effect. The byproduct NO2 produced by the NH3-SCR reaction promotes the oxidation of CB, which is beneficial for CB removal. Moreover, the consumption of NO2 indirectly promotes the NH3-SCR reaction, which partially compensates for the decrease in the NO removal efficiency caused by competitive adsorption between NH3 and CB. Ti doping promotes the participation of the SCR byproduct NO2 in the CBCO reaction and promotes the formation of maleic acid, an intermediate product of CB oxidation. In summary, the Mn5CeTi5Ox catalyst exhibits good activity for the synergistic removal of NOx and CB and is a promising candidate for the effective and economical removal of NO and CB during waste incineration.

Constructing dual-channel carrier transport in AgBr/BiOBr/Ag3PO4 heterojunctions for enhanced photocatalytic NO removal

Efficient and stable photocatalysts are indispensable for effectively reducing nitrogen oxide (NOx) emissions. This study presents a facile method for synthesizing AgBr/BiOBr/Ag3PO4 composites and investigates their application in photocatalytic NO removal. The optimized composite exhibited notable performance, achieving 54.95 % removal of NO (approximately 568 ppb reduced to 256 ppb) under visible light irradiation, which is about 1.6 and 2.0 times higher than single Ag3PO4 (34.95 %) and BiOBr (28.01 %), respectively. Comprehensive physicochemical characterization highlighted enhancements in light absorption and the generation of reactive radicals within the AgBr/BiOBr/Ag3PO4 composite. The favorable electronic structure, characterized by well-aligned redox band positions, facilitated efficient dual carrier transport routes, thereby promoting the separation of photo-generated charge carriers. Additionally, in-situ DRIFTS analysis revealed that the composite facilitated the conversion of intermediates into nitrates during the NO purification process. This work contributes valuable insights into designing and preparing of ternary heterojunction photocatalysts with dual carrier transport channels, advancing strategies for achieving superior photocatalytic performance.

Metals doping effect of perovskite–type La-Mn oxides for NH3-SCR reaction at low temperature

Doping of perovskites with the heteroatoms has emerged as an additional lever, a dimension beyond structural perfection and compositional distinction, for the alteration of many properties of perovskites. In this work, a series of different metals were doped via citric acid sol–gel method to investigate their influences on the structure and catalytic performance of La-Mn perovskite oxides for NH3-SCR reaction. It is found that Zr doped La-Mn oxides (LMZr) displays better low-temperature deNOx performance (T90 = 118 °C) than other metal doped catalysts. Such a result is mainly attributed to the increase of Lewis acid sites, surface Mn4+ and adsorbed oxygen species. Besides, La-Mn perovskite doped with Sr, Ce, Y and Al can also obviously improve low-temperature deNOx activity and N2 selectivity. These doped metals mainly change the electron transfer between different cations, thus changing the valence distribution of Mn on the surface, meanwhile, metal doping changes the crystalline size of the catalysts, thereby affecting the adsorption and activation of NH3 and O2 involved in the removal of NO. Although other metal doping alters the tolerance of the La-Mn catalyst to SO2 and/or H2O, SO2 is inevitably oxidized to S6+ and deposits on the catalyst surface. Zr or Ce doping significantly enhances the tolerance to SO2 and/or H2O, but they have a different mechanism. Zr reduces the deposition rate of sulfate while Ce reacts with SO2 to form Ce2(SOx)3 to protect Mn active species. This paper highlights the importance of Lewis acid, Mn4+ content and adsorbed oxygen in the NH3-SCR reaction.

Research over the effect of activated carbon treated with calcium nitrate solution on the catalytic ability in the reduction of Co(III)Triethylenetetramine

AbstractActivated carbon can be used as a catalyst for the reduction of Co(III)TETA to Co(II)TETA so as to maintain the ability of removing NO from gas stream with Co(II)TETA solution. Calcium nitrate has been utilized to treat activated carbon to improve its catalytic ability in the regeneration of Co(II)TETA. The biggest Co(III)TETA conversion is gained by the carbon being soaked in 0.3 mol/L calcium nitrate solution at 65°C for 12 h with a solid/liquid ratio of 1 g/50 mL followed being carbonized at 400°C for 2 h in nitrogen. The characterization with Fourier transform infrared spectroscopy, XPS, BET (Brunauer‐Emmett‐Teller) and Boehm titration indicates that the modification with calcium nitrate increases the specific surface area and acidic groups on activated carbon. The continuous experiments reveal that the NO removal efficiency obtained by the modified carbon is over 12% up to that by the original one.

Selective photocatalytic reduction of nitric oxide to dinitrogen via bimetallic bond incorporation

In this study, we addressed the challenge of optimizing the first rate-limiting NO adsorbate state, which has received limited attention in previous research on the photoreduction of NO. We prepared BiFeWO6 (BFWO), which improved not only the NO removal rate under illumination but also the selectivity of photocatalytic NO conversion to N2. To further optimize the performance, we introduced platinum into BFWO, achieving a 57.5 % NO conversion rate with ∼80 % N2 selectivity under 425 nm light-emitting diode illumination (50 mW/cm2), which is optimal for converting NO into less harmful compounds at low concentrations. FeOBi bonds were identified as the key active sites of the first rate-limiting NO adsorbate state in BFWO through time-resolved operando infrared (IR) spectroscopy and density functional theory (DFT) analysis. The specific adsorption configuration of NO on the FeOBi group accelerated the photoreduction reaction kinetics, resulting in superior photocatalytic NO removal performance.

Online in-situ modification of biochar for the efficient removal of elemental mercury and co-benefit of SO2/NO removal

In this study, non-thermal plasma discharge was proposed for online in-situ modification of biochar injected into coal-biomass co-combustion flue gas, aiming to achieve the combined removal of elemental mercury (Hg0), NO, and SO2 from flue gas. After plasma discharge, the pore structure of biochar was slightly improved whereas the surface morphology of biochar was almost unchanged. After plasma discharge under O2, SO2, and HCl atmospheres, the oxygen, sulfur, and chlorine contents of biochar were obviously increased. More exactly, additional functional groups were formed on the modified biochar surface, such as CO, C(O)OC, CS, and CCl. Compared with raw biochar, the biochar modified under HCl, SO2, O2, H2O and CO2 atmospheres exhibited higher Hg0 removal efficiency, and longer modification time resulted in better Hg0 removal performance. The optimal modification atmosphere and reaction temperature were the simulated flue gas (SO2 + HCl + CO2 + O2 + H2O + NO + N2) and 20 ℃-100 ℃, respectively. The modified biochar exhibited excellent resistance to SO2 and H2O. The addition of HCl, CO2, NO, and O2 contributed to Hg0 removal. The removal efficiency of NO and SO2 attained a maximum of 100 %. The Hg0 removal mechanism was further revealed, where CO, C(O)OC, CS, and CCl served as active components.

Synergistic removal of NO and CO in industrial waste gas by Fe-modified Cu/TiO2 catalysts: The synergistic effect of metal oxides interaction

NH3-based selective catalytic reduction (NH3-SCR) combined with carbon monoxide (CO) catalytic oxidation is a productive way to synergistically remove nitrogen oxides (NOx) and CO from industrial waste gas. Catalyst is the undoubtedly centerpiece of the synergistic removal technology, which has aroused tremendous attention. Herein, in this investigation a variety of Cu/TiO2 catalysts modified by various metal oxides were prepared by impregnation method, and the excellent synergistic removal performance of Fe-modified Cu/TiO2 catalyst was observed. The Cu/TiO2 catalyst with a 7 wt% Fe doping amount exhibited the highest NO and CO removal efficiency (86 % for NO at 300 °C and over 98 % for CO from 300 ∼ 400 °C). Through a series of characterization techniques, it was discovered that Cu and Fe oxides interacted to evenly distribute them throughout the surface of TiO2 support, resulting in smaller particle size and abundant variable valence species (Cu+/Cu2+ and Fe2+/Fe3+) to enhance the redox performance of the catalysts. Moreover, the creation of additional surface chemisorbed oxygen, the adsorption of NO and CO, and the improvement of surface acidity were all facilitated by the electron transfer between various Cu and Fe species. In addition, in-situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS) results revealed the interaction between NH3-SCR and CO oxidation. This study proposes a viable approach to develop efficient catalysts for the synergistic removal of NO and CO in industrial applications.

Synthesis of CdS QDs/NH2-Nb2O5 via electrostatic self-assembly method for highly efficient photocatalytic removal of NO and synchronous inhibition of NO2

A two-step electrostatic self-assembly method was used to first graft –NH2 groups onto the Nb2O5 followed by loading of CdS QDs onto the NH2-Nb2O5 to obtain CdS/NH2-Nb2O5. The performance of the samples under visible light was evaluated under simulated conditions of 25 °C and varying relative humidity (RHs). The results showed that with the increase of RH, the NO removal efficiency by CdS/NH2-Nb2O5 increased first and then decreased, reaching the maximum NO removal efficiency when RH = 50 %. The selectivity of NO2 on CdS/NH2-Nb2O5 (9.01 %) was significantly lower compared to that of Nb2O5 (24.44 %) and NH2-Nb2O5 (19.72 %). The introduction of –NH2 groups and CdS QDs significantly enhanced visible light absorption and improved the separation efficiency of photogenerated charge carriers. In-situ DRIFTS analysis revealed that Cd2+ served as an additional active site for NO adsorption. Furthermore, CdS had a relatively negative conduction band position, which was conducive to the generation of O2–, further inhibiting the generation of NO2. This work provides a new approach to the design and preparation of catalysts for photocatalytic oxidation of NO.

Na-doped nitride-rich carbon nitride for efficient photocatalytic NO abatement

Nitride-rich carbon nitride (C3N5) is gaining prominence as a substantial catalyst for photocatalytic reaction because of its narrow bandgap, extensive light responsiveness, and photocatalytic stability. To enhance the efficiency of photogenerated carrier separation in C3N5, we propose a strategy for Na-doped modification. Photocatalytic NO removal efficiency of C3N5/Na achieved 73.9 % under 15 % relative humidity, which is 3.5 times higher than that of C3N5. Besides, the NO removal efficiency of C3N5/Na maintained above 70 % even after six cycles under different relative humidities. Detailed analytical characterization revealed that Na doping of C3N5 not only increased its specific surface area by 5.5-fold but also modulated its energy band structure and molecular structure, leading to improved hole-carrier separation efficiency and enhancing the photocatalytic performance of C3N5/Na. ESR and reactive species trapping experiments confirmed that electrons and superoxide are the main reactive species, and modulation of the energy band structure accelerates the reaction. This work explains the effect of Na doping on C3N5 and provides a new strategy for designing efficient for photocatalytic treatment of air pollution.

Theoretical investigation of graphdiyne-supported single-cluster catalysts for electroreduction of nitric oxide

The electrochemical NO reduction reaction (NORR) to NH3 offers an efficient, environmentally friendly strategy for NO removal and NH3 production, but developing effective catalysts to facilitate the conversion of NO into NH3 remains a challenge. Single-cluster catalysts (SCCs) with multi-metallic sites show promise due to the synergistic interactions among the active atoms. Herein, utilizing density functional theory (DFT) and grand-canonical DFT (GC-DFT), we systematically investigated the potential of late transition metal (TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt) clusters on graphdiyne (TMx/GDY, x = 1–5) for NORR. Ni3/GDY, Pd3/GDY, and Pt3/GDY emerged as the most promising candidates, demonstrating stability, excellent NORR activity, and HER suppression. Their outstanding performance is attributed to the moderate adsorption of NO, with the dxz/dyz orbitals playing a key role in NO activation. GC-DFT results highlight nonlinear variation of intermediate grand free energies with the applied potential. Detailed electronic property analyses were conducted to reveal the charge effects induced by the applied chemical potential. This study provides valuable insights into SCC-catalyzed NO reduction and highlights the significance of potential effects in theoretical simulations of electrochemical systems.

Degradation of the AMP/PZ-based solvent CESAR1 and effects of solvent management in two longtime pilot plant tests

Two 24/7 longtime testing campaigns at the CO2 capture pilot plant at Niederaussem with an accumulated testing time of more than 40,000 h with the CESAR1 solvent, an aqueous solution of 26.7 wt% 2-amino-2-methylpropan-1-ol (AMP) and 12.9 wt% piperazine (PZ), provide a unique data base for the development of solvent management technologies and the evaluation of hypotheses on amine degradation. In the first campaign with a testing time of 34,000 h without replacement of the solvent inventory, three solvent management strategies with different effect mechanisms were investigated: adsorptive removal of trace elements from the solvent by two kinds of active carbon, removal of ionic contaminants by ion exchange using cation and anion exchange resins, and removal of NO2 from the flue gas by treatment with a thiosulfate/sulfite solution. After replacement of the solvent inventory the second campaign was conducted, in which none of the solvent management technologies mentioned have been applied for 10,000 h. The results of the two campaigns allow a direct comparison of the solvent degradation behavior. It is shown that active carbon does not significantly affect the accumulation rate of degradation products in CESAR1, and that an inappropriate kind of active carbon can cause foaming. Anionic degradation products, metal complexes, trace components and cationic contaminants can be effectively removed from the aged solvent by ion exchange. However, after their removal, accelerated formation of oxidative degradation products by a factor of up to 3 higher than before the anion exchange was observed. Removal of NO2 from the flue gas did not affect the NH3 emissions from the CO2 absorber, but it led to the highest observed increase rate of the accumulation of acidic degradation products for aged CESAR1. The results show that exaggerated efforts for solvent management are contra-productive and that a reassessment of the effect mechanisms of solvent management technologies is necessary.

Effects of organic ligands and photoactive substances on MOFs-derived Co3O4@MnOx hollow-sphere structure for efficient energy transfer and photothermocatalysis of acetone and NO

A set of MOFs-derived Co3O4@MnOx hollow-sphere were synthesized to develop a catalyst for the photothermal catalytic removal of NO using acetone as a reducing agent. The study systematically investigated the impact of organic ligands and photoactive substances on energy transfer and photothermocatalytic reactions involving acetone and NO under 5 vol % H2O with the catalysts. At 240°C, sample C-5/1 (with an organic ligand added and Co/Mn molar ratio of 5/1) demonstrated 75 % NO conversion and 65 % acetone conversion. The highest catalytic performance was observed in the L-Py sample (with photoactive substance was added), achieving 80 % NO and 69 % acetone conversion at 240°C. The catalyst demonstrated low crystallinity, and the introduction structural defects through ligands adjusted the ratio of active components. Meanwhile, enhanced catalytic performance was attributed to light energy scattering in the inner space of microspheres, resulting in the efficient transfer of 2.17 eV energy with the addition of two photoactive substances. The elevated concentration of surface-active oxygen facilitated oxidation, while Mn/Mn+1 (Mn3+/Mn4+ and Co2+/Co3+) redox cycling supplied surface oxygen in the photothermal low-temperature response. The proposed mechanism for the simultaneous degradation of acetone and NO was elucidated using Density Functional Theory calculations.

Type-II heterojunction In2O3/TiO2 with highly efficient charge separation for boosted photocatalytic NO abatement

Photocatalytic NO degradation often suffers from sluggish charge carrier separation and low selectivity. Herein, a series of In2O3/TiO2 (P25) composites were synthesized to enhance NO abatement. Benefiting from the conspicuous synergistic effect between In2O3 and P25, the In2O3/P25 catalysts demonstrated more than double the NO elimination performance compared to pure P25 and In2O3. The In2O3/P25 sample with 75 wt% In2O3 (In-P25-75) achieved a NO removal efficiency of 51.7 %, higher than reported catalysts (30.0–49.0 %). It was the successful formation of type-II heterostructure that enabled intimate interfacial contact and provided ample electron transfer channels. Moreover, photoluminescence spectra and photoelectrochemical measurement confirmed the improved separation and inhibited recombination of photogenerated charge carriers in In-P25-75, thereby boosting the NO photocatalytic efficiency. ·O2− and ·OH radicals generated by photoinduced electron transfer to the conduction band of P25, along with the induced holes confined to the valence band of In2O3, facilitated the targeted deep oxidation of trace NO into NO3− rather than harmful NO2. This work discloses a promising strategy for the efficient removal of NO from the atmosphere by reducing the emission of hazardous intermediate NO2.

Boosting photocatalytic NO remove and H2 production by Co(ii,iii)-modified carbon dots assembly into metal–organic frameworks: The Co(ii,iii)-modified carbon dots location matters

Inhibiting electron-hole recombination and improving the utilization efficiency of photogenerated carriers perform a central role in photocatalysis. Herein, a “ship-in-a-bottle” strategy and an impregnation method were employed to incorporate highly active Co(II,III)-modified carbon dots (Co-CDs) inside or supported on a representative metal–organic framework (i.e., NH2-MIL-125), denoted as Co-CDs-N-MIL and Co-CDs/N-MIL, respectively, for photocatalytic removal of NO and H2 production. Compared with pure NH2-MIL-125, the photocatalytic activities of both Co-CDs-N-MIL and Co-CDs/N-MIL were significantly enhanced but distinctly different, suggesting that the photocatalytic efficiency closely correlates with the Co-CDs location relative to the NH2-MIL-125. A series of characterizations confirmed that Co-CDs-N-MIL shortens the electron transport distance to some extent, which is conducive to the suppression of electron-hole complexation, and thus has a better efficiency than Co-CDs/N-MIL.

Enhancing the activity and sulfur resistance of CuFeAlOx catalyst via the structure effect for the simultaneous removal of Hg0 and NO at wide temperature

The efficient strategy for improving SO2 resistance and catalytic activity is structural modification. Herein, the CuFeAlOx catalysts with different structures, including one-dimensionally disordered mesoporous nanoparticles structure (CuFeAl-N), one-dimensionally ordered mesoporous nanoparticles structure (CuFeAl-C), three-dimensionally ordered porous honeycomb-like structure (CuFeAl-P) and three-dimensionally ordered porous flower-like structures (CuFeAl-CP), were synthesized via a template method to investigate structure effect on activity and sulfur resistance of the catalyst for simultaneously removing NO and Hg0 at wide temperature. The results showed that the various surface characteristics resulted in distinct behaviours with regards to SO2 tolerance. CuFeAl-CP and CuFeAl-C exhibits excellent SO2 resistance, but CuFeAl-N catalyst presents poor SO2 resistance. The CuFeAl-CP with the flower-like structure possesses large specific surface area, which can expose more active sites and exhibited highly dispersed active component. More importantly, it reacts with SO2 to generate reactive sulfate providing additional acid sites, which significantly promotes high-temperature catalytic performance. One-dimensionally ordered mesoporous and three-dimensionally ordered porous effectively facilitates mass transfer of reactants and ammonium sulphate decomposition, thereby inhibiting surface sulfation and ammonium sulfate species deposition. This work lays the foundation for developing highly efficient SCR catalysts that are tolerant to SO2.

Feasibility of using red mud as bed material for treating N2O in fluidized bed combustion

Red mud, a type of industrial waste, currently can’t be utilized effectively, and there are no efficient methods for controlling N2O emissions in circulating fluidized bed (CFB) boilers. Based on characteristics of N2O and the components of the red mud, the red mud was used in this study as bed materials of fluidized bed to treat N2O produced by coal combustion. The decomposition effect of red mud on N2O under various operating conditions during the coal combustion process was quantified in a bubbling fluidized bed, and the decomposition of N2O and NO after the flue gas passed through the bed material was investigated. In a variety of operational conditions, the presence of red mud has been observed to exert a pronounced inhibitory effect on the formation of N2O, while concurrently exhibiting the capacity to diminish the nitrogen conversion rate of N2O to varying degrees. Comparative analysis of N2O and NO emissions from char and coal revealed different levels of reduction, with the combination of CO and red mud being the most effective method. Red mud demonstrated superior N2O removal capabilities, while CO was more effective for NO removal. The issue of increasing NO can be resolved by balancing the iron-aluminum ratio of red mud, allowing the flue gas to pass through the red mud in the CFB’s low-temperature zone, and focusing on N2O removal in the furnace.

Screening of Silver-Based Single-Atom Alloy Catalysts for NO Electroreduction to NH3 by DFT Calculations and Machine Learning.

Exploring NO reduction reaction (NORR) electrocatalysts with high activity and selectivity toward NH3 is essential for both NO removal and NH3 synthesis. Due to their superior electrocatalytic activities, single-atom alloy (SAA) catalysts have attracted considerable attention. However, the exploration of SAAs is hindered by a lack of fast yet reliable prediction of catalytic performance. To address this problem, we comprehensively screened a series of transition-metal atom doped Ag-based SAAs. This screening process involves regression machine learning (ML) algorithms and a compressed-sensing data-analytics approach parameterized with density-functional inputs. The results demonstrate that Cu/Ag and Zn/Ag can efficiently activate and hydrogenate NO with small Φmax(η), a grand-canonical adaptation of the Gmax(η) descriptor, and exhibit higher affinity to NO over H adatoms to suppress the competing hydrogen evolution reaction. The NH3 selectivity is mainly determined by the s orbitals of the doped single-atom near the Fermi level. The catalytic activity of SAAs is highly correlated with the local environment of the active site. We further quantified the relationship between the intrinsic features of these active sites and Φmax(η). Our work clarifies the mechanism of NORR to NH3 and offers a design principle to guide the screen of highly active SAA catalysts.

A new denitrification strategy based on high-temperature catalytic coatings Y2O3-BaO-ZrO2 without using ammonia in a lab-scale natural gas combustion furnace

Catalytic decomposition of NO at high temperatures without the use of ammonia, offers an eco-friendly and sustainable solution for denitrification in industrial combustion or heating processes. To simulate a complex combustion flue gas, we designed a lab-scale natural gas industrial combustion furnace specifically for assessing the impacts of Y2O3-BaO-ZrO2 catalyst coated on SiC plates on NO emissions. Various factors including the plate number, excess air ratio, combustion power, and coating position were considered. Results demonstrated that arranging the Y2O3-BaO-ZrO2 coated plates shifted the high-temperature zone of the furnace downstream. When the excess air ratio was below 1.05, the catalytic coating significantly reduced NO emission concentration at the furnace outlet by over 40 %. However, this reduction coincided with a substantial presence of unburned CO in flue gases. Placing the coated SiC plates in the constant temperature zone of 1100–1200 °C within the middle of furnace offered significant advantages in NO removal, particularly as the combustion power increased. Based on a 60-h durability evaluation of Y2O3-BaO-ZrO2 coating, the observed good high-temperature thermal and chemical stabilities further enhanced the coating’s potential for industrial application. The possible mechanism of the reduction NO by CO over coating surfaces were analyzed by in situ optical measurements. After calculation, using 12 kg Y2O3-BaO-ZrO2 catalysts might decrease at least 642 kg of ammonia consumption under ideal conditions, and significantly reduce the investment cost on existing flue gas denitrification equipment. Therefore, the investigated technology is a green and sustainable denitrification strategy, which would potentially provide a novel approach towards attaining ultra-low NO emissions.

Application of a microalga, Tetradesmus obliquus PF3, for NO and CO2 removal from actual flue gas via cultivating in wastewater.

Greenhouse gas (GHG) emissions, particularly anthropogenic emissions, are the primary drivers of climate change. The cultivation of microalgae represents a highly promising strategy for mitigating atmospheric GHG levels. The growth characteristics and GHG mitigation capabilities of Tetradesmus obliquus PF3 were investigated in domestic wastewater at a thermal power plant. The maximum cell density and productivity were 1.52 ± 0.01 g L-1 and 0.33 ± 0.01 g L-1 day-1, respectively. Utilizing a serial configuration of two reactors, the elimination efficiency of NO and CO2 attained values of 78 ± 4% and 14 ± 4%, respectively. NO concentration at the outlet was less than 24.6 ± 2.9 mg m-3, meeting the latest Chinese discharge limits. Besides, the recovery efficiency of NO and CO2 increased to 77 ± 8% and 2.24 ± 0.04%, respectively, compared to that of the single reactor (40 ± 3%, 0.9 ± 0.0%). A removal efficiency of over 90% was achieved for TN and TP in domestic wastewater. The concentrations of COD (76.5 mg L-1), NH4+-N (0.9 mg L-1), TN(6.31 mg L-1), and TP (0.35 mg L-1) in effluent were below the thresholds of 100 mg L-1, 25 mg L-1, none data, and 3 mg L-1, respectively, complying with the Chinese Discharge Standard (Class II criteria set forth) for Municipal Wastewater Treatment Plants Pollutants. The harvested biomass exhibited a high content of carbohydrates and proteins, making it a viable feedstock for biofuels and bio-fertilizers. Our results demonstrate that Tetradesmus obliquus PF3-based flue gas treatment technology can simultaneously realize GHG removal, wastewater bio-remediation, and biomass recovery.

Synergistic integration of metallic Bi and defective TiO2 for enhanced photocatalytic NO removal

The construction of hybrid catalysts is an effective method to enhance catalytic performance, but research on the positioning of the load is limited. In this study, we synthesized two photocatalytic materials by controlling the bismuth-titanium ratio and the site value of Bi modification in the catalyst. The surface-modified photocatalyst, namely 1:0.9 Bi/TiO2, exhibits a photocatalytic efficiency of 68.9 % for the abatement of ppb-level NO in the presence of visible irradiation. This efficiency was significantly superior to that of the corresponding one-step synthesized Bi/TiO2 (48.7 %) and the TiO2 (18.6 %). Furthermore, it promotes nitrate formation and suppresses the generation of toxic NO2. Capture experiments indicate that the same active species are involved in both surface-loaded and uniformly loaded catalysts. The differences in their performance can be attributed to the higher vacancy concentration in the surface-loaded catalysts and the different local coordination environments of vacancies in the catalysts, altering the adsorption capability of oxygen molecules. This work offers fresh perspectives for the generation of efficient photocatalysts.