NO Removal Process Research Articles

Efficient photocatalytic decomposition of NO and mechanism insight enabled by NaBH4-reduced N(ligancy-3)-vacancy-rich-graphitic carbon nitride

Vacancy defect engineering is an effective means to improve the performance of g-C3N4 photooxidation for NO removal. In this paper, flake graphite-phase g-C3N4 is prepared by thermal polycondensation. Then g–C3N4–x (x = 0, 0.5, 1.0, 1.5, and 2.0) containing various amounts of vacancies of nitrogen atoms with (3 coordination number) ligancy 3 (N(ligancy-3)) was prepared by NaBH4 reduction at room temperature. The introduction of N vacancies in g-C3N4 narrowed the forbidden gap, enhanced optical absorbance, optimized photo exciton separation and migration, and functioned as traps to mitigate the recombination of photogenerated electron-hole pairs. As a result, g–C3N4–x shows a superior NO removal performance, especially g–C3N4–1.5, which exhibits a high NO removal rate of 66.7 %, excellent resistance to the by-product NO2, and excellent stability. The free-radical seizure experiments and electron paramagnetic resonance (EPR) studies proved the superiority of superoxide radicals, electrons and holes as the prominent free radicals in the photocatalytic NO removal process. In situ diffuse infrared Fourier transform spectroscopy (DRIFTS) confirmed that the cis-dimer (NO)2 produced from NO adsorption on the surface of g–C3N4–1.5 is an important intermediate. Additionally, NO2− is observed as an intermediate and a primary product, and NO3− is identified as the key product of NO photocatalytic oxidation. DFT calculations showed that the N(ligancy-3) vacancy introduces impurity energy levels in g-C3N4 and shortens the electron migration path. The adsorption calculation of NO demonstrated that g–C3N4–N(ligancy-3) exhibits good adsorption and conversion of NO. This study provides a practical defect engineering for the g-C3N4 to remediate environmental pollution.

Theoretical and experimental studies of NO removal in alkaline H2O2 system

NO in flue gas is one of the atmospheric pollutants, and it is necessary to study effective NO removal technology. It was identified that the alkaline H2O2 system achieved over 98 % NO removal efficiency with a gas–liquid contact time of 3 s in this paper. This paper investigates the mechanism of NO removal in alkaline H2O2 solution through both experimental and theoretical calculations. The results reveal the NO removal process can be divided into three phases by the NaOH/H2O2 molar ratio. (1) The ∙O2– dominated phase, where trace metal Fe catalyzes ∙O2– radical generation from H2O2 as Fe (OH)2+, reacting primarily with NO to form ONOO–. The energy barrier for this process is1.299 kcal/mol, with a reaction rate constant of 9.12 E + 11 s-1M−1. (2) The HO2– dominated phase, HO2– was generated through OH– and H2O2 neutralization, which converts NO to NO2 and regenerating OH–. The energy barrier for HO2– reacting with NO is 3.833 kcal/mol, and the reaction rate constant is 2.07E + 10 s-1M−1. (3) The O22– dominated phase, O22– was a further ionization of HO2– and converting NO to NO2– directly. The energy barrier for this process is 7.079 kcal/mol, and the reaction rate constant is 1.49 E + 08 s-1M−1.

Ozone oxidation of nitric oxide: Promoting effect of phosphorus and inhibitory effect of phosphoric acid

AbstractThis work presents experimental and density functional theory theoretical methods to carry out the catalytic role and reaction mechanism of phosphorus (P4) for liquid phase catalytic oxidation nitric oxide. Meanwhile, it carries out the promoting effect of phosphorus and inhibitory effect of phosphoric acid in the ozone oxidation of nitric oxide. The work reveals the significant involvement of P4 in facilitating the NO catalytic oxidation process by generating O3. Meanwhile, the presence of phosphoric acid (H3PO4) hindered the NO catalytic removal process. The calculation results highlight that P4 promoted the formation of O3 and favoured the oxidation pathway (oxidation‐hydration, NO ➔ NO2 ➔ HNO3). During the liquid‐phase NO catalytic removal process, O2 and NO dissolved into the solution, where O2 exhibited preferential adsorbed on P4, promoting the O3 formation. Subsequently, O3 first oxidized NO to NO2. Then, HNO2 and HNO3 were generated under the hydration reaction of NO2 and H2O. Next, O3 further oxidized the generated HNO2 to HNO3, realizing the complete oxidation of NO. The hydration step of NO2 was identified as the key step in the O3 oxidation processes. Furthermore, the generation of H3PO4 led to the consumption of P4 and inhibited the NO removal process. O3 played the crucial role in liquid phase NO oxidation.

Cyano/Hydroxyl Groups Co-Functionalized g-C3N4 for Photocatalytic NO Removal: A Synergistic Strategy towards Inhibition of Toxic Intermediate NO2

Photocatalytic NO removal is usually accompanied by the generation of NO2, an intermediate with a higher toxicity than NO. Therefore, it is critically important to develop new photocatalysts capable of NO selective conversion. Herein, we report on the synergistic roles of cyano and hydroxyl functional groups in photocatalytic NO removal. According to the results, the NO2 production efficiencies on cyano/hydroxyl-group-modified g-C3N4 (DCN-O-R) was limited to 4.8%, which was lower than that of cyano-group-modified g-C3N4 (DCN, 38.6%) and pure g-C3N4 (CN, 50.0%). Meanwhile, the photocatalytic NO conversion efficiency over DCN-O-R was higher than that of DCN and g-C3N4. It was found that the insertion of cyano groups favorably changes the energy band of g-C3N4 towards the generation of •O2−. NO can only be oxidized to NO2 by the photogenerated holes. When NO2 is adsorbed on the surface of hydroxyl groups, it can be further oxidized to the product NO3− by •O2−. The synergistic effect of bifunctional groups regulates the conversion pathway from NO→NO2 to NO→NO2→NO3−. This work provides a strategy to abate toxic intermediates during the NO removal process, underlining the importance of surface/interface molecular engineering in regulating catalytic reaction pathways.

Investigation of the NO removal process of ultra-low temperature adsorption-rapid regeneration

NO removal facility installed at the very tail-end of the flue gas could reduce the effects of dust and SO2 poisoning, the problem is to figure out how to remove NOx at ultra-low temperature. Relying on rotary reactors, a NOx adsorption-enclosed regeneration process (NAER) was proposed, by which NOx is adsorbed onto the adsorbent at ambient temperature and then to on-site degrade in a high-temperature and enclosed environment with the high-concentration CO. Metal-doped activated carbon emerged as the optimal catalyst for shortening the cooling temperature difference. The results indicated that the maximum adsorption capacity for NO is 38.67 mg/g at 50 ℃, and NO conversion reaches exceed 90 % at 250 ℃ when 1400 ppm CO and 700 ppm NO are introduced into the reactor. The novel enclosed high-concentration of CO reduction regeneration encourages more NO to participate in the reaction, promoting the deep decomposition of nitrate and avoiding the overflow of NOx at the outlet. The difference between the breakthrough time and regeneration time spans 12–21 min. The carbon consumption is 0.0087 %/min, ensuring the long-term and continuous operation of the material. The current study explains the reaction mechanism of NO adsorption via in-situ FTIR. Life cycle assessment method is applied to analyze NAER’s emission standards, while life cycle inventory method calculates the economic cost, which stands at 287.06 RMB. The reduced cost is primarily reflected in the energy and raw materials inputs. The proposed process holds significant potential for optimizing the ultra-low emission of flue gas.

Simultaneous removal of SO2 and NO by self-activated NaHCO3

Systematical experiments, mechanistic studies, and kinetic studies of SO2/NO removal with NaHCO3 were first carried out in this paper. The results showed that NaHCO3 was self-activated by an in-situ decomposition process that generated more active sites for SO2/NO removal. The efficiency of NO removal was sensitive to the oxygen concentration and the presence of SO2. The optimal SO2/NO removal efficiencies reached 100%/85% at 160 °C and with O2 concentrations over 5%. Additional mechanistic studies showed that the presence of NO facilitated the conversion of SO32-→SO42-. The intermediate NO2 generated by NO oxidation competed with SO2 for adsorption sites. Kinetic studies illustrated that the absorption of NO2 was the rate controlling step in the early NO removal process. The optimal parameters obtained were sulfur-to-sodium ratios of 2–3 and volume space velocities of 20,000–30,000 h−1. A potential application involving “Na2SO4 to NaHCO3” was proposed for Na2SO4 utilization and integrated SO2/NO2/CO2 removal.

Simultaneous removal of SO2, NO and Hg0 using porous carbon/heat-coactivated persulfate system

A novel simultaneous removal technique of SO2, NO, and Hg0 using porous carbon/heat-coactivated persulfate (PS) system was proposed. A series of experiments and theoretical analysis were conducted to explore simultaneous removal process of Hg0, SO2, and NO. Study demonstrates that the developed porous carbon/heat-coactivated PS system gains larger free radical yield and higher pollutants simultaneous removal efficiency than other comparison systems, which are associated with the synergism between porous carbon and heat. High temperature plays a vital role in this co-activation system. Both SO4−· and ·OH play an important role in NO and Hg0 removal, but ·OH is more important for NO removal while SO4−· is more important for Hg0 removal. Both NO and Hg0 removal processes meet pseudo-first-order rapid reaction kinetics, and their removal processes are controlled by mass transfer. Removal efficiencies of NO and Hg0 are increased first and then are decreased with increasing PS concentration, temperature and porous carbon concentration. Increasing pH and concentrations of SO2, NO and Hg0 reduce the NO and Hg0 removal efficiencies. The highest simultaneous removal efficiency of Hg0, SO2, and NO is up to 98.4% for Hg0, 100% for SO2, and 89.3% for NO under an optimized test condition.

Microwave-ultraviolet co-catalysis of chlorite-oxygen mixture for highly cost-efficient simultaneous removal of NO and Hg0

Developing novel advanced oxidation process (AOP) to simultaneously remove various air pollutants has received considerable attention in past years. This paper develops a novel cost-efficient AOP method of microwave (MW) induced ultraviolet (UV) co-catalyzing trace NaClO2-O2 to simultaneously remove NO and Hg0, the obtained removal efficiencies are 91.4% and 99%, respectively, under a molar ratio of NaClO2 to NO/Hg0 of 1.3:1. The effects of some key parameters including NaClO2 dosage, reaction temperature, input MW power, UV light intensity, concentrations of O2, NO and SO2, and gas flow on the removal of NO and Hg0 were studied. ESR and radical quenching tests demonstrated that superoxide radical (•O2–), hydroxyl radical (•OH), oxychloride radical (ClO•), chlorine dioxide (ClO2) and ozone (O3) were the major reactive species. With the assistance of Na2SO3 absorber, the produced NO2 was efficiently absorbed and controlled to below 5 mg/m3. IC and AFS analyses revealed the distribution of removal products: (i) 51% of NO3– and 85% of Hg2+ were preserved in the MW-UVEL reactor; (ii) the other NO3– and Hg2+ as well as the NO2– generated via the redox reaction between NO2 and SO32- were totally absorbed by the Na2SO3 solution. Mechanism analyses elucidated that the NO removal process was attributed to the radical-induced oxidation reaction, and the contribution order was •O2– > •OH > ClO•/ClO2 > O3; however, the Hg0 removal process was mainly determined by the produced NO2/NO3–, and UV light coupled with other active species contributed less 40%.

The excellent photocatalytic NO removal performance relates to the synergistic effect between the prepositive NaOH solution and the g-C3N4 photocatalysis

Photocatalysis technology is used to remove the low concentration NO in recent years. However, the effect of this process is not very satisfactory. In this study, it was found that the prepositive NaOH solution could significantly improve the photocatalytic NO removal activity of g-C3N4. The apparent quantum yield of g-C3N4 in the NO removal process was increased 3.5 times by the prepositive NaOH solution. The reason is that there was a synergistic effect formed between the prepositive NaOH solution and the photocatalytic NO removal process. The prepositive NaOH solution not only could increase the humidity and pH value in the photocatalytic unit, but also could improve the adsorption ability of g-C3N4 for the H2O, NO, and O2. Moreover, the prepositive NaOH solution reduced the difficulty of the photogenerated carriers’ transport and the ·OH generation. This study provided a new idea for the removal of low-concentration NOx.

Simultaneous catalytic oxidation of nitric oxide and elemental mercury over Cu-Fe binary oxide treated by oxygen non-thermal plasma

In this study, non-thermal plasma (NTP) was adopted to improve the catalytic oxidation performance of Cu-Fe binary oxides (CFs) for efficient simultaneous removal of NO and Hg0 from coal combustion flue gas. Sample characterization indicated that the pore structure, surface morphology, and crystalline phases of CF samples were not changed after plasma treatment whereas the contents of lattice oxygen (Ol), Fe3+, and Cu2+ were largely increased. The treated CF samples exhibited far better NO removal performance compared with raw CF over a wide reaction temperature range (150–450 °C). The influences of plasma discharge time, discharge power, discharge atmosphere, and reaction temperature on NO removal performance were analyzed. O2 facilitated Hg0 and NO removal·H2O had adverse effect on Hg0 and NO removal. To some extent, the CF samples exhibited better resistant to sulfur poisoning due to the presence of Fe species. Moreover, the simultaneous removal behavior of Hg0 and NO over the modified CF samples were analyzed. NO facilitated Hg0 removal, but Hg0 had a slight inhibitory impact on NO removal. The optimum reaction temperature of simultaneous removal of NO and Hg0 was 300 °C. Finally, the mechanism responsible for NO/Hg0 removal was revealed, where CuO and Fe2O3 served as active components. During NO removal process, Fe3+, Cu2+, and Ol were first consumed and then recovered due to the existence of O2. Hg0 catalytic oxidation dominated the Hg0 removal process because Hg0 adsorption equilibrium was reached in a short time.

Homogeneous Ni(I)tetra Sulfonated Phthalocyanine Electrocatalyst Generated at Low Overpotential Clubbed with a Wet‐Scrubbing Column for High Efficiency NO Reduction to NH3

AbstractAlthough the degradation of NO gas to a less toxic form is a promising strategy to help solve atmospheric health and ozone depletion problems, conversion to a useful gas is a recent strategy. The generation of NH3 from NO with high efficiency per catalyst area or weight is in the early stages. In this investigation, a tetra sulfonated phthalocyanine with a Ni(II) (Ni(II)TSPc) complex was used to produce a low valent homogenous electrocatalyst Ni(I)TSPc in an alkaline medium at a lower overpotential. Ni(I)TSPc formation at a lower overpotential was demonstrated by the initial change in oxidation/reduction potential from 25 mV to −360 mV during electrolysis, peak potential change in cyclic voltammetry, and UV‐Vis spectral analysis. A potentiometric titration method used to quantify the electrogenerated Ni(I)TSPc revealed 90 % efficiency in 1 h. The decrease of Ni(I)TSPc concentration when contacting NO gas at the wet scrubber column showed that the NO removal process followed a Ni(I)TSPc (Ni(I)) mediation or mediated electrocatalytic reduction (MER) process. The NO removal efficiency reached almost 100 % at a 0.2 L/min gas flow rate of 20 ppm. The selective formation of NH3 with a maximum of 1492 μmol/g Ni(I) was achieved for the first time in the homogeneous electrocatalytic reduction process. The developed process generated NH3 from NO gas and has the potential for scale‐up.

Highly efficient photocatalytic NO removal and in situ DRIFTS investigation on SrSn(OH)6

A novel SrSn(OH)6 photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method. The photocatalytic activity of the SrSn(OH)6 was evaluated by the removal of NO at ppb level under UV light irradiation. Based on the ESR measurements, SrSn(OH)6 photocatalyst was found to have the ability to generate the main active species of O2•−, •OH and 1O2 during the photocatalytic process. Moreover, SrSn(OH)6 photocatalyst not only exhibits high photocatalytic activity for NO removal (79.6%), but also has good stability after five cycles. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the NOx transfer pathway and the intermediate products distribution during the adsorption and photocatalytic NO oxidation process. The present work not only provides an efficient material for air pollutants purification at room temperature but also in-depth understanding of the mechanism involved in the photocatalytic NO removal process.

Effect of oxygen vacancies and its quantity on photocatalytic oxidation performance of titanium dioxide for NO removal

In this work, black TiO2 catalysts containing a large number of oxygen vacancies were prepared by sol-gel and calcination methods. The catalytic activity of the photocatalysts was evaluated by photocatalytic oxidation removal of NO. We found that black TiO2 calcined at 400 °C in an N2 atmosphere with appropriate oxygen vacancy removes up to 71.3 % of NO in 90 min under the illumination of UV light, which was significantly better than other samples. The prepared catalyst was characterized by X-ray diffraction, Raman spectroscopy, UV–vis, XPS, EPR, BET surface area analysis and Photo-electrochemical test. These results showed that oxygen vacancies played an important role in the photocatalytic NO removal process. An appropriate amount of oxygen vacancies in catalyst benefits the aggregation of electrons in oxygen vacancies and a large number of electrons reacted with H2O2 and NO under UV light, thereby the activity enhanced. It was also found through EPR that the number of oxygen vacancies increased with the rise of temperature, which means that the number of oxygen vacancies would affect the catalyst performance.

Insight into the catalytic performance and NH3 adsorption under high concentration of CO2 and/or H2O conditions on selective catalytic reduction of NO by NH3 over V2O5-WO3/TiO2 catalyst

Under various combustion process, CO2 and H2O both would exist in flue gas, the understanding of the influence mechanism of high concentration of CO2 and H2O on V2O5-WO3/TiO2 catalysts can provide needed information for the achievement of ultra-low emission. This study predominantly investigated NH3 adsorption and catalytic performance of V2O5-WO3/TiO2 catalyst under high concentration of CO2 and H2O conditions. Analyses of XRD, NH3-TPD, XPS and DRIFTS were performed to characterize the catalyst properties. Results show that the reaction between NO and NH3 followed E-R mechanism, CO2 and H2O mainly affect NO conversion by influencing the proportion of Oα, proportion of V4+ and NH3 adsorption, which would hardly change the physical and crystalline structure of the catalyst. NH3 adsorption on catalysts is complicated under CO2 and H2O conditions. The net effect of CO2 on NH3 adsorption was negligible, and H2O inhibited NH3 adsorption generally. Although the addition of 25%H2O increased the proportion of Oα on catalyst by forming hydroxy groups, the decreasing of V4+ proportion and NH3 adsorption play dominant roles in NO removal process, resulting in the significantly decrease of NO conversion under H2O-containing atmospheres.

In-situ generation of oxygen vacancies and metallic bismuth from (BiO)2CO3 via N2-assisted thermal-treatment for efficient selective photocatalytic NO removal

In this study, a N2-assisted thermal treatment method is proposed for in-situ formation of a series of oxygen vacancies (OVs)-rich Bi0/Bi-based photocatalysts, including OVs-(BiO)2CO3, Bi0/OVs-(BiO)2CO3, Bi0/OVs-(BiO)2CO3/β-Bi2O3, Bi0/OVs-β-Bi2O3, Bi0/OVs-β-Bi2O3/α-Bi2O3 and Bi0/α-Bi2O3. Mechanisms of in-situ formation of Bi0 nanoparticles and generation of OVs in Bi-based photocatalysts are clarified. Apart from their contribution to the effective separation of photogenerated charge carriers and enhancement of light absorption, the effects of Bi0 nanoparticles and OVs on selective photocatalytic oxidation of NO are also investigated. Among the synthesized Bi-based photocatalysts, Bi0/OVs-(BiO)2CO3 shows the best photocatalytic activity and stability for photo-oxidative removal of NO. The systematic study of photocatalytic mechanism demonstrated that the Ohmic contact between OVs-(BiO)2CO3 and Bi0 gradually promote the formation of •O2– and •OH species. It is found that •O2– plays an important role in the photocatalytic NO removal process, while •OH species can effectively inhibit the formation of NO2 during the NO removal process. The new approach demonstrated in this study can be applied for the in-situ formation of wide-solar-spectrum-responsive photocatalysts with efficient photocatalytic activity.

Catalytic Oxidation of NO on N-doped Carbon Materials at Low Temperature

By hetero atom doping, a nitrogen-doped porous carbon was synthesized and applied to catalytic oxidation removal of NO. The synthesis conditions and NO removal process conditions of the modified carbon material were investigated, including calcination temperatures, impregnation amount, NO inlet concentration (100–500 ppm) and catalytic reaction temperature. The results showed that the dicyandiamide impregnation solution concentration of 0.5 M, and the calcination temperature of 600 °C performed the best in the preparation of structurally stable nitrogen-modified carbon. Due to the formation of a large number active centers of pyridine nitrogen (N-6) groups and graphitic nitrogen (N-Q) groups, the optimal conversion rate of NO could reach 67.2%.

Predictor and optimizer system on selective catalytic reduction of NO in activated carbons based on experiment and computational intelligence technique

PurposeNitrogen oxides (NOx) have been considered as primarily responsible for many serious environmental problems. Removing NO is the key task to remove NOx hazards. To clarify, NO removal process for pitch-based spherical-activated carbons (PSACs), an online prediction and optimization technique in real-time based on support vector machine algorithm in regression (support vector regression [SVR]) is discussed. The purpose of this paper is to develop a predictor and optimizer system on selective catalytic reduction of NO (SCRN) using experimental data and data-driven SVR intelligence methods.Design/methodology/approachPredictor and optimizer using developed SVR have been proposed. To modify the training efficiency of SVR, the authors especially customize batch normalization and k-fold cross-validation techniques according to the unique characteristics of PSACs model.FindingsThe results present that SVR provides a property regression model since it can linkage linear and non-linear process and property relationships in few experimental data sets. Also, the integrated normalization and k-fold cross-validation show a satisfying improvement and results for SVR optimization. The predicted results of predictor and optimizer in single and double factor systems are in excellent agreement with the experimental data.Originality/valueSCRN-PO for predicting and optimization SCRN problems is developed by data-driven methods. The outperformed SCRN-PO system is used to predict multiple-factors property parameters and obtain optimum technological parameters in real-time. Also, experiment duration is greatly shortened.

Removal of NO by Using Sodium Persulfate Solution: Catalyzed by Different Nanostructured MnO2

In this study, MnO2 nanotubes, nanowires, and nanoparticles were synthetized by a hydrothermal method, after which the NO removal process with sodium persulfate solution catalyzed by MnO2 of differ...

Removal and recovery of SO2 and NO in oxy-fuel combustion flue gas by calcium-based slurry

This study investigates the use of calcium-based slurry for simultaneous removal NO and SO2 from oxy-fuel combustion flue gas, and recovery of the sulfur and nitrogen species in resulting solutions. The experiments were performed in a bubbling reactor in a transient mode under the pressure of 20 bar. The various influencing factors including the CaO amount, carrier gas (N2/CO2), and absorption time on the simultaneous NO and SO2 removal process, and the solution products were studied comprehensively. The results show that the NO2 removal efficiency can be improved by the presence of CO2, and the gas phase HNO2 produces in this process. The addition of CaO has positive effects not only on the NO2 removal efficiency but also on the formation of stable HNO3. With the presence of CO2, CaCO3 is formed in a solution initially. With the decrease of pH, CaCO3 is gradually converted to CaSO4, and in particular CaCO3 can be fully avoided through decreasing the pH of an absorption solution to 1.14. At the same time, the formation of unstable S(IV) and NO2- can be prevented when the solution pH is lower than 1.37. The nitrogen and sulfur compounds in the absorption solution (at pH 1.14) were further separated by the addition of different amounts of CaO. In particular, 95% of SO42- finally can be recovered in the form of CaSO4.2H2O with nitrogen in solution existing as NO3- by controlling the Ca/S ratio at 4.70. The effectiveness of calcium-based slurry on the removal and recovery of SO2 and NO is confirmed.

Novel Au/La-Bi5O7I Microspheres with Efficient Visible-Light Photocatalytic Activity for NO Removal: Synergistic Effect of Au Nanoparticles, La Doping, and Oxygen Vacancy.

Sphere-like Bi5O7I (BOI) doped with La (L-BOI) samples were prepared by a solvothermal method followed by calcination at 450 °C for 2 h. Au nanoparticles were loaded on 6% La-doped Bi5O7I (2%A-6%L-BOI) microspheres by a room-temperature chemical reduction method. The UV-vis absorption spectra show that the L-BOI and 2%A-6%L-BOI samples have a strong visible-light absorption in comparison with the pure BOI. The electron paramagnetic resonance results indicate that the number of oxygen vacancies in L-BOI samples is increased with an increasing amount of the La dopant. The band structure of the prepared photocatalysts is investigated by confirming the positions of the valence band (VB) measured by XPS-VB and the Fermi level computed by density functional theory, respectively. NO is selected as a target gaseous pollutant to confirm the influence of La doping and the plasmonic effect of Au nanoparticles on the photocatalytic activity of BOI microspheres. The 2%A-6%L-BOI sample exhibits an enhanced photocatalytic performance compared to BOI, L-BOI, and A-BOI photocatalysts under visible-light irradiation. Interestingly, the 2%A-6%L-BOI sample also can reduce the amount of intermediate NO2 during the NO removal process. The enhanced photocatalytic efficiency of the 2%A-6%L-BOI photocatalyst is profited from the synergy of La-ion doping, oxygen vacancy, and the surface plasmon resonance effect of Au nanoparticles. Based on the results of trapping experiments and electron spin resonance spectroscopy tests, h+, e-, and •O2- were involved in the NO oxidative removal.