Influence of Surface Basic sites and Oxygen Vacancies on the Performance of Metal-Modified Rod-Like Ceria Catalysts for Low-Temperature Hydrolysis of Carbonyl Sulfide.

This study utilized a hydrothermal method to synthesize various metal-modified rod-like ceria catalysts (Fe, Co, Cu, Ni, La), achieving efficient COS removal at low temperatures. The research identified surface oxygen vacancies and basic sites as critical factors that influence the catalytic performance of COS hydrolysis. The addition of different metals to pristine ceria rods increased the specific surface area, oxygen vacancy content (Ov), and basicity, which enhanced the catalysts' sulfur resistance and stability. Among all the catalysts tested, 10La-CeO2 demonstrated the highest COS removal rate. This is because La doping significantly augmented Ov, providing more H2O adsorption and activation sites. Furthermore, 10La-CeO2 showed enhanced Lewis basicity, making it easier for COS to adsorb and promote hydrolysis. The in situ DRIFTS results confirmed that appropriate oxygen vacancies and basic sites favored the formation of intermediates such as HCO3- and HSCO2-, promoting the decomposition of COS into H2S and CO2.

Structural/surface characterization of transition metal element-doped H-ZSM-5 adsorbent for CH3SH removal: identification of active adsorption sites and deactivation mechanism.

CH3SH is a potential hazard to both chemical production and human health, so controlling its emissions is an urgent priority. In this work, a series of transition metal-loaded H-ZSM-5 adsorbents (Si/Al = 25) (Cu, Fe, Co, Ni, Mn, and Zn) were synthesized through the wet impregnation method and tested for CH3SH physicochemical adsorption at 60 °C. It was shown that the Cu-modified H-ZSM-5 adsorbent was much more active for CH3SH removal due to its abundant strong acid sites than other transition metal-modified H-ZSM-5 adsorbents. The detailed physicochemical properties of various modified H-ZSM-5 adsorbents were characterized by SEM, XRD, N2 physisorption, XPS, H2-TPR, and NH3-TPD. The effects of metal loading mass ratio, calcination temperature, and acid or alkali modification on the performance of the adsorbent were also investigated, and finally 20% Cu/ZSM-5 was found to have the best adsorption capacity after calcined at 350 °C. Additionally, the Cu/ZSM-5 adsorbent modified by sodium bicarbonate could expose more active components, which improved the adsorbent's stability. However, the consumption and reduction of the active component Cu2+ and the accumulation of sulfate during the adsorption process are the main reasons for the deactivation of the adsorbent. In addition, the simultaneous purging of N2 + O2 can effectively restore the adsorption capacity of the deactivated adsorbent and can be used as a potential strategy to regenerate the adsorbent.

Cu/Biochar Bifunctional Catalytic Removal of COS and H2S:H2O Dissociation and CuO Anchoring Enhanced by Pyridine N.

Economic and environmentally friendly strategies are needed to promote the bifunctional catalytic removal of carbonyl sulfide (COS) by hydrolysis and hydrogen sulfide (H2S) by oxidation. N doping is considered to be an effective strategy, but the essential and intrinsic role of N dopants in catalysts is still not well understood. Herein, the conjugation of urea and biochar during Cu/biochar annealing produced pyridine N, which increased the combined COS/H2S capacity of the catalyst from 260.7 to 374.8 mg·g-1 and enhanced the turnover frequency of H2S from 2.50 × 10-4 to 5.35 × 10-4 s-1. The nucleophilic nature of pyridine N enhances the moderate basic sites of the catalyst, enabling the attack of protons and strong H2O dissociation. Moreover, pyridine N also forms cavity sites that anchor CuO, improving Cu dispersion and generating more reactive oxygen species. By providing original insight into the pyridine N-induced bifunctional catalytic removal of COS/H2S in a slightly oxygenated and humid atmosphere, this study offers valuable guidance for further C═S and C-S bond-breaking in the degradation of sulfur-containing pollutants.

Defect-Confinement Strategy for Constructing CuO Clusters on Carbon Nanotubes for Catalytic Oxidation of AsH3 at Room Temperature.

The efficient removal of the highly toxic arsine gas (AsH3) from industrial tail gases under mild conditions remains a formidable challenge. In this study, we utilized the confinement effect of defective carbon nanotubes to fabricate a CuO cluster catalyst (CuO/ACNT), which exhibited a capacity much higher than that of CuO supported on pristine multiwalled carbon nanotubes (MWCNT) (CuO/PCNT) for catalytically oxidizing AsH3 under ambient conditions. The experimental and theoretical results show that nitric acid steam treatment could induce MWCNT surface structural defects, which facilitated more stable anchoring of CuO and then improved the oxygen activation ability, therefore leading to excellent catalytic performance. Density functional theory (DFT) calculations revealed that the catalytic oxidation of AsH3 proceeded through stepwise dehydrogenation and subsequent recombination with oxygen to form As2O3 as the final product.

In situ formation of red/black phosphorus-modified SiO2@g-C3N4 multi-heterojunction for the enhanced photocatalytic degradation of organic contaminants.

A new heterojunction material BP/RP-g-C3N4/SiO2 was obtained by a one-step ball milling method, and its photocatalytic capacity was researched by the degradation of Rhodamine B (RhB) and ofloxacin (OFL) in simulated sunlight. The construction of an in situ BP/RP heterojunction can achieve perfect interface contact between different semiconductors and effectively promote the separation of photogenerated carriers. The composite material was well characterized, which proved that the multi-heterogeneous structure was prepared. Furthermore, the type II heterojunction was formed between the g-C3N4 and BP/RP interface, playing an important role in the degradation and promoting electron transfer. The degradation effect of BP/RP-g-C3N4/SiO2 on RhB reached 90% after 26 min of simulated solar irradiation, which was 1.8 times that of g-C3N4/SiO2. The degradation of OFL by BP/RP-g-C3N4/SiO2 reached 85.3% after illumination for 50 min, while the degradation of g-C3N4/SiO2 was only 35.4%. The mechanisms were further discussed, and ˙O2 - and h+ were found to be the main active substances to degrade RhB. The catalyst also revealed distinguished stability of catalyst and recyclability, and the degradation effect of RhB can still realize 85% after 4 runs of experiment. Thus, this study provided a novel method for the design and preparation of multi-heterojunction catalysts in the removal of organic pollutants from wastewater.

Catalytic Decomposition Mechanism of PH3 on 3DCuO/C and High Value Utilization of Deactivated Catalysts.

With the widespread application of lithium iron phosphate batteries, the production capacity of the yellow phosphorus industry has increased sharply, and the treatment of the highly toxic by-product PH3 is facing severe challenges. In this study, a 3D copper-based catalyst (3DCuO/C) that can efficiently decompose PH3 at low temperatures and low oxygen concentrations is synthesized. The PH3 capacity is up to 181.41 mg g-1 , which is superior to that previously reported in the literature. Further studies indicated that the special 3D structure of 3DCuO/C induces oxygen vacancies on the surface of CuO, which is beneficial to the activation of O2 , and then promotes the adsorption and dissociation of PH3 . The doping of P after dissociation determines the formation of Cu-P, and the eventual conversion to Cu3 P leads to the deactivation of CuO active sites. More strikingly, due to the appearance of Cu3 P, the deactivated De-3DCuO/C (Cu3 P/C) exhibited significant activity in the photocatalytic degradation of rhodamine B and photocatalytic oxidation of Hg0 (gas) and can also be a candidate as an anode material for Li batteries after modification, which will provide a more thorough and economical treatment scheme for deactivated catalysts.

Catalysts for gaseous organic sulfur removal.

Organic sulfur gases (COS, CS2 and CH3SH) are widely present in reducing industrial off-gases, and these substances pose difficulties for the recovery of carbon monoxide and other gases. The reaction pathways and reaction mechanisms of organic sulfur on different catalyst surfaces have yet to be fully summarized. The literature shows that many factors, such as catalyst synthesis method, loaded metal composition, number of surface hydroxyl groups, number of acid-base sites and methods of surface modification, have important effects on the catalytic performance of metal catalysts. Therefore, this paper presents a comprehensive review of the research on the application of catalysts such as zeolites, metal oxides, carbon-based materials, and hydrotalcite-like derivatives in the field of organic sulfur removal. Future research prospects are summarized, more in situ characterization experiments and theoretical calculations are needed for the catalytic decomposition of methanethiol to analyze the coke generation pathways at the microscopic level, while the simultaneous removal of multiple organic sulfur gases needs to be focused on. Based on previous catalyst research, we propose possible innovations in catalyst design, desulfurization technology and organic sulfur resource utilization technology.

Cu/ACF adsorbent modified by non-thermal plasma for simultaneous adsorption-oxidation of H2S and PH3.

Non-thermal plasma (NTP) surface modification technology is a new method to control the surface properties of materials, which has been widely used in the field of environmental protection because of its short action time, simple process and no pollution. In this study, Cu/ACF (activated carbon fiber loaded with copper) adsorbent was modified with NTP to remove H2S and PH3 simultaneously under low temperature and micro-oxygen condition. Meanwhile, the effects of different modified atmosphere (air, N2 and NH3), specific energy input (0-13 J/mL) and modification time (0-30 min) on the removal of H2S and PH3 were investigated. Performance test results indicated that under the same reaction conditions, the adsorbent modified by NH3 plasma with 5 J/mL for 10 min had the best removal effect on H2S and PH3. CO2 temperature-programmed desorption and X-ray photoelectron spectroscopy (XPS) analyzes showed that NH3 plasma modification could introduce amino functional groups on the surface of the adsorbent, and increase the types and number of alkaline sites on the surface. Brunauer-Emmett-Teller and scanning electron microscopy showed that NH3 plasma modification did not significantly change the pore size structure of the adsorbent, but more active components were evenly exposed to the surface, thus improving the adsorption performance. In addition, X-ray diffraction and XPS analysis indicated that the consumption of active components (Cu and Cu2O) and the accumulation of sulfate and phosphate on the surface and inner pores of the adsorbent are the main reasons for the deactivation of the adsorbent.

Developing a QSPR Model of Organic Carbon Normalized Sorption Coefficients of Perfluorinated and Polyfluoroalkyl Substances.

Perfluorinated and polyfluoroalkyl substances (PFASs) are known for their long-distance migration, bioaccumulation, and toxicity. The transport of PFASs in the environment has been a source of increasing concerned. The organic carbon normalized sorption coefficient (Koc) is an important parameter from which to understand the distribution behavior of organic matter between solid and liquid phases. Currently, the theoretical prediction research on log Koc of PFASs is extremely limited. The existing models have limitations such as restricted application fields and unsatisfactory prediction results for some substances. In this study, a quantitative structure-property relationship (QSPR) model was established to predict the log Koc of PFASs, and the potential mechanism affecting the distribution of PFASs between two phases from the perspective of molecular structure was analyzed. The developed model had sufficient goodness of fit and robustness, satisfying the model application requirements. The molecular weight (MW) related to the hydrophobicity of the compound; lowest unoccupied molecular orbital energy (ELUMO) and maximum average local ionization energy on the molecular surface (ALIEmax), both related to electrostatic properties; and the dipole moment (µ), related to the polarity of the compound; are the key structural variables that affect the distribution behavior of PFASs. This study carried out a standardized modeling process, and the model dataset covered a comprehensive variety of PFASs. The model can be used to predict the log Koc of conventional and emerging PFASs effectively, filling the data gap of the log Koc of uncommon PFASs. The explanation of the mechanism of the model has proven to be of great value for understanding the distribution behavior and migration trends of PFASs between sediment/soil and water, and for estimating the potential environmental risks generated by PFASs.

Investigation of the Role of Copper Species-Modified Active Carbon by Low-Temperature Roasting on the Improvement of Arsine Adsorption.

Traditional adsorbents undershot the expectations for arsine (AsH3) removal under low-temperature operation conditions in the industry. In this study, the copper (Cu) precursor was used to modify activated carbon and yield novel adsorbents by low-temperature roasting for high-efficiency removal of AsH3. The best conditions were determined as impregnation with 2 mol/L Cu(NO3)2 adsorbent and roasting at 180 °C. At a reaction temperature of 40 °C and an oxygen content of 1%, the AsH3 removal efficiency reached over 90% and lasted for 40 h and the best capacity of 369.6 mg/g was obtained with the Cu/Ac adsorbent. The characterization results showed the decomposition of Cu(NO3)2 during the low-temperature roasting process to form surface functional groups. The formation of the important intermediate Cu2(NO3)(OH)3 in the decomposition of Cu(NO3)2 into CuO plays a role in the good regeneration performance of the Cu/Ac adsorbent using water washing and the gas regeneration method. The results of in situ diffuse reflectance infrared Fourier transform spectroscopy combined with X-ray photoelectron spectroscopy demonstrated that the interaction of trace oxygen with Lewis (L) acid sites increased chemisorbed oxygen by 17.34%, significantly promoting the spontaneity of AsH3 oxidation reaction. These results provide a friendly economic method with industrial processes practical for AsH3 removal.

Cubic structured SrTiO3 with Ce/Cr Co-doping for photoinduced catalytic oxidation of gaseous mercury.

A cubic SrTiO3 (STO) composite material co-doped with Ce and Cr ions was synthesized by solvothermal method. The fully characterized samples were employed as photocatalysts for the oxidation of Hg0. The co-doped samples afforded excellent catalytic removal efficiency of 98.99% using UV irradiation and 89.9% using visible light irradiation for Hg0 compared with the single-doped samples. It was found that co-doped samples had a lower electron-hole recombination rate, largest Brunauer-Emmett-Teller specific surface area, and reduced band gap. The electron spin resonance results revealed that ·O2- and ·OH were the main active species in the catalytic process. Moreover, the co-doped samples exhibited the best electron transfer rate and the highest photocurrent response intensity. The electron transfer between the elements in the co-doped sample enables it to achieve stable and efficient catalytic performance. In addition, even after five consecutive catalytic runs, the co-doped sample maintained high catalytic activity. This work highlights the potential of the perovskite-type STO materials in the photocatalytic oxidation of gaseous mercury.

Theoretical study on simultaneous removal of SO2, NO, and Hg0 over graphene: competitive adsorption and adsorption type change.

In this work, the influence of competitive adsorption and the change of charge transfer for simultaneous adsorption removal of SO2, NO, and Hg0 over graphene were investigated using density functional theory method. The results showed that all the adsorptive effect of SO2, NO, and Hg0 were caused by physical interaction. The adsorptive energy of SO2 was the highest, and the adsorptive energy of Hg0 was the lowest. SO2 could be preferentially adsorbed and removed. NO/SO2 and Hg0 had the mutual promotion effect for simultaneous adsorption over graphene surface. SO2 and NO had the mutual inhibition effect for simultaneous adsorption over graphene surface. Compared with single molecular adsorption, the adsorption type of bi-molecular adsorption did not change. However, the simultaneous adsorption changed the adsorption type of Hg0 + SO2 + NO to chemical adsorption due to the interaction among Hg0, SO2, and NO. As such, this study provides a theoretical insight for future application and development. Graphical abstractNO/SO2 and Hg0 had the mutual promotion effect for simultaneous adsorption. SO2 and NO had the mutual inhibition effect for simultaneous adsorption.

Removal of low-concentration thiophene by DC corona discharge plasma.

This study focuses on the removal of C4H4S using DC corona discharge plasma. The influences of various factors such as C4H4S concentration (ppm), temperature (°C), O2 concentration (%), and dust concentration (mg/m3) on the conversion of C4H4S were studied. Furthermore, gaseous compositions were determined using Fourier transform infrared (FTIR) spectroscopy. Solid products, which were collected from earth and discharge electrodes, were analyzed using X-ray diffraction (XRD). The results showed that, under the condition of DC corona discharge plasma, C4H4S converted to CO, CO2, S, SO2, and SO42-, and that the conversion rate increased with the increase in specific input energy (SIE). The increase of O2 concentration led to further energy consumption that generated O3, which in turn decreased the conversion rate of C4H4S. The increase in temperature exhibited a positive influence on the conversion of C4H4S when the SIE was less than 268 J/L. However, above this value of SIE, the temperature affected the conversion of C4H4S negatively with the increase in SIE. When dust was introduced, the conversion of C4H4S was significantly improved and the yield of SO2 reduced due to the reaction which took place among C4H4S, SO2 and dust in the electric field. The results showed that the DC corona discharge plasma exhibited considerable potential to remove C4H4S, while dust contributed positively towards the disposal of C4H4S. Graphical abstract In this work, DC corona plasma was used to remove thiophene (C4H4S) from a dust-containing gas stream. The results showed that electron collision, oxidizability of radicals, and existence of O3 were the main causes of C4H4S decomposition. The electron collision effects, contents of radicals, O3, and the conversion rate of C4H4S were enhanced with the increase in SIE (specific input energy). The main products consisted of CO, CO2, SO2, and solid products. The solid products and dust moved to the earth electrode in the electric field.

Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulphide.

A tubular resistance furnace was used as a reactor to simulate mercury and arsenic in smelter flue gases by heating mercury and arsenic compounds. The flue gas containing Hg(2+), Hg(0) and As was treated with ammonium sulphide. The experiment was conducted to investigate the effects of varying the concentration of ammonium sulphide, the pH value of ammonium sulphide, the temperature of ammonium sulphide, the presence of SO2 and the presence of sulphite ion on removal efficiency. The prepared adsorption products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The results showed that the optimal concentration of ammonium sulphide was 0.8 mol/L. The optimal pH value of ammonium sulphide was 10, and the optimal temperature of ammonium sulphide was 20°C.Under the optimum conditions, the removal efficiency of Hg(2+), Hg(0) and As could reach 99%, 88.8%, 98%, respectively. In addition, SO2 and sulphite ion could reduce the removal efficiency of mercury and arsenic from simulated flue gas.