Amino-modified molecular sieves for adsorptive removal of H2S from natural gas

Amine-modified MCM-41 adsorbents (APTMS/MCM-41, PEI/MCM-41 and AAPTS/MCM-41) were prepared and characterized by XRD, N₂ adsorption–desorption, FT-IR, TEM, SEM and TG-DTA. The performance of each adsorbent in a fixed adsorption bed for H₂S removal was measured using a mixture of oxygen, nitrogen and hydrogen sulfide gases. It was found that the specific surface area decreased and the topography changed significantly after the use of each modified adsorbent. Nevertheless, all amine-modified MCM-41 adsorbents retained mesoporous silica of MCM-41. The H₂S removal rate and saturated H₂S capacity of APTMS/MCM-41 improved from 32.3% to 54.2% and 119.5 to 134.4 mg g⁻¹, respectively, compared with that of MCM-41, and it showed the best performance among all adsorbents. APTMS/MCM-41, PEI/MCM-41 and AAPTS/MCM-41 were regenerated by maintaining at 423, 523 and 373 K in nitrogen for 3 h, respectively, and thus possessed high regenerability.

Several amine-modified MCM-41 adsorbents (APTMS/MCM-41, PEI/MCM-41, AAPTS/MCM-41) by the grafting method were prepared, in which APTMS/MCM-41 showed much better adsorptive desulfurization performance and regenerability than the others.     

Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40 supported on amine-functionalized MCM-41

Supported catalysts with Keggin type heteropoly acids (H₅PMo₁₀V₂O₄₀) loaded onto amine-functionalized MCM-41 for the catalytic hydroxylation of benzene to phenol with H₂O₂ were prepared by a wet impregnation method. The effects of the preparation conditions on the properties and activity of the supported catalysts were fully investigated. The results showed that the catalyst retained the mesoporous structure of MCM-41 and H₅PMo₁₀V₂O₄₀ was dispersed uniformly on the surface of the amine-functionalized MCM-41. Meanwhile, the reusability and catalytic performance of the catalyst were affected by two key factors, i.e., the interaction between the heteropoly acid and the surface of MCM-41, and the hydrophobicity of the catalyst since they decide the leaching of H₅PMo₁₀V₂O₄₀ and the adsorption of benzene. The catalyst with H₅PMo₁₀V₂O₄₀ loaded onto amine-functionalized MCM-41, which was prepared using ethanol as the solvent, exhibited the highest phenol yield (20.4%), a turnover frequency value of 20.3 h⁻¹ and good reusability. We believe this work offers an effective and facile strategy for the preparation of a new catalyst for hydroxylation of benzene to phenol.

Supported catalysts with heteropoly acid loaded onto amine-functionalized MCM-41 for hydroxylation of benzene to phenol are prepared.     

The effects of Bi2O3 on the selective catalytic reduction of NO by propylene over Co3O4 nanoplates

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂. Their physicochemical properties were analyzed with SEM, XRD, H₂-TPR, XPS, PL and IR measurements. It was found that the deposition of Bi₂O₃ on Co₃O₄ nanoplates enhanced the catalytic activity, especially at low reaction temperature. The SO₂ tolerance of Co₃O₄ in C₃H₆-SCR activity was also improved with the addition of Bi₂O₃. Among all catalysts tested, 10.0 wt% Bi₂O₃/Co₃O₄ achieved a 90% NO conversion at 200 °C with the total flow rate of 200 mL min⁻¹ (GHSV 30 000 h⁻¹). No loss in its C₃H₆-SCR activity was observed at different temperatures after the addition of 100 ppm of SO₂ to the reaction mixture. These enhanced catalytic behaviors may be associated with the improved oxidizing characteristics of 10.0 wt% Bi₂O₃/Co₃O₂. XRD results showed that Bi₂O₃ entered the lattice of Co₃O₄, resulting in the formation of lattice distortion and structural defects. H₂-TPR results showed that the reduction of Co₃O₄ was promoted and the diffusion of oxygen was accelerated with the addition of Bi₂O₃. XPS measurements implied that more Co³⁺ formed on the 10.0% Bi₂O₃/Co₃O₂ catalysts. The improved oxidizing characteristics of the catalyst with the addition of Bi₂O₃ due to the synergistic effect of the nanostructure hybrid, thus enhanced the C₃H₆-SCR reaction and hindered the oxidization of SO₂. Therefore, the 10.0% Bi₂O₃/Co₃O₄ catalyst exhibited the highest NO conversion and strongest SO₂ tolerance ability.

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂.     

Effective solvent-free oxidation of cyclohexene to allylic products with oxygen by mesoporous etched halloysite nanotube supported Co2+

One dimensional mesoporous etched halloysite nanotube supported Co²⁺ is achieved by selective etching of Al₂O₃ from halloysite nanotube (HA) and immersing the etched HA (eHA) into the Co(NO₃)₂·6H₂O solution consecutively. By facilely tuning the etching time and the weight ratio of Co(NO₃)₂·6H₂O to eHA, the morphology, specific surface area and the supported Co²⁺ content of the mesoporous material can be tuned. The method for mesoporous material is scaled up and can be extended to other clay minerals. The mesoporous eHA supported Co²⁺ is used as catalyst for the selective catalytic oxidation of cyclohexene in solvent-free reaction system with O₂ as oxidant. The results shows the catalytic activity is dependent on etching time, weight ratio of Co(NO₃)₂·6H₂O to eHA, calcination treatment and reaction time/temperature. Among them, mesoporous eHA supported Co²⁺ prepared with 18 h etching time and 2 : 1 Co(NO₃)₂·6H₂O/eHA weight ratio without calcination (HA/HCl-18 h/Co²⁺-2 : 1) demonstrates the highest catalytic activity under 75 °C reaction temperature and 18 h reaction time (58.30% conversion and 94.03% selectivity to allylic products). Furthermore, HA/HCl-18 h/Co²⁺-2 : 1 has exhibit superior cycling stability with 37.69% conversion and 92.73% selectivity to allylic products after three cycles.

Mesoporous eHA@Co²⁺ nanorods with effective solvent-free oxidation of cyclohexene to allylic products with O₂ have been successfully fabricated by HCl selective etching of Al₂O₃ from halloysite nanotubes and the impregnation method consecutively.     

Room temperature oxidative desulfurization with MoO3 subnanoclusters supported on MCM-41

Subnano MoO₃/MCM-41 was successfully prepared through doping (NH₄)₆Mo₇O₂₄ in the synthesis process of MCM-41. The morphology of MoO₃/MCM-41 was visually observed by TEM and HADDF-STEM. N₂ sorption, XPS and Raman were further applied to investigate the structure of the material. MoO₃/MCM-41 was used in the oxidative desulfurization process with tert-butyl hydroperoxide as oxidant. MoO₃/MCM-41 showed outstanding catalytic activity and recycling ability at room temperature.

MoO₃ subnanoclusters encapsulated in MCM-41 exhibited enhanced catalytic activity and stability for oxidative desulfurization at room temperature.     

Co3O4 composite nano-fibers doped with Mn4+ prepared by the electro-spinning method and their electrochemical properties

In this work, based on the electrospinning method, pure Co₃O₄, pure MnO₂, and Co₃O₄ composite nano-fiber materials doped with different ratios of Mn⁴⁺ were prepared. XRD, XPS, BET and SEM tests were used to characterize the composition, structure and morphology of the materials. An electrochemical workstation was used to test the electrochemical performance of the materials. The results showed that the material properties had greatly improved on doping Mn⁴⁺ in Co₃O₄ nano-fibers. The relationship between the amount of Mn⁴⁺ doped in the Co₃O₄ composite nano-fiber material and its electrochemical performance was also tested and is discussed in this report. The results show that when n_Co : n_Mn = 20 : 2, the Co₃O₄ composite nano-fiber material had a specific surface area of 68 m² g⁻¹. Under the current density of 1 A g⁻¹, the 20 : 2 sample had the maximum capacitance of 585 F g⁻¹, which was obviously larger than that of pure Co₃O₄ nano-fibers (416 F g⁻¹). After 2000 cycles of charging/discharging, the specific capacitance of the 20 : 2 sample was 85.9%, while that of the pure Co₃O₄ nano-fiber material was only 76.4%. The mechanism of performance improvement in the composite fibers was analyzed, which demonstrated concrete results.

In this work, based on the electrospinning method, pure Co₃O₄, pure MnO₂, and Co₃O₄ composite nano-fiber materials doped with different ratios of Mn⁴⁺ were prepared.     

The synthesis of CoxNi1−xFe2O4/multi-walled carbon nanotube nanocomposites and their photocatalytic performance

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized, where Co_xNi_1−xFe₂O₄ was synthesized via a one-step hydrothermal approach. Simultaneously, methylene blue (MB) was used as the research object to investigate the catalytic effect of the catalyst in the presence of hydrogen peroxide (H₂O₂). The results showed that all the photocatalysts exhibited enhanced catalytic activity compared to pure ferrite. In addition, compared with the other photocatalysts, the reaction time was greatly shortened a significantly higher removal rate was achieved using 3-CNF/MWCNTs. There was no significant decrease in photodegradation efficiency after three catalytic cycles, suggesting that Co_xNi_1−xFe₂O₄/MWCNTs are recyclable photocatalysts for wastewater treatment. Our results indicate that the Co_xNi_1−xFe₂O₄/MWCNT composite can be effectively applied for the removal of organic pollutants as a novel photocatalyst.

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized. The results implied that this composites can be effectively applied for the removal of organic pollutant as novel photocatalysts.     

Self-template formation of porous Co3O4 hollow nanoprisms for non-enzymatic glucose sensing in human serum

A novel type of porous Co₃O₄ hollow nanoprism (HNP) was successfully prepared using tetragonal cobalt acetate hydroxide [Co₅(OH)₂(OAc)₈·2H₂O] as precursor by a facile solvothermal process and a subsequent calcination treatment. The morphology and structure of the Co₃O₄ HNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and N₂ adsorption–desorption measurements. An enzyme-free glucose sensor was constructed based on the Co₃O₄ HNPs, and the electrochemical performance was tested by cyclic voltammetry (CV) and chronoamperometry. The as-prepared sensor exhibited a good electrocatalytic activity for glucose oxidation at the applied potential of 0.6 V in alkaline solution, with a high sensitivity of 19.83 μA mM⁻¹ cm⁻² and a high upper limit of 30 mM, which provide the potential for direct determination of blood glucose without any dilution pretreatment. The Co₃O₄ HNPs had a porous and tubular structure with a large amount of accessible active sites, which enhanced the mass diffusion and accelerated the electron transfer. Moreover, the sensor also demonstrated a desirable stability, selectivity and reproducibility, and could verify the non-enzymatic analysis of glucose in real samples.

Co₃O₄ hollow nanoprisms based non-enzymatic glucose sensor were prepared by a self-template process, exhibiting wide linear range, good selectivity and stability, which can directly monitoring blood glucose without any dilution pretreatment.     

Effect of Pr/Zn on the anti-humidity and acetone-sensing properties of Co3O4 prepared by electrospray

Co₃O₄ is a P-type metal-oxide semiconductor which can realize acetone detection at a lower temperature, but the lower working temperature brings the enhanced humidity effect. In order to solve the problem of a Co₃O₄ gas sensor being easily affected by humidity, an acetone-sensing material of Co₃O₄ mixed with Pr/Zn was prepared by electrospray in this work. The optimal working temperature of Pr/Zn–Co₃O₄ is 160 °C, and the detection limit can reach 1 ppm. The fluctuation of the acetone response is about 7.7% in the relative humidity range of 30–90%. Compared with pure Co₃O₄, the anti-humidity property of this material is obviously enhanced, but the gas-sensing response deteriorates. Compared with Pr–Co₃O₄, the anti-humidity and acetone sensing properties of Pr/Zn–Co₃O₄ were both improved. The morphology, composition, crystal state and energy state of the material were analyzed by SEM, EDS, XRD and XPS. The material of Pr/Zn–Co₃O₄ is a multi-component mixed material composed of PrCoO₃, ZnO, Pr₆O₁₁ and Co₃O₄. The improved anti-humidity and acetone sensing properties exhibited by this material are the result of the synergistic effect of ZnO and Pr³⁺.

With the synergistic effect of Pr and Zn, the material of Co₃O₄ mixed with Pr/Zn exhibits improved properties of anti-humidity and acetone sensitivity.     

Integral structured Co–Mn composite oxides grown on interconnected Ni foam for catalytic toluene oxidation

Considering the three-dimensional ordered network of Ni foam-supported catalysts and the toxicity effects of volatile organic compounds (VOCs), the design of proper active materials for the highly efficient elimination of VOCs is of vital importance in the environmental field. In this study, a series of Co–Mn composite oxides with different Co/Mn molar ratios grown on interconnected Ni foam are prepared as monolithic catalysts for total toluene oxidation, in which Co_1.5Mn_1.5O₄ with a molar ratio of 1 : 1 achieves the highest catalytic activity with complete toluene oxidation at 270 °C. The Co–Mn monolithic catalysts are characterized by XRD, SEM, TEM, H₂-TPR and XPS. It is observed that a moderate ratio of Mn/Co plays significant effects on the textural properties and catalytic activities. From the XPS and H₂-TPR characterization results, the obtained Co_1.5Mn_1.5O₄ (Co/Mn = 1/1) favors the excellent low-temperature reducibility, high concentration of surface Mn³⁺ and Co³⁺ species, and rich surface oxygen vacancies, resulting in superior oxidation performance due to the formation of a solid solution between the Co and Mn species. It is deduced that the existence of the synergistic effect between Co and Mn species results in a redox reaction: Co³⁺–Mn³⁺ ↔ Co²⁺–Mn⁴⁺, and enhances the catalytic activity for total toluene oxidation.

A series of Co–Mn oxides with different Co/Mn molar ratios grown on interconnected Ni foam were prepared as monolithic catalysts for total toluene oxidation.     

Effect of Ni/Co mass ratio and NiO–Co3O4 loading on catalytic performance of NiO–Co3O4/Nb2O5–TiO2 for direct synthesis of 2-propylheptanol from n-valeraldehyde

In the direct synthesis of 2-propylheptanol (2-PH) from n-valeraldehyde, a second-metal oxide component Co₃O₄ was introduced into NiO/Nb₂O₅–TiO₂ catalyst to assist in the reduction of NiO. In order to optimize the catalytic performance of NiO–Co₃O₄/Nb₂O₅–TiO₂ catalyst, the effects of the Ni/Co mass ratio and NiO–Co₃O₄ loading were investigated. A series of NiO–Co₃O₄/Nb₂O₅–TiO₂ catalysts with different Ni/Co mass ratios were prepared by the co-precipitation method and their catalytic performances were evaluated. The result showed that NiO–Co₃O₄/Nb₂O₅–TiO₂ with a Ni/Co mass ratio of 8/3 demonstrated the best catalytic performance because the number of d-band holes in this catalyst was nearly equal to the number of electrons transferred in hydrogenation reaction. Subsequently, the NiO–Co₃O₄/Nb₂O₅–TiO₂ catalysts with different Ni/Co mass ratios were characterized by XRD and XPS and the results indicated that both an interaction of Ni with Co and formation of a Ni–Co alloy were the main reasons for the reduction of NiO–Co₃O₄/Nb₂O₅–TiO₂ catalyst in the reaction process. A higher NiO–Co₃O₄ loading could increase the catalytic activity but too high a loading resulted in incomplete reduction of NiO–Co₃O₄ in the reaction process. Thus the NiO–Co₃O₄/Nb₂O₅–TiO₂ catalyst with a Ni/Co mass ratio of 8/3 and a NiO–Co₃O₄ loading of 14 wt% showed the best catalytic performance; a 2-PH selectivity of 80.4% was achieved with complete conversion of n-valeraldehyde. Furthermore, the NiO–Co₃O₄/Nb₂O₅–TiO₂ catalyst showed good stability. This was ascribed to the interaction of Ni with Co, the formation of the Ni–Co alloy and further reservation of both in the process of reuse.

NiO–Co₃O₄/Nb₂O₅–TiO₂ catalyst with a Ni/Co mass ratio of 8/3 and NiO–Co₃O₄ loading of 14% shows the best catalytic performance.     

Mn-based catalysts supported on γ-Al2O3, TiO2 and MCM-41: a comparison for low-temperature NO oxidation with low ratio of O3/NO

Mn-Based catalysts supported on γ-Al₂O₃, TiO₂ and MCM-41 synthesized by an impregnation method were compared to evaluate their NO catalytic oxidation performance with low ratio O₃/NO at low temperature (80–200 °C). Activity tests showed that the participation of O₃ remarkably promoted the NO oxidation. The catalytic oxidation performance of the three catalysts decreased in the following order: Mn/γ-Al₂O₃ > Mn/TiO₂ > Mn/MCM-41, indicating that Mn/γ-Al₂O₃ exhibited the best catalytic activity. In addition, there was a clear synergistic effect between Mn/γ-Al₂O₃ and O₃, followed by Mn/TiO₂ and O₃. The characterization results of XRD, EDS mapping, BET, H₂-TPR, XPS and TG showed that Mn/γ-Al₂O₃ had good manganese dispersion, excellent redox properties, appropriate amounts of coexisting Mn³⁺ and Mn⁴⁺ and abundant chemically adsorbed oxygen, which ensured its good performance. In situ DRIFTS demonstrated the NO adsorption performance on the catalyst surface. As revealed by in situ DRIFTS experiments, the chemically adsorbed oxygen, mainly from the decomposition of O₃, greatly promoted the NO adsorption and the formation of nitrates. The Mn-based catalysts showed stronger adsorption strength than the corresponding pure supports. Due to the abundant adsorption sites provided by pure γ-Al₂O₃, under the interaction of Mn and γ-Al₂O₃, the Mn/γ-Al₂O₃ catalyst exhibited the strongest NO adsorption performance among the three catalysts and produced lots of monodentate nitrates (–O–NO₂) and bidentate nitrates (–O₂NO), which were the vital intermediate species for NO₂ formation. Moreover, the NO–TPD studies also demonstrated that Mn/γ-Al₂O₃ showed the best NO desorption performance among the three catalysts. The good NO adsorption and desorption characteristics of Mn/γ-Al₂O₃ improved its high catalytic activity. In addition, the activity test results also suggested that Mn/γ-Al₂O₃ exhibited good SO₂ tolerance.

The Mn/γ-Al₂O₃ catalyst exhibited excellent performance for NO conversion in the presence of a low ratio of O₃/NO, which was due to the coexistence of Mn³⁺ and Mn⁴⁺ and abundant chemically adsorbed oxygen.     

Sm2O3/Co3O4 catalysts prepared by dealloying for low-temperature CO oxidation

A series of Co₃O₄ catalysts modified by Sm were prepared by a combined dealloying and calcination approach, and the catalytic activities were evaluated using CO catalytic oxidation. The Sm₂O₃/Co₃O₄ catalysts were composed of a large number of nanorods and nanosheets, and exhibited a three-dimensional supporting structure with pores. The experimental results revealed that the addition of a small amount of Sm into the precursor AlCo alloy led to a dealloyed sample with improved catalytic activity, and the dealloyed Al₉₀Co_9.5Sm_0.5 ribbons (0.5 Sm₂O₃/Co₃O₄) calcined at 300 °C showed the highest activity for CO oxidation with complete CO conversion at 135 °C, moreover, CO conversion almost no attenuation, even after 70 hours of catalytic oxidation, which is superior to that of Co₃O₄. The enhanced catalytic activity of the Sm₂O₃/Co₃O₄ catalyst can be attributed to the large specific surface area, more reactive oxygen species and Co³⁺ ion, as well as electronic interactions between Sm and Co.

A series of Co₃O₄ catalysts modified by Sm were prepared by a combined dealloying and calcination approach, and the catalytic activities were evaluated using CO catalytic oxidation.     

Combustion of lean methane over Co3O4 catalysts prepared with different cobalt precursors

To investigate the effect of catalyst precursors on physicochemical properties and activity of lean methane catalytic combustion, a series of Co₃O₄ catalysts were prepared via a precipitation method by using four different cobalt precursors: Co(C₂H₃O₂)₂, Co(NO₃)₂, CoCl₂, and CoSO₄. The catalysts were characterized by BET, XRD, SEM, Raman, XPS, XRF, O₂-TPD and H₂-TPR techniques. It was found that the different types of cobalt precursor had remarkable effects on the surface area, particle size, reducibility and catalytic performance. In contrast, the Co₃O₄-Ac catalyst showed a relatively small surface area, but its activity and stability were the highest. XPS, Raman, O₂-TPD and H₂-TPR results demonstrated that the superior catalytic performance of Co₃O₄-Ac was associated with its higher Co²⁺ concentration, more surface active oxygen species and better reducibility. In addition, the activity of the Co₃O₄-S catalyst reduced significantly due to the residual impurity SO₄²⁻, which could reduce the concentration of surface adsorbed active oxygen species and inhibit oxygen migration.

The effects of cobalt precursor on the microstructure, surface properties, reducibility and catalytic performance for methane combustion were investigated.     

Novel mesoporous Co3O4–Sb2O3–SnO2 active material in high-performance capacitive deionization

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes. However, this technique still requires further development of the electrode materials to tackle the ion removal capacity/rate issues. In the present work, we introduce a novel active carbon (AC)/Co₃O₄–Sb₂O₃–SnO₂ active material for hybrid electrode capacitive deionization (HECDI) systems. The structure and morphology of the developed electrodes were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET)/Barrett–Joyner–Halenda (BJH) techniques, as well as Fourier-transform infrared (FT-IR) spectroscopy. The electrochemical properties were also investigated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The CDI active materials AC/Co₃O₄ and AC/Co₃O₄–Sb₂O₃–SnO₂ showed a high specific capacity of 96 and 124 F g⁻¹ at the scan rate of 10 mV s⁻¹, respectively. In addition, the newly-developed electrode AC/Co₃O₄–Sb₂O₃–SnO₂ showed high capacity retention of 97.2% after 2000 cycles at 100 mV s⁻¹. Moreover, the electrode displayed excellent CDI performance with an ion removal capacity of 52 mg g⁻¹ at the applied voltage of 1.6 V and in a solution of potable water with initial electrical conductivity of 950 μs cm⁻¹. The electrode displayed a high ion removal rate of 7.1 mg g⁻¹ min⁻¹ with an excellent desalination–regeneration capability while retaining about 99.5% of its ion removal capacity even after 100 CDI cycles.

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes.     

Removal of reactive brilliant red X-3B by a weak magnetic field enhanced Fenton-like system with zero-valent iron

The effect of a weak magnetic field (WMF) on the removal of reactive brilliant red X-3B (X-3B) by zero-valent iron (ZVI)/H₂O₂ was studied. The optimum conditions for the removal of X-3B by the ZVI/H₂O₂/WMF system were as follows: pH = 4.0, X-3B was 50 mg L⁻¹, H₂O₂ was 8 mM, and ZVI with particle size of 20 μm was 0.5 g L⁻¹. The X-3B decolorization rate could reach 99.41% in 10 minutes. The superposed WMF increased the working pH of ZVI from 3.0 to 4.0. The main part of ZVI/H₂O₂ removal kinetics of X-3B followed the zero order rate law. In this study, the removal effect of X-3B by pre-magnetization ZVI was not as good as that of real-time magnetization, but it was better than the removal of X-3B by the ZVI/H₂O₂ system. The ZVI/H₂O₂/WMF system still had the ability to remove X-3B after 4 consecutive cycles. The use of WMF improved the removal of X-3B by ZVI/H₂O₂ mainly due to the corrosion of ZVI. Under acidic conditions, WMF enhanced the activity of ZVI, which promoted the efficiency of the Fenton reaction. The use of WMF to enhance the ZVI/H₂O₂ removal X-3B was a promising and environmental friendly process because it did not require additional energy and expensive reagents and did not cause secondary pollution.

The effect of a weak magnetic field (WMF) on the removal of reactive brilliant red X-3B (X-3B) by zero-valent iron (ZVI)/H₂O₂ was studied.     

Performance of gamma-Al2O3 decorated with potassium salts in the removal of CS2 from C5 cracked distillate

Deep desulfurization is a key process for the production of high value-added products from C₅ distillates. In this work, different potassium salt modified gamma-Al₂O₃ adsorbents were prepared by an incipient-wetness impregnation method and characterized by N₂ adsorption–desorption, SEM-EDS, TEM, CO₂-TPD, XRD, FT-IR, and IC. The C₅ distillate with a 1200 μg mL⁻¹ sulfur content is desulfurized to less than 10 μg mL⁻¹ within 24 hours by the static adsorption method. For the desulfurization in the fix-bed reactor, the breakthrough sulfur capacity of K₂CO₃-decorated gamma-Al₂O₃ reaches 0.76 wt% under the optimized conditions, viz., at 30 °C, with a sulfur content of 50 μg mL⁻¹ in the raw oil, and a liquid hourly space velocity of 1 h⁻¹. The desulfurization activity of the exhausted adsorbent can be recovered after regeneration. Selective adsorption of CS₂ includes three processes: adsorption, hydrolysis, and oxidation. CS₂ is first adsorbed on the adsorbent and hydrolyzed to form H₂S. H₂S is further oxidized to form S/SO₄²⁻, and then deposits on the surface of the adsorbent. Adsorption, hydrolysis, and oxidation all play essential roles in the removal process of CS₂.

Deep desulfurization is a key process for the production of high value-added products from C₅ distillates.     

Efficient removal of chromate ions from aqueous solution using a highly cost-effective ferric coordinated [3-(2-aminoethylamino)propyl]trimethoxysilane–MCM-41 adsorbent

The present investigation involves synthesis and characterization of MCM-41–AEAPTMS–Fe(iii)Cl using coordinated Fe(iii) on MCM-41–AEAPTMS for efficient removal of hazardous Cr(vi) ions from aqueous solution. The adsorbent MCM-41–AEAPTMS–Fe(iii)Cl was characterized using small-angle X-ray diffraction (SAX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared (FT-IR) and Brunauer–Emmett–Teller (BET) surface analyzer techniques. The BET surface area was found to be 87.598 m² g⁻¹. The MCM-41–AEAPTMS–Fe(iii)Cl effectively adsorbs Cr(vi) with an adsorption capacity acquiring the maximum value of 84.9 mg g⁻¹ at pH 3 at 298 K. The data followed pseudo-second-order kinetics and obeyed the Langmuir isotherm model. The thermodynamic data proved the exothermic and spontaneous nature of Cr(vi) ion adsorption on MCM-41–AEAPTMS–Fe(iii). Further, the higher value of ΔH° (−64.339 kJ mol⁻¹) indicated that the adsorption was chemisorption in nature.

The present investigation involves synthesis and characterization of MCM-41–AEAPTMS–Fe(iii)Cl using coordinated Fe(iii) on MCM-41–AEAPTMS for efficient removal of hazardous Cr(vi) ions from aqueous solution.     

Co3O4–Ag photocatalysts for the efficient degradation of methyl orange

In this paper, a series of Co₃O₄–Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co₃O₄ catalyst, the Co₃O₄–Ag catalysts showed better activity; among these, the Co₃O₄–Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co₃O₄–Ag-0.3 was 2.72 times higher than that of Co₃O₄ under identical reaction conditions. The excellent photocatalytic activity of Co₃O₄–Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co₃O₄–Ag photocatalysts was proposed and explained.

A novel Co₃O₄–Ag catalyst covered on the Ni foam substrate was synthesized via facile hydrothermal and in situ photoreduction methods for the efficient degradation of methyl orange.     

Solution combustion derived oxygen vacancy-rich Co3O4 catalysts for catalytic formaldehyde oxidation at room temperature

Fabricating abundant oxygen vacancies is crucial for non-noble metal oxides to catalyze formaldehyde (HCHO) oxidation at room temperature. Here, a simple one-pot preparation method via solution combustion was found to produce oxygen vacancy-rich Co₃O₄ catalysts, avoiding delicate defect engineering. The catalyst was evaluated to result in 52% HCHO conversion in a dynamic flow reaction with ∼6 ppm HCHO, which was higher as compared to some other Co₃O₄ catalysts prepared in three methods of sol–gel, deposition precipitation and thermal decomposition. The optimal catalyst also exhibited high durability with steady HCHO conversion (∼47%) for more than 50 h. The catalyst characterizations revealed that the explosive solution combustion brought out two particular features of Co₃O₄, namely, the porous network structure with nano-holes and the abundant oxygen vacancies. The latter was demonstrated to increase the reactive oxygen species and to improve the reducibility and the oxygen transport capacity of Co₃O₄. The two features and the derived properties are beneficial to the activity and durability of Co₃O₄. The solution combustion method can serve as a simple and feasible way to fabricate abundant oxygen vacancies to provide room-temperature activity of Co₃O₄ for HCHO elimination at room temperature.

The rich oxygen vacancies in porous Co₃O₄ were generated in solution combustion, offering high room-temperature activity for formaldehyde oxidation.