Relationship between the structure of Fe-MCM-48 and its activity in catalytic ozonation for diclofenac mineralization

TS-1@MCM-48 Core-Shell Catalysts for Efficient Oxidation of p-Diethylbenzene to High Value-Added Derivatives

To expand the market capacity of p-diethylbenzene (PDEB), core-shell zeolite (TS-1@MCM-48) is designed as a catalyst for PDEB oxidation. TS-1@MCM-48 catalyst is synthesized by in-situ crystallization method and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, in-situ electron paramagnetic resonance (EPR) and 29Si nuclear magnetic resonance (29Si MAS-NMR). Oxidation of PDEB by H2O2 was investigated systematically in liquid phase. The conversion of PDEB over TS-1@MCM-48 was 28.1 % and the total selectivity was 72.6 %, where the selectivity of EAP (p-ethylacetophenone) and EPEA (4-ethyl-α-methylbenzyl alcohol) was 28.6 % and 44.0 %, respectively. Compared with TS-1 and MCM-48 zeolite, the conversion rate of reactants and the selectivity of products have been significantly improved. The catalytic performance of TS-1@MCM-48 is derived from its well-crystallized microporous core and mesoporous shell with regular channels, which make active sites of TS-1 zeolite in the catalyst be fully utilized and mass transfer resistance be largely reduced. Further through theoretical calculation, we propose that the oxidation of PDEB is the result of the combination and mutual transformation of free radical process and carbocation process. Core-shell structure ensures the conversion rate of raw materials and improves the selectivity of products.

Streamlined synthesis of iron and cobalt loaded MCM-48: High-performance heterogeneous catalysts for selective liquid-phase oxidation of toluene to benzaldehyde

Hydrothermal synthesis of MCM-48 molecular sieves featuring the incorporation of both iron and cobalt with Si/M ratios of 20, 40 and 80 (where M represents either iron or cobalt) was performed using tetraethyl orthosilicate as the silica source and cetyltrimethylammonium bromide as a template. To gain a comprehensive understanding of the synthesized materials, these were thoroughly characterized using various techniques, including XRD, XPS, UV-Vis (DRS), FT-IR, N2 adsorption-desorption analysis, SEM with EDX, TEM, TGA and NH3-TPD analysis. XRD analysis revealed the presence of well-ordered MCM-48 structure in the metal-incorporated materials, while XPS and UV-Vis DRS confirmed the successful partial incorporation of metal ions precisely in their desired tetrahedral coordination within the framework. To assess their catalytic performance, we studied the activity and selectivity of these catalysts in liquid phase oxidation of toluene using tert-butyl hydroperoxide as the oxidant. Under optimized conditions, employing a 6% (w/w) Fe-MCM-48 (40) catalyst and maintaining a toluene to oxidant molar ratio of 1:3 at 353 K in a solvent-free environment for 8 h, the oxidation reaction resulted in the formation of benzaldehyde (88.1%) as the major product and benzyl alcohol (11.9%) as the minor product.

Efficient catalytic ozonation via Mn-loaded C-SiO2 Framework for advanced wastewater treatment: Reactive oxygen species evolution and catalytic mechanism

Heterogeneous catalytic ozonation (HCO) is attractive for water decontamination and catalyst is a core element. However, it is difficult to maintain high efficiency and stability of catalysts under stern conditions. In this study, we proposed Mn-loaded C-SiO₂-Framework (Mn-CSF) which contained stable silica core and robust carbon shell for efficient catalytic ozonation. The pseudo-first-order kinetic rate constant for oxalic acid removal of Mn-CSF catalytic ozonation was 160 % and 875 % higher than those of Mn-SiO₂ and pristine CSF, respectively. Mn-CSF was also proven effective in gasification wastewater treatment, where the COD was decreased to 46 mg·L^-1, 37 % lower than that of Mn-SiO₂. These results indicated that the graphitization carbon layer and Mn significantly enhanced the activity of the catalyst. Furthermore, a fulvic-like component and a protein-like component were recognized through 3D-EEM in coal gasification wastewater. It was proven that Mn-CSF catalytic ozonation exhibited higher fulvic-like component and protein-like component removal compared with ozonation. Moreover, O₂^- and ¹O₂ were identified to be responsible for organic degradation in this research. Sufficient external specific surface area and porous structure were important for complex wastewater treatment. Specifically, external specific surface area could enhance the degradation of macromolecular organics while porous structures were vital for smaller molecular pollutant removal. The results highlighted that Mn-CSF was a promising HCO catalyst for advanced wastewater treatment, and this study provided evidence of relationship between structure of catalysts and HCO efficiency.

Treatment of Phenol-Containing Coal Chemical Biochemical Tailwater by Catalytic Ozonation Using Mn-Ce/γ-Al2O3

In this study, a Mn-Ce/γ-Al2O3 catalyst with multiple active components was prepared through the doping–calcination method for advanced treatment of coal chemical biochemical treatment effluent and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy, and BET analysis. In addition, preparation and catalytic ozonation conditions were optimized, and the mechanism of catalytic ozonation was discussed. The Mn-Ce/γ-Al2O3 catalyst significantly enhanced COD and total phenol removal in reaction with ozone. The characterization results suggested that the pore structure of the optimized Mn-Ce/γ-Al2O3 catalyst was significantly improved. After calcination, the metallic elements Mn and Ce existed in the form of the oxides MnO2 and CeO2. The best operating conditions in the study were as follows: (1) reaction time of 30 min, (2) initial pH of 9, (3) ozone dosage of 3.0 g/h, and (4) catalyst dosage of 30 g/L. The removal efficiency of COD and total phenol from coal chemical biochemical tail water was reduced with the addition of tert-butanol, which proves that hydroxyl radicals (•OH) played a leading role in the Mn-Ce/γ-Al2O3 catalytic ozonation treatment process of biochemical tailwater. Ultraviolet absorption spectroscopy analysis indicated that some conjugated structures and benzene ring structures of organics in coal chemical biochemical tail water were destroyed. This work proposes the utilization of the easily available Mn-Ce/γ-Al2O3 catalyst and exhibits application prospects for the advanced treatment of coal chemical biochemical tailwater.

Advanced catalytic ozonation for degradation of pharmaceutical pollutants-A review

Various chemical treatment techniques are involved in removing refractory organic compounds from water and wastewater using the oxidation reaction of hydroxyl radicals (^•OH). The use of catalysts in advanced catalytic ozonation is likely to improve the decomposition of molecular ozone to generate highly active free radicals that facilitate the rapid and efficient mineralization and degradation of numerous organics. For the degradation of toxic organic pollutants in wastewater, the advanced catalytic ozonation process has been widely applied in recent years. Low utilization efficiency of ozone and ineffective mineralization of organic contaminants by ozone can be remedied with advanced catalytic ozonation. Advanced catalytic ozonation has gained popularity because of these merits. However, homogeneous catalytic ozonation has the disadvantage of producing secondary contaminants from the addition of metallic ions. Heterogeneous catalytic ozonation can overcome this drawback by utilizing metals, metallic oxides, and carbon materials as a catalyst of efficacy and stability. This review discusses various aspects of catalytic ozonation in wastewater treatment of pharmaceutical pollutants, application of catalytic ozonation process in typical wastewater, and prospects in advancing the techniques in heterogeneous catalytic ozonation.

Efficient catalytic ozonation of bisphenol A by three-dimensional mesoporous CeOx-loaded SBA-16

Herein, we demonstrated the construction of three-dimensional (3D) cerium oxide (CeO_x)/SBA-16 nanocomposites for efficient removal of bisphenol A (BPA) via a catalytic ozonation, with a high BPA mineralization up to 60.9% in 90 min. On one hand, the CeO_x/SBA-16 mesoporous structured materials presented large surface area and uniform pore distribution, which was conducive to the adsorption of transformation by-products (TBPs) and then, the mass transfer. On the other hand, CeO_x/SBA-16 could enhance the ozone utilization efficiency and meanwhile facilitate the formation of OH, the main reactive oxygen species. Through the exploration of dissoluble organic matters and the identification of the reaction intermediates, two BPA degradation pathways were proposed. This approach reported here will benefit the design and construction of mesoporous structured materials for catalytic elimination of hazards to remediate the environment.

Fabrication of vessel-like biochar-based heterojunction photocatalyst Bi2S3/BiOBr/BC for diclofenac removal under visible LED light irradiation: Mechanistic investigation and intermediates analysis

In this work, a novel, economical and effective vessel-like biochar-based photocatalyst Bi₂S₃/BiOBr/BC was synthesized by a facile one-pot solvothermal method for the first time. A series of characterization analyses demonstrated the successful preparation of photocatalyst Bi₂S₃/BiOBr/BC. Furthermore, diclofenac (DCF) as the target contaminant was applied to elucidate the enhanced photocatalytic performance (93.65%, 40 min) under energy-saving visible LED light irradiation. Comparison experiments among different photocatalysts and photoelectrochemical tests results illustrated that excellent photocatalytic performance of Bi₂S₃/BiOBr/BC 10% might be attributed to the electrons transfer of biochar and higher charge separation efficiency of heterojunction structure. Besides, lower electrical energy per order value indicated photocatalyst/visible LED light system was more energy-saving. Proper photocatalyst dosage (0.6 g/L) and relatively acidic water environment (pH = 5.0) would be beneficial to DCF photodegrdation by Bi₂S₃/BiOBr/BC. Good reusability and stability of Bi₂S₃/BiOBr/BC were verified via five consecutive recycle experiments. Furthermore, the role of active species was determined through trapping experiments and O₂- and h⁺ dominated the photodegradation reaction to mineralize DCF molecules. Eleven main intermediates and four possible photodegradation pathways were proposed by HRMS analysis. Accordingly, photocatalyst Bi₂S₃/BiOBr/BC would provide potential technical support for emerging pollutant removal in water matrix.

Pt Modified Heterogeneous Catalysts Combined with Ozonation for the Removal of Diclofenac from Aqueous Solutions and the Fate of by-Products

The degradation of the pharmaceutical compound diclofenac in an aqueous solution was studied with an advanced oxidation method, catalytic ozonation. Diclofenac was destroyed in a few minutes by ozonation but several long-lasting degradation by-products were formed. For this reason, the combination of heterogeneous catalysts and ozonation was applied to eliminate them completely. The kinetics of the diclofenac degradation and the formation of by-products were thoroughly investigated. Loading of Pt on the catalysts resulted in an improvement of the activity. The Mesoporous Molecular Sieves (MCM) were one of the promising catalysts for the degradation of organic pollutants. In this study, six heterogeneous catalysts were screened, primarily MCM-22-100 catalysts with different Pt concentrations loaded via the evaporation-impregnation (EIM) method, and they were applied on the degradation of diclofenac. It was found that the presence of Pt improved the degradation of diclofenac and gave lower concentrations of by-products. The 2 wt % Pt-H-MCM-22-100-EIM demonstrated the highest degradation rate compared to the proton form, 1% or 5 wt % Pt concentration, i.e., an optimum was found in between. Pt-H-Y-12-IE and Pt-γ-Al2O3 (UOP)-IMP catalysts were applied and compared with the MCM-22 structure. Upon use of both of these catalysts, an improvement in the degradation of diclofenac and by-products was observed, and the 2 wt % Pt-H-MCM-22-100-EIM illustrated the maximum activity. All important characterization methods were applied to understand the behavior of the catalysts (X-ray powder diffraction, transmission electron microscopy, nitrogen physisorption, scanning electron microscopy, energy dispersive X-ray micro-analyses, pyridine adsorption-desorption with FTIR spectroscopy, X-ray photoelectron spectroscopy). Finally, leaching of Pt and Al were analyzed by inductively coupled optical emission spectrometry.

Catalytic ozonation for water and wastewater treatment: Recent advances and perspective

Ozonation process has been widely applied in water and wastewater treatment, such as for disinfection, for degradation of toxic organic pollutants. However, the utilization efficiency of ozone is low and the mineralization of organic pollutants by ozone oxidation is ineffective, and some toxic disinfection byproducts (DBPs) may be formed during ozonation process. Catalytic ozonation process can overcome these problems to some extent, which has received increasing attention in recent years. During catalytic ozonation, catalysts can promote O₃ decomposition and generate active free radicals, which can enhance the degradation and mineralization of organic pollutants. In this paper, the history of ozonation application in water treatment was briefly reviewed. The properties of the ozone molecule, the ozonation types and several ozone-based water treatment processes were briefly introduced. Various catalysts for catalytic ozonation, including homogeneous and heterogeneous catalysts, such as metal ions, metal oxidizes, carbon-based materials and their possible catalytic mechanisms were analyzed and summarized in detail. Furthermore, some inconsistent results of previous research on catalytic ozonation were analyzed and discussed. The application of catalytic oxidation for the degradation of toxic organic pollutants, including phenols, pesticides, dyes, pharmaceuticals and others, was summarized. Finally, several key aspects of catalytic ozonation, such as pH effect, the catalyst performance, the catalytic mechanism were proposed, to which more attention should be paid in future study.

Effective adsorption of diclofenac sodium from neutral aqueous solution by low-cost lignite activated cokes

Activated cokes have attracted great interest inwater treatment to remove organic pollutants due to their low cost and specific textural properties. In this study, adsorptive removal of diclofenac sodium (DCF) from neutral aqueous solution by available lignite activated cokes (LACs) was reported for the first time. Diclofenac sodium could be quickly removed from aqueous solution by LAC-2, with the maximum Langmuir adsorption capacity q_m of 224 mg/g at pH 6.5. Characterization results (including scanning electron microscopy, transmission electron microscopy, elemental analyses, Boehm titrations, N₂ adsorption-desorption isotherms and Fourier transform infrared spectroscopy) and a series of adsorption kinetics, adsorption isotherms model studies revealed that high porosity with developed macro- and micropore structures on LAC-2, as well as high content of phenolic groups, could obviously enhance the DCF adsorption capacity and rate. Moreover, LAC-2 showed high affinity towards DCF at low concentrations, as well as good reusability after three adsorption-desorption cycles. pH effect studies revealed that hydrogen-bonding interaction plays an important role during adsorption, accompanied with certain contribution from electrostatic interaction and π-π interaction. This study indicates the promising potential of LAC-2 as an efficient, low-cost and recyclable material for DCF removal from water bodies.

Effective mineralization of quinoline and bio-treated coking wastewater by catalytic ozonation using CuFe2O4/Sepiolite catalyst: Efficiency and mechanism

In this study, CuFe₂O₄ nanocomposite loaded on natural sepiolite (CuFe₂O₄/SEP) was prepared by the citrate sol-gel method. CuFe₂O₄/SEP was characterized by X-ray diffraction, Brunauer-Emmett-Teller adsorption analysis, scanning electron microscopy, and energy dispersive spectroscopy. The CuFe₂O₄/SEP composite was stable and showed an excellent catalytic activity for ozonation. The efficiency of quinoline mineralization in the catalytic ozonation with CuFe₂O₄/SEP was 90.3%, and this value was 5.4 times higher than that of the uncatalyzed ozonation (16.8%). The quinoline mineralization followed a pseudo first-order kinetics with all the catalysts. The rate constant for the mineralization of quinoline by ozonation in the presence of CuFe₂O₄/SEP was 0.0885 min^-1, which was 16.7 times higher than that in ozone alone (0.0053 min^-1). Radical scavenging tests revealed that hydroxyl radical (OH) and superoxide radical (O₂^-) were the reactive oxygen species (ROS) in the quinoline degradation. In the presence of CuFe₂O₄/SEP, ozone and hydrogen peroxide were rapidly converted into the ROS. Although neutral and alkaline pH were more beneficial for the quinoline mineralization, CuFe₂O₄/SEP exhibited significant catalytic activity even under acidic conditions. Meanwhile, five-cycle successive tests suggested that CuFe₂O₄/SEP was recyclable and hence, stable. Furthermore, the feasibility of the catalytic ozonation for the treatment of biologically treated coking wastewater was evaluated. The catalytic ozonation resulted in 57.81% total organic carbon removal efficiency at 60 min, which was 2.9 times higher than that in the uncatalyzed ozonation (19.99%).

Intensification of the O3/TiO2/UV advanced oxidation process using a modified flotation cell

A novel approach for the ozone and TiO₂ intensification process for wastewater treatment is presented using a modified flotation cell.