Microwave-induced Catalytic Degradation Research Articles

Microwave heating system for CuFe2O4/rGO/PMS enhanced catalytic-oxidative pre-treatment, water, and salt recovery from reverse osmosis reject of textile industry effluent

Microwave (MW) heating mechanism was investigated for reverse osmosis (RO) reject management of real textile effluent, i.e., pre-treatment, water, and salt recovery. For pre-treatment, microwave-induced catalytic degradation (MICD) enhanced with CuFe2O4/rGO for PMS activation was applied for organics degradation. The synthesized CuFe2O4/rGO (average particle size ∼16.44 nm) was characterized for XRD, SEM with EDAX, FTIR, VSM and TGA. MICD (1 g/L catalyst (80 %:20 %), 400 mg/L PMS, 90℃ MW temperature, 450 W MW power, and pH 11.32) showed 100 % color, 80.4 % TOC, and 91.1 % COD reduction within 16 min of MW irradiation. Radical quenching studies and EPR analysis revealed that SO4•− and ⦁OH were the dominant reactive species followed by non-radical O21. Recyclability study of CuFe2O4/rGO showed 72 % color, 65 % TOC, and 71.4 % COD removal after 5 cycles. XRD and FTIR of reused CuFe2O4/rGO hold similar crystallinity and structural properties as fresh catalyst. ATR-FTIR spectrum of before and after degradation of RO reject showed considerable degradation of organic dye molecules. Subsequently, the MW heating system was optimized for water recovery (110℃ MW temperature, 700 W MW power, and 100 mL reject volume), showing 100 % water recovery within 6 min, and its characterization showed a high distillate purity. NaCl and Na2SO4 salts were recovered under different MW operating temperatures, exploiting solubility equilibrium, and characterized for XRD, SEM with EDAX, and PSA.

High-performance carbon@ metal oxide nanocomposites derived metal–organic framework-perovskite hybrid boosted microwave-induced catalytic degradation of norfloxacin: Performance, degradation pathway and mechanism

Herein, FeCo@C-LFCx (FeCo@C-xLaFeCoO3) materials were prepared by high-temperature carbonation based on the construction of Fe/Co metal–organic framework columns with LaCoO3 (FeCo-MOF-LFCx) by in-situ extraction and synchronous coordination growth strategy. This strategy could improve the defects of perovskite materials such as easy aggregation, poor stability and poor specific surface area. The results demonstrated that the degradation rate of FeCo@C-LFC1.0 for norfloxacin (NOR, 20 mg/L) was 93.81% within 15 min. Co-BTC column nanocolumns and spongy Fe-BTC were successfully formed. Compared with LaFeCoO3, the specific surface area (89.9 m2/g) and pore volume (0.101 cm3/g) of FeCo@C-LFC1.0 after carbonization were increased by 16.3 times and 9.2 times, respectively. FeCo@C-LFCx could produce more structural defects and coordination unsaturated sites, promote microwave absorption. Vo and C = O on the material surface were involved in the activation of PMS. Moreover, quenching experiments and EPR verified that 1O2, OH, and SO4− were the main reactive radicals in the degradation process. The FeCo@C-LFC1.0 showed excellent reusability and stability. After five experiments, the removal rate of NOR remained at 91.15%. The toxicity of intermediate products was reduced. This work provided new avenues for using FeCo@C-LFC1.0 for environmental remediation.

Role of holes in microwave-induced catalyst Co3O4 for efficient high-concentration tetracycline degradation

Microwave-induced catalytic is a potential organic wastewater treatment technology. In this work, a new type of microwave-induced catalyst Co3O4 was synthesized and used to remove tetracycline (TC) under microwave (MW). The results have shown that the spherical Co3O4 exhibited impressively high catalytic activity with 100 mg·L-1 TC degradation efficiency of 100 % under MW at 800 W within 30 min. Importantly, Co3O4 catalyst displayed excellent stability with the degradation efficiency. The electron-hole pairs were generated under MW in the presence of Co3O4, which was confirmed by electron paramagnetic resonance and active species scavenging experiments. Part of the electrons (e-) was captured by oxygen vacancies produced under MW, and holes (h+) acted as the main active species for participating in the degradation process of TC. This work indicated the effect of MW for the separation of electrons and holes and provides new ideas for the mechanism of microwave-induced catalytic degradation.

Co nanoparticles/N-doped carbon nanotubes hybrids as highly efficient catalysts for microwave-induced catalytic degradation of tetracycline

Large-scale magnetic Co nanoparticles/N-doped carbon nanotubes (Co@NCNTs) hybrids have been designed by pyrolyzing the mixture of cobalt nitrate and melamine for microwave (MW)-induced tetracycline (TC) degradation. The results demonstrated that Co@NCNTs-5, annealed from cobalt nitrate and melamine (mole ratio: 1:5), possessed a good MW absorption ability, resulting in excellent degradation performance towards TC. Specifically, 99.5 % TC (20 mg/L, natural pH) could be removed after 6 min of MW irradiation (520 W) in the presence of Co@NCNTs-5. Meanwhile, Co@NCNTs-5 exhibited competitive degradation efficiency over TC at various concentrations (20–100 mg/L) and pH values (3−8). Results of reusability experiments identified the magnetic recovery ability and stability of Co@NCNTs-5. Based on free radical experiments and electron paramagnetic resonance (EPR) results, HO• and O2−• radicals participated in the catalytic degradation process. The degradation pathway of TC was proposed with the assistance of ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS). This work develops a facile, low-cost and large-scale method to synthesize Co@NCNTs, which demonstrates great potential in MW-induced catalytic treatment of antibiotic pollutants as high-efficient catalysts.

Co Nanoparticles/N-Doped Carbon Nanotubes Hybrids as Highly Efficient Catalysts for Microwave-Induced Catalytic Degradation of Tetracycline

Co Nanoparticles/N-Doped Carbon Nanotubes Hybrids as Highly Efficient Catalysts for Microwave-Induced Catalytic Degradation of Tetracycline

Co Nanoparticles/N-Doped Carbon Nanotubes Hybrids as Highly Efficient Catalysts for Microwave-Induced Catalytic Degradation of Tetracycline

Co Nanoparticles/N-Doped Carbon Nanotubes Hybrids as Highly Efficient Catalysts for Microwave-Induced Catalytic Degradation of Tetracycline

Microwave-induced catalytic degradation of methyl violet by a Ni-TiO2/ACFs composite catalyst

A hierarchically porous and magnetic Ni-TiO2/ACFs (activated carbon fibers) composite catalyst was prepared by loading Ni-TiO2 nanoparticles on ACFs to realize microwave-induced catalytic degradation for methyl violet (MV).The effect of synthesis conditions and compositions on Ni-TiO2/ACFs were investigated and characterized by XRD, BET, SEM and FT-IR. Results indicated that Ni-TiO2/ACFs exhibited higher catalytic activity than ACFs and TiO2/ACFs. After calcining at 900 °C for 2 h, Ni-TiO2/ACFs with respective weight ratio of 2:8 achieved 96.13% degradation ratio of MV after 3 min microwave.

Highly effective microwave-induced catalytic degradation of Bisphenol A in aqueous solution using double-perovskite intercalated montmorillonite nanocomposite

A series of new layered composite catalysts LaCu0.5Co0.5O3-MMTx (LCCOMx) (x = 0.1, 0.2, 0.3, 0.4) were prepared by montmorillonite (MMT) in situ intercalation of B-site double perovskite, which were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and microwave network analysis. The degradation of BPA (BPA) by microwave-induced catalytic performance of the prepared catalyst was studied. The LCCOMx catalyst with an appropriate amount of MMT had a unique lamellar structure and perovskite was uniformly and dispersedly distributed between layers so as to prevent the loss of active components. The material with a smaller particle size, better microwave absorption performance and higher Co3+/Co2+ and Oads/Olatt ratio, resulting in surprising microwave catalytic activity. The results showed that LCCOM0.2 had the most obvious effect on the removal of BPA. Simultaneously, reaction conditions were optimized and degradation process was found to follow the pseudo first-order kinetic equation. Microwave mechanism was discussed in detailed. Microwave can rapidly and selectively heat the surface active sites of the catalyst and generate strong oxidizing free radicals by reactions of electron-hole transport to degrade BPA.

Synthesis of a Novel Catalyst MnO/CNTs for Microwave-Induced Degradation of Tetracycline

Microwave-induced catalytic degradation (MICD) has been considered as one of the most prospective approaches to remove organic contaminants from water. High-performance catalysts, ideally offering efficient degradation ability, are essential to this process. This work reports the fabrication of manganese oxide on carbon nanotubes (MnO/CNTs) as an efficient catalyst under microwave irradiation (MI) to remove tetracycline (TC) from aqueous solution. The hybrid MnO/CNTs structure shows excellent performance in TC degradation. Combining experimental characterization and theoretical calculations, synergistic mechanisms are revealed: (i) Strong MnO/CNTs interaction stabilizes Mn(II) through interfacial bonding; (ii) high-spin states associated with low coordinated Mn(II) play a major role in MICD; and (iii) superoxide radicals (•O2−) and hydroxyl radicals (•OH) induced by microwave input are identified as the major active species.

Anchoring Fe3O4 Nanoparticles on Carbon Nanotubes for Microwave-Induced Catalytic Degradation of Antibiotics.

Microwave-induced catalytic degradation is considered amongst the most efficient techniques to remove antibiotic such as chlortetracycline from contaminated water. Described here is a new microwave-induced oxidation catalyst based on carbon nanotubes (CNTs) decorated uniformly with nanoparticles of Fe3O4. The combination of dielectric loss and magnetic loss of the material contributed to its stronger microwave absorption and the ability to produce more "hot spots". These hot spots promoted the oxidation of common antibiotics such as chlortetracycline, tetracycline, and oxytetracycline under microwave irradiation. Experiments with the addition of scavenger showed that hydroxy radicals (•OH) together with superoxide radicals (•O2-) contributed to the antibiotics removal as well. The final degradation products included CO2 and NO3- as confirmed by mass spectroscopy and ion chromatography analyses. The results indicated that the Fe3O4/CNTs was an efficient catalyst for microwave-induced oxidation.

Degradation of Azo dye direct black BN based on adsorption and microwave-induced catalytic reaction

The novel microwave catalyst MgFe2O4-SiC was synthesized via sol-gel method, to remove azo dye Direct Black BN (DB BN) through adsorption and microwave-induced catalytic reaction. Microwave-induced catalytic degradation of DB BN, including adsorption behavior and its influencing factors of DB BN on MgFe2O4-SiC were investigated. According to the obtained results, it indicated that the pseudo-second-order kinetics model was suitable for the adsorption of DB BN onto MgFe2O4-SiC. Besides, the consequence of adsorption isotherm depicted that the adsorption of DB BN was in accordance with the Langmuir isotherm, which verified that the singer layer adsorption of MgFe2O4-SiC was dominant than the multi-layer one. The excellent adsorption capacities of MgFe2O4-SiC were kept in the range of initial pH from 3 to 7. In addition, it could be concluded that the degradation rate of DB BN decreased over ten percent after the adsorption equilibrium had been attained, and the results from the result of comparative experiments manifested that the adsorption process was not conducive to the process of microwave-induced catalytic degradation. The degradation intermediates and products of DB BN were identified and determined by GC-MS and LC-MS. Furthermore, combined with the catalytic mechanism of MgFe2O4-SiC, the proposed degradation pathways of DB BN were the involution of microwave-induced $OH and holes in this catalytic system the breakage of azo bond, hydroxyl substitution, hydroxyl addition, nitration reaction, deamination reaction, desorbate reaction, dehydroxy group and ring-opening reaction. Open image in new window

Microwave-Assisted Catalytic Degradation of Crystal Violet with Barium Ferrite Nanomaterial

A novel magnetically separable nano-BaFe2O4 was prepared as an effective catalyst for microwave (MW)-induced catalytic degradation (MICD) of crystal violet (CV), and its catalytic degradation mechanism and process were investigated. The nano-BaFe2O4 displayed enhanced catalytic activity for CV degradation under MW irradiation. The intermediates and final products were investigated by HPLC-MS and ion chromatography (IC), respectively. By combining the band structure and radical trapping studies, holes (h+), superoxide radicals (•O2–), and hydroxyl radicals (•OH) were identified as the main active species in the reaction. The possible catalytic mechanism and process were proposed. The results showed that the catalytic activities of catalyst depend not only on its element constituents but also on chemical structure and energy band structure. This work provided some essential information on the catalytic behavior and mechanisms.

Superior performance of 3 D Co-Ni bimetallic oxides for catalytic degradation of organic dye: Investigation on the effect of catalyst morphology and catalytic mechanism

An application of novel magnetic separable NiCo2O4 in microwave-induced catalytic degradation (MICD) of organic dye was found, and the structures of NiCo2O4 significantly affect its catalytic activity. Diverse NiCo2O4 structures, including NiCo2O4 nanoplates (NiCo2O4-P), NiCo2O4 nanorods (NiCo2O4-R), NiCo2O4 nanoparticles (NiCo2O4-N) and three-dimensional (3D) hierarchical dandelion-like NiCo2O4 spheres (3D NiCo2O4-S), have been successfully synthesized. Among them, 3D NiCo2O4-S displayed superior catalytic activity for congo red (CR) under microwave (MW) irradiation. Enhanced catalytic activity of 3D NiCo2O4-S can be attributed to the higher MW energy harvesting capacity resulted from multiple absorption of MW and relatively high specific surface area. Various scavengers, the band structure, as well as Mott–Schottky analysis, were utilized to identify the roles of active species. A possible catalytic mechanism was proposed. The 3D NiCo2O4-S is expected to have potential applications in pollutants degradation because of its efficient catalysis, easy separation and good reusability.

Magnetic nano-sized cadmium ferrite as an efficient catalyst for the degradation of Congo red in the presence of microwave irradiation

A highly active nano-sized CdFe2O4 catalyst was prepared by a hydrothermal process and characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), BET specific surface area method, and vibrating sample magnetometer (VSM) at room temperature. Application of the microwave-induced catalytic degradation method in the abatement of Congo red (CR) using the magnetic catalyst was studied. The degradation ratio of CR with CdFe2O4 reached 94.4% with 10 min microwave irradiation (MW), proving CdFe2O4 to be an excellent microwave catalyst. The intermediate products from CR degradation were investigated by UV-Vis, HPLC and ion chromatography. The reaction kinetics, effects of different ion species (SO42−, NO3−, HCO3−, and CH3COO−), pH of the solution, dye initial concentration, dosage of catalyst, as well as degradation mechanism were comprehensively studied. Radical trapping studies and the fluorescence technique revealed the holes (h+) and hydroxyl radicals (˙OH) were involved as the main active species in the reaction. The band structure of CdFe2O4 was analyzed by UV-Vis diffuse reflectance spectroscopy and Mott–Schottky measurements. The mechanism of the degradation was discussed in detail. This work can provide an effective technology for dye wastewater treatment.

Microwave-induced catalytic degradation of a textile dye using bentonite–poly(o-toluidine) nanohybrid

The present study highlights the potential use of natural clay based organic–inorganic hybrids as eco-friendly catalysts for the degradation of Malachite Green under microwave irradiation.

Magnetic nanosized calcium ferrite particles for efficient degradation of crystal violet using a microwave‐induced catalytic method: insight into the degradation pathway

AbstractBACKGROUNDMagnetic iron based catalysts with high oxidation performance are generally effective for many catalytic reactions and can be magnetically recovered after application, showing advantages over other metal oxides. In this work, a highly active nanosized CaFe2O4 was prepared by a sol–gel method. Application of the microwave‐induced catalytic degradation (MICD) method to the abatement of crystal violet (CV) using the magnetic catalyst was studied.RESULTSMore than 90% of CV was degraded within 10 min. The intermediate products were investigated by UV–vis, HPLC and NMR. The results confirmed that CV was completely degraded and converted into harmless products. The reaction kinetics, effect of different ion species (Cl−, SO42−, NO3−, H2PO4− and HPO42−), pH, dye initial concentration, dosage of catalyst, and degradation mechanism were comprehensively studied. It was found that CaFe2O4 presented high activity to produce hydroxyl radicals and holes for degradation of CV under microwave radiation (MW). Surface hydroxyl groups of CaFe2O4 were a critical part in the generation of radicals, and iron on CaFe2O4 surface formed active sites to catalyze CV suggesting that CaFe2O4 plays a significant role in degradation of dyes.CONCLUSIONThis work provides valuable knowledge on the development of CaFe2O4 catalyst for environmental remediation technology. © 2014 Society of Chemical Industry