Microwave Regeneration Research Articles

Designing perovskite catalysts for controlled active-site exsolution in the microwave dry reforming of methane

The dry reforming of methane (DRM) is a promising process for generating syngas (CO + H2) while consuming CO2, but industrial applications have been limited due to the high temperatures required to prevent coke formation. Microwave-assisted DRM (MW-DRM) is a promising approach to enable high temperature reactions because it can utilize excess renewable electrons to rapidly and selectively heat the catalyst bed without wasting time and energy heating the entire reactor. Here we demonstrate the MW-DRM reaction by modifying lanthanum strontium cobaltite (LSC) to serve as both microwave absorber and catalyst. Catalyst doping studies revealed the addition of oxophilic transition metals prevented over-reduction and stabilized the perovskitic phases under reaction conditions. In situ, synchrotron-based x-ray diffraction revealed the catalyst becomes active once metallic cobalt forms on a retained perovskitic support. The best performing Mn doped LSC catalyst showed 80–90 % single-pass conversions, stable operation for over 10 h, and easy microwave regeneration.

Insights into the glyphosate removal efficiency by using magnetic powder activated carbon composite

In this study, co-precipitation was used to prepare Fe3O4 magnetic powder activated carbon (PAC) (Fe3O4-PAC) and MnFe2O4 magnetic PAC (MnFe2O4-PAC) for the in-depth treatment of glyphosate pesticide wastewater. Magnetic adsorbent characterization results indicate that MnFe2O4 was successfully loaded on the activated carbon powder. Adsorption experiment results show that the maximum adsorption capacity of MnFe2O4-PAC for glyphosate is two to three times that of the original PAC. The adsorption of glyphosate by using magnetic PAC conforms to the Langmuir adsorption isotherm, and the adsorption kinetics is consistent with the quasi-second adsorption kinetic model. The adsorption capacity of Fe3O4-PAC and MnFe2O4-PAC showed the same trend effect with the change in pH, temperature, and adsorbent dosage. The adsorption capacity of Fe3O4-PAC and MnFe2O4-PAC for glyphosate decreased with the increase in pH and magnetic PAC and rises with temperature. Regeneration experiment results showed that the order of the regeneration method of MnFe2O4-PAC is: microwave combined Fenton reagent regeneration > wet microwave regeneration > microwave combined hydrogen peroxide regeneration. MnFe2O4-PAC after regeneration still exhibited good magnetic properties and adsorption capacity.

Screening and Performance Evaluation of Triethylenetetramine Nonaqueous Solutions for CO2 Capture with Microwave Regeneration

While CO2 capture with nonaqueous solutions is a promising approach, regeneration of the solutions often requires high energy consumption. This energy consumption can be potentially reduced by micr...

Experimental and computational study on the microwave energy based regeneration in diesel particulate filter for exhaust emission control

The uncontrolled combustion and early-life failure of the Diesel Particulate Filter substrate during fuel-based regeneration has raised the requirement for an alternate regeneration technique. The Latest emission norms have made it a mandatory requirement to retrofit the Diesel Particulate Filtration system in the exhaust line of CI engines to bring down the Particulate emissions. In this work, a novel technique through application of microwave energy has been developed for active regeneration of soot particles accumulated in the filter channel. Modelling of soot layer formation and microwave regeneration were carried out using CFD software (COMSOL MULTIPHYSICS). Performance and emission characteristics of multi-cylinder CI engine were evaluated after retrofitting the developed after-treatment system comprising of Diesel Oxidation Catalysis (DOC) and microwave regeneration based Diesel Particulate Filtration (DPF) systems. Soot accumulation rate and regeneration rate were experimentally investigated at different engine loads and magnetron (microwave radiation source) power levels. The experimental results showed that the developed after-treatment system has an average filtration efficiency of 90% for brake specific particle number emissions and 55% for hydrocarbon emissions. The regeneration rate was observed to be a maximum of 0.21 g/min at 50% power levels owing to the non-linear behaviour of magnetron. Energy consumption pattern of other regeneration techniques has been compared with the developed microwave regeneration system. The effect of soot accumulation and regeneration on the morphology, microstructure, chemical composition and particle size of DPF substrate were examined using characterization studies like Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infra-Red spectroscopy (FTIR), Particle Size Analysis (PSA) and microscopic imaging.

Comprehending adsorption of methylethylketone and toluene and microwave regeneration effectiveness for beaded activated carbon derived from recycled waste bamboo tar

ABSTRACT Beaded activated carbons (BACs) were derived from waste bamboo tar through carbonization (500°C for 2 hr) followed by physical activation using carbon dioxide (800–900°C for 2–4 hr). The adsorbent was examined for their physical and chemical properties, adsorption capacities toward methylethylketone (MEK) and toluene, and regenerabilities under microwave heating. It was found that the maximum total surface area reached for bamboo-tar-derived BAC after physical activation was 1364 m2 g−1, and more than 95% of the area was attributed to the microporous structures. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models were applied to the adsorption isotherm fitting, and the minimum R2 for each model was 0.986, 0.915, and 0.943, respectively. The isosteric heats of adsorption calculated based on D-R parameters for methylethylketone and toluene were 44.04 to 51.50 and 45.88 to 73.27 KJ mol−1, respectively. They were slightly over the range of physisorption and increased with adsorbate loading, which might be related to the micropore filling mechanism. Microwave regeneration under 600 W of power output removed most of the adsorbate (>93.03%) within 8 min. The results of this study are intended to benefit future study on waste-derived adsorbent in environmental applications. Implications Recycling waste bamboo tar for the novel adsorbent preparation is shown feasible in this study. Beaded activated carbon (BAC) synthesized from this waste bamboo tar possessed a high specific surface area, which aided in the capturing of volatile organic compounds (VOCs). Three adsorption isotherms, Langmuir, Freundlich, Dubinin-Radushkevich (D-R) models can be applied in interpreting the experimental adsorption data, providing information on adsorption heat and possible adsorption mechanism. A potential microwave regeneration method for BAC is tested, showing high desorption efficiencies with minimum heel formation. These findings can provide a new pathway for waste bamboo tar management and VOC abatement using adsorbents.

Preparation, Adsorption Properties and Microwave-Assisted Regeneration of Porous C/SiC Ceramics with a Hierarchical Structure

Porous C/SiC ceramics were prepared by chemical vapor reaction of SiO and porous C/C composites. The porous C/SiC ceramics presented a hierarchical structured consisted of carbon fibers, SiC layer, microspheres and nanowires. The density of porous C/C composites control the growth of SiC nanowires and nanolayer, and influence the pore size distribution and specific surface area of the porous C/SiC ceramics. The C/SiC samples converting from the C/C composites with a density of 0.46 g/cm3 possess the superior adsorption properties. The adsorption efficiency can reach 98.2% within 80 min, indicating that C/SiC samples have a promising adsorption property for MB from aqueous solution. Furthermore, the adsorption efficiency after five cycles microwave regeneration still reached 80.2%, which present excellent regeneration stability.

An efficient method for removal of pentachlorophenol using adsorption and microwave regeneration with different magnetic carbon nanotubes.

Various magnetic carbon nanotubes (CNTs) Co0.5M0.5Fe2O4-CNTs (M = Cu, Mn, Ni, Zn) were successfully prepared and applied for treatment of pentachlorophenol (PCP) with adsorption and microwave irradiation process. The Co0.5M0.5Fe2O4-CNTs were characterized by transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, and microwave absorption spectroscopy. The adsorption experiment results showed the adsorption capacity for PCP was in the following order: Co0.5Cu0.5Fe2O4-CNTs > Co0.5Mn0.5Fe2O4-CNTs > Co0.5Ni0.5Fe2O4-CNTs > Co0.5Zn0.5Fe2O4-CNTs. After adsorption, the Co0.5M0.5Fe2O4-CNTs was separated by magnetic field and regenerated by microwave irradiation at 850 W for 180 s. It was confirmed that after six adsorption and microwave regeneration cycles, the regeneration efficiency maintained over 90%. In particular, Co0.5Cu0.5Fe2O4-CNTs exhibited excellent adsorption capacity and reusability. These results can open a new avenue for treatment of chlorinated organic compounds with efficiently and non-secondary pollution.

Regeneration performance of activated coke for elemental mercury removal by microwave and thermal methods

The purpose of this study was to recover mercury and reuse active coke in the field of active coke adsorption of Hg0. The powdered active coke (AC) with high adsorption performance of Hg0 was prepared by a simple way. The regeneration characteristics of AC as a Hg0 sorbent were also investigated using microwave (MG-AC) and thermal methods (TG-AC). Of the two regeneration methods, microwave heating exhibited a faster heating rate to achieve complete regeneration. Following regeneration, adsorption performance of regenerated AC increased due to AC reactivation by microwave. Brunauer-Emmett-Teller (BET) measurements, X-ray photoelectron spectroscopy (XPS), and Laser particle size analyzer were used to analyze surface physical and chemical properties as well as particle size distribution of the samples. The results indicated that regeneration could greatly influence properties of AC, such as specific surface area, pore structure, surface chemical functional groups, and average particle size. Thermal methods had higher desorption content (CO2, CO and NO) than microwave methods. Hence, microwave regeneration had a smaller carbon consumption of 0.12% compared to thermal methods (0.23%). The Hg0 that desorbed from AC was collected using the deep adsorption technique in order to avoid secondary pollution.

Hydrophobic design of adsorbent for VOC removal in humid environment and quick regeneration by microwave

Abstract Absorption is an effective method for the removal of volatile organic compounds (VOCs). However, humidity can sharply decrease the adsorption capacity because part of the adsorbed VOCs will be replaced by water molecules. A hydrophobic adsorbent combined with rapid regeneration has considerable advantages in industrial applications. In this study, NaY zeolite, modified by hydrothermal dealumination, acid treatment and silanization, was selected as the adsorbent for toluene adsorption. The adsorption curves revealed that modifications improved the adsorption capacity of toluene from 8 mg/g to 46 mg/g in a humid environment (RH = 50%). The used adsorbent was instantly regenerated by exposing to microwave irradiation, mainly because the water adsorbed in the adsorbent can be efficiently heated and thereby pump the toluene out through evaporation. The adsorption capacity of the modified zeolite keeps well after performing absorption and desorption for five cycles. Moreover, as a good VOC adsorbent and microwave absorber, hydrophobic activated carbon can be added with zeolite to enhance the adsorption capacity and microwave regeneration rate. The adsorption capacity was improved to 95 mg/g when 30% activated carbon were added. Importantly, the composite adsorbent can be efficiently regenerated with few losses in adsorption capacity. Therefore, this work can provide an important reference for effective adsorption of VOCs in humid environment.

Removal of Congo red and methylene blue using H2O2 modified activated carbon by microwave regeneration: isotherm and kinetic studies

Microwave-assisted heating technology was used for treating paracetamol decolorizing spent activated carbon (SAC). The regenerated activated carbon (RAC) was modified using hydrogen peroxide (H2O2) to obtain modified activated carbon (MRAC), which was used for removing Congo red (CR) and methylene blue (MB) in aqueous solution, achieving the goal of utilizing hazardous waste resources. The RAC BET surface area was 1254.46 m2 g−1, and the results showed that microwave treatment could effectively regenerate the spent carbon. To increase the adsorption capacity of activated carbon, the surface was modified with H2O2 to increase oxygen-containing functional groups. The adsorption behavior of CR and MB on MRAC was studied, and equilibrium data were simulated by using the Langmuir, Freundlich, Redlich–Peterson, and Temkin isotherm models. The isotherm experimental data were best fitted by the Redlich–Peterson model, and the maximum sorption capacities obtained were 254 and 318 mg g−1 for CR and MB on MRAC (7% H2O2), respectively. The adsorption kinetics were best described by the pseudo-second-order model, and the Weber–Morris model showed that the adsorption process includes three stages: boundary layer diffusion and two intra-particle diffusion stages. The kinetic and isotherm experimental evidence showed the high efficiency of MRAC (7% H2O2) adsorption for CR and MB and its potential for organic pollutant removal.

Effects analysis on optimal microwave energy consumption in the heating process of composite regeneration for the diesel particulate filter

It is difficult for diesel vehicle battery to meet microwave energy consumption during regeneration of diesel particulate filter, which restricts the application of microwave regeneration technology. In order to minimize the microwave energy consumption during the composite regeneration heating phase of the diesel particulate filter, an optimal microwave energy consumption model is established in this study based on the Functional Analysis Principles. The solution of this optimal model is simulated by the Adaptive Variable Scale Chaos Immune Algorithm. The optimized results are got and verified by experiments under different experimental cases. The simulation results show that an optimal microwave power and regeneration heating time can be effectively obtained during the composite regeneration heating phase. The experimental results indicate that optimization microwave energy consumption under 4 experimental cases decrease by 5.65%, 5.70%, 10.64% and 14.64% compared with that unoptimized data of 93.8 kJ, 75.6 kJ, 65.8 kJ and 56.7 kJ, respectively. The ratio of efficiency to energy of the optimized cases is higher than that of the cases without optimization. The effects of optimal microwave energy consumption in the heating process of composite regeneration are investigated. Moreover, the microwave assisted composite regeneration can save about 24% and 48% energy by contrast of the microwave regeneration and fuel post-injection regeneration. The proposed microwave energy consumption optimization method can save microwave energy and meet the regeneration performance requirement of the diesel particulate filter.

Soot deposition effects and microwave regeneration modelling of diesel particulate filtration system

Regeneration of accumulated soot particles in the substrate walls of the diesel particulate filtration system is one of the major challenges faced by the automotive industry. This study investigated the conversion efficiency and filtration behaviour of the after treatment system comprising of diesel oxidation catalysis (DOC) and diesel particulate filtration (DPF) system. The average conversion efficiency of hydrocarbons was close to 54% and filtration efficiency of the particle number emissions was around 92%. Characterization of the DOC and DPF substrate were conducted using microscopic imaging, Fourier transform infrared spectroscopy (FTIR) and particle size analysis (PSA). The results of FTIR study indicated the presence of carcinogenic agents trapped in the porous walls of the filter substrate. A model for microwave based regeneration system is proposed in this article and CFD analysis were conducted to determine the temperature and electric field distribution in the DPF substrate for a regeneration time of 180 s. Results of simulation showed that the microwave radiations raise the temperature close to soot oxidation temperature (873 K), ensuring effective regeneration.

Preliminary Investigation on Regeneration of Simulated Radionuclide-contaminated Activated Carbons by Microwave Irradiation

This work investigates the feasibility of microwave (MW) irradiation for the regeneration of activated carbon (AC) spent with cesium. Adsorption batch experiments were carried out using commercially available granular activated carbon (Norit GAC 830). The Cs-saturated AC was treated using a controllable bench-scale 2.45-GHz MW oven at the power of 440 W for 3 min. The adsorption-regeneration cycle was repeated three times. The potentiality of the MW regeneration was assessed as regeneration efficiency (RE) and weight loss percentage of the AC samples during the adsorption/regeneration cycles. Textural properties of saturated and regenerated ACs were also evaluated by nitrogen adsorption isotherms at 77 K. Overall, results demonstrated a relatively low adsorption capacity for cesium, although the dielectric nature of the GAC allowed a rapid and effective regeneration process. Specifically, the weight loss percentage was found less than 2% jointly with an important increase in RE after 3 regeneration cycles. A preservation of the pore structure of regenerated ACs during MW regeneration was also observed.

Novel non-aqueous MEA solutions for CO2 capture

Present obstacles for CO2 capture involve reducing capital and energy costs. This study describes carbon dioxide capture with monoethanolamine (MEA) in organic solvents as a way to reduce the energy consumption during desorption. The solvents used in this study are a mixture of ethylene glycol and 1-propanol (EG/PrOH), diethylene glycol monoethyl ether (DEGMEE), and N-methylformamide (NMF). A microwave regeneration technique was used to easily and quickly screen the performances of the amine solutions and experiments were designed to investigate the solvent effects on CO2 capture by MEA. Globally, DEGMEE solutions resulted in the lowest energy consumptions and good CO2 cyclic capacities; the best solutions reducing the energy consumption by 78% in comparison to the traditional 30 wt% MEA aqueous solution. These findings show that organic solvents have much promise in improving CO2 capture technology. It was also found that using NMF greatly enhanced the CO2 absorption kinetics but was detrimental during the desorption step.

PARTICULARS OF ADSORBENT REGENERATION WITH THE USE OF MICROWAVE ENERGY

Energy conservation issues are acute in the world. Compressed air is widely used in the modern industrial production. The production of compressed air is a very energy-intensive process, since most of the energy, which is expended by the compressor, passes into the energy of heating. Compressed air cannot be used in modern production without a prior drying and cleaning. Industrial dryer’s air losses is up to 20% of compressed air additionally. Therefore, the issue of saving air during its drying stage is important. In the presented article, the thermal and aerodynamic processes that occur in the classical adsorption tower with the most modern design are considered. The processes that occur in the adsorption column with the microwave regeneration of the adsorbent are also considered. A comparative analysis of these constructions from the point of view of energy saving is made.

Microwave desorption and regeneration methods for activated carbon with adsorbed radon

This paper introduces a microwave desorption and regeneration methods for activated carbon with adsorbed radon. The influencing factors and objectivity in the process of desorption were tested, and the feasibility of the microwave regeneration of activated carbon with adsorbed radon was analyzed. The results showed that activated carbon with adsorbed radon can be heated uniformly by microwave, after 20 min of heating, the temperature differences between different depths in the activated carbon were within ± 6 °C; When the temperature reaches 150 °C, the microwave takes three minutes, and the electric heating takes 9 min, the energy consumption of microwave heating is lower, and the cooling performance after microwave heating was better than that after electric heating. A better desorption rate was achieved with a higher microwave power, a constant airflow rate (an airflow rate that is too high or too low will reduce the desorption rate), a higher moisture content and a lower activated carbon packing density. The effect of microwave desorption activated carbon is remarkable, in our experiment, the maximum desorption rate of the activated carbon reached 97.6%;The loss rate of the activated carbon after regeneration was low, and the total loss rate was 2.65% after five cycles of continuous absorption and desorption. The results can provide guidance for the development of key desorption technologies for implementation in radon reduction devices based on activated carbon.

Microwave regeneration of spent catalyst coupled with ultrasound augmented copper impregnation as a potential adsorbent photocatalyst

The present work attempts to regenerate the spent catalyst loaded with mercuric chloride utilizing microwave heating, followed by ultrasound augmented impregnation of Cu(NO3)2. The ultrasound augmented impregnation as compared to conventional impregnation has resulted in adsorption capacity higher by 12.5 mg g−1. The impregnated Cu(NO3)2 inside the carbon porous matrix was converted to copper, copper oxide, and cuprous oxide after thermal treatment. The optimal microwave regeneration process conditions were identified to microwave power 500 W, roasting temperature 800 °C and roasting duration of 25 min. The CuO loaded samples prepared at optimal regeneration conditions exhibited a MB removal capacity is 122.5 mg g−1. The physico-chemical properties of Cu-spent catalyst were examined by XRF, XRD, XPS, SEM, FTIR and N2 adsorption. Additionally, the photocatalytic effectiveness of the Cu loaded porous matrix was tested based on the MB degradation efficiency. The ultrasound augmented impregnation was found to be far superior to conventional impregnation based on the ability to photocatalytically degrade MB.

Effect of microwave regeneration on the textural network, surface chemistry and adsorptive property of the agricultural waste based activated carbons

Abstract This paper describes laboratory-scale experiments for examining the impact of microwave-irradiation on the regeneration of agricultural-waste based activated carbons loaded with methylene blue (MB). The efficacy of the regeneration study was analyzed by determining the carbon yield and amount of MB adsorbed in successive adsorption–regeneration cycles. The virgin characteristics were examined by pore-structural-analysis, nitrogen adsorption-desorption curve, surface acidity/basicity and zeta-potential-measurement. Microwave heating preserved the porous structure of the regenerated activated carbons efficiently to restore the original activate sites and adsorption capacity, with the specific surface areas (SBET) of 605.88–711.74 m2/g and monolayer adsorption capacities for MB of 199.74–231.68 mg/g. Besides, the regeneration time was considerably shortened over conventional regeneration method, which represents a dramatic improvement in the adsorption chemistry.

Performance Study of a Novel Solar Solid Dehumidification/Regeneration Bed for Use in Buildings Air Conditioning Systems

In this paper, a novel solar solid dehumidification/regeneration bed has been proposed, and its three regeneration methods, i.e., simulated solar radiation regeneration, microwave regeneration, and combined regeneration of the microwave and simulated solar radiation, were experimentally investigated and compared, as well as the dehumidification performance. The degree of regeneration of the proposed system under the regeneration method combining both microwave irradiation and simulated solar radiation could reach 77.7%, which was 3.77 times higher than that of the system under the simulated solar regeneration method and 1.05 times higher than that of the system under the microwave regeneration. The maximum energy efficiency of the proposed system under the combined regeneration method was 21.7%, while it was only 19.4% for the system under microwave regeneration. All these proved that the combined regeneration method of the simulated solar and microwave radiation not only improved the regeneration efficiency of the system, but also enhanced the energy efficiency. For the dehumidification performance, the maximum transient moisture removal was 14.1 g/kg, the maximum dehumidification efficiency was 68.0% and the maximum speed of dehumidification was 0.294 g/(kg·s) when the inlet air temperature was at 26.09 °C and the air relative humidity was at 89.23%. By comparing the testing results with the semi-empirical results from the Page model, it was indicated that the Page model can predict the regeneration characteristics of the novel solar solid dehumidification/regeneration bed under the combined method of microwave and simulated solar regeneration. The results of this research should prove useful to researchers and engineers to exploit the potential of solar technologies in buildings worldwide.

Regeneration of activated carbon saturated with chloramphenicol by microwave and ultraviolet irradiation

To reduce the secondary pollution of volatile organic compounds generated from adsorbent regeneration, a regeneration method for granular activated carbon (GAC) saturated with chloramphenicol is studied. The saturated GAC is regenerated by microwave and ultraviolet irradiation which radiated from electrodeless lamps activated by microwave. The existence of ultraviolet rays can affect the degradation of chloramphenicol, and it is analyzed by adsorption capacity recovery percentage, mineralisation percentage and the amount of inorganic chloride. The saturated GAC is regenerated in microwave reactor at 2450MHz for 10min. The mineralisation percentage increases to 37% from 5% when adds the electrodeless lamp into the regeneration reactor. Besides, 83% of the total chloride in chloramphenicol can transform into inorganic chloride. Add ultraviolet radiation in microwave regeneration reactor can enhance the oxidizability of microwave regeneration method. Furthermore, the adsorption ability of GAC can maintain at a high level after five absorption/regeneration cycles. These results show a great potential use of microwave and ultraviolet irradiation to regenerate activated carbon saturated with chlorinated organic compound. This regeneration method can reduce the risk of secondary pollution of chlorinated organic compound during adsorbent regeneration.