•Supported bimetallic catalysts typically possess superior performances than monometal catalysts and the impregnation method has been widely applied for the bimetallic catalyst ...preparations.•Impregnation sequences could play their significant roles on the physical and chemical properties of supported bimetallic catalysts.•A host of characterizations from impregnation sequential effects were briefly evaluated by reviewing the recent representative literatures.•The investigation of the nature of active sites and the structural dynamics on bimetallic catalysts are prospected accordingly to enhance the fundamental understanding of sequential influences.•The appropriate measurement of reaction rates is much required to compare the bimetallic catalysts that are prepared by different sequences of impregnations.
Supported bimetallic catalysts have been paid great attention regarding their excellent catalytic performances in chemical process. Notably, comparing to monometallic catalysts, the synergetic properties of dual-metal-based materials demonstrate unique physiochemical functionalities that single metal materials do not possess. The preparation of supported bimetallic materials is widely conducted with applying the impregnation method because of the straightforward and inexpensive technique. Wherein, the impregnation of dual metals on support could either undergo co-impregnation or sequential impregnations. It has been frequently reported that there are substantial differences in physiochemical properties and catalyst performances by impregnation sequences. Specifically, during the investigation of various sequential impregnated bimetallic catalysts, a host of characterization strategies are employed to compare the physical and chemical properties that play vital role to impact the catalyst activity/selectivity/stability. However, it is still not well understood regarding the impregnation sequential effects, such as the nature of bimetallic active sites and the dynamics of bimetallic surface structures along with reaction progress. This presenting perspective article is devoted to take a succinct review regarding the general sequential impacts on the physiochemical properties and further profoundly address the research outlook in this topic.
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•KOH was impregnated on rice husk KOH-activated carbon, named as DKOH-AC.•DKOH-AC involved both chemi- and physi-sorption when KOH-AC allowed physi-sorption.•CO2 adsorption on DKOH-AC ...followed Freundlich and pseudo second order models.•DKOH-AC adsorbed 2.1 mmol/g in an indoor condition.
Relatively high indoor CO2 concentration (greater than 1000 ppm) has a negative impact on human health. In this work, a cost-effective CO2 adsorbent (DKOH-AC) was developed by impregnating KOH on rice husk-based KOH activated carbon (KOH-AC, 1439 m2/g). KOH can be successfully loaded on the surface of KOH-AC and significantly changed its surface properties. DKOH-AC still remained a considerable surface area (206 m2/g) and showed a similar Smicro/SBET ratio. In-situ FTIR analysis confirmed that the major CO2 adsorption mechanism of KOH-AC was based on physisorption while that on DKOH-AC involved both chemisorption and physisorption. DKOH-AC showed a higher heat of adsorption (34 ∼ 41 KJ/mol) and gas selectivity (16.6) than these of KOH-AC. KOH-AC quickly reached an adsorption equilibrium (about 50 min) as compared to that of DKOH-AC. In addition, DKOH-AC exhibited an excellent adsorption performance of 2.1 mmol/g for a low concentration of CO2 (2000 ppm ∼ 500 ppm) under indoor conditions. Both the CO2 adsorption isotherm on KOH-AC and DKOH-AC well followed the Langmuir and Freundlich models. The CO2 adsorption kinetics on KOH-AC followed the pseudo-first order model whereas that on DKOH-AC obeyed the pseudo-second order model. The adsorption process was controlled by the intraparticle diffusion combined with the film diffusion model.
•Thymol was impregnated in LLDPE films using sub and supercritical CO2 as impregnation solvent.•Impregnation pressure is the key parameter that affects the content of thymol in the polymeric ...films.•Supercritical impregnation ensures a high incorporation of thymol in LLDPE without structural modification.
The impregnation of organic compounds in polymeric materials using supercritical carbon dioxide (scCO2) is a well-known technique, which is currently used in drug/polymer formulation. In this work, near critical and supercritical impregnation of thymol in linear low-density polyethylene (LLDPE) films was done in order to develop a new technique for preparation of active polymers to be used as food packages. The properties of thymol as a natural antimicrobial and antioxidant agent have motivated this study about the assessment of its migration from the polymer to different food simulant. Impregnation assays of thymol in LLDPE films were done in a high-pressure cell, where pure thymol was solubilized in supercritical carbon dioxide at 313K and pressures varying from 7 to 12MPa. This procedure allowed the preparation of plastic films with thymol concentrations ranged between 5100 and 13,200ppm. Migration tests showed that the pressure applied during the impregnation procedure is a key parameter that affects the content of the active compound into the polymer, since thymol solubility in scCO2 and absorption phenomena in the polymer increased with the pressure. The correlation between experimental data and a phenomenological transfer model allowed the estimation of the diffusion coefficient of thymol in LLDPE, which was ranged from 7.5×10−13 to 3.0×10−12m2s−1.
This study aimed to evaluate the effects of enzymatic hydrolysis on the chewing and swallowing properties of potato cubes using a freeze-thaw impregnation technique. The texture properties, ...microstructure, rheological properties, and suitability as a dysphagia diet of the potato cubes after enzymatic hydrolysis were studied. The results indicated that pectinase reduced the texture of the potato cubes more than cellulase and α-amylase. Pectinase hydrolysis could improve the safety of potato cubes as food for the elderly. Pectinase improved the stability of the mashed potatoes by increasing their viscosity and elastic modulus after chewing, thus improving their swallowing properties. The concentration at 200 U/mL and the hydrolysis time at 60 min were the best hydrolysis condition for pectinase to make dysphagia-suitable potato cubes. This study provides insights into the development of potato-based foods that can be used as dysphagia diet for the elderly.
•The effects of enzymatic hydrolysis using freeze-thaw impregnation were tested.•Pectinase had the greatest impact on texture compared to cellulase and α-amylase.•Pectinase hydrolysis could improve the safety of potato cubes as elderly food.•The best pectinase hydrolysis condition of potato for the elderly was confirmed. 200 U/mL and 60 min.
Iron-impregnated food waste biochar (Fe-FWB) was synthesized for Se(Ⅵ) removal from aqueous solution. The effect and interactive effects of different parameters including pyrolysis time, temperature, ...and Fe concentration were explored using response surface methodology (RSM) to enhance conditions to achieve the highest Se(Ⅵ) removal using Fe-FWB. Pyrolysis time was not significant for Se(Ⅵ) adsorption capacity of Fe-FWB, but temperature and Fe concentration were found to be significant. The highest adsorption was achieved at 3.47 h and 495.0 °C with an Fe concentration of 0.44 M. Fe-FWB synthesized under optimum conditions were used to investigate the kinetic, equilibrium, and thermodynamic adsorption of Se(Ⅵ). Se(Ⅵ) adsorption reached equilibrium within 6 h, and both pseudo-second order and pseudo-first order models were suitable for describing kinetic Se(Ⅵ) adsorption. The Freundlich model was found to suitably fit the equilibrium adsorption data than the Langmuir model. The highest adsorption capacity of Fe-FWB for Se(Ⅵ) was 11.7 mg g−1. Se(Ⅵ) adsorption on Fe-FWB was endothermic and spontaneous. The enthalpy change for Se(Ⅵ) adsorption was 54.4 kJ mol−1, and the entropy change was negative at 15–35 °C. The increment of solution pH from 3 to 11 decreased the Se(Ⅵ) adsorption from 19.2 to 7.4 mg g−1. The impact of interfering anions on Se(Ⅵ) adsorption followed the lineup: HCO3− > HPO42− > SO42− > NO3−. When compared to some adsorbents, the adsorption capacity of Se(Ⅵ) onto Fe-FWB was comparable even at neutral pH and the Fe-FWB was granular. These results indicate that Fe-FWB has prospective application in the removal of Se(Ⅵ) from aqueous solutions.
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•Temperature, time, and Fe concentration for the synthesis of Fe-FWB were optimized.•Temperature and Fe concentration were significant factors for removal of Se(Ⅵ) by Fe-FWB.•The maximum adsorption Se(Ⅵ) adsorption capacity of Fe-FWB was 11.727 mg g−1.•The mechanism of Se(Ⅵ) adsorption on Fe-FWB was outer-sphere complex.
The incorporation of active compounds into polymeric matrices using traditional methods has several drawbacks mainly due to the high volatility and thermal sensitivity of these substances. A solution ...to this problem could be the incorporation of bioactive compounds forming inclusion complexes as a strategy to improve the chemical stability, bioactivity and achieve controlled release.
In this work, β-cyclodextrin/carvacrol inclusion complex was prepared by spray drying to be incorporated into poly(lactic acid) (PLA) and Mater-Bi® films by supercritical CO2 impregnation. The impregnation process was carried out at pressures of 10, 15 and 20 MPa and at 40 °C. Both polymers showed the highest amount of incorporated inclusion complex at 15 MPa, where the percentage of impregnation varied from 0.6 % to 7.1 % in Mater-Bi® and PLA, respectively.
Release tests for PLA films impregnated with inclusion complex showed a slow release of the active compound, which did not reach equilibrium after 350 h under the experimental conditions. This prolonged release was not observed in Mater-Bi® due to the lower incorporation of the inclusion complex. The release rate was described herein by a comprehensive phenomenological model considering the decomplexation kinetics combined with the equilibrium and mass transfer expressions.
A “wet gel impregnation” method (WGI) was applied to prepare modified CO2 sorbents derived from alumina-extracted residue of coal ash (AR). Tetraethylene pentamine (TEPA) was selected as an amine ...polymer and it was evenly dispersed on the surface of AR. And the effects of loading amount, impregnation method, and adsorption temperature on CO2 adsorption capacity of the sorbent were investigated by thermogravimetric analyzer (TGA). The results showed that the desired sorbent with 60% TEPA loading via WGI had the maximum CO2 adsorption capacity of 3.45 mmol/g under 100% CO2 at 75 °C. This was attributed to the fact that the loading in wet gel state dramatically improved TEPA dispersion on the supports and increased the saturated loading of amine. Moreover, the sorbent still maintained stable CO2 uptake after five repeated adsorption-desorption cycles. These results suggested that amine-impregnated AR sorbent synthesized by WGI was an excellent and low-cost sorbent for CO2 capture.
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●Alumina-extracted residue of coal ash was used to prepare CO2 sorbents for the first time.●Low-cost sorbents with excellent capture capacity was prepared by novel wet gel impregnation.●The mechanism of wet gel impregnation promoting CO2 adsorption performance was elaborated.
This paper reports the successful preparation of high-strength 3D-printed alumina ceramic cores using stereolithography (SLA) and vacuum sol impregnation. Zirconia, alumina, and silica sols (ZS, AS ...and SS) were chosen as impregnating agents for alumina ceramics. The effects of different types of sols, various ratios of alumina sol to silica sol, and different pH values of sols on the mechanical properties of the ceramics were investigated. The flexural strength of the samples increased significantly after silica sol impregnation, reaching a maximum of 63.51 ± 3.67 MPa, which is 2.06 times higher than that of the unimpregnated samples (UN). Silica particles fill the original pores of the ceramics, and after high-temperature sintering, mullite is formed to increase the density and strength of the ceramics. The flexural strength of alumina ceramics decreases and then increases as the percentage of silica sol in the alumina-silica mixed sol increases. The optimal impregnation ratio for the mixed sols was found to be 1:4, which led to a flexural strength of 62.2 ± 2.09 MPa for the alumina ceramics. In addition, the pH of the sol plays a crucial role in maintaining stable sols. The silica sol is more susceptible to gelation as the pH of the sol increases within the range of 3.5–5.5, which can have a negative impact on its impregnation effectiveness. At a pH of 6.5 in the silica sol, the alumina ceramics exhibited the highest flexural strength of 92.57 ± 2.43 MPa, which is 3.01 times higher than the flexural strength of the unimpregnated samples. The research of impregnation process parameters suitable for 3D printing of alumina ceramics aim to enhance the material's strength, offering a novel solution for applications as high-performance components in the energy sector.
The presence of organic and inorganic contaminants such as pesticides, antibiotics, dyes, and heavy metals poses a risk to a human and the environment and therefore needs to be removed. The ...combination of natural zeolites and magnetic nanoparticles is employed as an excellent adsorbent for these pollutants removal from water. Magnetic zeolites are synthesized by incorporating magnetic nanoparticles, such as iron oxides or ferrites, into the zeolite framework. Various techniques, including co-precipitation, impregnation, and hydrothermal synthesis, have been employed by researchers to create the necessary magnetic zeolite composites and employed them for removing or reducing recalcitrant pollutants present in water or aqueous solutions. Magnetic zeolites have shown great promise in the removal of contaminants present in water. One of its best sides is its ability to separate and reuse materials easily. This review emphasizes magnetic zeolite as an effective adsorbent for water remediation and demonstrates its potential for water treatment. Magnetic zeolite can be used especially in regions where water treatment technologies are not yet met and can address waterborne disease issues. Due to its magnetic properties, and easier recovery and reuse of the adsorbents, the magnetic zeolite adsorption method is cost-effective and convenient
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•Addressing Emerging Contaminant.•Efficiency and Effectiveness of magnetic zeolite.•Innovative Technological Approach.•Environmental and Health Implications.•Potential for Practical Application.
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•Na+ is introduced to Mo/ZSM-5 via post-impregnation to maintain Mo-dispersion.•Bronsted acids are exclusively regulated to investigate the influence.•Coke and naphthalene are ...suppressed after introducing Na+.•MDA reaction is found to follow mono-functional pathway.•Confined hydrocarbon pool serves as precursors for both aromatics and coke.
Methane dehydroaromatization is a potential technique in converting natural gas into value-added aromatics and clean hydrogen. However, severe coking hinders industrial application of conventionally prepared Mo/ZSM-5 catalyst for methane dehydroaromatization. Usually, Bronsted acid sites (BAS) were considered the key for coking. To gain deeper insight into the coke, here we present a simple post-impregnation of Na+ to Mo/HZSM-5 to regulate its surface acidity. Influences of BAS on catalytic performance and coking behavior were thus exclusively studied. Na+ modified catalysts exhibit lower naphthalene and higher C2 selectivity, while selectivity for benzene is not obviously changed. These results contradict conventional bi-functional pathway that methane is dehydrogenated on Mo while BAS act as the center for intermediates cyclization. Characterizations and calculations indicate restricted growth of hydrocarbon pools confined in zeolite channels of Na+ modified catalysts. Hence, it is proposed that aromatization is the intrinsic property of Mo, and the Mo-associated carbonaceous species act as precursors for both coke and aromatics production.
