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1.
This study investigated a low-energy-consuming procedure for the synthesis of zeolite materials from coal fly ash (CFA). Materials containing zeolite phases, namely Na–X, Na–P1, and zeolite A, were produced from F–class fly ash, using NaOH dissolved in distilled water or in wastewater obtained from the wet flue gas desulphurization process, under atmospheric pressure at a temperature below 70 °C. The influence of temperature, exposure time, and alkaline solution concentration on the synthesized materials was tested. In addition, chemical, mineralogical, and textural properties of the obtained materials were determined by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and cation exchange capacity (CEC). Cd(II), Ni(II), NH4+ cation, and Se(VI) anion sorption experiments were conducted to compare the sorption properties of the produced synthetic zeolites with those of the commercially available ones. Zeolitization resulted in an increase of CEC (up to 30 meq/100 g) compared to raw CFA and enhanced the ability of the material to adsorb the chosen ions. The obtained synthetic zeolites showed comparable or greater sorption properties than natural clinoptilolite and synthetic Na–P1. They were also capable of simultaneously removing cationic and anionic compounds. The structural, morphological, and textural properties of the final product indicated that it could potentially be used as an adsorbent for various types of environmental pollutants.  相似文献   

2.
Unlike odorants that mask odors, natural zeolite acts as a molecular sieve that captures and eliminates odors. Different treatment methods can be applied to influence the properties of the natural zeolites. To enhance the odor adsorption capacities of the natural zeolite two types of treatment methods were applied: chemical (acid, basic) and thermal. The initial natural zeolites and the activated one were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM-EDX). Two experiments were performed to establish the odor adsorption capacity of the activated natural zeolites. The best zeolite for the adsorption of humidity, ammonia and hydrogen sulfide was the 1–3 mm zeolite activated through thermal treatment. For the adsorption of PAHs, the best zeolite was the one activated through basic treatment, with an adsorption capacity of 89.6 ng/g.  相似文献   

3.
Nowadays, using fly ash for zeolites production has become a well-known strategy aimed on sustainable development. During zeolite synthesis in a hydrothermal conversion large amount of post-reaction solution is generated. In this work, the solution was used as a substrate for Na-A and Na-X zeolites synthesis at laboratory and technical scale. Obtained materials were characterized using particle size analysis, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherm. Produced zeolites revealed high purity (>98%) and monomineral zeolitic phase composition. The SiO2 content was in the range 39–42% and 40–38%, whereas Al2O3 content was 23–22% and 25–26% for Na-X and Na-A, respectively. TEM and BET analyses revealed Na-X zeolite pores were almost identical to commercial 13X with SBET in the range 671–734 m2/g. FTIR indicated slight differences between materials obtained at laboratory and technical scale in Si-O-(Si/Al) bridges of the zeolitic skeleton. The results showed good replicability of the laboratory process in the larger scale. The proposed method allows for waste solution reusability with a view to highly pure zeolites production in line with circular economy assumptions.  相似文献   

4.
The aim of this study was to investigate the use of natural zeolite as support for microbial community formation during wastewater treatment. Scanning electron microscopy (SEM), thermal decomposition and differential thermogravimetric curves (TGA/DGT) techniques were used for the physicochemical and structural characterization of zeolites. The chemical characterization of wastewater was performed before and after treatment, after 30 days of using stationary zeolite as support. The chemical composition of wastewater was evaluated in terms of the products of nitrification/denitrification processes. The greatest ammonium (NH4+) adsorption was obtained for wastewater contaminated with different concentrations of ammonium, nitrate and nitrite. The wastewater quality index (WWQI) was determined to assess the effluent quality and the efficiency of the treatment plant used, showing a maximum of 71% quality improvement, thus suggesting that the treated wastewater could be discharged into aquatic environments. After 30 days, NH4+ demonstrated a high removal efficiency (higher than 98%), while NO3+ and NO2+ had a removal efficiency of 70% and 54%, respectively. The removal efficiency for metals was observed as follows (%): Mn > Cd > Cr > Zn > Fe > Ni > Co > Cu > Ba > Pb > Sr. Analysis of the microbial diversity in the zeolite samples indicated that the bacteria are formed due to the existence of nutrients in wastewater which favor their formation. In addition, the zeolite was characterized by SEM and the results indicated that the zeolite acts as an adsorbent for the pollutants and, moreover, as a support material for microbial community formation under optimal conditions. Comparing the two studied zeolites, NZ1 (particle size 1–3 mm) was found to be more suitable for wastewater treatment. Overall, the natural zeolite demonstrated high potential for pollutant removal and biomass support for bacteria community growth in wastewater treatment.  相似文献   

5.
This study deals with the impact of calcination, alkalinity, and curing time parameters on the hydrothermal synthesis of zeolite A. The zeolite A sample, produced from corncob-stalk-and-leaves (corn stover) ash was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that calcination, alkalinity, and curing time have significant effects on the crystallization and the morphology of zeolite A. In addition, these parameters also impacted the cation exchange capacity. Furthermore, the synthesized zeolite A was obtained using a calcination temperature of 500 °C within two hours of airflow, which is much lower than the temperatures previously reported in the literature for an agricultural waste and other waste materials. A fusion ratio of corn stover ash:NaOH of 1.0:1.5 and a curing time of nine hours were achieved. This is a major result as this curing time is much lower than those featured in other studies, which can reach up to twenty-four hours. In this paper, cubic crystal with rounded edge of zeolite A, having a cation exchange capacity of 2.439 meq Na+/g of synthesized anhydrous zeolite A, was obtained, which can be a good candidate for ion-exchange separation.  相似文献   

6.
Production of a high value zeolite from fly ash has been shown to be an avenue for the utilization of South African fly ash which presently constitutes a huge disposal problem. The synthesis of zeolites Na-P1 and analcime on a micro-scale has been successful and preliminary investigation shows that scale-up synthesis is promising. However, the post-synthesis supernatant waste generated contains high levels of NaOH that may constitute a secondary disposal problem. A waste minimization protocol was developed to reduce the volume of waste generated with a view to enhancing the feasibility of the scale synthesis. Series of experiments were conducted in 100 mL jacketed batch reactors. Fly ash was reacted with 5 Mol NaOH on a 1:1 mass basis during the aging step, followed by hydrothermal treatment in which ultrapure water was added to the slurry. This study shows that by re-introducing the supernatant waste into the experiments in such a way that it supplies the required reagent (NaOH) for the zeolite synthesis, zeolite Na-P1 and analcime can be synthesized. It also shows that the synthesis process can be altered to allow up to 100% re-use of the supernatant waste to yield high value zeolitic products. This study effectively constructed two protocols for the minimization of waste generated during the synthesis of zeolites from South African coal fly ash. This result could be used to establish a basis for legal and environmental aspects involved in the commission of a full-scale plant synthesizing zeolites NaP1 and analcime.  相似文献   

7.
Aim: We examined the impact of baseline high-density lipoprotein cholesterol efflux capacity (CEC) on major cardiac adverse events (MACE) in patients with coronary artery disease (CAD) during a long-term secondary prevention. Method: CEC was measured using a cell-based efflux system in (3)[H]-cholesterol-labeled J774 macrophages in apolipoprotein B-depleted plasma between January 2011 and January 2013. Patients with CAD were divided into 2 groups as a boundary CEC value of 1: 0.19 ≤ CEC <1 (impaired CEC group, mean CEC of 0.76±0.16, n =136), and 1 ≤ CEC ≤ 2.08 (enhanced CEC group, 1.20±0.19, n =44). MACE, comprised the incidence of cardiac death, non-fatal myocardial infarction, and any revascularizations (RV) without restenosis approximately 1 year after vascularization, was retrospectively investigated at September 2019. Impact of enhanced CEC on MACE among 22 variables was examined by applying a Cox proportional hazard model. Result: The frequency of MACE in impaired CEC group (16.9%, mean observational interval of 2111±888 days) was significantly higher than that in enhanced CEC group (2.3%, 2,252±685, p =0.013), largely driven by the significantly higher RV incidence (14.0 % versus 2.3 %, p =0.032). Enhancement of CEC was the significant predictor of MACE (hazard ratio: 0.11; 95% CI: 0.013-0.879; p =0.038). Conclusion: A baseline CEC level of more than 1 in patients with CAD brought favorable long-term clinical outcomes, suggesting that CEC is a useful prognostic and therapeutic surrogate for secondary prevention of CAD.  相似文献   

8.
Activity of gold supported catalysts strongly depends on the type and composition of support, which determine the size of Au nanoparticles (Au NPs), gold-support interaction influencing gold properties, interaction with the reactants and, in this way, the reaction pathway. The aim of this study was to use two types of zeolites: the three dimensional HBeta and the layered two-dimensional MCM-36 as supports for gold, and modification of their properties towards the achievement of different properties in oxidation of glucose to gluconic acid with molecular oxygen and hydrogen peroxide. Such an approach allowed establishment of relationships between the activity of gold catalysts and different parameters such as Au NPs size, electronic properties of gold, structure and acidity of the supports. The zeolites were modified with (3-aminopropyl)-trimethoxysilane (APMS), which affected the support features and Au NPs properties. Moreover, the modification of the zeolite lattice with boron was applied to change the strength of the zeolite acidity. All modifications resulted in changes in glucose conversion, while maintaining high selectivity to gluconic acid. The most important findings include the differences in the reaction steps limiting the reaction rate depending on the nature of the oxidant applied (oxygen vs. H2O2), the important role of porosity of the zeolite supports, and accumulation of negative charge on Au NPs in catalytic oxidation of glucose.  相似文献   

9.
The total blood flow and microvessel blood flow in the mesentery and the intestine anesthetized rabbits were measured while systemic hemodynamics were altered by baroreceptor stimulation and by noradrenaline injection. The percent change of the total peripheral resistance (Rt) was greater than the change in resistance in the intestinal vascular bed (Ri) during baroreceptor stimulation. The capillary blood flow in the intestinal muscle layer (Qs) and villus (Qv) increased slightly while the intestinal arterial flow (Qa) and the arteriolar flow in the mesentery (Qm) decreased. These data indicated that Qs and Qv were not controlled by the sympathetic vasoconstrictor system. The percent change of Ri was greater than that of Rt during noradrenaline injection. Noradrenaline decreased Qa, but Qs and Qv were decreased while Qm was increased. These results show that noradrenaline stimulates alpha-adrenoceptors on small arteries and arterioles in the intestine. The observed Qm changed was in response to the systemic hemodynamic change caused either by the baroreceptor input or by noradrenaline.  相似文献   

10.
Soil amendments are substances added to the soil for moisture increment or physicochemical soil process enhancement. This study aimed to assess the water conservation efficiency of available organic soil amendments like bentonite, attapulgite, biochar and inorganics like superabsorbent polymer, and nonwoven geotextile in relation to the newly developed water absorbing geocomposite (WAG) and its biodegradable version (bioWAG). Soil amendments were mixed with loamy sand soil, placed in 7.5 dm3 pots, then watered and dried in controlled laboratory conditions during 22-day long drying cycles (pot experiment). Soil moisture was recorded in three locations, and matric potential was recorded in one location during the drying process. The conducted research has confirmed that the addition of any examined soil amendment in the amount of 0.7% increased soil moisture, compared to control, depending on measurement depth in the soil profile and evaporation stage. The application of WAG as a soil amendment resulted in higher soil moisture in the centre and bottom layers, by 5.4 percent point (p.p.) and 6.4 p.p. on day 4 and by 4.5 p.p. and 8.8 p.p. on day 7, respectively, relative to the control samples. Additionally, an experiment in a pressure plate extractor was conducted to ensure the reliability of the obtained results. Soil density and porosity were also recorded. Samples containing WAG had water holding capacity at a value of −10 kPa higher than samples with biochar, attapulgite, bentonite, bioWAG and control by 3.6, 2.1, 5.7, 1 and 4.5 percentage points, respectively. Only samples containing superabsorbent polymers and samples with nonwoven geotextiles had water holding capacity at a value of −10 kPa higher than WAG, by 14.3 and 0.1 percentage points, respectively. Significant changes were noted in samples amended with superabsorbent polymers resulting in a 90% soil sample porosity and bulk density decrease from 1.70 g∙cm−3 to 1.14 g∙cm−3. It was thus concluded that the water absorbing geocomposite is an advanced and most efficient solution for water retention in soil.  相似文献   

11.
Synthetic zeolites and other microporous oxide molecular sieves   总被引:4,自引:0,他引:4       下载免费PDF全文
Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.  相似文献   

12.
Considering the growing needs of environmental remediation, new effective solutions should be sought. Therefore, the adsorbed amounts of heavy metal ions, such as lead(II) and zinc(II), on the surface of high-carbon fly ash (HiC FA), zeolite-–carbon composite (Na-P1(C)) and pure zeolite (Na-P1), were investigated. The applied solids were characterized using the following techniques: XRD, SEM-EDS, TEM, porosimetry, SLS, electrophoresis and potentiometric titration. The heavy metal concentration in the probes was determined by applying ICP-OES spectroscopy. Adsorption/desorption and electrokinetic measurements were performed in the systems containing one or two adsorbates. The obtained results indicated that Pb(II) ions are adsorbed in larger amounts on the investigated solid surface due to the molecular sieving effect. The largest adsorption capacity relative to lead(II) ions was observed for pure Na-P1 zeolite (407 mg/g). The simultaneous presence of Pb(II) + Zn(II) mixed adsorbates minimally affects the amount of adsorbed Pb(II) ions and causes a significant decrease of Zn(II) ion adsorption (in comparison with analogous systems containing single adsorbates). It was also shown that all solids can be efficiently regenerated using hydrochloric acid. Thus, the selected pure zeolite can be successfully applied in soil remediation or other purifying technologies as an effective Pb(II) adsorbent.  相似文献   

13.
Nanosized zeolite Y is used in various applications from catalysis in petroleum refining to nanofillers in water treatment membranes. Ball milling is a potential and fast technique to decrease the particle size of zeolite Y to the nano range. However, this technique is associated with a significant loss of crystallinity. Therefore, in this study, we investigate the effect of adding biodegradable and recyclable cellulose nanofibrils (CNFs) to zeolite Y in a wet ball milling approach. CNFs are added to shield the zeolite Y particles from harsh milling conditions due to their high surface area, mechanical strength, and water gel-like format. Different zeolite Y to CNFs ratios were studied and compared to optimize the ball milling process. The results showed that the optimal zeolite Y to CNFs ratio is 1:1 to produce a median particle size diameter of 100 nm and crystallinity index of 32%. The size reduction process provided accessibility to the zeolite pores and as a result increased their adsorption capacity. The adsorption capacity of ball-milled particles for methylene blue increased to 29.26 mg/g compared to 10.66 mg/g of the pristine Zeolite. These results demonstrate the potential of using CNF in protecting zeolite Y particles and possibly other micro particles during ball milling.  相似文献   

14.
To broaden the application of silver nanoparticles (AgNPs), which are well-known antibacterial agents, they are supported on different substrates to prevent aggregation, increase their surface area and antibacterial efficiency, and to be separated from the system more effectively at the end of treatment. To produce nanocomposites that consist of silver nanoparticles on natural and modified zeolites, silver ions (Ag+) were loaded onto zeolite (natural, Na-modified, H-modified) and then thermally reduced to AgNPs. The effect of the exchangeable cations in zeolite on Ag+ uptake, AgNPs formation, size and morphology was investigated by the TEM, SEM, EDX, XPS, UV-vis, XRD and BET methods. The silver amount in the nanocomposites decreased in the following order Na-modified zeolite > natural zeolite > H-modified zeolite. Microscopic techniques showed formation of AgNPs of 1–14 nm on natural and Na-modified zeolite, while the diameter of metal particles on H-modified zeolite was 12–42 nm. Diffuse reflectance UV-vis and XPS methods revealed the presence of both silver ions and AgNPs in the materials indicating that partial reduction of Ag+ ions took place upon heating at 400 °C in air. Additionally, antibacterial properties of the nanocomposites were tested against Escherichia coli, and it was found that Ag–containing composites originating from the Na-modified zeolite demonstrated the highest activity.  相似文献   

15.
The hydrothermal alteration of perlite into zeolites was studied using a two-step approach. Firstly, perlite powder was transformed into Na-P1 (GIS) or hydro(xy)sodalite (SOD) zeolites at 100 °C and 24 h using 2 or 5 M NaOH solutions. Secondly, the Si:Al molar ratio of the reacted Si-rich solution was adjusted to 1 by Na-aluminate addition to produce zeolite A (LTA) at 65 or 95 °C and 6 or 24 h at an efficiency of 90 ± 9% for Al and 93 ± 6% for Si conversion. The performance of these zeolites for metal ion removal and water softening applications was assessed by sorption experiments using an artificial waste solution containing 4 mmol/L of metal ions (Me2+: Ca2+, Mg2+, Ba2+ and Zn2+) and local tap water (2.1 mmol/L Ca2+ and 0.6 mmol/L Mg2+) at 25 °C. The removal capacity of the LTA-zeolite ranged from 2.69 to 2.86 mmol/g for Me2+ (=240–275 mg/g), which is similar to commercial zeolite A (2.73 mmol/g) and GIS-zeolite (2.69 mmol/g), and significantly higher compared to the perlite powder (0.56 mmol/g) and SOD-zeolite (0.88 mmol/g). The best-performing LTA-zeolite removed 99.8% Ca2+ and 93.4% Mg2+ from tap water. Our results demonstrate the applicability of the LTA-zeolites from perlite for water treatment and softening applications.  相似文献   

16.
Various metal-β zeolites have been synthesized under similar ion-exchange conditions. During the exchange process, the nature and acid strength of the used cations modified the composition and textural properties as well as the Brönsted and Lewis acidity of the final materials. Zeolites exchanged with divalent cations showed a clear decrease of their surface Brönsted acidity and an increase of their Lewis acidity. All materials were active as catalysts for the transformation of acetone into hydrocarbons. Although the protonic zeolite was the most active in the acetone conversion (96.8% conversion), the metal-exchanged zeolites showed varied selectivities towards different products of the reaction. In particular, we found the Cu-β to have a considerable selectivity towards the production of isobutene from acetone (over 31% yield compared to 7.5% of the protonic zeolite). We propose different reactions mechanisms in order to explain the final product distributions.  相似文献   

17.
The first zeolite structure (ITQ-40) that contains double four (D4) and double three (D3) member ring secondary building units has been synthesized by introducing Ge and NH4F and working in concentrated synthesis gels. It is the first time that D3-Rs have been observed in a zeolite structure. As was previously analyzed [Brunner GO, Meier, WM (1989) Nature 337:146–147], such a structure has a very low framework density (10.1 T/1,000 3). Indeed, ITQ-40 has the lowest framework density ever achieved in oxygen-containing zeolites. Furthermore, it contains large pore openings, i.e., 15-member rings parallel to the [001] hexagonal axis and 16-member ring channels perpendicular to this axis. The results presented here push ahead the possibilities of zeolites for uses in electronics, control delivery of drugs and chemicals, as well as for catalysis.  相似文献   

18.
Natural clinoptilolite tuff (CL) and chabazite-clinoptilolite tuff (CH) were modified in fixed-bed column by immobilization of hexadecyltrimethylammonium bromide (HDTMA-Br), then investigated as a sorbent for inorganic anions of Cr(VI). The proposed modification technique combined with surfactant solution batching allows minimizing the surfactant loses through foaming and crystallization and creation of stable organic coverage. The HDTMA loading depended on the mineral composition of the zeolitic tuff, the topology of its external surface, and process conditions. The maximum surface coverage was obtained by gradually dosing surfactant solution in the smallest volume of batches and corresponded up to 100% and 182% of external cation exchange capacity (ECEC) for mono and double layer coverage, respectively. In case of mono layer coverage, modification proceeds until the exhaustion of surfactant in supply solution, while in the double layer one, until equilibrium of HDTMA concentration in both zeolitic and liquid phases was established. The efficiency of Cr(VI) uptake by prepared surface modified zeolites (SMZs) increased with increasing of HDTMA loading. In the case of mono layer SMZs, the capacities of CH-HDTMA and CL-HDTMA were 10.3 and 5.4 mg/g, respectively, while in the case of double layer SMZs, the amount of Cr uptake on CH-HDTMA and CL-HDTMA were 16.8 and 15 mg/g, respectively. Ion exchange is the predominant mechanism of Cr(VI) sorption but it takes place only if modification resulted in at least partial double layer coverage. The XPS analysis reveals Cr(VI) reduction to a less-toxic Cr(III) by the electron donating N-containing groups and by reaction with Fe+2 ions on the zeolite external surface.  相似文献   

19.
Zeolites obtained from fly ash are characterized by very good anion- and cation-exchange properties and a developed porous structure. This paper presents the results of surface modification studies of synthetic zeolites obtained from calcined coal shale (clay materials). Calcium compounds and hexadecyltrimethylammonium bromide (HDTMA) were used as modifying substances. The characteristics of the raw material and the zeolite obtained as a result of its synthesis are presented. The surface modification method is described. Furthermore, the results of sorption and desorption of NO3, PO4, and SO4 from raw and modified samples are presented. The results of anion- and cation-exchange capacities for other zeolite types were also compared. Modification of the materials with Ca ions and HDTMA surfactant only improved the sorption of sulfates. The 90% desorption of nitrates, phosphates, and sulphates from the zeolite material without modification indicates a good release capacity of these compounds and their potential use as fertilizer additives.  相似文献   

20.
This study explores the characteristics of a micronized natural zeolitic volcanic tuff (MZ) as ingredient in cosmetic formulations. In particular, the purpose was to prepare and investigate the organoleptic and physicochemical properties of two representative cosmetic formulations containing MZ. The MZ samples were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. pH, cation exchange capacity (CEC), apparent density, chemical composition and particle size distribution of MZ samples were also determined. The micronization treatment applied did not produce significant structural and physicochemical changes with respect to the raw zeolitic volcanic tuff. The prepared formulations containing 5% MZ with different particle sizes (100–125 µm and 125–250 µm) were subjected to preliminary and accelerated stability tests, and the pH and organoleptic properties were also evaluated. The cosmetic formulations presented a pH of 4.3, a pleasant touch, good spreadability, easy application on skin, no color alteration and a good stability after 15, 30 and 60 days of storage at room temperature, low temperature and freezer during the accelerated stability tests. The obtained results endorse the MZ as suitable for the development of formulations exploiting the clinoptilolite properties as a cosmetic ingredient.  相似文献   

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