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In the present work, Zeolite A was modified by using hexadecyltrimethylammonium bromide (HDTMABr) for adsorption of the Congo red (CR) dye from synthetic aqueous solutions. The Modified Zeolite A (MZA) was characterized by XRD, SEM, and FTIR. The influence of solution pH (in the 4-12 range), ionic strength (0.1-1 M), contact time (180 min), initial CR concentration (20-60 mg/L), temperature (24-36 °C), and an adsorbent dose (1-3 g m/L) on the % dye removal and adsorbent capacity were studied. A combined effect of the initial CR concentration and temperature on the CR removal % by MZA was also studied by applying response surface methodology (RSM). Experimental values were in a good agreement with those predicated by a second-order quartic model. A maximum of 99.24% dye removal and adsorbent capacity of 21.11 mg/g was achieved under the following conditions: pH = 7, initial CR concentration = 60 mg/L, temperature = 24 °C, ionic strength = 0.1 M, adsorbent dose = 3 g/L and 90 min contact time. The equilibrium data were subjected to the Langmuir, Freundlich and Temkin isotherms, with the latter providing the best fit while kinetic adsorption studies were conducted by applying three models. The results indicated that the removal process was best described by the pseudo-second-order model. The present study demonstrates that modified MZA can be utilized for the highly efficient CR dye removal.

Linde-type A zeolite (LTA) was prepared from coal fly ash (CFA) and used as an adsorbent to remove acidic dye (Acid red 66, AR66) from its aqueous solution. The effectiveness of synthesized (LTA) in adsorbing (AR66) from an aqueous solution was studied using batch experiments. The equilibrium data were studied using the Langmuir and Freundlich models and it was found that the data fit better to Freundlich model. Kinetic adsorption studies were done in terms of intra-particle diffusion model, pseudo-first-order and pseudo-second-order models. The results showed that the data followed a pseudo-second-order model. [ABSTRACT FROM AUTHOR]

The Na-P1 zeolite was produced from coal fly ash and modified with different environmental friendly surfactants. The potential of these green modified zeolites was investigated as adsorbents for Cr(VI) ions in a batch system. XRD, SEM, XRF, and ICP-AES analyses were used for the characterization of raw materials and zeolite samples. The environmental friendly modified zeolites successfully immobilized different toxic elements in their framework inhibiting the transfer of these toxic elements to the surrounding liquid phase. The effects of various operational parameters on Cr(VI) removal were studied. The Hexamethylenediamine (HDTMA) and Ammonyx KP (KP) modified zeolites had larger chromium removal potential than the other samples at all temperatures. The effectiveness of Cr(VI) ions elimination became greater as the pH decreased and the adsorbent dose increased. The Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were fitted to the equilibrium data. The Dubinin–Radushkevich and Langmuir models gave a better fitness to equilibrium data of HDTMA-Na-P1 and KP-Na-P1, respectively. The positive and high ΔH° values showed the endothermic nature of the total Cr(VI) sorption procedure and indicated that Cr(VI) adsorption onto HDTMA-Na-P1 and KP-Na-P1 is a chemisorption. The negative ΔS° values also showed that chromium ions were stable on the surface of adsorbents. The adsorption potential of the developed eco-friendly KP-Na-P1 was higher than those of other adsorbents reported in the literature. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work was to study the removal of anionic Biebrich Scarlet (BS) dyes from aqueous solution by using magnetic Fe 3 O 4 zeolite 13X (Fe 3 O 4 /13X). The composite adsorbent, synthesized by co-precipitation method, was characterized by X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Vibrating Sample Magnetometry (VSM), as well as Inductively Coupled Plasma (ICP) and Zeta Potential (ZP) measurements. The three-factor Central Composite Design (CCD) combined with Response Surface Modeling (RSM) was used for maximizing the BS dye removal from aqueous solution. The three independent variables, namely the solution pH (in the 3–9 range), initial dye concentration (30–100 mg/L) and adsorbent mass (90–350 mg/L) served as inputs to the quadratic model of adsorption capacity. The findings yielded by analysis of variance (ANOVA) confirmed the high significance of the regression model. The predicted values of the BS adsorption capacity were in good agreement with the corresponding experimental values. Optimized conditions for maximum BS dye removal by Fe 3 O 4 /13X were pH 3.10, 98.05 mg/L initial dye concentration, and 288.82 mg/L adsorbent mass. The validity of the quadratic model was examined by conducting experiments in which the optimum values of process variables were employed, and good agreement was found between the experimental and predicted values. The present study shows that magnetic zeolite can be used as an adsorbent for highly efficient BS dye removal. [ABSTRACT FROM AUTHOR]

Studying the removal of rhodamine B (RB) dye by using zeolite 13X molecular sieves supported by Fe2O3 nanoparticles (denoted as Fe2O3-13X) is the main objective of this study. Fe2O3-13X was synthesized and modified by the addition of sodium dodecyl sulfate (SDS). The prepared Fe2O3-13X was characterized by XRD, TEM, SEM, and zeta potential. The effects of the solution pH, SDS amount, contact time, initial dye concentration, and adsorbent dosage on the removal efficiency of RB were studied. A maximum removal efficiency of 99.3% was achieved. The adsorption equilibrium data of RB were fitted using the Freundlich model, yielding the maximum adsorption capacity of 89.3 mg/g. The findings revealed that the RB adsorption onto Fe2O3-13X modified with SDS (Fe2O3-13X-Ms) was described by a pseudo-second-order kinetic equation. The results reported in this paper indicate that a high RB removal percentage was attained by adding SDS to Fe2O3-13X. [ABSTRACT FROM AUTHOR]

Abstract: Zeolites are microporous crystalline hydrated aluminosilicates, which have found various applications because of their very unique physicochemical characteristics such as ion exchange and adsorption–desorption properties. Significant progress has been made in recent years on applications of these inorganic adsorbents in different industries including agriculture, aquaculture, water and wastewater treatment, air purification and petrochemicals. This review article intends to summarize the published reports on the applications of natural, synthetic and modified zeolites in aquaculture industry. Application of zeolitic materials for water quality improvement of fish farms and fish transportation tanks by selective capturing of ammonia and toxic heavy metals and zeolite application as feed additive to enhance fish growth and promote their health and nutritional parameters are the most important discussed areas. According to the technical data that are discussed in this review, natural and synthetic zeolites should be considered as materials with tremendous potential of applications in the aquaculture industry. Considerable amounts of research works are under way to explore other opportunities for application of zeolites to benefit aquaculture industry. [ABSTRACT FROM AUTHOR]

Eight-membered ring small-pore zeolites Rho and KFI have been synthesized, characterized and tested for dehydration of methanol to dimethyl ether at low-temperature, and compared with other zeolites and three different samples of γ-Al 2 O 3 . Both the zeolites were mainly crystallized from the synthesis gels with the Si/Al ratio of 5.0 by a conventional hydrothermal method without any agitation. The amount of total solid-acid sites was 1.65 mmol g −1 and 2.53 mmol g −1 for zeolite KFI and Rho, respectively. In addition, zeolites SSZ-13, RUB-13, and ZSM-5 were also employed for the reaction. Reaction conditions were optimized for a low-temperature catalytic dehydration of methanol selectively to dimethyl ether. Methanol dehydration efficiency of various zeolitic frameworks is discussed against the strength of solid-acidity, type of channel structure, specific surface area, and particle size. At temperatures ≤ 200 °C, the overall catalytic efficiency of the small-pore zeolites with appropriate medium-strong acidity and 3-D channels was superior to that of the reference γ-Al 2 O 3 materials. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of single mode microwave irradiation on the synthesis of zeolite Na-A from sodium aluminate and sodium silicate gel at atmospheric pressure. Microwave irradiation has been shown to accelerate the zeolitization process from several hours to several minutes. The microwave irradiation employed was produced in a single mode lab scale microwave, which enabled control of irradiated power and temperature of the reaction mixture, while the pressure was controlled by affixing a condenser to a Teflon reactor vessel with a working volume of 20 mL. Two sets of experiments were conducted, the first with three levels of temperature and reaction time, and the second with three levels of power and reaction time. The characteristics and physical properties of the synthesized samples were analyzed with different instrumental techniques including XRD, Rietveld refinement, SEM, BET, TGA, and by determination of cation exchange capacity (CEC). It was observed that the crystallinity of the product was influenced by both power and time of microwave irradiation; moreover power and time of microwave irradiation influenced the phase selection between Na-A and Na-X. Single phase zeolite Na-A was achieved with a crystallinity of 80 % at 300 W using single mode microwave irradiation at atmospheric pressure after 30 min of exposure to radiation. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of microwave irradiation on the synthesis of zeolite Na-A from coal fly ash at atmospheric pressure. Microwave irradiation has shown to accelerate zeolitization from several hours to several minutes. A single-mode laboratory-scale microwave was employed, which enabled control of irradiated power and temperature of the reaction mixture, while the pressure was controlled by affixing a condenser on the 40 mL Teflon reactor vessel with a working volume 20 mL. Design of Experiment was used to compare two methods of converting CFA to zeolite-A, direct hydrothermal method and indirect fusion method. Experiments conducted were two level four factorial designs. The first factor considered was the categorical factor of conversion method (hydrothermal vs fusion), while the other three factors investigated were power ( P), time ( θ), and aluminate concentration ( δ). Zeolite produced from CFA (CFAZA) was characterized using XRD, FTIR, SEM, TGA, BET, and cation exchange capacity. It was observed that the crystallinity of the product was influenced by factors such as, conversion method, power, time, and aluminate concentration. The hydrothermal and fusion products were comparable to each other in their characteristics, however, hydrothermal CFAZA performed better at immobilizing heavy metal ions and showed better crystalline structure, whereas fusion CFAZA had a higher BET surface area and a slightly higher CEC. Regardless of the performance of the categorical factors the other factors, i.e., power, time, and aluminate concentration followed the same trend for both types of CFAZA. [ABSTRACT FROM AUTHOR]

In this study, a relevant literature has been reviewed focusing on the carbon dioxide capture technologies in general, such as amine-based absorption as conventional carbon dioxide capturing technology, aqueous ammonia-based absorption, membranes, and adsorption material (e.g., zeolites, and activated carbons). In more details, metal organic frameworks (MOFs) as new emerging technologies for carbon dioxide adsorption are discussed. The MOFs section is intended to provide a comprehensive overview of MOFs including material characteristics and synthesis, structural features, CO adsorption capacity, heat of adsorption and selectivity of CO. [ABSTRACT FROM AUTHOR]

• Sole gismondine-type zeolite was synthesized with blast furnace slag. • The formation mechanism of zeolite was investigated. • All major components of blast furnace slag were utilized fully. • The route reduces the overall cost of CO 2 mineralization. CO 2 mineralization is one of the most important strategies for reduction of anthropogenic CO 2 emissions. Preparation of high-value products during this process would improve its economy and make it more promising for industrial applications. In this study, sole gismondine-type zeolite (zeolite P) was synthesized during the CO 2 mineralization process by using blast furnace slag as feedstock. The optimal experimental conditions and regression model for synthesis of zeolite was determined through Response surface methodology. The results showed that a well-crystallized zeolite was obtained with a short hydrothermal time at high temperature even at low alkalinity. However, too high temperature and alkalinity can promote the formation of sodalite, reducing the relative content of zeolite P in the product. Different analysis methods such as XRD, FTIR, SEM were applied to characterize the products and investigate the synthesis mechanism of zeolite formation. The analysis indicated that zeolite products with a uniform shape of octahedron can be obtained under mild conditions (NaOH concentration of 1.5 mol·L−1, 120 °C, 2∼4 h). The formation of zeolite from blast furnace slag can be divided into four steps, i.e., dissolution of aluminate ions and silicate ions from raw material, formation of the amorphous intermediate aluminosilicate gel precursor, rearrangement of the structure of aluminosilicate precursor to form nuclei of zeolite, and crystal growth. Based on the results in this study, major components of blast furnace slag were utilized fully (Mg and Ca for CO 2 storage, whilst Al and Si for synthesis of zeolite), reducing the overall cost of CO 2 mineralization. [ABSTRACT FROM AUTHOR]

In the present work, natural clinoptilolite was converted to zeolite NaP using ultrasonic energy, in which the transformation time shortened remarkably. The effect of post-synthesis treatment using conventional hydrothermal was also investigated. The synthesized powders were characterized by XRD, TGA/DTA, SEM, and PSD analysis. The results showed that, increasing the sonication time (energy) has no significant effect on the product's morphology. The crystallinity of the synthesized samples increased slightly with increasing sonication time, but their yield remained relatively unchanged. Furthermore, post-synthesis hydrothermal treatment showed very little influence on properties of the final product. Because the ultrasonic irradiation creates acoustic cavitation cracks on the surface structure of clinoptilolite particulates and increases the concentration of soluble alumino-silicate species, which favors the prevailing super-saturation, crystallization and crystal growth of zeolite NaP happen faster. The particles of zeolite NaP synthesized by ultrasonic irradiation consist of small crystallites of uniform size. [ABSTRACT FROM AUTHOR]

It is essential to capture carbon dioxide from flue gas because it is considered one of the main causes of global warming. Several materials and different methods have been reported for CO2 capturing including adsorption onto zeolites and porous membranes, as well as absorption in amine solutions. All such methods require high energy input and high cost. A new class of porous materials called Metal Organic Frameworks (MOFs) exhibited excellent performance in extracting carbon dioxide from a gas mixture. In this study, the breakthrough curves for the adsorption of carbon dioxide on CPM-5 (crystalline porous materials) were obtained experimentally and theoretically using a laboratory-scale fixed-bed column at different experimental conditions such as feed flow rate, adsorption temperature, and feed concentration. It was found that the CPM-5 has a dynamic CO2 adsorption capacity of 11.9 wt % (2.7 mmol/g) (corresponding to 8 mL/min, 298 K, and 25% v/v CO2). The tested CPM-5 showed an outstanding adsorption equilibrium capacity (e.g., 2.3 mmol/g (10.2 wt %) at 298 K) compared to other adsorbents, which can be considered as an attractive adsorbent for separation of CO2 from flue gas. [ABSTRACT FROM AUTHOR]

Successful conversion of coal fly ash (CFA) to synthetic NaP zeolite with zero liquid discharge is reported in this article. The process eliminates the need for large amounts of water and the need for a huge wastewater treatment unit. The need for water, as a make-up stream, is only to compensate water losses during sampling and drying. Savings associated with minimizing make-up water and eliminating wastewater treatment unit can be substantial. Water and sodium hydroxide consumption is reduced by 90% and 50%, respectively. Furthermore, quality of the NaP zeolite (CFA-ZP) obtained is comparable to conventional method. The zeolitized product shows high crystallinity and leach resistance toward heavy metal and trace element content of the product. Leaching tests revealed that the concentrations of most of trace elements in leachate of CFA-ZP were less than threshold limit for landfill leachate and wastewater effluent for discharging into river and surface water. [ABSTRACT FROM AUTHOR]

The ever increasing consumption of coal around the world has given rise to the by-product coal fly ash that requires an urgent attention and is gaining much needed research attention. This paper introduces pioneering work on zeolitization of coal fly ash utilizing conventional heating methods and reviews the progress made in the conversion of coal fly ash to zeolite and its applications while strongly focusing on the utilization of microwave and ultrasound energies in achieving this goal. An introduction to coal fly ash and zeolitic materials is given and the conversion of the formal to the latter is discussed. Zeolites are multi-utility crystals that have attracted much attention in the research community. Zeolites synthesized from pure chemical precursors are inherently different from zeolites produced from coal fly ash therefore; published works which have investigated the application of zeolites produced from coal fly ash are also discussed. Microwave and ultrasound energies have been reported to dramatically decrease reaction times due to the influences on the induction periods and nucleation. In the last few years these novel energies have blossomed in a useful technique for many applications. As novel energies they hold great promise in rapid and efficient conversion of coal fly ash to value added materials such as zeolites. [ABSTRACT FROM AUTHOR]

Abstract: SAPO-34 zeolite-like particles were successfully synthesized at high temperature environment. An L9 orthogonal array of the Taguchi method was implemented to investigate the effects of experimental conditions to prepare SAPO-34 with respect to crystallinity of the final product phase. The results showed that the favorable phase crystallinity was improved by increasing the hydrothermal synthesis temperature and organic template content, whereas increasing the water content in synthesis mixture decreased the crystallinity. No significant changes in crystallinity of the final products were observed by increasing the synthesis duration. In addition, zeolite SAPO-5, which was formed as the impurity in the mid temperature runs, was not be formed at high temperature environment due to its low hydrothermal stability. [Copyright &y& Elsevier]

CO 2 mineralization is a technological solution to reduce anthropogenic CO 2 emissions. It is more cost-effective to use industrial wastes as feedstock than natural minerals and eliminate some of the energy-consuming operations, to recover various value-added byproducts. In this study, hydroxycancrinite zeolite was synthesized by a solvent-free method during the carbonation of blast furnace slag (BFS) as the waste feedstock. The effects of various process factors such as the alkaline dosage, crystallization temperature, and crystallization batch time on the synthesis of hydroxycancrinite were systematically investigated. A well-crystallized spherical hydroxycancrinite was obtained by mixing with NaOH solid and then crystallizing at 100 °C for 4 h. The as-synthesized products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, and Brunauer-Emmett-Teller analysis. The results revealed that pure microspheres of hydroxycancrinites are obtained with a diameter of ∼1 μm and a surface area of 37.2 m2/g. Based on the material balance and preliminary economic evaluation, 361 kg CO 2 /t BFS can be stored by calcium and magnesium components, whereas almost all of the silicon and aluminum are recovered as value-added zeolites, which significantly improve the process economy. Image 1 • Hydroxycancrinite zeolite was synthesized by a solvent-free method from blast furnace slag. • The synthesis process of zeolite was optimized. • All major elements in blast furnace slag could be utilized fully. • The route enhances the economy of CO 2 mineralization. [ABSTRACT FROM AUTHOR]