Zeolite Surface Research Articles

Novel Wastewater Treatment by Using Newly Prepared Green Seaweed-Zeolite Nanocomposite.

A dependent step-by-step study that included experimental and field study was applied to explore the simplest and most effective system that could be applied for adsorption of Congo Red (CR) dye from the effluent of wastewater that comes out from different industries. Zeolite (Z) surface and pores were subjected to a modification process using green seaweed (GS) algae. Thereafter, each Z, GS, and composite from both were evaluated based on the adsorption efficacy to clean up CR dyes from aqueous solutions. A wet impregnation method was followed to fabricate the zeolite/algae (ZGS) nanocomposite which was characterized using the most appropriate characterization techniques. Batch experiments were selected to be the method of choice in order to follow up the performance of the adsorption process versus different practical variables. Moreover, dye adsorption kinetics and isotherms were investigated as well. At lowered concentrations of CR, the novel nanocomposite ZGS revealed more efficacy than its counterparts, Z and GS, in terms of the adsorption capacity. The maximum adsorption capacities were found to be 8.10, 10.30, and 19.70 mg/g for Z, GS, and ZGS, respectively. Laboratory tests confirmed that the novel nanocomposite ZGS could be introduced as a new and economical nanoadsorbent to capture and remove negatively charged dyes from wastewater effluents that come out from industries at lower concentrations of CR dye and analogous compounds. The dye adsorption on GS, Z, and ZGS coincide with the pseudo-first, Langmuir isotherm, and second-order models. Evaluation for the sorption mechanism was conducted using a diffusion model known as Weber’s intraparticle. Depending on the last findings, field experiments on removing dyes from industrial wastewater revealed optimistic findings as the efficiency of our modern and eco-friendly nanoadsorbent reached 91.11%, which helps in the reuse of industrial wastewater.

Physical and hydraulic properties of bioretention substrate using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite

ABSTRACT This study using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite as a component of bioretention substrate, to investigate the effect of HDTMA modification on the basic physical and hydraulic properties of substrate layer. Two different levels of HDTMA modified zeolite (ZHD10 and ZHD50) were mixed with a mixture consists of peat soil, river sand and compost (fixed volumetric proportion at 5:4:1) with varying volumetric percentage (25%, 50%, and 75%) to form substrate media. The modification only changes the physical properties of zeolite and media with zeolite slightly, while significant changes in surface hydrophobicity and hydraulic properties were observed. A distinct decline of saturated hydraulic conductivity () values of zeolite can be observed after the modification, values drop 36.5% for ZHD10 and 55.1% for ZHD50. In contrast, values of substrate media using zeolite increase after the modification at the same volumetric ratio of zeolite. When 50% of zeolite (v/v%) was used in substrate, for natural zeolite, ZHD10 and ZHD50 was 0.024, 0.038 and 0.075 cm/s, respectively. Such alterations in are associated with the changes of surface hydrophobicity after the modification and ion exchange between modified zeolite and other materials after soaking into water. Changes in water retention characteristics (WRC) curves were in good accord with the variations in , and can be interpreted by the changed of tested materials. The orientations of HDTMA molecules loaded on zeolite surface were suggested to play crucial roles in altering the hydraulic properties of zeolite added substrate.

The mechanisms and monitoring of zeolite remediating chemical oxygen demand, NH4+, and Pb2+

Zeolite is utilized as an effective filling material in a permeable reactive barrier (PRB) at contaminated sites. Evaluation of the long-term performance of such barrier demands thorough understanding of the remediation mechanisms and real-time monitoring technique. In this study, the processes of zeolite remediation of three typical major contaminants from municipal solid waste sites (Chemical Oxygen Demand (COD), NH4+, and Pb2+, respectively) were simulated with column test, analyzed with microscopic methods (MIP, BET, SEM, XPS, FTIR, and XRD) and monitored with the spectral induced polarization (SIP) technique. Zeolite remediates COD simulant, KC8H5O4, through cation exchange of K+ and surface complexation of C8H5O4−. Patchy distribution of K+ with size range of 16–60 μm was both observed and calculated from the peak frequency of imaginary conductivity of SIP responses, which was attributed to the preferential complexation of C8H5O4− at low velocity regions (dents) on zeolite surfaces. Zeolite remediates NH4+ mainly through ion exchange due to the higher affinity of NH4+ to zeolite surfaces than that of Na+. Zeolite remediates Pb2+ mainly through surface complexation, with clusters of complexed Pb (II) of wide size range (a few μm to 25 μm) residing on zeolite particle surfaces. The real conductivity of SIP responses for zeolite under contaminant flow-through is primarily sensitive to the ionic strength of influx fluid. A mean size of near 270 μm was calculated from SIP responses in all three cases, which was attributed to the pore throat of zeolite. Spectral induced polarization demonstrated its capability of monitoring three processes of zeolite remediating COD, NH4+, and Pb2+, respectively, and held promise of non-invasively monitoring of long-term performance of contaminant containing barriers.

Electrical Method for In Vivo Testing of Exhalation Sensors Based on Natural Clinoptilolite

Natural substances with a complex chemical structure can be advantageously used for functional applications. Such functional materials can be found both in the mineral and biological worlds. Owing to the presence of ionic charge carriers (i.e., extra-framework cations) in their crystal lattice, whose mobility is strictly depending on parameters of the external environment (e.g., temperature, humidity, presence of small gaseous polar molecules, etc.), zeolites can be industrially exploited as a novel functional material class with great potentialities in sensors and electric/electronic field. For fast-responding chemical-sensing applications, ionic transport at the zeolite surface is much more useful than bulk-transport, since molecular transport in the channel network takes place by a very slow diffusion mechanism. The environmental dependence of electrical conductivity of common natural zeolites characterized by an aluminous nature (e.g., chabasite, clinoptilolite, etc.) can be conveniently exploited to fabricate impedimetric water-vapor sensors for apnea syndrome monitoring. The high mechanical, thermal, and chemical stability of geomorphic clinoptilolite (the most widely spread natural zeolite type) makes this type of zeolite the most adequate mineral substance to fabricate self-supporting impedimetric water-vapor sensors. In the development of devices for medical monitoring (e.g., apnea-syndrome monitors), it is very important to combine these inexpensive nature-made sensors with a low-weight simplified electronic circuitry that can be easily integrated in wearable items (e.g., garments, wristwatch, etc.). Very low power square-wave voltage sources (micro-Watt voltage sources) show significant voltage drops under only a minimal electric load, and this property of the ac generator can be advantageously exploited for detecting the small impedimetric change observed in clinoptilolite sensors during their exposition to water vapor coming from the human respiratory exhalation. Owing to the ionic conduction mechanism (single-charge carrier) characterizing the zeolite slab surface, the sensor biasing by an ac signal is strictly required. Cheap handheld multimeters frequently include a very low power square-wave (or sinusoidal) voltage source of different frequency (typically 50 Hz or 1 kHz) that is used as a signal injector (signal tracer) to test audio amplifiers (low-frequency amplifies), tone control (equalizer), radios, etc. Such multimeter outputs can be connected in parallel with a true-RMS (Root-Mean-Square) ac voltmeter to detect the response of the clinoptilolite-based impedimetric sensors as voltage drop. The frequency of exhalation during breathing can be measured, and the exhalation behavior can be visualized, too, by using the voltmeter readings. Many handheld multimeters also include a data-logging possibility, which is extremely useful to record the voltage reading over time, thus giving a time-resolved voltage measurement that contains all information concerning the breathing test. Based on the same principle (i.e., voltage drop under minimal resistive load) a devoted electronic circuitry can also be made.

Micropore blocking strategy for mitigating adsorption and diffusion limitations in the direct epoxidation of propylene

The direct epoxidation of propylene has been a hot topic in the academic field for years. Researchers have spent extensive effort on the development of catalyst, however, only limited attention on the effect of reaction conditions, especially pressure. In this paper, we found for the first time that elevated pressure should favor the forward epoxidation reaction, it actually led to a drop of reaction rate in this system. We proposed explanation by considering the difficulty of gas molecules diffusing into and out of the micropores on the TS-1 zeolite surface. Higher pressure would inhibit the escaping of the gas molecules from the micropores and lead to carbon deposition inside the channel. To validate this hypothesis, we designed and compared catalysts with micropores blocked (BTS-1) and unblocked (TS-1) and found that the BTS-1 showed higher resistance to pressure change and significantly longer life time than the TS-1.

Zeolites as initial structures for the preparation of functional materials

Functional materials that have a prominent place in high technology are not classified according to their origin (metals, ceramics, polymers, glass, etc.) or processing technology, but by the functions they can perform. Zeolites are an interesting and important raw material for preparing a variety of target substances. From a traditional point of view, they are aluminosilicate oxide with a nanoporous structure. However, zeolites are adsorbents, ion exchangers, catalysts, and can be used in medicine, agriculture, construction and many other applications. The availability of natural minerals, as well as methods of synthesis of their analogues, and modification of both natural and synthetic materials, developed in sufficient detail, allows to obtain a variety of substances with predetermined properties, which are tailored for specific purposes. This paper will discuss a wide range of existing and also possible applications of these materials, such as catalysis, photocatalysis and sensor design. The specified modifications are achieved through controlled changes in the chemical composition of the zeolite surface.

Effect of promoter in hierarchical hollow Pt/Beta catalysts on the hydrodeoxygenation of phenol

An efficient hydrodeoxygenation (HDO) catalyst (i.e., Pt/Beta) is designed to improve the quality of bio-oil by removing chemicals with oxygen-containing functional groups (e.g., phenol). Hierarchical hollow Beta molecular sieves are obtained via an alkaline treatment with surfactants (i.e., dodecyl trimethyl ammonium bromides (DTAB) and stearyl trimethyl ammoium bromide (STAB)). Surfactants adsorb on the surface of zeolitic surface to inhibit alkaline etching and finally to form a hollow morphology. A competitive adsorption of phenol on acid and metallic sites is observed on Pt/Beta catalysts. A large amount of Brønsted acids with a higher acidic strength have a stronger adsorption ability of phenol. Therefore, more metallic sites are required to provide adsorption and HDO sites for phenol molecules. As for cyclohexane, more acids with a higher acidic strength are desired. However, coke covers acid sites and inhibits the dehydration reaction. These results provide a hierarchical hollow molecular sieves preparation method and propose the importance of acid regulation in the design of HDO catalysts.

Ethane conversion in the presence of CO2 over Co-based ZSM-5 zeolite: Co species controlling the reaction pathway

Two cobalt-based ZSM-5 catalysts CoZ-IE and CoZ-IM were prepared by ion-exchange and incipient wetness impregnation method, respectively, and characterized by XRD, N2 adsorption, TEM, XPS, UV–vis, H2-TPR and Py-IR. The catalytic performance towards ethane conversion over the two catalysts in the presence of CO2 was compared. Despite of their similar textual properties and Co contents, the product distributions over the two catalysts were quite different. Ethylene with high selectivity of 95% formed over CoZ-IE while syngas was produced as the main product on CoZ-IM, indicating dry reforming becomes the dominant reaction pathway instead of dehydrogenation. The difference pathway can be ascribed to the different nature of Co species in two catalysts. The isolated Co2+ anchored at zeolitic framework in CoZ-IE is quite stable and can only act as Lewis acid sites for ethane dehydrogenation. In contrast, the cobalt oxides on the zeolitic surface in CoZ-IM can proceed oxidation-reduction cycles in the CO2-C2H6 system, facilitating the activation of CO2 and the scission of C−C bonds, leading to the dry reforming of ethane.

Catalytic synergistic effect of bis-ZSM-5 zeolite with different crystal sizes for xylene isomerization

High-performance xylene isomerization catalysts were prepared by physical mixing of two types of ZSM-5 after reasonable modification. Here, SZ/LZ catalysts were prepared by simple physical mixing of two modified Pt–3Si/SZ-5 and Mo/LZ-5 with different crystal sizes. The catalytic performance of the catalysts was evaluated in the mixed xylene isomerization reaction on a fixed bed. The catalysts were characterized by XRD, BET, SEM, TEM, XPS, Py-IR, NH 3 -TPD and probe molecular reactions. The results demonstrated that the deposition of silica finely adjusted the size of the pore opening and passivated the acid sites on the external surface of the SZ-5 zeolite. The loading of MoO 3 reduced the distribution of acidic site density of LZ-5. The reaction sites of ethylbenzene, m-xylene and o-xylene were precisely distributed by the 2SZ/8LZ catalyst. Optimizing the mixing ratio and reaction temperature of the catalysts further improved their synergistic catalysis. High EB conversion rate (74.9%), high PX yield (23.3%) and low xylene loss (1.41%) were obtained by controlling the reaction path of ethylbenzene, m-xylene and o-xylene. High performance xylene isomerization catalysts (2SZ/8LZ) were obtained by a simple mixture of the dealkylation catalyst (Pt–3Si/SZ-5) and the isomerization catalyst (Mo/LZ-5). It demonstrates excellent catalytic activity in mixed xylene isomerization reactions. • The SiO 2 deposition effectively covers the acidic sites on the external surface and adjusts the pore-opening size. • The modification of MoO 3 reduces the acidic site density of LZ-5 with large crystal size and improves the MX and OX isomerization activity. • The ethylbenzene conversion rate, xylene loss rate and PX yield of 2SZ/8LZ reached 74.9%,1.41% and 23.3% at 380 °C, respectively.

Development of polyfunctional sorbents based on zeolites for wastewater treatment

The article presents technological approaches to solving the problem of involving production waste in the technology of sorption treatment of wastewater by component composition. Zeolites of the Holinsky deposit of Eastern Transbaikalia of the klinoptilolite type were taken as the initial matrix for creating a sorbent. We propose to use chloroanic wastes as an adsorbent of heavy metal ions, as which we propose to consider epichlorohydrin. The analysis of existing technologies for the disposal of organochlorine wastes, as well as known sorption materials, using sulfur as one of the modifier components. As a result of the deposition of a sulfur-containing polymer network on the surface of natural zeolite, not only its hydrophobization occurs. Sulfur atoms appear in its composition, which contributes to an increase in the selective ability to heavy metal ions, while copper ions are sorbed most rapidly. Previously, we proposed a method for modifying natural zeolites with highly organosilicon compounds, which made it possible to effectively neutralize oily wastewater.

Nanoarchitectonics of AgBr/4A Zeolite Composites with Enhanced Photocatalytic Properties Under Visible Light

AgBr/zeolite photocatalysts with different mass ratios were synthesized by depositing AgBr on the surface of 4A zeolite via the one-step precipitation method. AgBr/zeolite with mass ratios of 1:1 exhibited the highest photocatalytic activity, resulting in the complete degradation of the methyl orange (MO) dye under visible-light irradiation for 30[Formula: see text]min. The photocatalysts were characterized by N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The AgBr particles around 4A zeolite were smaller than pure AgBr. The specific surface area of 1:1 AgBr/zeolite was much larger than that of pure AgBr, which indicates that 1:1 AgBr/zeolite possessed more active sites. The photocatalytic stability of 1:1 AgBr/zeolite was investigated, and MO degradation rate of 90.4% was achieved after five cycling runs. The trapping experiments showed that hydroxyl radical ([Formula: see text]OH), superoxide radical ([Formula: see text]O[Formula: see text]), and hole (h[Formula: see text]) were the reactive species responsible for removing MO, and h[Formula: see text] played a key role in MO removal. A possible reaction mechanism in AgBr/zeolite photocatalytic system for MO degradation was proposed.

Adsorption of CO2 on ZSM-5 Zeolite: Analytical Investigation via a Multilayer Statistical Physics Model

In this paper, a synthesized zeolite (ZSM-5) is used as an adsorbent to analyze the adsorption phenomenon of carbon dioxide. This investigation, based on the statistical physics treatment, applied the multilayer model with saturation to understand the CO2 adsorption on four samples, namely M-ZSM-5 (M = Na+, Mg2+, Zn2+, La3+), at various temperatures T = 0 °C, 30 °C and 60 °C. The modeling results indicated that CO2 adsorption occurred via a non-parallel orientation on the ZSM-5 surface. The CO2 adsorption capacities varied from 26.14 to 28.65 cm3/g for Na-ZSM-5, from 25.82 to 27.97 cm3/g for Mg-ZSM-5, from 54.82 to 68.63 cm3/g for La-ZSM-5 and from 56.53 to 74.72 cm3/g for Zn-ZSM-5. Thus, Zn-ZSM-5 exhibits the highest adsorption amount. The analysis of the adsorption energies shows that the adsorption of CO2 on ZSM-5 zeolite is a physisorption phenomenon that could be controlled thanks to the energy parameters obtained via the numerical findings using the multilayer statistical model. Finally, the distribution of site energy was determined to confirm the physical character of the interactions between adsorbate/adsorbent and the heterogeneity of the zeolite surface.

Phosphate Fixation and P Mineralogy on Natural and Ca-Modified Zeolites During Simultaneous Nutrient Removal

The recovery and recycling of nutrients (N&P) from wastewater are one of the major topics to save primary energy and resources, to raise the efficiency of wastewater treatment plants, and to foster a future circular economy. In the present study, the removal of ammonium (NH4+) and phosphate (PO43−) using natural and Ca-treated zeolite is investigated in detail. Special emphasis is put on the simultaneous removal of both species from model solutions followed by elaborate mineralogical analyses (XRD, EPMA, FEG-SEM) for zeolite characterization and in order to determine the type, structure, and crystal sizes of CaP-phases precipitating on the zeolites surface. The effectivity of the phosphate segregation and chemical composition and the crystalline structure of the CaP-phase precipitating on the surface of the zeolite depend on the physico chemical conditions in particular on pH, molar ratio of Ca and P (due to zeolite modification), and the presence of NH4+. Results of simultaneous removal experiments of N&P revealed that Ca pretreatment enhances P segregation and increases the obtainable P-loadings of Ca–zeolites. Maximum P-loadings of 25 mg g−1 Ca–zeolite in binary solutions containing both ammonium and phosphate were obtained. Simultaneous phosphate removal by surface precipitation of CaP-phases does not significantly influence ammonium ion exchange and the type of CaP-precipitates formed on the zeolite surface is assumed to be mainly brushite and apatite.

THE CHEMICAL AND MINERAL COMPOSITION OF NATURAL ZEOLITES AND THEIR SORPTION PROPERTIES DURING OZONATION WITH DRAIN WATER FROM NUCLEAR POWER PLANTS

The article reveals the regularities of the overall process of ozonolytic destruction of organic components of model drain water from nuclear power plants and sorption of imitators of the main dose-forming radionuclides (Cs — with the isotopic 137Cs label; stable isotopes of Co, Sr, Mn salts) by natural zeolite of the Sokyrnytsky deposit and sorption-reagent compounds — salts of ferrous and manganese (II). The chemical composition of the main elements of zeolite after ozonation with the addition of iron and manganese salts practically does not differ from the composition of natural zeolite. Its phase composition in the ozonation process in the presence of ferrum salts is represented by the main rock-forming mineral clinoptilolite and the secondary mineral — quartz. The main ferrum-containing phase on the zeolite surface is goethite. Secondary phases include Fe(II)-Fe(III) layered double hydroxides (Green Rust) and lepidocrocite, but their relative content is insignificant. For zeolites, after ozonation with the addition of both ferrous and manganese (II) salts, the main phases are clinoptilolite and quartz. Manganese-containing phases on the zeolite surface are represented by hausmannite Mn3O4, manganese (II) oxide, and manganese oxyhydroxide MnO(OH)2. The iron- and manganese-containing phases deposited on the surface of the zeolite in the process of ozonation are mainly characterized by a weakly crystallized or amorphized structure. The main sorbent of dose-forming radionuclides is zeolite, not the iron- and manganese-containing compounds that formed on its surface during ozonolysis. The maximum degree of sorption of 137Cs by zeolite is up to 90% when the concentration of Fe2+ is increased to 50 mg/dm3 or Mn2+ to 100 mg/dm3. The degree of cobalt sorption is 97.5% at the initial typical concentration of competing cations (Fe2+ — 5 mg/dm3; Mn2+ — 10 mg/dm3) and when Mn2+ concentration increases to 100 mg/dm3. The maximum degree of extraction of Sr2+ and Mn2+ is 99.4% and 99.9%, respectively. For effective extraction of 137Cs and Co2+ by zeolite in the ozonation process, an increase in the concentration of competing Fe2+ cations is permissible — 50 mg/dm3; Mn2+ — 100 mg/dm3 in solutions. The efficiency of extraction of Sr2+ and Mn2+ practically does not depend on the concentration of competing cations (Fe2+, Mn2+) in the drain water solutions.

An in situ grown amorphous ZrO2 layer on zeolite for enhanced phosphate adsorption.

Zeolite supported amorphous metal oxide nanolayers with high specific surface area, abundant adsorption sites, and excellent reusability hold a bright prospect in the efficient removal of contaminants, yet it is proven to be still challenging to precisely regulate and control their synthesis. Herein, we reported a facile synthetic strategy for rational design and achieving the uniform and firm in situ growth of an amorphous ZrO2 layer decorated on the surface of zeolite (ZEO@AZ) for enhanced phosphate adsorption. The Langmuir isotherm model and pseudo-second order kinetic equation well described the adsorption process towards phosphate solution, and the synthetized ZEO@AZ exhibited an excellent maximum adsorption amount of 24.98 mgP g−1. Furthermore, the adsorption of phosphates on ZEO@AZ was confirmed to be chemisorption, endothermic and spontaneous. This approach for fabricating amorphous metal oxide nanolayers on a robust matrix may provide a new route for constructing composites with superb phosphate adsorption performance.

Sorption of Yb(III) from aqueous solution on Na-clinoptilolite

The sorptive properties of the Na-modified Transcarpathian clinoptilolite towards Yb(III) under dynamic conditions were investigated. The sorption capacity of the Na-form of Transcarpathian clinoptilolite towards Yb(III) significantly depends on the concentration of ytterbium salt, the pH of solution and the temperature of the preliminary calcination of the sorbent. The buffer solution has been used to maintain the constant value of pH, ioniс strength of the solutions and to improve the metrological characteristics of preconcentration methods of Yb. The trace amounts of Yb(III) most effectively are sorbed with borate buffer solution. The final concentration of the borate buffer in the sample solution is 4·10 - 4 М. The sorption capacity of Na-clinoptilolite under optimal conditions (diameter of zeolite grains was 0.20–0.31 mm; flow rate of ytterbium(III) solution with concentration 1.0 µg/mL through sorbent was 5 mL/min; temperature of preliminary thermal treatment ~ 50 ºC and pH 9.5) was 8.1 mg ytterbium per 1 g of Na-modified clinoptilolite. The sorption of Yb(III) is carried out mainly by means of the adsorption of soluble hydrolyzed forms of Yb(III) on the zeolite surface. The influence of the most common water ions on the preconcentration of Yb(III) on the Na-form of Transcarpathian clinoptilolite has been established. The solutions of 1 M KCl acidified by a hydrochloric acid to pH 4.0 are the most effective desorbents of ytterbium(III) ions from Na-clinoptilolite. It provides a 99 % withdrawal of Yb from the zeolite matrix. The method for ytterbium trace amounts preconcentration from aqueous solutions in a solid phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. Keywords: sorption, solid phase extraction, ytterbium, Na-clinoptilolite.

Deposition of Carbon Particulates Surfaces on Zeolites by Electron-Beam Evaporation of Graphite

Disordered carbon particulates were deposited on the surface of natural acid treated zeolite through graphite evaporation by electron beam to improve adsorption properties of the porous material. This study focuses on the development of the new material and not on applications. The effect of acid treatment and carbon deposition on the physical properties of the natural material was investigated. The zeolites were characterized via spectroscopic and microscopic methods, thermal analysis, and gas sorption analysis. Analysis revealed that the surface area and volume increased by a factor of ten after the carbon-coating was deposited onto the zeolite surface and indicated that the Si/Al ratio was higher with the acid treated sample. The acid treatment promoted dealumination of the zeolite and increased overall surface area, whereas the carbon coating re-aluminated the zeolite while adding silica back to the main molecular framework, thus increasing crystallinity and thermal stability and further improving the high surface area produced by the acid treatment.

Oxidative carbonylation of methane to acetic acid over micro-mesoporous rhodium-modified zeolites

It was first demonstrated that under liquid-phase conditions, an increase in the mesoporosity of ZSM-5 zeolite boosts a rhodium-containing catalyst activity in the oxidative carbonylation of methane to acetic acid (the acetic acid yield is 570 μmol g cat −1 ). To increase the mesoporosity of zeolite, two approaches were used: ultrasonic treatment and desilication of zeolite. The ultrasonic pretreatment leads to an increase in the acetic acid yield with a decrease in the total yield of oxygenates (methanol/acetic acid molar ratio is 0.2). On the contrary, preliminary desilication contributes to an increase in the total yield of oxygenates, mainly due to methanol (methanol/acetic acid molar ratio is 1.8). The combination of ultrasonic pretreatment and desilication of zeolite improves the total yield of oxygenates with an increase in the acetic acid yield. Such a change in the catalytic properties is attributed both to the acidity of the parent zeolite and the local atomic environment of rhodium. XAS spectroscopy showed that rhodium can be present on the zeolite surface either as nanoclusters giving rise to methanol or as isolated rhodium atoms, which promote the acetic acid formation. • Oxidative conversion of methane to acetic acid with the assistance of СО was studied. • Rhodium-modified microporous and micro-mesoporous zeolite catalysts were used. • Ultrasonic treatment of the zeolite leads to an increase in the yield of acetic acid. • Desilication of the zeolite leads to an increase in the yield of methanol. • The formation of acetic acid is facilitated by the monoatomic distribution of rhodium.

Amino-acid modulated hierarchical In/H-Beta zeolites for selective catalytic reduction of NO with CH4 in the presence of H2O and SO2.

Selective catalytic reduction of NO with CH4 (CH4-SCR) has been studied over a series of amino-acid mediated hierarchical beta zeolites with indium exchange. Amino acid mesoporogens greatly affect the NO reduction (DeNOx) efficiency of In/H-Beta catalysts. Mesoporous In/H-Beta-P synthesized using proline exhibits the highest NOx removal efficiency of 40% in excess oxygen and poisonous SO2 and H2O, 10% higher than our previously optimized In/H-Beta catalyst using commercial beta zeolites with a similar Si/Al ratio. Analyses using XRD, N2 adsorption-desorption, EPR, SEM, TEM, EDX, ICP, 27Al and 29Si MAS NMR, XPS, H2-TPR, NH3-TPD, and Py-IR reveal that amino acids promote beta crystallization, modulate zeolite acid sites and surface oxygen species, and generate hierarchical pore architectures without affecting the Si/Al ratio, indium content, and percentage of the active InO+ species. The mosaic-structured In/H-Beta-P exhibits the strongest Brønsted acidity and surface labile oxygen which enhance the oxyindium interaction with the zeolite framework, promoting CH4-SCR activity. The strong acidity, surface active oxygen species, and mesopores lead to excellent stability of the In/H-Beta-P catalyst in the presence of SO2 and H2O, withstanding several catalytic DeNOx cycles under harsh reaction conditions.

Kajian Kemampuan Adsorpsi Zeolit Alam Terimpregnasi Asam Lemak Hidroksamat sebagai Agen Pengkelat Ion Logam Tembaga

One of the way to recycle heavy metals in the prevention of environmental pollution is by using a solid-liquid extraction method through the impregnation mechanism of chelating agent in the adsorbent to increase its ability to bind heavy metal ions. In this study, the impregnation of fatty hydroxamic acids (FHA) successfully carried out on active natural zeolite (ZAA). This is has been done to increase the maximum adsorption capacity of ZAA towards heavy metals. The purpose of this study was to examine the adsorption ability of FHA impregnated onto ZAA as a chelating agent in copper metal ions by using column chromatography. This column contains FHA, which synthesized from crude rice bran oil and impregnated onto ZAA. There are several parameters were investigated, they are, the effect of FHA concentration, mass of FHA-ZAA resin and pH of the metal ion sample. From this study, the concentration of FHA impregnated on the zeolite surface reached 41.60%. The optimum conditions for Cu(II) adsorption by FHA-ZAA were as follows: mass ratio of FHA-ZAA resin with Cu(II) concentration (g : ppm) was 1:100 and the optimum condition of Cu(II) ion was at pH 5