Synthetic Zeolite NaX Research Articles

Studies of the effect of zeolites after acid modification on the chemical stability of sulfonylurea herbicides

The possibility of removing the phytotoxicity of soil residues of herbicides using zeolites, which have the ability to catalyze the decomposition of such xenobiotics, has been shown. The sorption characteristics of natural zeolite of the ZPS brand and its acid-modified form were studied by the method of low-temperature nitrogen sorption. Metsulfuron-methyl in aqueous solutions undergoes destruction in the presence of natural acid-modified zeolite. The concentration of MSM in aqueous solutions decreases only for suspensions with ZP-N + -1. In 96 hours, the destruction of MSM is 70%, and in 14 days (336 hours) by 93%. Acid modification of zeolite leads to an increase in the number of micropores and has little effect on their composition. No significant destruction of MSM was observed on synthetic zeolites NaX and 10X.

INVESTIGATION OF THE GAS MIXTURE ADSORPTION PROCESS IN A FIXED LAYER OF THE NaX ADSORBENT

The paper describes a 4-adsorbent installation for cleaning gas mixtures from H2S, CO2 and NO2 with zeolite. The lower and upper limits of the condensate level in the separator were controlled by electric contact pressure gauges, and the pressure was recorded on the operator panel. The number of adsorbers is 4, the height of the fixed zeolite layer is 3.6 m. Long-term operation of the adsorption unit under real operating conditions has shown that the temperature of zeolite regeneration largely depends on the quality of the gas entering the adsorption unit. As can be seen, the desorption of carbon dioxide is completed at the beginning, then hydrogen sulfide, and at the end - moisture vapor, and the time for complete desorption of all adsorbed components is limited by internal diffusion inhibition of the sorbed components. The greatest desorption time, as expected, is due to moisture vapors. It has been experimentally established that when heated with hot gas at the maximum permissible speed, the time for complete desorption of moisture is 150-160 minutes. For practical calculations, the time required for complete dehydration of the zeolite is taken at least 3 hours, which is confirmed experimentally. Keywords: adsorption, synthetic zeolite NaX, fixed adsorbent layer, gas mixture, desorbed substances.

Process optimization for copper sorption onto synthetic zeolite NaX

Process optimization for copper sorption onto synthetic zeolite NaX

Синтетический цеолит NaX как кормовая добавка для цыплят-бройлеров

Синтетический цеолит NaX как кормовая добавка для цыплят-бройлеров

Experimental Study on the Removal of VOCs and PAHs by Zeolites and Surfactant-Modified Zeolites

Synthetic zeolite Na-X and clinoptilolite (Cp) as well as their modifications with quaternary ammonium salts were used to remove volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. A novel procedure was developed for the synthesis of organo-zeolites which consisted of surface modification with hexadecyltrimethylammonium bromide (HDTMA) in amounts of 1.0 and 2.0 of external cation exchange capacity (ECEC). Modification of both zeolites with HDTMA improved sorption properties. p-Xylene and dibenz[a,h]anthracene were adsorbed in amounts of 6.82 and 0.65 mg/g, respectively. Ethylbenzene and naphthalene were the lowest-removed hydrocarbons (2.99 and 0.058, respectively). The removal efficiencies for BTEX followed the order p-xylene > toluene > benzene > ethylbenzene, and for PAHs they followed the order dibenz[a,h]anthracene > benzo[a]pyrene > anthracene > naphthalene. Efficiency of sorption depends on the chemical properties of the various organic compounds (d...

Sorption of organic compounds by organo-zeolites [abstract

Organic compounds such as BTEX and PAHs are one of the most common contaminants in water system. These contaminants would take decades to degrade and they have harmful effects on human health (Qin et al., 2008). Several treatment methods have been developed to remove those contaminants from industrial wastewater. They include ion-exchange, filtration, adsorption and the use of various types of sorbents for example zeolites (Kibazohi et al., 2004; Mathur et al., 2007; Aivaliotiet al., 2012; Almeida et al. 2012). Natural clinoptilolite (Cp) from the Bystre deposit in Slovakia and zeolite Na-X synthesized from fly ash has been modified with a hexadecyltrimethyl ammonium bromide (HDTMA) in amounts of 1.0 and 2.0 of external cation exchange capacity (ECEC) of the zeolites (Szala et al., 2013). The sorption properties of unmodified zeolites and organo-zeolites in terms of aqueous solutions of benzene, ethylobenzene, toluene, p-xylene (BTEX) and their mixtures as well as anthracene, naphthalene, benzo[a]pyrene, dibenzo[a,h]anthracene (PAHs) and their mixtures at different concentrations were evaluated. The results showed that the modification of the zeolite Na-X and Cp with HDTMA improves the sorption properties. Modification in the amount of 1.0 ECEC proved to be the best in terms of p-xylene, anthracene, naphthalene, benzo[a]pyrene, dibenzo[a,h]anthracene. On the other hand benzene, ethylobenzene and toluene were adsorbed the most effectively by 2.0 ECEC modification of Na-X and Cp. Based on experimental data, the removal efficiencies for BTEX follows the order: p-xylene > toluene > benzene > ethylobenzene, for POHs: dibenzo[a,h]anthracene > benzo[a]pyrene > anthracene > naphthalene. P-xylene and naphtalene were adsorbed in the greatest quantity and benzene and anthracene in the lowest quantity from the mixtures of BTEX and PAHs, respectively. The sorption efficiency depends on the physicochemical properties of the organic compounds (dipole moment, molar mass, molecule structure and the time of the sorption process) as well as natural Cp and synthetic zeolite Na-X properties, such as Si/Al ratio, texture parameters and external cation exchange capacity. With an increasing concentration of the hydrocarbons in the solution the sorption capacity increases (Szala et al., 2015). Natural Cp is a better sorbent than synthetic zeolite Na-X in case of BTEX sorption, while PAHs are adsorbed more effectively by zeolite Na-X and its modifications. The mechanism of the sorption consists on the dissolving of the organic compounds into the organic layer of the surfactant (on the zeolites’ surface) as well as on the organic compounds’ penetration into the mesopores.

Experimental study of mercury removal from exhaust gases

An initial study has been made of the use of synthetic zeolites for mercury capture from exhaust gases. Synthetic zeolites (Na-X and Na-P1), and for comparison a natural zeolite (clinoptilolite) and activated carbon with bromine (AC/Br) were tested for mercury uptake from a gaseous stream. The materials were subjected to mercury adsorption tests and their thermal stability was evaluated. The untreated synthetic zeolites had negligible mercury uptake, but after impregnation with silver, the adsorption of mercury was markedly improved. The synthetic zeolite Na-X impregnated with silver adsorbed significantly more mercury before breakthrough than the activated carbon impregnated with bromine, indicating the potential of zeolite derived from coal fly ash as a new sorbent for capture of mercury from flue gases.

Evaluation of kinetic and mass transfer parameters for adsorption of clavulanic acid into natural and synthetic zeolites

This work investigates the adsorption of clavulanic acid using natural six cationic forms (Na+, Ca+2, Ba+2, Sr2+, K+, and Mg2+) of the X and NZ zeolites in a stirred tank reactor since the separation is an important step of the biomolecule production. A mathematical model was proposed taking into account the transport of CA molecules from the liquid phase to the surface of the adsorbent and after diffusion into the particles. The estimated kinetic and mass transfer parameters were used to evaluate adsorption rates and mass transfer resistances involved in the separation of clavulanic acid from the broth. It has been shown that mass-transfer phenomena were a limiting step in the clavulanic acid adsorption process and that the adsorption rate should be considered to evaluate the system. Amongst the materials, the synthetic zeolite NaX was selected as the most appropriate material to separate clavulanic acid because this material presented the highest values for the observed reaction rate, compensating for the external mass transfer resistance. Modeling and simulation of clavulanic acid purification using the zeolite NaX showed a satisfactory fitting of experimental data. The model was used to simulate the process and it was evaluated for its technical and economical viability by comparisons considering the influence of the solid:liquid ratio on the adsorption equilibrium time and on the hydrolysed mass of biomolecule.

Heterogeneous photodegradation catalysis of o-phenylenediamine using CuO/X zeolite

In this paper, the photocatalytic degradation of o-phenylenediamine as the deputy of organic pollutant in aqueous solutions with CuO/X zeolite as a photocatalyst under UV irradiation has been studied. Photocatalyst was prepared by ion exchanging process of parent synthetic zeolite NaX with copper(II) nitrate aqueous solution (0.1 M) for 8 h followed by drying and calcination at 450 °C for 4 h. The parent zeolite, ion exchanged media, and photocatalyst were characterized by X-ray diffraction, infrared spectroscopy, atomic absorption spectroscopy, BET and thermal analysis methods. The degradation process was monitored during the experimental runs through UV/vis absorption as well as COD and TOC concentration determination and HPLC methods. The effects of various key operating parameters and the effect of hydrogen peroxide and potassium bromate on the degradation rate of o-phenylenediamine were studied. The optimum values were 0.1 g L −1 of photocatalyst, 10 ppm of o-phenylenediamine, pH of 9, 25 °C, 20.0 mM of H 2O 2 and 10.0 mM of KBrO 3. The results showed that the degradation kinetic of OPD can be described by Langmuir–Hinshelwood equation.

Solar photodecolorization of methylene blue by CuO/X zeolite as a heterogeneous catalyst

Semiconductor photocatalysis has proved to be an efficient method for decolorization and degradation of pollutants. In this study, a common semiconductor, CuO, as doped with synthetic zeolite NaX via wet impregnation of parent zeolite with Cu(NO 3) 2 aqueous solution was prepared. The potential of the obtained photocatalyst in decolorization of methylene blue (MB) dye under sunlight irradiation was studied. Characterization of parent zeolite NaX and prepared samples were studied using X-ray powder diffraction (XRD) patterns, infrared spectroscopy (FT-IR) spectra, diffuse reflectance spectroscopy (DRS), thermo analytical techniques (TG/DTG and DSC), SEM and BET methods. The active component value (CuO) on parent zeolite was also determined by atomic absorption spectroscopy (AAS) method on digested catalyst. The influence of experimental parameters on the dye photodecolorization process was studied and it was observed that photoreactivity of photocatalyst (CuO/X) varied with the amount of catalyst, initial dye concentration, pH of the dye solution, temperature, and active component value (CuO) loading. The role of zeolite NaX as a support was also investigated on decolorization rate. The optimal experimental conditions were determined as follow: catalyst amount; 1.0 g L −1, concentration of the dye solution; 0.03 mM, pH of solution; 11, and active component value; 88 mg CuO per gram of the catalyst. Under these optimum conditions, the obtained decolorization efficiency for MB dye was 94%. The reusability of the intended catalyst was also investigated.

Modeling batch kinetics of copper ions sorption using synthetic zeolite NaX

The sorptive removal of copper ions from aqueous solutions using zeolite NaX has been studied by a batch technique. The influences of solute concentration, temperature and particle size on the sorption process were examined. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the sorption process. Lagergren pseudo-first order, the pseudo-second-order (Ho) and Ritchie second-order models were analyzed using nonlinear regression technique while Weber–Morris model was analyzed using linear least squares method. The obtained results indicated that synthetic zeolite NaX could be used as an efficient material for the sorption of copper ions. A kinetic study has shown that the best fit is achieved when the Ritchie model was applied and that sorption did not involve film or intraparticle diffusion, i.e., they were not the rate controlling steps. The activation energy was found to be 12 kJ/mol in the present study.

Two Head Vacuum Pump를 이용한 차랑용 산소 발생기 개발

An oxyge generator, which is applied to a particular space such as automobile, must consider compactness and lightweight as well as problems caused by noise, vibration and heat dissipation. For these matters, a BLDC motor was adopted to reduce heat while a bed using synthetic zeolite NaX made it possible to generate high-density oxygen with relatively small size. Moreover, owing to the characteristic of synthetic zeolite Nax, a two-head vacuum pump was designed to desorb nitrogen without additional pump unit.

Ion-exchange of amminated palladium and platinum in synthetic sodium zeolites

The ion-exchange characteristics of amminated Pt(II) and Pd(II) ions in the synthetic zeolites Na-X, Na-Y and sodium mordenite were measured. Equilibrium studies were conducted at 25°C and at a total solution normality of 0.1 g equiv. dm −3. Highly selective isotherms, exhibiting partial exchange, were observed in all cases. For both the [Pt(NH 3) 4] 2+ and the [Pd(NH 3) 4] 2+ ions, the selectivity sequence was observed to be MOR>Y> X. The results are compared with other recent work on ion-exchange in zeolites involving amminated transition or noble metal ions.

Ion exchange of the transition metal ions Mn2+, Co2+, and Ni2+ in synthetic zeolites NaX and NaY

Abstract The exchange of Mn2+, Co2+, and Ni2+ in zeolites X and Y has been studied. At 25 °C, these metal ions cannot replace sodium ions present in the network of smaller cavities of both the zeolites. It is possible to describe the ion exchange data by a mathematical equation. The mathematical model assumes two groups of active sites in the supercages.

Effect of carbon dioxide on transformations of isobutylene in the presence of synthetic zeolites

1. The extent of isobutylene conversion on synthetic zeolites NaX and NaY at 200° and atmospheric pressure increases when CO2 is added to the starting olefin. 2. On Na- and Ca-containing zeolites of the X and Y types the addition of CO2 changes the direction of the isobutylene transformations toward an increase in the yield of the products of hydrogen redistribution and cleavage of the C-C bonds with the formation of “nonmultiple” forms, and to a decrease in the selectivity with respect to the dimerization of the starting olefin. 3. The addition of nitrogen fails to exert a similar effect under comparable conditions, while the addition of NH3 sharply lowers the extent of isobutylene transformations on NaY and CaNaY, and the selectivity of the process with respect to the dimerization of isobutylene.

Differential adsorption heats of water on powdered synthetic zeolite NaX

1. Employing a Tyan-Calvet calorimeter, a four-step curve was obtained for the differential adsorption heat of water on zeolite NaX. 2. Four mechanisms for the adsorption of H2O molecules on various energetically homogeneous sections of the large cavities in zeolite NaX were examined.

A study of the catalytic properties of synthetic zeolites in the dehydration of butane-1,4-diol

A study of the catalytic dehydration of butane-1, 4-diol in the presence of synthetic zeolites—NaX, CaX, HNaA, HNaX, and DcX—has shown that the best catalysts for the preparation of tetrahydrofuran (THF) are HNaX and DcX. The maximum yield of tetrahydrofuran (98%) was obtained on HNaX and DcX at 240°C with a space velocity of 0.7 hr−1(ml/ml · hr).