Hemolitic Activity and Sorption Ability of Beta Zeolite Nanoparticles

The work is devoted to studying the influence of synthesis conditions on the hydrothermal crystallization of zeolite nanoparticles with a Beta structure and studying their properties. The experimentally optimal conditions for the preparation of Beta zeolite nanoparticles of various sizes are determined by varying the temperature and time parameters of the process. The synthesized samples are characterized by X-ray diffraction analysis, scanning electron microscopy, and low-temperature nitrogen adsorption. The sorption ability of zeolite samples of different sizes with respect to inorganic cations (for example, lead ions) and organic molecules (for example, thiamine hydrochloride), as well as their hemolytic activity in relation to human red blood cells, is studied. It is found that the sorption ability of the samples decreases with increasing particle size. For the first time, the results of the dependence of the hemolytic activity of nanoparticles on their size are obtained. Based on the results obtained, conclusions are drawn about the possibility of using nanozeolites in medicine.     

Synthesis of hierarchical MFI zeolite microspheres with stacking nanocrystals

MFI nanozeolite microspheres with intercrystal mesopores were synthesized by a steam-assisted crystallization–aggregation method, starting with close packed amorphous SiO₂ or Al-containing SiO₂ colloidal nanoparticles. The obtained samples with different Si/Al ratios were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM)/ transmission electron microscopy (TEM) observations, nitrogen adsorption analyses and ²⁷Al magic angle spinning nuclear magnetic resonance (NMR). The SEM images clearly showed that the mean size of nanozeolite microspheres was ca. 0.5–3 μm, agglomerated from zeolite nanocrystals and varied with different Si/Al ratios. N₂ sorption analyses as well as TEM micrographs indicated the dual-porosity of samples, one is from intracrystal micropores, and the other is from intercrystal mesopores. ²⁷Al MAS-NMR suggested nearly all of the Al atoms were located at tetrahedral-coordinated sites in the framework. Furthermore, nanozeolite microspheres with various Si/Al ratios, even Si/Al equal to five, could be prepared by this facile route and less structure-directing agent was needed compared to conventional approach. This simple method could be easily extended to prepare other hierarchically structured zeolites.     

Surface Modification of Synthesized Nanozeolite NaX with TEAOH for Removal of Bisphenol A

In the present study, the surface modification of a freshly synthesized nanozeolite NaX was done with tetraethylammonium hydroxide (TEAOH) and applied as an adsorbent for the removal of bisphenol A (BPA) from its aqueous solutions. The adsorbent was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the synthesized adsorbent can remove BPA rapidly and effectively because of its high surface area (572 m²/g) and small particle size (35 nm). Uptake of BPA was greatly influenced by pH, stirring rate, temperature, contact time, and adsorbent dose. The optimum values of these parameters were 10.5 pH, 250 rpm, 25°C, 2 h, and 0.6 g/L. The adsorption was found to be spontaneous and exothermic. The Freundlich isotherm model and pseudo-first-order kinetic model fitted the experimental results well. The monolayer and multilayer adsorption capacities were found to be 42.8 and 122.6 mg/g, respectively.     

Sorption of Natural Uranium on Weakly Basic Anion Exchangers

The effects of the sorption of naturally occurring uranium on weakly basic anion exchangers (WBA) have been investigated. Systematic investigations on the effects of various parameters show in general three important factors influencing the adsorption equilibrium. First, the sorption depends on the presence of competing anions, with sulfates showing the greatest influence. Second, the speciation of uranium (VI), which in carbonate-containing waters in a pH range between 6.5 and 9 exists mainly as anionic complexes UO₂(CO₃)₂^2- and UO₂(CO₃)₃^4-, is changed by calcium and bicarbonates. Calcium forms neutral complexes with uranium and carbonate, and with these complexes no ion exchange occurs. On the other hand, increasing concentrations of carbonate species support the formation of anionic uranyl complexes of higher charge, and an increased uranium uptake arises. Third, the effective capacity of WBA depends on the pH. With increasing pH, the amount of protonated functional groups decreases and the sorption capacity decreases.

It has been demonstrated that WBA sorb uranium very selectively out of drinking water. WBA Amberlite IRA 67 reached the uranium loading of 10 mg/g at the uranium concentration of 10 µg/L by sorption out of tap water at pH 7.     

Carbon monoxide electrooxidation on Pt and PtRu modified zeolite X

Zeolite NaX was modified by Pt and Pt/Ru nanodispersed metallic clusters. This modification was achieved by zeolite impregnation with acetylacetonate salt/acetone solution, followed by acetone evaporation and thermal decomposition of organometallic complex. Samples characterization was performed by X-ray diffraction analysis, nitrogen adsorption?Cdesorption measurements and Raman spectroscopy. The incorporation of metal into zeolite cavities induced the amorphisation of the zeolite framework on the local level. The mixture of modified zeolite and 10?wt% of carbon black, in a form of thin layer, was pasted to a glassy carbon surface by Nafion. Electrocatalytic properties of metal-modified zeolites were tested in CO electrooxidation reaction. The mutual influence between Pt and Ru atoms enhanced electroactivity of Pt/Ru-modified zeolite toward carbon monoxide electrooxidation. The behavior of untreated 13X zeolite was investigated under the same condition in order to asses the influence of the support. Gradual deactivation of 13X electrode occurred.     

Tailoring of nanozeolite NaX for enhanced removal of a phytoestrogen from its aqueous solutions

This study represents the application of nanozeolite NaX (NZX) synthesized by hydrothermal treatment without addition of any expensive structure directing agent for the highly effectual adsorption of biochanin A from aqueous solution. The characteristics and surface morphology of NZX were determined using FT-IR, SEM, TEM, BET, and XRD. The adsorption performance of NZX was analyzed at different conditions such as temperature, pH, contact time, adsorbent dose, and initial adsorbate concentration. The adsorption mechanism was well verified by pseudo-second-order kinetic and Redlich–Peterson isotherm models. The thermodynamic parameters revealed that the removal process was exothermic and spontaneous.     

十六烷基三甲基溴化铵改性X分子筛对铬酸盐的吸附平衡及动力学

用十六烷基三甲基溴化铵(HTAB)对X分子筛改性,考察改性分子筛对水中铬酸盐的吸附平衡及吸附动力学。采用XRD和FT-IR对样品进行表征,结果表明改性后HTAB-X分子筛在保持原有结构和形貌同时,接枝了一定量的长链季铵盐阳离子功能基团。吸附实验表明,0.7 g改性分子筛在25℃、pH=6条件下,去除率为94.14%,比X分子筛提高了近36%。HTAB-X分子筛对铬酸盐的吸附遵循Langmuir模型,最大吸附容量为16.33 mg/g。热力学和动力学分析表明,该吸附过程为自发的放热过程,适合在常温下进行;吸附过程遵循准二级动力学模型,平衡吸附容量qe,cal达到2.71 mg/g,速率常数k2为0.362 g/(mg·min)。     

Adsorption of tetrahydrothiophene on faujasite type zeolites: Breakthrough curves and FTIR spectroscopy study

Adsorption of tetrahydrothiophene (THT) on NaX, CaX, AgX, and H-USY was studied by dynamic adsorption method and FTIR spectroscopy. The stoichiometric adsorption capacities are not very different for all materials, which is indicative of a complete micropore filling. In contrast, the overall rate constant of adsorption, determined from fitting the breakthrough curves with Bohart–Adams equation, is two times greater for H-USY than for type X zeolites. For NaX, CaX and H-USY, heating under N₂ flow at 300 °C allows to restore completely their initial adsorption capacities. In the case of AgX the same treatment results in a twofold lose of capacity accompanied by a collapse of the zeolite structure as evidenced by XRD. The nature of interaction between THT molecules and zeolites was characterized by FTIR spectroscopy. Only a weak interaction through hydrogen bonding was observed for THT on H-USY leading to an almost complete desorption at 100 °C. For NaX and CaX adsorbed molecules are gradually eliminated when heated to 300 °C while completely different pattern was observed for THT adsorbed on AgX on which the amount of the adsorbate remains nearly constant between 25 and 200 °C, but rapidly decreases on further heating. Such a behavior is indicative of much stronger interaction between THT molecules and Ag⁺ cations in agreement with the data on the regeneration of the adsorbents.     

Structural characteristics of modified natural zeolite

Natural zeolite of Slovak provenience has been modified with magnetic nanoparticles at selected temperatures of 20, 50 and 85 °C with the aim to enhance its sorption properties. The pore, surface and structural properties of zeolite/iron oxide composite were characterized using nitrogen adsorption measurements, electron probe microanalysis and powder X-ray diffraction. The crystallinity of the host zeolite was strongly influenced by the temperature of iron oxide particles precipitation, but it was still retained. It followed from the nitrogen adsorption measurements that the surface area and the pore volume of zeolite composites have increased in relation to the precipitation temperature, the best sorption properties were revealed at the composite prepared at 85 °C. As followed also from the SEM images, the iron oxide nanoparticles being of size 30 nm are forming mesoporous aggregates adsorbed on the zeolite surface. Fractal analysis used to describe the modified geometry of zeolite composites has given the values of surface fractal dimension between 2.36 and 2.51.     

Application of natural hydroxyapatite in the treatment of polluted water: Utilization of dromedary bone as bioadsorbent

In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis X-ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo-second-order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.     

Water–alcohol separation by pervaporation through zeolite‐modified poly(amidesulfonamide)

Pervaporation membranes were fabricated by blending different amount of zeolite NaA or NaX with three types of poly(amidesulfonamide) (PASA). The zeolite‐filled membranes were characterized by IR spectroscopy, SEM, sorption measurements, and wide‐angle X‐ray diffraction. By adding the proper amount of NaA into the polymer casting solutions, the resultant zeolite‐filled membranes exhibited improvement in both selectivity and permeability in the separation of 10% aqueous solutions of ethanol and propan‐1‐ol, as compared with the zeolite free membrane. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1323–1329, 2001     

Kinetic Modeling of Arsenic Removal from Water by Ferric Ion Loaded Red Mud

A laboratory study was conducted to investigate the ability of ferric ion loaded red mud (FRM) for the removal of arsenic species from water. The adsorbent material was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. For an initial arsenic concentration lower than 0.3 mg/L, the FRM with a dosage of 1 g/L was able to reduce As(III) at pH 7 below 10 µg/L, the maximum contaminant level (MCL) of arsenic in drinking water set by the World Health Organization. In the case of As(V) removal, FRM was also particularly effective in reducing the initial arsenic concentration value of 1 mg/L at pH 2, below the MCL requirement of arsenic for drinking water. According to kinetic sorption data, the initial stage of adsorptions of As(III) and As(V) onto FRM were mainly governed by the external diffusion mechanism; however, upon saturation of the external adsorbent surface, the arsenic species were eventually adsorbed by intraparticle diffusion mechanism. The present results are promising for using the very inexpensive FRM as a low-cost material that is effective in remediating drinking waters contaminated with low concentrations of arsenic species. We report here the sorption kinetics and adsorption mechanisms of As(III) and As(V) on the FRM that has not been decsribed previously.     

Biosorption of Uranium by Magnetically Modified Wheat Bran

The wheat bran was magnetically modified with microwave-synthesized magnetic iron oxides particles. Magnetic wheat bran was chosen as a biosorbent for removal of uranium from aqueous solutions. The uranium sorption increased with increasing pH and reached a plateau between pH 4.0 and 10.0. The increase of temperature slightly improved the sorption process. The uranium adsorption followed the Langmuir adsorption isotherm.     

Kinetic studies of cobalt ion removal from aqueous solutions using fly ash-based geopolymer and zeolite NaX as sorbents

This study explored the cobalt ions removal efficiency from aqueous solutions by the sorption process on geopolymer and zeolite NaX. The influence of concentration and temperature on the sorption process was examined. FTIR and SEM analyses were conducted to elucidate the structure of sorbents. An additional goal was to test the experimental kinetic data using several kinetic models. A kinetic study has shown that the best ?t is achieved when the Blanchard model was applied, suggesting that the sorption of cobalt ions on geopolymer and zeolite NaX is a second-order reaction.     

偏高岭土微波加热合成NaX分子筛及其机理探讨

本文以偏高岭土为主要原料,采用微波加热法合成了静态饱和吸水量超过32.0％的NaY分子筛.进行了单因素实验,考察了晶化时间、胶化时间、n(Na2 O/Al2O3)对合成分子筛的影响.通过静态水吸附测定、XRD、IR和SEM等测试手段考察反应条件对合成NaX分子筛的影响,并对NaY分子筛晶体生长规律进行了探讨研究.实验得...     

Surface complexation model of uranyl sorption on Georgia kaolinite

The adsorption of uranyl on standard Georgia kaolinites (KGa-1 and KGa-1B) was studied as a function of pH (3–10), total U (1 and 10 μmol/l), and mass loading of clay (4 and 40 g/l). The uptake of uranyl in air-equilibrated systems increased with pH and reached a maximum in the near-neutral pH range. At higher pH values, the sorption decreased due to the presence of aqueous uranyl carbonate complexes. One kaolinite sample was examined after the uranyl uptake experiments by transmission electron microscopy (TEM), using energy dispersive X-ray spectroscopy (EDS) to determine the U content. It was found that uranium was preferentially adsorbed by Ti-rich impurity phases (predominantly anatase), which are present in the kaolinite samples. Uranyl sorption on the Georgia kaolinites was simulated with U sorption reactions on both titanol and aluminol sites, using a simple non-electrostatic surface complexation model (SCM). The relative amounts of U-binding >TiOH and >AlOH sites were estimated from the TEM/EDS results. A ternary uranyl carbonate complex on the titanol site improved the fit to the experimental data in the higher pH range. The final model contained only three optimised log K values, and was able to simulate adsorption data across a wide range of experimental conditions. The >TiOH (anatase) sites appear to play an important role in retaining U at low uranyl concentrations. As kaolinite often contains trace TiO₂, its presence may need to be taken into account when modelling the results of sorption experiments with radionuclides or trace metals on kaolinite.     

分子筛对重金属废水吸附性能的实验研究

为验证分子筛对重金属废水的处理效果,以实际含锰废水为研究对象,采用13X分子筛,通过实验研究了吸附材料用量、吸附时间、搅拌转速和溶液pH对Ca²⁺、Mn²⁺、Mg²⁺吸附效果的影响。结果表明：吸附材料用量增加对Mn²⁺、Mg²⁺的吸附影响较大;随着吸附时间增长,各金属离子去除率增加;适当的转速有利于金属离子的吸附,但各金属离子对应的最佳转速各不相同;pH提高,能够促进分子筛对金属离子的吸附。13X分子筛对金属离子的吸附机理为离子交换吸附和表面吸附。研究表明,13X分子筛在处理低浓度含锰重金属废水方面表现出良好的应用前景。     

Biosorptive uranium uptake by a Pseudomonas strain: characterization and equilibrium studies

The biosorptive uranium(VI) uptake capacity of live and lyophilized Pseudomonas cells was characterized in terms of equilibrium metal loading, effect of solution pH and possible interference by selected co‐ions. Uranium binding by the test biomass was rapid, achieving >90% sorption efficiency within 10 min of contact and the equilibrium was attained after 1 h. pH‐dependent uranium sorption was observed for both biomass types with the maximum being at pH 5.0. Metal uptake by live cells was not affected by culture age and the presence of an energy source or metabolic inhibitor. Sorption isotherm studies at a solution pH of either 3.5 or 5.0 indicated efficient and exceptionally high uranium loading by the test biomass, particularly at the higher pH level. At equilibrium, the lyophilized Pseudomonas exhibited a metal loading of 541 ± 34.21 mg g^?1 compared with a lower value by the live organisms (410 ± 25.93 mg g^?1). Experimental sorption data showing conformity to both Freundlich and Langmuir isotherm models indicate monolayered uranium binding by the test biomass. In bimetallic combinations a significant interference in uranium loading was offered by cations such as thorium(IV), iron(II and III), aluminium(III) and copper(II), while the anions tested, except carbonate, were ineffective. Uranium sorption studies in the presence of a range of Fe³⁺ and SO₄^2? concentrations indicate a strong inhibition (80%) by the former at an equimolar ratio while more than 70% adsorption efficiency was retained even at a high sulfate level (30 000 mg dm^?3). Overall data indicate the suitability of the Pseudomonas sp biomass in developing a biosorbent for uranium removal from aqueous waste streams. © 2001 Society of Chemical Industry     

Catalytic combustion of hexane over transition metal modified zeolites NaX and CaA

Hexane deep oxidation was studied over NaX and CaA zeolites modified by ion exchange with transition metals (Mn²⁺, Co²⁺, Fe³⁺), the percentage of ion exchanged, determined by ICP-MS, varying between 39 and 98%. Parent and exchanged zeolites were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature-programmed reduction (TPR), oxygen and ammonia temperature-programmed desorption (TPD) and inverse gas chromatography (IGC). Catalytic activities were evaluated through the recording of light-off curves in a pulsed microreactor, catalytic activity being correlated with physicochemical properties of the solids (crystallinity, surface acidity, adsorption properties and morphological parameters). As general trend, CaA zeolites are more active than NaX zeolites. Mn-exchanged CaA zeolite was the most active catalyst for hexane oxidation, whereas the addition of Fe to the zeolites leads to strong chemical and morphological changes in the parent zeolite.     

Characterization and Dehydration Behavior of a Natural,Ammonium Hydroxide,and Thermally Treated Zeolitic Tuff

Aqueous NH₄OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma–atomic emission spectroscopy (ICP-AES), volumetric N₂ adsorption at ?196°C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH₄OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite. Changes in the infrared bands corresponding to vibrations of the O–H and N–H bonds upon in situ heating under vacuum were analyzed.