Forms Of Clinoptilolite Research Articles

Natural and pretreated Gördes clinoptilolites for ammonia removal: effect of exchangeable cations (Na+, K+, Ca2+and Mg2+)

AbstractIn this study, the effects of two different ammonium-exchange methods to improve the ammonia (NH3) gas adsorption of raw clinoptilolite (CLN) from Gördes (Türkiye) was investigated. The first method involved direct modification of CLN by 0.5 or 1.0 M NH4NO3solutions at 80°C for 4 and 8 h followed by calcination. In the second method, CLN was converted to the Na+form prior to modification with ammonium nitrate and calcination under the same conditions. Both methods yielded H+forms of CLN through the removal of exchangeable cations without damaging the crystal structure. Ammonia adsorption isotherms were determined at 298 K for a total of eight different H+forms synthetized using both methods. The Na-1.0-8h CLN sample with the highest NH3adsorption capacity obtained using the second method was selected as the parent CLN. In addition, to determine the effects of doping different cations into the structure on the NH3adsorption properties of the selected parent CLN sample, cation-exchange processes were carried out using 0.5 and 1.0 M NaNO3, KNO3, Ca(NO3)2and Mg(NO3)2solutions at 80°C for 4 h. The raw and modified CLNs were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy and N2adsorption analyses. Cation-exchanged samples with a wide range of NH3adsorption capacities (3.61–4.93 mmol g–1) were compared with other zeolites from the literature.

Zeolite-Clinoptilolite conditioning for improved heavy metals ions removal: A preliminary assessment

The emerging problem of nickel allergy is increasingly widespread due to the increase in nickel content in everyday foods. The physicochemical structure of the zeolites makes it possible to adsorb nickel ions in solution. The properties of molecular sieves, together with those of a size and a chemical composition compatible with the human gastrointestinal tract, are present in a particular zeolite called clinoptilolite. In this work, a type of natural clinoptilolite was characterized before and after being subjected to two different conditioning processes with NaCl to increase its adsorption efficiency and specificity against nickel. The three forms of clinoptilolite, natural, conditioned, and biconditioned, were compared based on analysis of absolute density, X-ray diffraction pattern, granulometry, porosity, chemical composition, and grain morphology. Finally, nickel ion removal tests were performed in an aqueous solution that simulates the conditions of the gastrointestinal tract. The Ni2+ removal efficiency of natural clinoptilolite is 73.2%, while after conditioning it reaches 96.6%. Double conditioning with Na does not generate a considerable increase in removal efficiency which remains at 96.8%.

SORPTION OF LANTHANUM(III) IONS IN MODIFIED CLINOPTILOLITE

Under static conditions, using the limited volume method, the equilibrium and sorption kinetics of lanthanum ions on H+ and Na+-clinoptilolite were studied. It is shown that the sorption of lanthanum ions from dilute solutions occurs in the micropores of clinoptilolite. It has been established that the main capacity of modified clinoptilolites is realized in the secondary porous structure, the sorption of lanthanum ions is limited by diffusion in the zeolite grain. It is concluded that lanthanum ions are uniformly distributed in the H+ and Na+ forms of clinoptilolite and interact with Brönsted centers of large cavities of clinoptilolite

Clinoptilolite/electrolyte interface probed by a classical molecular dynamics simulations and batch adsorption experiments

Classical molecular dynamics (CMD) simulations were used to describe clinoptilolite/electrolyte interface with an atomistic resolution. The most abundant (010) surface cut was chosen together with two forms of clinoptilolite (CL) skeleton: neutral siliceous form (CL-SIL) and charged natural form with aluminum substitutions (CL-SUB). Structural properties of adsorbed water molecules, sodium, and ammonium cations are described in very detail and compared to the experimental findings. It is shown that the structure of water molecules and ions near the surface is significantly influenced by the framework charge. To improve our understanding of CL(010)/electrolyte interactions, umbrella sampling (US) simulations were performed to get free energies of adsorption of Na+ and NH4+ cations. These are compared with complementary experimental numbers obtained by batch adsorption experiments. The qualitative agreement was found but the origins of quantitative disagreement are discussed.

Structural steel bond to concrete with waste aggregate

The article presents the results of bond tests of B500SP structural steel to concretes subjected to thermal stress. Concretes were designed purely on the basis on waste aggregate made of soft clay pottery with using two types of cements: Portland CEM 32.5R and aluminous cement Górkal 70. In the research was used the method of direct pulling the steel rod out of the concrete cover (Pullout Test). For the tests were prepared four types of concretes: two bases of aluminous cement and two on Portland cement without additions. In the remaining mixtures containing the additive in the form of clinoptilolite, the method of simple weight replacement of the selected type of cement with clinoptilolite in the amount of 10% was used. Mineral puzzolana additives are intended to modify the phase composition of hardened cement slurry towards reducing the portlandite and changing the CaO/SiO2 ratio in the C-S-H phase. The results of the tests confirmed that the bond of the selected steel type to concrete on the recycle aggregate does not differ from the results achieved with natural aggregate. It was also confirmed that addition of clinoptilolite to concrete with Portland cement has beneficial effect when it is subjected to thermal stress.

Removal of uranium ions from synthetic wastewater using ZnO/Na-clinoptilolite nanocomposites

Abstract Uranium is one of the heavy metals that is found in industrial wastewater and is very toxic for human and environment. In this work, natural clinoptilolite is used as a low-cost adsorbent for uranium removal from aqueous solutions. The sodium form of clinoptilolite and ZnO/Na-clinoptilolite nanocomposite were prepared. The sample sorption capacities for uranium removal from simulated drinking water in the presence of other anions and cations were investigated. Natural zeolite and its modified forms were characterized by XRD, XRF, FTIR, TEM and BET. Batch experiments were used to determine the best adsorption conditions. The effects of various parameters such as contact time, pH, initial uranium concentration, temperature and mass sorbent on the removal efficiency of uranium ions were studied. The equilibration was attained after 2 and 6 h for the Na-clinoptilolite and ZnO/Na-clinoptilolite nanocomposite, respectively. Both adsorbents showed relatively fast adsorption. Effective removal of uranium was demonstrated at pH values of 4–8 for both forms of zeolite. Temperature had no significant effect on adsorption. The maximum removal efficiency of uranium by the ZnO/Na-clinoptilolite nanocomposite in pH=7.2 and room temperature was 98.55%. Langmuir, Freundlich and Sips models were used for describing the equilibrium isotherms for uranium uptake. The Sips model corresponded well with the experimental data. The thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, have been calculated and interpreted. The pseudo-first order and pseudo-second order models were applied to describe the kinetic data. The pseudo-second order kinetic model had excellent kinetic data fitting (R2=1).

Removal of Cs ions from aqueous solutions by using matrices of natural clinoptilolite and its safe disposal

The possibility to use natural zeolite - clinoptilolite as a host material for radioactive Cs immobilization has been investigated. Cs-exchanged form of clinoptilolite which was prepared by treatment of clinoptilolite powder with 0.25 M CsCl solution was compacted. Both, powder and powder compact of exchanged clinoptilolite were thermally treated at 1200?C. The XRPD analysis showed that Cs was successfully immobilized after heat treatment by formation of stable cesium dodecaoxo-alumopentasilicate in both, powder sample and compact. The newly formed compound showed satisfactory Cs ions retention during leaching test. The sintered compact showed somewhat better resistance to Cs leaching than the thermally treated powder. The compressive strength of sintered compact was close to 200 MPa which is more than enough for easy handling and safe storage.

Solid phase extraction–inductively coupled plasma spectrometry for adsorption of Co(II) and Ni(II) from radioactive wastewaters by natural and modified zeolites

Natural and modified clinoptilolite as low-cost adsorbents have been used for adsorption of Co(II) and Ni(II) from nuclear wastewaters both in batch and continuous experiments. Zeolite X was also synthesized and its ability towards the selected cations was examined. Kinetic and thermodynamic behaviors for the process were investigated and adsorption equilibrium was interpreted in term of Langmuir and Freundlich equations. The effect of various parameters including the initial concentration, temperature, ionic strength and pH of solution were examined to achieve the optimized conditions. The clinoptilolite was shown good sorption potential for Co(II) and Ni(II) ions at pH values 4–6. Based on desorption studies, nearly 74 and 85% of adsorbed Co(II) and Ni(II) were removed from clinoptilolite by HCl. The Na+ and NH4 + forms of clinoptilolite were the best modified forms for the removal of investigated cations. It is concluded that the selectivity of clinoptilolite is higher for Co(II) than Ni(II). The synthesized zeolite showed more ability to remove cobalt and nickel ions from aqueous solution than the natural clinoptilolite. The microwave irradiation was found to be more rapid and effective for ion exchange compared to conventional ion exchange process.

The effect of clinoptilolite on 137 Cs binding in broiler chickens

The objective of this study was to evaluate the 137 Cs binding capacity of clinoptilolite.In the first in vitro experiment we investigated sorption of 137 Cs to natural and modified forms of clinoptilolite in highly acid solution,prepared to be similar to that of the gut of pigs (pH =2 3)at 37 ºC.In the second in vivo experiment 137 Cs binding to a modified form of clinoptilolite was studied in orally contaminated broiler chickens.137 Cs sorption in the high acidity solution depended on clinoptilolite concentration and varied between 30 85 %of the initial activity.In the chickens,three hours after 137 Cs administration,there was 67%and 63%lower accumulation of 137 Cs in meat and edible organs (respectively)and seven hours after 137 Cs administration,there was 69% and 49% lower accumulation of 137 Cs in meat and edible organs (respectively)compared to the controls with no clinoptilolite added in food. Natural and modified forms of clinoptilolite have been shown to high sorption efficiency towards 137 Cs ions and could be recommended as possible radiocaesium binders in domestic animals.;

Thermal study of surfactant and anion adsorption on clinoptilolite

The mechanism of surfactant adsorption on various forms of clinoptilolite was studied by DTA, TG and DTG analyses. The examined series of surfactant modified clinoptilolite (SMC) was previously prepared by the adsorption of the surface-active oleylamine on Ca2+, Na+, H+ and mechanochemically treated forms of clinoptilolite. The oleylamine was most strongly adsorbed on H+-forms of clinoptilolite due to the largest number and strength of adsorption sites. The surfactant adsorption mechanism on H+-form of clinoptilolite was studied by recording the series of variously surfactant-loaded samples. The products of sulphate, dihydrogenphosphate and hydrogenchromate adsorption on SMC were analyzed by DTA, TG and DTG in order to investigate the mechanism of anion adsorption.

Differential heats of adsorption of water vapors on the lithium form of clinoptilolite

The maximum possible lithium form of clinoptilolite (K1) with an ion-exchange capacity of 2.3 mEq/g, corresponding to 85% Kl in nature, was prepared. The isotherm of adsorption of water vapors on LiKl at 25°C in the region of maximally low equilibrium pressures (10−10 torr) was calculated by the adsorption-isostere method and permits determining the complete thermodynamic functions of the system. The adsorption isotherm is completely described by the two-term equation from the theory of volume filling of micropores (TVFM). The wavy-stepwise shape of the curve of the heat of adsorption permitted establishing the stoichiometric correlation between the adsorption values and concentration of Li+ in LiKl. The energy of the Li+-OH2 adsorption complex is 97 kJ/mole for a zero degree of filling. The integral average molar entropy of adsorption is 20 J/(mole·K) less than the entropy of a normal liquid. The state of the H2O molecules in LiKl is ice-like.

Sorption of cobalt on modified clinoptilolites

The sorption of cobalt on natural and modified clinoptiolites has been studied. It has been demonstrated that the higher sorption of cobalt on modified clinoptinolites than on natural ones is due to precipitation reactions. The precipitates formed on the sorbent have been investigated by infrared spectrometrical, microscopical, and X-ray analyses. The capacity values of the corresponding metal forms of clinoptilolite have been obtained with cobalt. Desactivation of radioactive solutions containing134Cs,137Cs204Tl and