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Abstract
The possibility of the use of granulated zeolites for the removal of cerium(III) species from solutions labelled with cerium-141 radioisotope, has been investigated. Measurements of cerium(III) species in solutions and of the distribution of cerium(III) species in column fillings (granulated zeolites), after passing the solution through columns filled with various granulated zeolites have shown that cerium(III) ions can be effectively removed from weakly acidic solutions using granulated mordenite. The influence of pH, of the concentration of cerium(III) ions in solution and of the flow rate of the solution through the column on the efficiency of cerium(III) species removal and on the distribution of cerium(III) species in the column has been investigated. The mechanism of exchange of cerium(III) ions from solution with sodium ions from granulated zeolites has been discussed.
Summary
The pozzolanic reactivity of thermally treated zeolites was studied on the basis of the Chapelle test combined with X-ray diffraction (XRD) and Fourier Transform (FTIR) spectroscopy, as well as thermogravimetric analysis (TG/DTG) and differential thermal analysis (DTA). The raw zeolite samples are from the Pentalofos area, Thrace, NE Greece. Their main mineral constituent is 'heulandite type-II', an intermediate type of the heulandite-clinoptilolite isomorphous series. Calcination of the samples was carried out up to 400, 500, 600, 700 and 1000C for 15 h. The changes were recorded using the above methods. The deformation of the zeolite crystal lattice starts at about 400C and proceeds as the temperature of thermal treatment rises. The thermal treatment of zeolite at 400C improves its pozzolanic reactivity and accelerates the reaction with Ca(OH)2.
Summary
The sorptive behavior of tritiated water on natural, irradiated, chemically treated and heated at high temperatures Armenian zeolites was studied and their capacity for the separation and enrichment of tritiated water was evaluated. The distribution coefficients from the batch experiments were calculated for different zeolites and vary between 0.23 and 3.01. The influence of temperature, acidity, basicity, specific activity, electron and gamma-irradiation on sorption has been studied.
Abstract
The acid properties of the Ca/NaY zeolite were investigated by means ofn-butylamine desorption and thermal decomposition, using both thermogravimetry (TG) and differential scanning calorimetry (DSC). The total acidity of the zeolite was calculated from the TG data, while DSC was used with the Borchardt-Daniels kinetic model to determine the relative acid strength of the catalyst, given in J per acid site. The enthalpies of these processes are proportional to the acid site strength in each specific temperature range.
iron(II) on a NaY zeolite as a heterogenous photo-Fenton catalyst for the degradation of methylene blue (MB) used as a dye model pollutant under λ > 420 nm visible light irradiation and studied the kinetics of photo-Fenton degradation of this dye after
Summary
Natural clinoptilolite tuffs from the Semnan region in Iran was used for the synthesis of zeolite A. The tuffs and synthesized zeolites were characterized by XRD and XRF. The sorption behavior of the synthesized zeolite toward cerium was studied. Using the Lagergren’s equation, the absorption constant was calculated. The measured distribution coefficient values (K d) indicated that cerium uptake is higher in lower initial concentrations, higher temperature and higher pH values. Thermodynamic parameters of the exchange were calculated through construction of ion-exchange isotherms at three temperatures of 298, 323 and 343 K. The dynamic absorption of cerium was also studied by passing the solution through a column in the presence and absence of sodium ions.
Abstract
Water content in zeolites has been determined by an improved neutron reflection method using a Pu-Be neutron source of 106 n·s–1 intensity and a BF3 counter. It was found that the water content of different types of zeolites collected in Hungary varies between 9 and 12 wt.%. The standard deviation of the determination does not exceed 0.5 wt.%. The matrix effect on the sensitivity and accuracy was also studied. An approximate relation is given between the count rate and the neutron physical parameters of the samples.
Abstract
Some properties of natural zeolite from Zalo
ka gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g–1. The migration rate of Cs+ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.
Abstract
The subject of this paper was to study Co2+-ion removal from aqueous solutions by means of natural mordenite and clinoptilolite. The mentioned zeolites were of Slovak origin (
SFR). The static and dynamic equilibrium adsorption of Co2+-ions by zeolites, the influence of pH, quality and quantity of interfering ions on adsorbate/adsorbent system were investigated. The influence of flow rate, activation and initial concentration on the shape of the breakthrough curve was examined in dynamic regime. Mathematical expression was found for the breakthrough curve description.
create the demand for supported catalysts [ 14 – 22 ]. Zeolites, in most cases, have been chosen as suitable supports because of their high thermal and chemical stabilities and good crystalline structures [ 1 , 23 – 26 ]. These types of molecular sieves
