Chromatographic properties of zeolites modified for analysis of atmospheric pollutants

Chromatographic properties of different types of synthetic zeolites and samples of natural mordenite, modified by ion-exchange have been studied. The influence of degree of replacement and character of cations of alkali and alkaline-earth metals and also of silver and copper on chromatographic retainment of constant components of air and its most spread pollutants have been shown. Recommendations are made of optimal sorbents and conditions for extraction, concentration, desorption and quantitative chromatographic analysis of oxides of carbon, nitrogen and sulfur and also hydrocarbon gases C1-C4. INTRODUCTION The present level of industrial development is associated with the disposal of many different types of waste. A serious threat to the environment is posed also by the atmospheric pollution by motor exhaust gases and the outlet from thermal power stations. The first step in the solution of the problems of environmental pollution is the development of analytical methods for the determination of microconcentrations of pollutants. The next step should be the development of effective ways of removing undesirable components from exhaust gases. In this connection adsorbents, especially zeolites, are of great importance for the extraction of components such as the oxides of carbon, nitrogen and sulfur. The development of physico-chemical methods for the analysis of atmospheric pollutants will also involve the application of zeolites. modified forms of cationic zeolites and to ascertain the optimum conditions for the chromatographic analysis of gaseous pollutants. The aim of the work described here was to develop METHODS OF INVESTIGATION AND APPARATUS Powdered synthetic zeolites, produced in USSR, were washed in water and cleaned to pH 8,4 8,6. ions by cations of respective salts. the degree of replacement. The samples were compressed into tablets, heated, pounded and later separated into fractions (0,5-1 and 0,25-5 mm) of granules which were used to fill chromatographic columns (ref. 1) of chromatographs models "Tsvet-4" and "Tsvet-162". Samples of natural Carpathian zeolites (a solid mineral; ref.2) were directly subjected to compression to the above mentioned sizes, and later to additional acidic treatment by keeping them in solutions of HC1 of different concentrations. After cleaning granules from excess acid,they were dried and subjected to additional modification (ref. 3) by treating them with salts (silver nitrate, copper sulfate and others) and later to chromatographic analysis. Granules of zeolites in columns were subjected to further thermal activation (573 K, 3 hours) in a stream of gas-carrier (helium or nitrogen) with a flow rate of 50 cm3/min. Later, the retention times of components of model mixtures containing low-boiling hydrocarbon and oxide gases at temperatures of 273-573 K were taken at intervals of 20 K. From the data obtained were calculated absolute specific retention volumes and their logarithms. On the basis of logarithmic dependence of experimental values of absolute specific retention volumes Vg on reciprocals of absolute temperatures of chromatographic columns straight lines were obtained. Extrapolations helped to calculate the values of Vg at room temperatures (293 K) for cases of very strong retention of components in zeolites. of obtained absolute specific retention volumes of the gas and nitrogen (the main component of air) gave a quantitative idea of selectivity of retention of the gas by zeolites. The powder was subjected to ion-exchange with replacement partly (or wholly) of initial From the results of chemical analysis was calculated