GRANULATED LOW-MODULUS ZEOLITES FOR EXTRACTION OF CO CATIONS

Abstract

The paper gives a characteristic of LTA and SOD zeolite pellets, which were synthesized using preliminary ultrasonic processing. By X-ray diffraction and IR spectroscopy methods, it was established that the investigated samples contained about 100% of the LTA or SOD phase. It was shown that zeolite LTA particles have a dimension of coherent scattering region of 780 nm and root mean square microdeformations of 0.05%, while SOD zeolite particles have this parameter about 460 nm and the defectiveness of crystal lattice is 0.15%. The values of the specific surface area of zeolite pellets were determined, the values of which are 148.8 and 115.6 m2/g for LTA and SOD, respectively. It was noted that the SOD zeolite pellets have virtually no micropores. Equilibrium curves were obtained for the saturation of zeolite pellets with cobalt cations depending on the concentration of Co2+ in an aqueous solution of cobalt chloride. It was shown that in the entire investigated range of Co2+ concentrations, the LTA zeolite capacity is 30% higher than that of the SOD zeolite which can be explained by two main reasons. Firstly, this is a higher specific surface area of the LTA zeolite. Secondly, these are structural features of the zeolite frameworks, namely, LTA zeolite has α-cavities which are more accessible for Co2+. It is also shown that with increasing temperature, the zeolites capacity on cobalt cations grows. It was discovered that a new absorption band with a wave number at 1390 cm–1 appears on the IR spectra of both zeolites after saturation. In addition, an increase in the size of the unit cell and a growth in the defectiveness of particles were noted in cobalt-saturated zeolites. Taken together, these facts point to the cation exchange. It was shown that 1 g of LTA zeolite provides almost complete purification of 50 ml of the solution from 57Co cations in a dynamic mode.