Powder XRD Study of Changes of Cd2+ Modified Clinoptilolite at Different Stages of the Ion Exchange Process

Cadmium exchange on clinoptilolite is performed and structurally studied for different durations of the ion exchange process (2 h, 24 h, 72 h, 168 h, 12 days, 22 days) at room temperature and 90 degrees C. The distribution of Cd2+ ions in all samples is elucidated after exchange on clinoptilolite using powder XRD data processed by Rietveld structural software. Clinoptilolite is not selective for cadmium cations, but at 90 ffiC the exchange is similar to 2.5 cations per unit cell. At RT it reaches similar to 1.25 cations per unit cell being twice as low. The obtained maximum exchanged sample for 22 days 90 degrees C was structurally refined in order to find the cadmium positions in the clinoptilolite voids. The structural refinements of the occupations of the incoming and outgoing cations give an idea of how the intracrystalline diffusion is processed. A good correlation between results obtained by structural refinement of the Cd-exchanged samples and the data of the EDS measurements was achieved.

Automated summary

The exchange of cadmium ions on clinoptilolite was studied at different temperatures and durations, revealing that the distribution of chromium ions depends on temperature conditions. The efficiency of exchange showed significant differences at different temperatures.