X-ray analysis in the study of sorption processes on clinoptilolites used as geochemical barriers

Abstract

Kinetics of Sr²⁺ sorption from potable water on clinoptilolite tuffs (CLPT) of different deposits (Honguruu (Yakutia), Holinskoe (Transbaikalia) and white Plast (Bulgaria)) is studied in detail. A technique of X-ray fluorescence analysis (XRF) is developed to determine the chemical composition of CLPT from a small sample (0.05 – 0.1 g). The emitters are prepared by pressing 10-mm tablets from the initial material added with polystyrene as a binder in a weight ratio 5:1. Reference standards (reference standards of composition) of rocks close in chemical composition to the CLPT are used for calibration. Using the empirical model of α-correction, the equations are derived to calculate the content of macro components of the sample in the «saturated» layers. To calculate the strontium content in the «intermediate» layers for the CLPT from different deposits the correction equations are derived. It is shown that the correction equation can be the same for all the CLPT used in the experiment. Kinetics of Sr²⁺ sorption on CLPT consists of 3 stages: (a) the intra-diffusion process, described by the coefficient of internal diffusion, (b) deceleration of the sorption process, described by the corresponding kinetic coefficient, and c) secondary increase in Sr²⁺ sorption which terminates when the equilibrium is reached. The results can be used to develop a mathematical model describing the dynamics of the ion-exchange process on CLPT in NH₄ form from dilute solutions.