Low-temperature desorption of lRW simulant from perlite: temperature and purging influence according to TGA/DSC–MS data

Abstract

This paper presents the results of a comprehensive study of the desorption characteristics of expanded perlite grade M100 (LLP “UNION PERLITE”, Republic of Kazakhstan) impregnated with a liquid radioactive waste (LRW) simulant at a sorbent-to-solution mass ratio of 1:6. The investigations were performed by TGA/DSC-MS simultaneous technique using the “TiGrA” experimental complex under isothermal conditions at 40 and 70 °C with a holding time of 24 h in two modes: without gas purging and with a flow of dry air (50 mL/min). Desorption was found to be purely physical and associated with the evaporation of free water. The observed mass loss (~51% of the initial sample mass) is consistent with the water content of the LRW simulant used for impregnation. Increasing the temperature from 40 to 70 °C results in a 4.6-fold reduction in the time required to reach a steady state (from 9.2 to 2.0 h without purging; from 9.4 to 1.8 h with purging), whereas gas purging under laboratory conditions has only a minor effect on the process kinetics (<10% acceleration at 70 °C).

Mass spectrometric analysis confirmed the absence of gaseous release of organic or inorganic volatile compounds other than water vapor (dominant signal at m/z = 18). No exothermic or endothermic effects were observed on the DSC curves. The obtained results confirm the chemical and thermal inertness of the investigated perlite and its potential applicability in technologies for low-temperature drying and interim storage of conditioned LRW.