Selective sorption of heavy metals and radionuclides by natural and modified layered silicates

Abstract

Traditionally, natural layered silicates – clay minerals – are widely used in various environmental protection technologies. However, they have significant drawbacks, the most important of which is insufficient sorption capacity, especially for anionic forms of pollutants. To increase the effectiveness of layered silicates, various methods of surface modification using surfactants, intercalation of complex cations in the interlayer space of minerals of the smectite group, application of nanoparticles of active metals to the surface, etc. are carried out. The use of these methods makes it possible to significantly increase the sorption properties of modified dispersed minerals, as well as to significantly expand the scope of their possible application in environmental protection technologies. The monograph is devoted to the development based on the evolution of physical-chemical ideas about the mechanism of sorption processes of the system approach to purposeful regulation of sorption properties of layered silicates at their modification for removal of heavy metal compounds and radionuclides. Highly selective sorption materials based on layered silicates were obtained. This was achieved through detailed physicochemical substantiation of the structure of active sorption centers on the surface of layered silicates with analysis of the porous structure of the obtained sorbents and determination of the mechanism of sorption processes for heavy metals and radionuclides. It has been shown that surface modification of layered silicates using cationic surfactants allows effective sorption of toxicants in their anionic forms (compounds of chromium and uranium) on the surface. The obtained pillared minerals have significantly increased selectivity. The developed composite sorbents based on nano-sized particles of zero-valent iron and dispersed minerals are highly reactive materials to heavy metals and radionuclides in both cationic and anionic forms. Successful purposeful regulation of the surface properties of layered silicates made it possible to expand the scope of application of new sorption materials for the treatment of surface, underground, and wastewater of various types, contaminated with compounds of heavy metals and radionuclides. The monograph presents the results of the practical use of zero-valent iron to remove uranium compounds from contaminated groundwater. Its effectiveness as reactive treatment media in permeable reactive barriers built near the uranium ore processing tailings in Zhovti Vody city has been proven.The monograph is intended for specialists in the field of physical, colloidal chemistry, radiochemistry, and ecology, and will also be useful for lecturers and students of universities specializing in chemical and environmental departments.