Permeable reactive barriers as a way to protect the environment from pollutions. Natural sorbents for solving environmental problems. Mathematical modeling and calculation of processes. Review.

Abstract

          To solve large-scale environmental problems in the United States and Europe, a new technology is used - permeable reactive barriers (PRB). The purpose of the review is to estimate according to the literature the advantages and limitations of geochemical barriers, the types of materials used, including combined reactive materials, their properties, mechanisms for removing contaminants from the reaction medium, as
well as practical problems solved using them. It has been shown that clinoptilolite-containing tuffs (CLT), whose significant deposits are located in different regions of the world, including Russia, are considered to be inexpensive, affordable and highly effective natural sorbents. A list of the main deposits of Russia CLT developed and used in various industries and agriculture is presented, and the reserve deposits of CLT are
listed also. The sorption properties of CLT and its structural features that turn this material into a natural nanostructured sorbent with unique properties are considered. The properties of CLT modified in various ways (both organic and inorganic modifiers, including magnetite, giving CLT magnetic properties), which can also be used as permeable geochemical barriers, are also shown. The literature data on the operational
properties of CLT are presented. When developing geochemical barriers, an important point is the economic factor, which is the main rationale for the need of mathematical modeling of sorption processes occurring in geochemical barriers. For many years, the theory of ion exchange dynamics for single-component and multicomponent systems has been developed in the Laboratory of Sorption Methods of GEOKHI RAS with
the participation of members of the Department of Mathematical Physics of the Moscow State University for subsequent modeling and calculation of various practically important ion-exchange processes on various sorbents, including CLT. In this regard, the article describes in more detail the main principles used to develop mathematical models of sorption processes. Based on the existing experience in mathematical
modeling, the sizes of geochemical barriers for specific natural СLT and specific environmental conditions are calculated. The first task is decontamination of natural waters polluted as a result of the accident in Yakutia («Kraton» object) from radioactive Sr2 + and Cs + at the CLT of the Khonguruu deposit. The second task is the decontamination of polluted groundwater in Kazakhstan at the local CLT of the Chankanai
deposit. The results of the calculation of the protective action time of geochemical barriers are given.