New Sorption Properties of Diatomaceous Earth for Water Desalination and Reducing Salt Stress of Plants

Abstract

A new practical application of the unique sorption abilities of Diatomaceous Earth (DE) or diatomite, a widely accessible and promising natural mineral, has been studied. By analyzing aqueous extracts of natural diatomite, it was shown that DE probably contains various inorganic salts, which are released into the solution in the form of ions, such as Cl-, SO42-, Na+, Ca2+, Mg2+, K+ and, apparently, others. Diatomite was able to exchange these ions with the environment, exhibiting the properties of a natural ion exchanger. Studying the kinetics of ion release from diatomite showed that the ion desorption process continues for 4‒5 h until the surrounding solution is saturated with ions, after which it is dynamically balanced by the sorption process. In order to significantly reduce the ionic content of diatomite, DE samples were processed in a technologically simple and environmentally friendly way. Thus, as a result of deionization, the content of ions released from diatomite significantly decreases. Deionized diatomite was applied to study the adsorption of sodium and chloride ions from aqueous solutions. The maximum adsorption was 50.2 mg/g, and the maximum degree of extraction, corresponding to the concentration range of 5‒100 mg/l, was 53.9%. The observed effect was also applicable for increasing the resistance of plants to salt stress, improving the germination and growth of wheat samples. The developed method can be used in the manufacturing of filters for water desalination, both drinking and technological; in ecology; in agriculture to reduce salt stress of plants, as well as for the restoration of lands contaminated by salt.