USE OF MODIFIED CLAYS FOR CONTROLLING SOIL ENVIRONMENTAL QUALITY

Abstract

In the last two decades, progress has been made in the modification of the properties of clay materials in order to produce new clay nanocomposite products that can be used for controlling soil environmental quality. Pillared organoclays and nanocomposites constitute a novel class of materials, prepared by propping apart the lamellae of 1:2 clays, thus changing their properties from hydrophilic to hydrophobic, and building an inorganic/organic hybrid by grafting interlayers with selective pore sizes or by dispersion of the mineral component as a reinforcing phase. Acid and salt treatments lead to modification of the catalytic properties of clays. Thermal and mechanical treatments are also ways to modify the capacity of clays to retain both water and chemicals. These modified clays may be used for pollution prevention and for remediation of the soil environment. Selected examples are presented to show the role of various modified clays in engineering formulations intended to minimize the application of agrochemicals, for tailoring high rate adsorbents to prevent the redistribution of both organic and inorganic contaminants in the environment, and for enhancing the degradation of toxic organics. In situ modification of the soil clay properties with the aim of increasing the retention of micropollutants and avoiding their transport into the groundwater is another important use of modified clays. This analysis of the status of studies of clay modification and use leads to the conclusion that fundamental studies at the molecular level should be the basis for future developments in producing new nanocomposite clay materials, especially multifunctional compounds able to retain/degrade organic an inorganic pollutants simultaneously.