Solving Environmental Problems with Latvian Clay-Based Sorbents

Abstract

Currently there is an increasing interest in application of natural clay minerals in production of various products, including sorbents for waste water treatment. For practical application of clay as a sorbent, it is significant not only to establish its properties, but also to be able to modify them. Only during the last twenty years, an increasing effort has been directed to systematic studies of clay sorption properties. A special attention has been devoted to improvement of clay sorption properties, which could allow to scientifically develop various sorbents for collection of oil products, such as oil spills from water surface, water processing and cleaning of waste waters from heavy metal ions, organic and inorganic admixtures, etc. In this study, surface properties of Latvian Triassic (Vadakste deposit) smectite-containing clay samples were examined, in order to develop cheap, clay-based sorbents of high quality. Using sedimentation method, the granulometric composition of natural clay samples was determined. Surface morphology of the obtained samples was studied by using scanning electron microscopy. Sorption properties of natural Vadakste deposit clay samples were modified by thermal treatment, as well as by adding a natural modifier based on hemicellulose and lignin (HLS). This type of clay modification has almost never been used in practice. Optimal thermal treatment conditions and HLS modification conditions were determined for the natural clay samples. It was found that water absorption decreased with increasing the thermal treatment temperature from 300 to 500 and 800 °C, however silicone oil and rapeseed oil absorption doubled at the same time. After adding HLS to clays within the range of 0.053% to 0.13%, both water and oil absorption doubled. The ability of natural and modified clay samples to adsorb copper and zinc ions from the corresponding salt solutions was investigated. The obtained results proved that the developed clay-based sorbent granules can be used for removal of copper and zinc ions from waste water, for collection of oil and oily substances; and as a cheap, environmentally safe pet litter.