Nanochemistry and biotechnology

Saponite based composite materials for removal of inorganic toxicants
Antonina Bondarieva, Junje Yu, Viktoriia Tobilko
Department of Chemical Technology of Ceramics and Glass, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”.
Ave. Peremohy 37, Kyiv-03056, Ukraine 
E-mail: a.i.bondarieva@gmail.com

One of the most dangerous pollutants in groundwater and wastewater are inorganic toxicants in anionic forms. Nowadays, adsorption technologies are the most effective for treating water systems from contaminants of this type. For this reason, the important task is to modernise this technology constantly, including path obtaining new, highly efficient, low-cost and technologically simple sorbents.
Sorbents fulfil these requirements based on clay minerals. Among them is saponite (Sap), use of it is possible due to properties such as high surface area and cation exchange capacity. Nevertheless, the natural saponite is characterised by relatively low adsorption capacity. Therefore, the further modiﬁcation of Sap is necessary to make it more competitive in its practical application. For this purpose, the use of iron (III) oxides-hydroxides is promising, which are characterised by high values of the specific surface area and increased reactivity due to a large number of hydroxyl centres. 
This work aimed to obtain composite material based on natural saponite (Tashkiv deposit, Ukraine) to remove anionic forms toxicants from water systems. Modifications of saponite were performed with Co-doped iron-based layered double hydroxides subject to different molar ratios of clay:modifier.
The structure of materials is studied using physicochemical methods (X-ray powder diffraction and the low-temperature N2 adsorption-desorption method).
 The adsorption experiments were performed in the range of initial concentrations, under static conditions, at room temperature (20 ± 2 °C), and the ratio of solid and liquid phases S:L = 1:500. The equilibrium As(V) and Cr(VI) concentrations were determined by the inductively coupled plasma atomic emission spectroscopy (Thermo Scientific iCAP 7400 ICP-OES, USA).
The results showed that the synthesised materials have significantly higher sorption properties than the original saponite or ferrihydrite. It indicates the prospects for using such materials to purify contaminated water from heavy metal anions.