Obtaining of a sorbent from waste sweet sorghum for use in the contaminated with Cd(II), Pb(II) and Sr(II) soils

Abstract

Goal. To develop a method of obtaining new, more effective sorbent of heavy metal ions by mercerizing the lignocellulosic bagasse of sweet sorghum and to determine the sorption properties of the resulting product to the ions of Cd(II), Pb(II) and Sr(II) during extraction from aqueous extracts of contaminated soils. Methods. Sorption experiments were performed under static conditions with model solutions of groundwater samples contaminated with heavy metal ions [14, 15]. Determination of the concentration of heavy metal ions was carried out on atomic-absorption spectrometer CAS-1 (SELMA) after the atomization of the sample in the air-acetylene flame. The method is based on the property of atoms in the basic state to absorb light of definite and specific for each kind of atoms wavelengths. Results. At use of waste of production of sweet sorghum for obtaining sorbents, they carried out their chemical modification, since the waste in its raw form has weak sorption properties because of fibrillar structure and low content of available functional groups. Processing of waste with alkali solution (mercerizing) destroyed partially molecular bonds between the fibers of biopolymers, however, the structural frame of the lignocellulosic matrix keeps and improves its structural-pore form due to the increase in the internal adsorption surface. The conducted research gave the chance to develop the method of mercerizing waste, as well as to determine that the optimal condition for that process is the hydro-module 10 at initial alkali concentration 120 g/L. Under such conditions of the mercerization process, it is possible to obtain sorbent with high sorption and kinetic properties. Conclusions. The results obtained, taking into account the availability of lignocellulosic wastes and sweet sorghum for complex processing, will give the chance to find a reasonable approach to the solution of specific practical problems related to the development of modified biosorbents and their use as soil additives for soil purification from heavy metal ions.