The dynamically developing industrial sector, as one of the significant anthropogenic factors, is a source of a huge number of pollutants – organic, inorganic and biological, which negatively affect ecological integrity [1]. Despite the huge variety of methods suitable for removing pollutants from various wastes, there is still a shortage of highly efficient, eco-friendly materials. Adsorption methods have great potential for applications in the field of environmental protection [2, 3]. Therefore, it is promising to search for cost-efficient and biocompatible adsorbents possessing high adsorption capacity.
Currently, one of the most prospective adsorbents is clay minerals, which are not inferior in efficiency to commercial adsorbents, and in some cases even surpass them. Clays are being actively modified in order to increase their efficiency and selectivity towards specific pollutants. Another advantage of using clays is their possible combining with other potential adsorbents, that can increase the effectiveness of the composite due to a synergistic effect, while the most important is the ability of clays to minimize the toxic effect of other components in the composite, for example, graphene oxide [4], as well as various other modifiers [5].
The main challenges in this research area are possible additional pollution after the use of these adsorbents, the toxicity aspect of modified clays that are not fully understood, and that the data obtained in vitro and in vivo are contradictory.
The aim of this study was to develop composites of Clay-Graphene Oxide (GO)-Magnetite (MG)/Maghemite (MGH).
The first step of preparation of composites includes synthesis of all components. GO was obtained by the Hammers method, MG/MGH by a co-precipitation reaction of ferrous and ferric ions. Triassic clay (Šaltiškiai in North Lithuania) was used in this study. The clay was treated with 0.5 M HCl solution while for synthesis both treated and untreated clays were used. The synthesis of the composite included dispersing GO and MG/MGH in an ultrasonic bath for 2 h, followed by the addition to acid-treated (ATC) or untreated clay (UTC) to the solution, keeping the mixture under constant stirring in a flow of argon for 1.5 hours, at 60 °C. Then this mixture is centrifuged, the resulting composite is taken and dried in vacuum for 24 hours.
Thus, four composites were obtained based on acid-treated and untreated clay with different weight ratio (%) - ATC (43.48)-GO (13.04)-MG/MGH (43.48); ATC (66.67)-GO (16.67)-MG/MGH (27.78); UTC (43.48)-GO (13.04)-MG/MGH (43.48); UTC (66.67)-GO (16.67)-MG/MGH (27.78). These composites were characterized using X-ray diffraction analysis (XRD), X-ray fluorescence analysis (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and FTIR spectroscopy (FTIR). The obtained composites were applied to remove heavy metals from aqueous solutions. Preliminary results of studying the adsorption of copper on composites showed the adsorption efficiency from 90 to 99%.