Technology of Nanocomposites Preparation for Sorption Purification of Aqueous Media

A technique is described for the preparation of a universal composite nanomaterial for effective sorption purification of water from pollutants of different chemical nature. The proposed material is a nanocomposite based on reduced graphene oxide, which is modified with polyaniline as a functional organic component and also includes oxidized carbon nanotubes as a reinforcing agent. The use of polyaniline makes it possible to substantially increase the activity and sorption capacity of the developed graphene material. A number of nanocomposites are developed, the preparation technologies of which differ in the final stage, i.e., the drying of the preliminarily obtained hydrogel. Furthermore, the effect of the additional stage of final sample carbonization is studied. The surface morphology of the materials is examined by scanning electron microscopy. The specific surface area and the parameters of the porous space are determined by nitrogen adsorption. The specific surface area of the materials increases in accordance with the choice of drying technology for the initial hydrogel (drying oven, 80 m2/g → freeze drying, 180 m2/g → supercritical drying, 290 m2/g), increases additionally after the carbonization stage, and reaches a value of about 350 m2/g. The sorption capacities of nanocomposites with respect to organic dyes methylene blue (MB) and sunset yellow (SY) and with respect to heavy metals (for example, zinc ions) are determined. It is found that the sorption value ranges from 1380 to 1800 mg/g for MB, from 159 to 300 mg/g for SY, and from 31 to 230 mg/g for zinc. At the same time, the sample processed under supercritical conditions with subsequent carbonization exhibits the best characteristics.