Technology of obtaining nanocomposites for sorption purification of aqueous media
The paper presents a technique for obtaining a universal composite nanomaterial for effective sorption water purification from pollutants of various chemical nature. The proposed material is a nanocomposite based on reduced graphene oxide modified with a functional organic component - polyaniline, which also includes oxidized carbon nanotubes as a structure former. The use of polyaniline makes it possible to significantly increase the activity and sorption capacity of the developed graphene material. The authors were developed a number of nanocomposites, which differ in the final stage of the pre-prepared hydrogel technology: drying in air (drying oven), freeze drying, drying under supercritical conditions (supercritical fluid - isopropyl alcohol). In addition, the effect of carbonization as an additional stage (T = 800 °C, argon) was studied in the article. The materials surface morphology was evaluated using scanning electron microscopy. The specific surface area and the parameters of the porous space were determined by nitrogen adsorption. The materials specific surface area increases depending on the choice of drying technology for the initial hydrogel (drying oven - 80 m2/g → freeze drying - 180 m2/g → supercritical drying - 290 m2/g), and also increases after the carbonization stage and reaches a value of ~ 350 m2/g. The nanocomposites sorption capacity to the organic dyes (methylene blue (MB) and solar yellow (SY)), as well as to heavy metals (for example, zinc ions) was determined. It was found that the value of MB sorption is up 1380 to 1800 mg/g, for SY - up 159 to 300 mg/g, for zinc - up 31 to 230 mg/g. At the same time, the sample processed under supercritical conditions, followed by carbonization, were shown the best characteristics.