Investigation of pH effect on adsorption properties of the nanostructured graphene-containing composite materials, modified by polyaniline, in the adsorption of various chemical nature pollutants

Abstract

Liquid-phase sorption is a multi-stage process, the success of which depends on many factors. One of the key parameters that determines the extraction efficiency is the liquid medium pH value. In this study, the effect of the pH value of model aqueous solutions containing separately heavy metal ions (using zinc and lead ions as an example), as well as organic dyes methylene blue (MB) and sunset yellow (SY), was evaluated. The required pH value was achieved by preparing the solutions in appropriate buffer systems. As a sorbent, a nanostructured composite material was used, represented by a matrix of carbon nanotubes and graphene oxide modified with polyaniline, where phenol-formaldehyde resin acted as a binding agent. Various forms of this material were considered — xerogel, cryogel, aerogel, as well as their carbonized modifications. As a result of experimental studies, it was found that for all used heavy metal ions (zinc and lead) and MB for all sorbents forms, the maximum adsorption capacity was noted at pH = 6. At the anionic dye SY adsorption, the best result was achieved at pH = 2.