Selective adsorption of anionic dyes and carbon dioxide using uncarbonized PVA aerogels incorporated with GO/PANI hybrids

Abstract

The environmental devastation, caused by unscrupulous and recurrent human intervention in the ecosystem is a global concern. Within the scope of relevance, this work discusses the development of adsorbents which eliminate both water and air pollutants. Graphene oxide/polyaniline hybrid incorporated polyvinyl alcohol (PVA) composite aerogels were successfully fabricated by environmentally friendly lyophilization method. Various fillers such as polyaniline (PANI), graphene oxide (GO), reduced graphene oxide (rGO), binary hybrids of GO/PANI and rGO/PANI was synthesized and characterized for structural and morphological peculiarities. The filler system which shows the highest anionic dye (model organic pollutant) adsorption ability was selected for the preparation of PVA composite. The freeze dried aerogel samples were characterized and it shows 98% removal of anionic dye (methyl orange, MO) within 24 h. The high percentage of anionic dyes removal from aqueous solutions is attributed to different mechanisms such as electrostatic attraction between positively charged PANI backbones and negatively charged MO molecules, π-π interaction & hydrogen bond formation between different functional groups present in adsorbate and adsorbent. The dye adsorption mechanism was well established based on the Boyd, Werber & Morris models and the adsorption isotherms were fitted in agreement with the Freundlich and pseudo-second-order models. The reusability studies on dye adsorption were also carried out up-to three cycles without much loss in the adsorption capacity. In addition, the preliminary analysis of CO₂ adsorption at 25 °C and 900 bar indicates the suitability of the proposed composite aerogels for environmental remediation.