Amino-Functionalized Activated Carbon/Graphene Aerogel with Broad-Spectrum Adsorption/Absorption for Organic Contaminants

Abstract

Environmentally friendly carbon-based aerogels have been regarded as effective adsorbents and/or absorbents for the removal of water-soluble contaminants and the extraction of leaking organic solvents. A practical and facile method was proposed for preparing amino-functionalized activated carbon/graphene aerogels (KAC-GA@N) with a highly porous structure and good hydrophilicity, wherein microbubble technology, a one-step freezing process (−18 °C for 6 h), two-step hydrothermal reduction (85 and 120 °C), and amino-functionalization (in ammonium citrate solution (60 mg/mL)) were employed. Our preparation strategy provided it with extraordinary chemical and mechanical stability. It can be used as an excellent adsorbent for the removal of different organic pollutants. Moreover, KAC-GA@N had a better affinity toward cationic dye (methylene blue, MB) than anionic dye (methyl orange, MO) (183.73 mg/g vs 88.31 mg/g at equilibrium), showing a good capability of selectively separating ionic dyes. Its batch adsorption process could be well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. The fixed-bed dynamical adsorption–desorption cycle experiments proved the excellent practical application potential (about 88.2% MB and 39.7% MO were separately trapped for the first filtration) and good reusability of KAC-GA@N. A possible adsorption mechanism was proposed and discussed in detail. KAC-GA@N had a higher absorption capacity and rate toward various organic solvents. The KAC-GA@N aerogel efficiently addresses the recycling issue of powdery activated carbon particles and shows strong potential for practical use in the water treatment of organic pollutants.