L-cysteine-reduced graphene oxide/poly(vinyl alcohol) ultralight aerogel as a broad-spectrum adsorbent for anionic and cationic dyes

It is a challenge to develop broad-spectrum, high-efficiency, easy-recyclable adsorbents for the removal of water contaminants. Herein, L-cysteine-reduced graphene oxide/poly(vinyl alcohol) (CRG/PVA) ultralight aerogels with good mechanical strength and reusability are prepared via a direct sol-aerogel transition strategy by freeze drying. At optimized composition, the aerogel shows high adsorption efficiency toward both cationic and anionic dyes, overcoming the defect of many traditional adsorbents that usually can only remove one type of organic dyes. The adsorption is proved to involve in pi-pi interaction between CRG and dyes, endowing the aerogel with universality in adsorbing a wide range of conjugated dyes. Moreover, a remarkable synergetic effect is observed for removal of two oppositely charged dyes from aqueous system, yielding exceptionally high total adsorption capacities surpassing all known adsorbents examined for removing binary dyes. Thus, the CRG/PVA aerogel demonstrates great potential for usage as reusable, high-efficiency, and broad-spectrum adsorbent in water treatment.