Ice segregation induced self-assembly of salecan and grapheme oxide nanosheets into ion-imprinted aerogel with superior selectivity for cadmium (II) capture

Abstract

Water pollution by highly toxic cadmium ion (Cd2+) poses a great threat to the human health and the ecosystem security. Thus, it is of great urgency and prime importance to develop green and effective strategies to remove Cd2+ from our environment. However, as a kind of potential heavy metal absorbent, graphene oxide (GO) materials are severely limited in practical applications due to the complicated collection procedure from effluent and bad selectivity toward certain metal ion. Here, we constructed a new aerogel by incorporating GO nanosheets into the salecan matrix through ice segregation induced self-assembly and ion-imprinting technologies. The hydrogen bond interactions between salecan and GO led to the complexation of aerogel network and were investigated systematically. The swelling ability, microstructure, and mechanical strength of the aerogel could be progressively modulated by simply changing the salecan content. Most strikingly, the Cd2+ adsorption onto the aerogels was dependent on the salecan content, pH, initial ion concentration, and contact time. The maximum adsorption capacity of the ion-imprinted aerogel was calculated to be 412.5 mg/g, notably higher than other Cd2+ adsorbents recently reported in literature. The adsorption kinetics and isothermal studies performed on Cd2+ matched the pseudo-second-order model and Langmuir model, implying the monolayer chemisorption mechanism. Simultaneously, the ion-imprinted aerogel showed an excellent selectivity for capturing Cd2+ and still maintained high adsorption capacity after five consecutive adsorption/desorption cycles. This work opened a door to construct an effective and eco-friendly aerogel system for thorough cleanup of Cd2+ in wastewater.