Aromatic Amine-Supported N-Functionalization of Nanoscale-Thick Graphene Oxide Membranes for Preferential Adsorption of Strontium Ions from Aqueous Solutions

Aromatic amine-supported N-functionalization of graphene oxide (GO) was carried out via aniline vapor exposure for different durations (15–240 min), and the repercussions on the strontium (Sr(II)) adsorption ability of nanoscale-thick GO membranes (0.1–0.5 mg) were investigated. Characterization of aniline vapor-subjected GO substantiates significant amendments in the GO layer as well as functional group structures, restoration of the π-conjugation network, and integration of diverse N moieties, including precursor aniline molecules and its derivatives. Incorporation of aniline derivatives escalated the Sr(II) adsorption ability of the GO membrane from ∼310 to ∼600 mg/g and induced Sr(II) preferential sites that facilitate ∼540 mg/g adsorption, even in the presence of competing Mg2+/Ba2+ ions. Aniline-subjected GO membranes displayed a cumulative Sr(II) sorption capacity of ∼1500 mg/g via multiple filtration cycles, a notable Sr(II) desorption of ∼25%, and an overall adsorption capacity of ∼1295 mg/g when subjected to multiple (Sr2+/Mg2+/Ba2+) ions. Further, the pronounced enhancement in the Sr adsorption capacity of aniline-subjected GO nanoparticle (GONP) membranes reiterated the affinity of N-group-amended GO layers toward Sr2+ ions despite the limitations on surface area. These aniline-supported N-functionalization and Sr(II) sorption studies unveil the efficiency of the acquiescent aromatic ring allied with the electron-donating amine group in generation of abundant/versatile N moieties and the resultant enhancement of Sr(II) adsorption ability.