Noncovalent Magnetic Control and Reversible Recovery of Graphene Oxide Using Iron Oxide and Magnetic Surfactants

Abstract

The unique charging properties of graphene oxide (GO) are exploited in the preparation of a range of noncovalent magnetic GO materials, using microparticles, nanoparticles, and magnetic surfactants. Adsorption and desorption are controlled by modification of pH within a narrow window of <2 pH units. The benefit conferred by using charge-based adsorption is that the process is reversible, and the GO can be captured and separated from the magnetic nanomaterial, such that both components can be recycled. Iron oxide (Fe2O3) microparticles form a loosely flocculated gel network with GO, which is demonstrated to undergo magnetic compressional dewatering in the presence of an external magnetic field. For composites formed from GO and Fe2O3 nanoparticles, it is found that low Fe2O3:GO mass ratios (<5:1) favor flocculation of GO, whereas higher ratios (>5:1) cause overcharging of the surfaces resulting in restabilization. The effectiveness of the GO adsorption and magnetic capture process is demonstrated by separating traditionally difficult-to-recover gold nanoparticles (d ≈ 10 nm) from water. The fully recyclable nature of the assembly and capture process, combined with the vast adsorption capacity of GO, presents obvious and appealing advantages for applications in decontamination and water treatment.

Optimization of cadmium adsorption from aqueous solutions by functionalized graphene and the reversible magnetic recovery of the adsorbent using response surface methodology

“…Fe 3 O 4 /G nanocomposites have been successfully used for the removal of various heavy metals such as arsenic, chromium, cadmium, selenium and mercury . The drawback to using magnetic graphene nanocomposites is that their production often changes the structural makeup of the GO and the presence of Fe 3 O 4 nanoparticles on the GO surface reduces its effective adsorption area…”

Magnetic surfactants

“…Various proof of principle experiments have been highlighted that have already been demonstrated in areas of protein separations [44,46], water treatment [62] and environmental clean-up [37]. Furthermore, the concept that these complexes may be considered as novel molecular magnets has been highlighted [10].…”

“…Covalently binding GO to magnetic nanoparticles has been attempted but requires high energy, complex and multistep synthetic procedures and effects adsorption capacity of the sheets [60,61]. Tabor et al used magnetic surfactants (DTAF) to bind to the GO (at pH 5.5 to ensure GO had a negative charge) [62]. The surfactant was reported to bind with moderate affinity, leading to significant flocculation.…”

Tailoring environment friendly carbon nanostructures by surfactant mediated interfacial engineering

“…Graphene-copper nanocomposite prepared with graphite M a n u s c r i p t oxide and copper sulfate was used an antifriction application [129]. Surfactant treated graphene is also effective for many purposes [131][132][133].…”