Preparation and characterization of graphene oxide-based nanocomposite materials for solar energy sorption

Two series of nanocomposite materials based on graphene oxide (GO) (Al2O3/GO (Al/GO), Fe3O4/GO (Fe/GO), and Fe3O4–Al2O3/GO (Fe–Al/GO)), and reduced graphene oxide (rGO) (Al2O3/rGO (Al/GO), Fe3O4/rGO (Fe/GO), and Fe3O4–Al2O3/rGO (Fe–Al/rGO)) were prepared and characterized by X-ray and infrared spectra, SEM, TEM and EDX analyses. Graphene oxide was synthesized from graphite by improved Hummers method, then it was reduced by ascorbic acid to obtain rGO. Composite materials were prepared by suspension mixing. GO- and rGO-based materials were dispersed into brine water to form nanofluids. Transmittance spectra and thermal conductivity of nanofluids and reflectance spectra of the three-component composites were systematically investigated to evaluate their thermal sorption capacity. It can be seen from the transmittance spectra that nanofluids capture almost incident light and from the reflectance that synthesized materials absorbed more than 97.5% and 96% of the irradiated solar power. The thermal conductivity results show that hybrid nanofluid showed high thermal conductivity than single nanofluids. The thermal absorption ability of nanofluids was evaluated by change in temperatures and weights of nanofluids. Results showed that all prepared materials (either single form such as GO, rGO, Al2O3 or composite form such as Al/GO, Fe/GO, Fe–Al/GO, Al/rGO, Fe/rGO, Fe–Al/rGO) raised thermal sorption of brine water. The combination of two or three components leaded to higher thermal sorption ability. Fe–Al/GO and Fe–Al/rGO give the highest thermal absorption efficiency (the temperature difference between the blank sample and the sample containing material with content of 0.5 mg mL−1 is 7 °C and 8.5 °C, respectively). Evaporation ability of Fe–Al/GO and Fe–Al/rGO nanofluids increased to 67% and 79%, respectively. The thermal sorption increased with increasing the concentration of materials in nanofluid and lightening intensity (the temperature difference between the blank sample and investigated sample using two lamps was 21 °C). Moreover, 98% of Fe–Al/GO (Fe–Al/rGO) was simply recovered by magnet and the recovered material can be reused with only slight decrease in thermal sorption performance. Prepared nanocomposite was dispersed in brine water (0.15 mg mL−1 in 3.5% NaCl solution) to be distillated using solar energy and the results show that distillation process can be profoundly speeded up.