Graphene oxide based composites for organic pollutant removal and polymer modification

Abstract

In this study three graphene oxide (GO) based materials of graphene oxide-magnetite (GO-Fe3O4), reduced graphene oxide-calcium aluminosilicate (rGO-CAS) nanocomposites and reduced graphene oxide-lithium iron phosphate (rGO-LiFePO4 or rGO-LFP) were synthesized by chemical precipitation and hydrothermal method, respectively.

By chemical precipitation of iron(II) and iron(III) ions with ammonia in graphene oxide solution, GO-Fe3O4 nanocomposites were obtained. The influences of GO/Fe3O4 weight ratio on the morphology, crystallization and catalytic property of GO-Fe3O4 nanocomposites were investigated. In XRD pattern, the intensity of Fe3O4

peaks rapidly decreased with the increasing of GO/Fe3O4 weight ratio, which indicated GO may interfere the crystallization of Fe3O4 during GO-Fe3O4 composites formation process. FTIR technique revealed C-O-Fe coordination behavior in the as-synthesized GO-Fe3O4 nanocomposite. The catalytic performance of GO-Fe3O4 nanocomposites in the degradation of isatin showed that 3/20 for GO/Fe3O4 was the optimal weight ratio of GO-Fe3O4 catalyst. Optimal GO/Fe3O4 weight ratio reduced aggregation of Fe3O4, provided more effective electron transportation and avoided the overlapping of GO-Fe3O4 nanosheets, which led to about 98% isatin removal efficiency and 60% TOC removal efficiency in heterogeneous Fenton reaction. The rGO-CAS nanocomposites with different rGO/CAS weight ratios were synthesized by using calcium aluminosilicate (CAS) particles and grapene oxide (GO) solution under hydrothermal condition. The FT-IR spectrum and XRD pattern confirmed graphene oxide (GO) was reduced under hydrothermal condition. GO/CAS weight ratio showed great impact on methylene blue adsorption, sulphate radical generation and asphalt modification of rGO-CAS nanocomposites. Methylene blue adsorption efficiency increased with the increasing of CAS/rGO weight ratio (0.25/0.1, 0.5/0.1 and 1.0/0.1) and it dropped at high weight ratio of 1.5/0.1. In optimal ratio of 1.0/0.1 for CAS/rGO, CAS particles prevented stacking structure formation of rGO sheets with few active site occupations. In high CAS/rGO weight ratio, more active site of rGO nanosheets was occupied by CAS particles leading to low dye adsorption efficiency. Similar results were observed in the catalytic properties of sulphate radical generation for 1, 4-dioxene degradation. Sample with CAS/rGO weight ratio of 1.0/0.1 also showed comprehensive improvements including storage stability,

softening point, penetration and rutting resistance results for styrene-butadiene-styrene block polymer modified asphalt (SBSMA) materials modification.

The reduced grapheme oxide-lithium iron phosphate (rGO-LFP) nanocomposites were successfully synthesized through hydrothermal method. Ascorbic acid was an important chemical for LFP hydrothermal synthesis. All of LFP nanoparticles and LFP-rGO nanocomposites were measured by x-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy to characterize their crystallization, purity and morphology. The GO concentration showed effort on the morphology of rGO-LPF nanocomposite. At optimum concentration, LFP particle size was reduced to about 500 nm. LPF nanoparticle and rGO-LFP nanocomposite were sealed into cell battery and their electrical properties were also measured. The rGO-LFP showed pretty high electrical capacity because of rGO sheets was an active material with high conductivity.