Synthesis, Characterization of α-GaOOH Self-Assembly and Its Application in Removal of Perfluorinated Compounds.

This article discusses the hydrothermal synthesis of well-dispersed faceted α-GaOOH in the presence of sodium acetate by the self-assembly method. The synthesized α-GaOOH possesses a mixture of hexagonal and rectangular plates, cubic and diamond-like morphologies. The presence of ethanol as a co-solvent with water (1:1) facilitates scroll-like cylindrical morphology. The influences of sodium acetate concentration, hydrothermal temperatures, time and solvent on the formation of the above-mentioned morphologies were investigated. The synthesized α-GaOOH was characterized using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM), thermal analysis and nitrogen adsorption analysis. The XRD pattern confirmed the formation of orthorhombic α-GaOOH. The increase of the sodium acetate concentration from 0.031 mol/L to 0.250 mol/L facilitates the formation of more cubic and diamond-shaped particles than plate-like particles. The formation of faceted α-GaOOH is slow at 150 degrees C, and a further increase in hydrothermal temperature from 175 degrees C to 225 degrees C had no appreciable effect. Similarly, an increase in hydrothermal time from 5 h to 20 h at 200 degrees C facilitates hexagonal to cubic shaped plates. The solution pH strongly influenced the aspect ratio of the nanoplates. Hydrothermal temperature and time had no appreciable effect from 175 degrees C to 225 degrees C. The removal perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using the synthesized α-GaOOH was studied. A plausible mechanism for the formation of nanoplates is proposed.