Novel and Reusable Graphene Oxide-Coated Reticulated Open-Cell Mullite Foams for Methylene Blue Dye Adsorption.

Reticulated open-cell mullite (ROM) foams coated with graphene oxide (GO) multilayers as novel and reusable composites (ROM/GO) were first fabricated and functionalized to remove methylene blue (MB) dye from aqueous solutions. In this study, the ROM foams were produced via a replica technique utilizing rice husk as a starting raw material of silica (SiO2) mixed with commercially available alumina (Al2O3) in the step of slurry preparation. GO was synthesized by a modification of Hummer's method and dispersed in a fixed weight ratio in an aqueous solution. The HCl-pretreated ROM foams were dip-coated for up to 5 cycles using a fixed weight ratio of GO in an aqueous solution. The experimental results revealed that the ROM/GO foams provided 100% adsorption efficiency for MB within 30 min. The adsorption kinetics of the ROM/GO foams followed the first-order model. Based on the microstructural investigations on the surfaces of the ROM foams compared with the ROM/GO foams, the adsorption performance was related to the unique porous structure of the ROM foams, incorporating the physicochemical properties of the GO-multilayered coating. Finally, the ROM/GO foams are considered as sustainable and cost-effective adsorbents due to their reusable functionality for at least 5 cycles of MB removal.

Synthesis and characterization of a novel composite of rice husk-derived graphene oxide with titania microspheres (GO-RH/TiO2) for effective treatment of cationic dye methylene blue in aqueous solutions.

Graphene oxide (GO) was synthesized utilizing rice husk (RH) as the starting raw material via a modified Hummers' method. Ground pencil leads were used as a control powder of the starting raw material to monitor the consistency of the synthesis method. TiO2 microspheres were synthesized via a precipitated method using the pluronic F127 solution as the pore template. GO derived from RH (GO-RH) was composited with TiO2 microspheres as GO-RH/TiO2 composites by an impregnation method with weight ratios of 3:1, 2:2, and 1:3. Characterized results revealed GO-RH formed a ternary phase material of graphene oxide, graphite oxide, and silica. A typical microstructure of the calcined TiO2 microspheres was found as the agglomerated anatase nanoparticles. Furthermore, the composites belong to large surface areas and numerous oxygen-containing functionalities on their surfaces. Removal efficiencies of cationic dye methylene blue (MB) from aqueous solutions by the composites, GO-RH and TiO2, were studied under UV illumination for 180 min. Due to the effective combination of adsorption and photodegradation for the MB removal, the composites provided the higher efficiencies (99-100%) faster than those of GO-RH and TiO2 and could be reused at least 4 times. Finally, a mechanism of the MB removal by the composites was proposed.

Hydroxyapatite nanoparticles formed under a wet mechanochemical method.

Hydroxyapatite (HA) nanoparticles were synthesized using a wet mechanochemical method without a calcination process. Dicalcium phosphate dihydrate (CaHPO4 ·2H2 O) and calcium carbonate (CaCO3 ) were mixed and milled in a planary mill using ethanol or water as liquid media in the two different synthesized routes. Effects of rotation speed and milling time on the final products formed have been studied. Experimental results showed that HA phase having a characteristic of low crystallinity could be formed under the synthesis route using water. The original phases of both starting chemicals were remained without HA formation in the synthesis route using ethanol. Particle size and morphology of HA nanoparticles were obviously depended on optimum conditions of rotation speed and milling time. Differences on phase formation in both synthesized routes have been considered and discussed based on occurring chemical reaction possibilities. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 679-688, 2017.

3D interconnected porous HA scaffolds with SiO2 additions: effect of SiO2 content and macropore size on the viability of human osteoblast cells.

3D interconnected porous scaffolds of HA and HA with various additions of SiO2 were fabricated using a polymeric template technique, to make bioceramic scaffolds consisting of macrostructures of the interconnected macropores. Three different sizes of the polyurethane template were used in the fabrication process to form different size interconnected macropores, to study the effect of pore size on human osteoblast cell viability. The template used allowed fabrication of scaffolds with pore sizes of 45, 60, and 75 ppi, respectively. Scanning microscopy was used extensively to observe the microstructure of the sintered samples and the characteristics of cells growing on the HA surfaces of the interconnected macropores. It has been clearly demonstrated that the SiO2 addition has influenced both the phase transformation of HA to TCP (ß-TCP and α-TCP) and also affected the human osteoblast cell viability grown on these scaffolds.