Preparation Of Graphene Composites And Applications In The Adsorption Of Dye

Human has various requirements for the color, at the same time dyes are widely used in food industry, coating industry, papermaking industry, etc. Producers are developing all kinds of artificial dyes, which are applied to all walks of life. Due to the imperfection of the wastewater treatment technology, dyes will be discharged in the environment, which causes environmental pollution. Adsorption method is the simplest and most widely used methods for wastewater treatment. In order to adsorb large amount of pollutants, adsorbents should have a larger specific surface area. Graphene has large specific surface area and good thermal stability, which is considered as an idea sorbent material. Herin, Fe3O4 and SiO2 decorated graphene were prepared. The Fe3O4 and SiO2 on the surface of graphene can effectively prevent its aggregation at the same time, it endows graphene with magnetic properties. On the other hand, the SiO2 is coated on the surface of Fe3O4, which can prevent Fe3O4 from leaching in acid solution. Mg(OH)2/SiO2/graphene composites and Fe3O4/Al(OH)3/graphene composites are also fabricated and applied as adsorbents for the removal of organic dyes.1. Adsorption of MB onto G-Fe3O4-SiO2 composites.Graphene oxide, ethylene glycol, anhydrous sodium acetate and FeCl3·6H2O were mixed by ultrasonic and the above mixture was hydrothermal treated for 8 hours. With the help of external magnet, the collected product was seperated. The final product is denoted as G-Fe3O4. The obtained G-Fe3O4 was mixed with TEOS and CTAB by ultrasonic treatment, the pH of the mixture was adjusted to 8.5 by NaOH solution. The above mixed solution was stirred under ambient environment for 20 hours, and G-Fe3O4-SiO2 composites were obtained. The obtained G-Fe3O4-SiO2 composites are used for the adsorption of methylene blue (MB). XPS and XRD were applied for the characterization of the G-Fe3O4-SiO2 composites. SEM and TEM are used for observation of the G-Fe3O4-SiO2 composites. The G-Fe3O4-SiO2 was further studied as adsorbents for the removal of MB from aqueous solution. The solution pH, adsorption time, temperature and initial concentration of MB were investigated for the MB adsorption. Pseudo-second dynamics and Langmuir isotherm model can accurately describe the adsorption data.2. Adsorption of MB onto GO-Mg(OH)2-SiO2 composites.Firstly, graphene oxide, Mg(NO3)2·6H2O, NaNO3, Na2C2O4, and ammonium hydroxide were mixed in deionized water. The above mixture was transferred into a stain-less-steel autoclave and hydrothermal treated for 24 hours. The obtained GO-Mg(OH)2 was further mixed with TEOS and CTAB, the pH value of which is adjusted to 8.5 by NaOH solution. The above mixture solution was stirred for 20 hours in room temperature, and GO-Mg(OH)2-SiO2 composites were obtained. XPS, XRD, SEM and TEM techniques were applied to for the characterization of GO-Mg(OH)2-SiO2. The obtained GO-Mg(OH)2-SiO2 composites were applied for the adsorption of methylene blue (MB). Effect of solution pH, adsorption time, temperature and initial concentration of MB on adsorption was investigated. The experimental data can be well fitted by the Pseudo-second dynamics model and the Langmuir isotherm model.3. Adsorption of MB onto G-Fe3O4-Al(OH)3 composites.For the preparation of G-Fe3O4, graphene oxide, ethylene glycol, anhydrous sodium acetate and FeCl3·6H2O were well dispersed in aqueous solution. The above mixture was hydrothermal treated for 8 hours and the final product was seperated from solution by an external magnet. The obtained product was denoted as G-Fe3O4 G-Fe3O4-Al(OH)3 composites was prepared by adding sodium aluminate in the G-Fe3O4 suspension and stepped by sonication for 24 hours. The pH of the above mixture was adjusted between 7.5 and 9.0 by NaOH solution. Effect of solution pH, adsorption time, temperature and initial concentration of MB on the adsorption were investigated. Pseudo-second dynamics model and the Langmuir isotherm model were applied to fit the experimental data. The results showed that the adsorption process is endothermic.