Fabrication And Adsorption Performances Of Graphene/Hydroxyapatite Aerogels

Over the past decade, graphene or reduced-graphene oxide (RGO) aerogels have received increasing attention in the field of carbon-based materials, due to their fascinating properties, such as three dimensional architectures, a large surface area, and excellent stability, enabling them to be carrier materials and adsorbents. Hydroxyapatite (HA), as the inorganic component of hard tissue, has good biocompatibility. And HA is also an excellent metal ions adsorption material. In this paper, we prepared three dimensional network structure RGO/HA aerogels adsorption materials by combining their own advantages. And we studied respectively the adsorption properties of RGO/HA aerogels for heavy metal ions Cu2+, congo red (CR), Cu2+ and CR existence (Cu2+ -CR)at the same time from aqueous solution.Firstly, RGO/HA aerogels were prepared by hydrothermal treatment of graphene oxide (GO) and HA slurry, and were physicochemical characterized. The results showed that some of the oxygen-containing functional groups on GO could be restored in hydrothermal process, and adding the appropriate amount of HA would not affect the self-assembly of RGO. At the same time, compared with RGO aerogels, RGO/HA aerogels have more functional groups due to the addition of HA. The as-prepared RGO/HA aerogels have large specific surface area.Secondly, the adsorption properties of RGO/HA aerogels were studied in Cu2+ and CR mono-component system. And the possible adsorption mechanism of RGO/H A aerogels for Cu2+ and CR was discussed. The results showed that RGO/HA aerogels have better absorption properties for Cu2+ and CR than RGO aerogels and HA. The pH value of solution affects significantly the adsorption of RGO/HA aerogels for Cu2+ and CR. Adsorption isotherm in Cu2+ and CR mono-component system conforms to Langmuir model, the maximum adsorption capacities for Cu2+ and CR are 107.8 mg/g and 367.0 mg/g respectively. However, the maximum adsorption capacities of HA for Cu2+ and CR are 73.0 mg/g and 220.6 mg/g respectively, and the maximum adsorption capacities of RGO aerogels for Cu2+ and CR are 49.8 mg/g and 107.5 mg/g. The adsorption process coincides with pseudo-second order kinetic model, and reaches equilibrium for Cu2+ and CR in 500 min and 360 min respectively. The adsorption of RGO/HA aerogels for Cu2+ and CR is spontaneous endothermic process.Finally, adsorption behavior in Cu2+ -CR binary system of RGO/HA aerogels was investigated. The results showed that the adsorption capacity of RGO/HA aerogels for Cu2+ is inhibited in Cu2+ -CR binary system containing low concentration (0～75 mg/L) of CR, and the adsorption capacity of RGO/HA aerogels for Cu2+ can be reduced by 19.2% at most. While high concentration (75～200 mg/L) of CR in Cu2+ -CR binary system has a positive effect on the adsorption capacity of RGO/HA aerogels for Cu2+, and the adsorption capacity of RGO/HA aerogels for Cu2+ is 1.2 times that in Cu2+ mono-component system at most. And in Cu2+ -CR binary system, Cu2+ always plays a promoting role on the adsorption capacity of RGO/HA aerogels for CR, and the adsorption capacity of RGO/HA aerogels for CR is 1.8 times that in CR mono-component system at most.