Surface Chemistry Interaction of Graphene Oxide/Eggshell Adsorbent towards Fluoride Removal

Abstract

Fluoride removal is crucial in water sources because its existence is very harmful towards human and environment. With this concern, graphene oxide (GO) has been selected as an adsorbent due to its adsorptive characteristics. GO was modified with eggshell (GO/ES), a natural based of calcium precursor. The modification of the GO/ES adsorbent was done via ultra-sonification. The effects of each synthesis parameter toward fluoride removal were investigated and related to surface functional groups found in the modified GO/ES adsorbent. From the analysis, eggshell has been successfully decorated over GO structure, where GO-calcium bond was observed in the FTIR spectra. The interaction between GO and ES showed the increment of hydroxyl (O-H) and carboxyl (C-O) functional groups as increasing in ES amount. This resulted in increasing of fluoride removal, as high as 54.30 mg/g adsorption capacity. The effects of GO/ES ration, sonication temperature and synthesis time in tailoring the modified GO/ES adsorbent were also significant in the arrangement of these functional groups towards fluoride removal. Based on the results obtained, it can be concluded that modified GO/ES adsorbent, from natural calcium source is comparable with chemical based calcium source, where the same functional groups were observed from FTIR spectra.