Geopolymerization is a developing reaction process for the utilization of solid wastes. In the present study, fly ash-based geopolymer and its derivative (Fe(II)-modified geopolymer) were synthesized and characterized using XRD, SEM, FTIR, BET, UV-Vis DRS as well as TG-DTA, and adopted as adsorbents for removal of Csþ and Sr2þ, and AsO3 4 from solutions. Each sorption kinetic was well fitted to the pseudo-second-order model. The sorption of Csþ and Sr2þ onto original geopolymer were better fitted to the Langmuir model. However, the Freundlich model is more befitting for sorption of AsO3 4 onto Fe(II)-modified geopolymer. The free energies calculated from the D-R isotherm indicated that the sorption for Csþ and Sr2þ were dominantly ion exchanges. Ring size plays a decisive role in ion exchanges for both Csþ and Sr2þ. Furthermore, the arrangement of SiO4 and AlO4 tetrahedrons has significant impacts on the ion exchange of Sr2þ. XPS results indicated that a part of Fe2þ in Fe (II)-modified geopolymer had been oxidized to Fe3þ after sorption. Precipitation of FeAsO4 could partially contribute to the arsenate removal from solution. AsO3 4 sorption has also occurred through the formation of inner-sphere complexes via ion exchange reaction, which could be predominantly attached by bidentate linkages.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Water Science and Technology