Tian Quanzhi, Sasaki Keiko
Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishiku, Fukuoka 819-0395, Japan E-mail:
Water Sci Technol. 2019 Jun;79(11):2116-2125. doi: 10.2166/wst.2019.209.
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 Cs and Sr, and AsO from solutions. Each sorption kinetic was well fitted to the pseudo-second-order model. The sorption of Cs and Sr onto original geopolymer were better fitted to the Langmuir model. However, the Freundlich model is more befitting for sorption of AsO onto Fe(II)-modified geopolymer. The free energies calculated from the D-R isotherm indicated that the sorption for Cs and Sr were dominantly ion exchanges. Ring size plays a decisive role in ion exchanges for both Cs and Sr. Furthermore, the arrangement of SiO and AlO tetrahedrons has significant impacts on the ion exchange of Sr. XPS results indicated that a part of Fe in Fe (II)-modified geopolymer had been oxidized to Fe after sorption. Precipitation of FeAsO could partially contribute to the arsenate removal from solution. AsO sorption has also occurred through the formation of inner-sphere complexes via ion exchange reaction, which could be predominantly attached by bidentate linkages.
地质聚合是一种利用固体废弃物的发展中的反应过程。在本研究中，合成了基于粉煤灰的地质聚合物及其衍生物（Fe(II)改性地质聚合物），并使用XRD、SEM、FTIR、BET、UV-Vis DRS以及TG-DTA对其进行了表征，将其用作从溶液中去除Cs、Sr和AsO的吸附剂。每种吸附动力学都很好地符合准二级模型。Cs和Sr在原始地质聚合物上的吸附更符合Langmuir模型。然而，Freundlich模型更适合AsO在Fe(II)改性地质聚合物上的吸附。根据D-R等温线计算的自由能表明，Cs和Sr的吸附主要是离子交换。环大小对Cs和Sr的离子交换起决定性作用。此外，SiO和AlO四面体的排列对Sr的离子交换有显著影响。XPS结果表明，Fe(II)改性地质聚合物中的一部分Fe在吸附后被氧化为Fe。FeAsO的沉淀可能部分有助于从溶液中去除砷酸盐。AsO的吸附也通过离子交换反应形成内球络合物而发生，该络合物可能主要通过双齿键连接。
