Preparation and simultaneous ion uptake properties of CaO-Fe_2O_3-SiO_2 compounds(<Feature> Innovative Ceramic Materials and Technologies for Global Environmental Protection)

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CaO-Fe_2O_3-SiO_2 (CFS) compounds were prepared from mixtures of Ca(OH)_2, FeOOH and SiO_2 and their simultaneous uptake properties for cations and anions were investigated. The starting powders were mixed in various ratios using a planetary ball mill and heated at various temperatures in air and flowing N_2 atmospheres. Amorphous compounds were formed by heating up to <600℃ while hematite (α-Fe_2O_3) was crystallized at *600℃ and calcium silicates and/or calcium iron silicates at *800℃. Simultaneous ion uptake experiments were carried out by a batch method using solutions containing same concentrations of Ni^<2+>, NH_4^+ and H_2PO_4^-. The samples heated at 600℃ showed the highest ion uptake ability. The uptake abilities were higher for Ni^<2+> and H_2PO_4^- than for NH_4^+ and increased with increasing CaO content in the CFSs. The uptake abilities for three ions enhanced by heating the samples in flowing N_2. The simultaneous uptake mechanisms are thought to be similar to those observed in the CAS compounds, i.e. ligand change (Ca^<2+>→Ni^<2+>), compound precipitation and adsorption. The CFS compounds have the following advantages compared with CaO-Al_2O_3-SiO_2 (CAS); (1) higher uptake ability for phosphate ions (a model for harmful oxyanions) and (2) easy separation of a contaminated sorbent from the solution after uptake using a magnet.
社団法人日本セラミックス協会の論文
2008-02-01