2005 年 12 巻 315 号 p. 122-130
For the purpose of recovering calcium resource from such solid wastes as coal burnt ash, iron slag, paper sludge, concrete sludge and shell waste, which involve calcium-derived compounds to a large extent, an attempt was made to extract calcium component with 6 organic acids : formic acid, acetic acid, propionic acid, oxalic acid, malonic acid and succinic acid.
It was found that propionic acid was most effective among the employed 6 organic acids, in terms of extracted amount of calcium component. The CaO content in the extract was concentrated in the range of 70-94 mass% The enrichment of CaO extracted was correlated with pKa of organic acid. The increase in pKa value resulted in higher yield of CaO content with lower amount of the impurities such as SiO2, Al2O3 and Fe2O3.
The HCl sorption capacity of CaO obtained by calcination of calcium propionate which was extracted from calcium-derived solid wastes employed in the present study, was 0.6-3.7 times higher than that of Ca (OH) 2. The increase in HCl sorption capacity of CaO obtained by the calcination of organic calcium compound may be attributed to a highly porous structure of the CaO.