化学処理による斜プチロルフッ石系凝灰岩の物理化学的特性の変化 ＩＩＩ 水酸化ナトリウム溶液処理による影響

Abstract

The effect of alkali treatment on some physico-chemical properties of clinoptilolite tuff from Futatsui, Akita Pref., was investigated by means of powder X-ray diffraction, chemical analyses, measurement of CO2 adsorption and gaschromatography. The material was treated with 0.01-5N NaOH aqueous solution at 97-98°C in the water bath for 2 hrs. At the concentration of NaOH below 1N, only silica in the tuff was dissolved without changing of the clinoptilolite structure. The content of clinoptilolite relatively increased a little due to the removal of α-cristobalite in the concentration range of 0.25-1N and hence the ratio of silica to alumina decreased from 9.9 in the original tuff to 8.1-7.7. The chemical compositions such as silica, alumina, etc. were dissolved at the concentration of 2-5N and therefore the ratio of silica to alumina in the treated tuff decreased sharply. Intensity of X-ray diffraction peak 132 of clinoptilolite and the amount of CO2 adsorbed also decreased with the increasing of the concentration of NaOH above 2N. These decreases corresponded to the degree of clinoptilolite structure collapsed. By alkali treatment, Na+ ion exchanged H+ and a part of K+ in the clinoptilolite but not Ca++ and Mg++. In the concentration range of 0.25-1N, the ratio of Na to all cations in the samples increased from 29.6% in the original tuff to around 50%. Alkali treatment for clinoptilolite tuff contracted the pore size of clinoptilolite. Consequently the adsorption rate of CO2 became slowly with the increase of NaOH concentration. Also evil affections were observed for the gascrhomatographic separation.