ペーパースラッジ(PS)焼却灰からのゼオライト合成その1 : PS焼却灰の鉱物学的・化学的特性と模擬PS焼却灰との比較

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Paper sludge (PS) ash discharged from Fuji area. Shizuoka prefecture reach in about 160,000 tons/year. Therefore, the development of a technique for utilizing of PS ash is essential for recycling waste materials. Generally, PS ash contains not only Si and Al, but also significant amount of Ca and Mg, in comparison with the conventional raw material of zeolite for the recyclying purposes (e. g. coal fly ash). PS mainly consists of calcite, talc and kaolinite, which are originally present in paper. These minerals are converted to gehlenite, lime and thermally metamorphosed materials of talc and kaolinite under high temperature incineration. For this reason, PS ash has excess Ca and low Si in amount. In this study, the mineralogical and chemical characteristics of PS ash and "model PS ash" prepared by heating the mixture of pure calcite, talc and kaolinite samples have been elucidated in relation to their suitability as raw materials for zeolite. Mixture of calcite and talc and kaolinite, referred to as "model PS", was adjusted in chemical composition of representative real PS ash. The model PS was heated at 600℃, 800℃, 950℃, and prepared "model PS ash". We examined the dissolution of Si and Al from real PS ash and model PS ash by the treatment of diluted alkali (NaOH) solution. In a similar way, Ca and Mg were examined by the treatment of diluted nitric acid solution. Co existing Ca is expected to inhibit the synthetic process of zeolite, because of the preferential formation of amorphous Ca silicate hydrate resulting in hindrance to Si O Al bonds. Observed effects of co existing Ca which is included in calcite on dissolution of Si and Al from real PS ash and model PS ash by the treatment of diluted acid and alkali solution were as follows : 1. Selective dissolution of Mg component by diluted nitric acid showed that PS ash contained dolomite about 3.5% in amount. 2. Upon heating at temperature over 800℃, a formation of gehlenite was recognized in the PS ash and the model PS ash, but excess CaO still existed in both ashes amounting to 17.6% in the former and 13.6% in the latter. 3. Selective dissolution analysis of Si and Al using diluted NaOH for the model PS ash subject to heating at 800℃ showed that the excess CaO present in the ash caused to block Si and Al preventing crystal growth of zeolite, resulted in formation of amorphous Ca silicate hydrate. 4. On heating at 950℃, Mg and Si in talc replaced Al of gehlenite and generated akermanite. As a result, amount of Al in akermanite decreased and the Si/Al ratio lowered for the model ash. 5. The PS ash, coal fly ash and Shirasu (rhyolitic volcanic glass) were classified to S type (Si/Al<0.5), P1 type (0.5<Si/Al<2), P2 type (Si/Al>2) respectively, on the basis of the result from the difference in dissolution behavior of Si and Al in diluted NaOH solution. 6. Controllable formation of zeolite was found possible by utilization of waste PS ash as raw material with an addition of Si as supplementary component, even the case of the ash containing considerable amount of Ca in it. After all, an NaP1 type zeolite was synthesized and crystallized by an autoclave processing at 120℃ for 2 hours.
日本粘土学会の論文
2003-03-28

ペーパースラッジ(PS)焼却灰からのゼオライト合成その1 : PS焼却灰の鉱物学的・化学的特性と模擬PS焼却灰との比較

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