Alkali Fusion Process of Waste Stone Dust to Synthesize Faujasite Using Rotaky Kiln

During quarrying, a large amount of waste stone dust is discharged as industrial wastes, and most parts of it dumps at landfill sites. The lack of landfill sites in Japan causes an increase of disposal cost, and new effective use is needed. In our previous studies, we attempted to synthesize zeolite from the dust using alkali fusion treatment to increase the solubility of silicon and aluminum in the dust, and we succeeded to synthesize faujasite zeolite from the dust. However, little information can be available on alkali fusion treatment of waste stone dust to synthesize zeolite. In this study, we attempted to treat continuously the dust by alkali fusion using a rotary kiln, and the effect of alkali fusion process on synthesis of faujasite from the fused material was examined. The mixture of the dust and NaOH powder with the weight ratios of 1:1.2, 1:1.4 and 1:1.6 was put into a rotary kiln, and heating at 400 -500 oC for 30 min, and the obtained fused material was converted into zeolite product by heating at 80 oC for 12 h followed by shaking 24h in distilled water at room temperature. It was confirmed that sodium silicate was formed using a rotary kiln, and the dissolution of Si and Al in the fused material increases with increasing NaOH addition. Faujasite can be synthesized on all fused conditions, and the cation exchange capacity of the product decreases with increasing NaOH addition. Regardless of fusion temperature, sodium silicate was formed using a rotary kiln, and the dissolution of Si and Al in the fused materials obtained on all condition are almost same. Faujasite can be synthesized on all fused conditions, and the cation exchange capacity of the product decreases with increasing temperature.