In the case of zeolite synthesis from paper sludge, PS ash, it is necessary to investigate its chemical and mineralogical stability.
Our previous study showed that the suitability of PS ash for zeolite synthesis remarkably depended on the CaO content of PS ash.
The relationship between CaO content (X) and XRD intensity (y) assigned to zeolite, Z index, was found as y=-0.36 Ln (X) +1.33. Less than 21.5% of CaO content was suitable for zeolite synthesis, on the contrary, more than 28.8% content was not suitable. When the content was in the range between 21.5% and 28.8%, hydroxyl sodalite was dominantly synthesized. The fairly well linier relation between the atomic ratio of Ca to Si, X
Ca⁄Si, and Ca to Al, X
Ca⁄Al, was found, that is, X
Ca⁄Si⁄X
Ca⁄Al=0.86∼0.97. The mineralogical ratios (talc, kaolinite and calcite) of representative PS ashes were determined by the normative method and ideal mineralogical composition ranges for zeolite synthesis were summarized in talc-kaolinite-calcite triangle figure. PS ashes were classified into4types of mineralogical composition ranges. The ranges (A) and (B) were suitable for the zeolite synthesis and ranges (C) and (D) were not suitable. The PS ashes in the ranges (A) and (B) never changed into the rage (C)and (D) for 5 days.
In this study, we investigated the weekly change of PS ashes mixture gathered from 16 paper mills, which compose a cooperative association for the PS disposal in Fuji city of Shizuoka prefecture, for 4 weeks. The PS ashes unsuitable for the zeolite synthesis contained less than 10% of the ash fraction and more than 30.6% of CaO. We compared the chemical composition of PS ashes mixture discharged from the association with the calculated chemical composition excluding the above unsuitable PS ashes. As a result, the following conclusions were obtained.
(1) Even if the unsuitable PS ashes for zeolite synthesis are excluded from PS ashes mixture, the chemical composition will scarcely changes.
(2) PS’s discharged from the paper mills that are manufacturing the paper products including a lot of kaolinite are suited for zeolite synthesis.
(3) To obtain zeolite more easily for industrial purpose, it is desirable only to use the PS involving much kaolinite.
View full abstract