We have been investigating the zeolite synthesis from paper sludge ashes (denoted as PS zeolite) by alkali hydrothermal treatment as a new effective utilizing technique of the paper sludge (PS) . In this study, 102 samples of PS gathered from 16 paper mills in Fuji city for a half year were chemically and mineralogically examined and statistically evaluated in terms of fitness to the zeolite synthesis. The chemical composition of PS and the characteristics of PS zeolite led us to fallowing results. The relationship between CaO content (x) and the intensity of XRD peak assigned to zeolite (Z index⁄10,000 = y) was found as y= -0.37 Ln (x) +1.48. Also, 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 as X
Ca⁄Si⁄X
Ca⁄Al= 0.89. Based on these relationships, we classified the PS’s into new chemical ranges of (A) to (D) in order to distribute almost the same number of samples in each range ; that is, 21, 23, 22, 24, respectively. Here, Z index⁄10,000 at the boundary of the ranges (A) to (B) was 0.41, (B) to (C) 0.25 and (C) to (D) 0.20. This new classification was then converted to the mineralogical ranges (A) to (D) in a talc-kaolinite-calcite trigonal diagram through the calculation by normative method. It was found that the PS ashes in the ranges (A) in the diagram never changed into the rage (D) during a half year, and the reverse relationship was also correct. The mixture of PS’s discharged from the16mills, as is in practice, contained 25.0% CaO, which was classified into the range of (B) and would formed hydroxysodalite. We proposed a new technique in order to obtain zeolite from the PS mixture for industrial output, in which1. 0M Si was added to the alkali solution with the PS mixture.
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