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We have been investigating zeolite synthesis from paper sludge (PS) ashes. This technique is essential from the viewpoint of recycling of wasting materials.In our previous study, the PS ashes from 20 paper mills in Fuji area of Shizuoka Pref. were examined on suitability for starting materials in the zeolite synthesis, and they were classified into 4 types of compositional ranges in terms of talc-kaolinite-calcite composition ; that is, ranges (A) and (B) were suitable for the zeolite synthesis and ranges (C) and (D) were not suitable.In this study, we selected representative 4 mills that had discharged PS corresponding to the above 4 types of compositional ranges, and the chemical and mineralogical compositions of PS from these 4 mills were analyzed for 5 days. As a result, the following conclusions were obtained.The PS samples from the mills that had initially discharged PS belonged in the ranges (A) and (B) did not change into the ranges (C) and (D) for the period of 5 days. The samples belonged in (A) and (B) showed again being suitable for the zeolite synthesis.PS discharged from a paper mill that makes products including a lot of kaolinite is suitable for the zeolite synthesis. However. PS containing too much calcite is not suitable.

Paper sludge ash (PS ash) discharged from Fuji area, Shizuoka prefecture reach about 160, 000 tons/year. Therefore, the development of a technique for utilizing of PS ash is essential for recycling waste materials.PS ash collected in Fuji area has little of SiO2 and much Al2O3, CaO, in comparison with the general material of the artificial zeolite (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, meta-kaolinite, meta-talc and lime by incineration. For this reason, the PS ash has excess Ca and low Si containt.We synthesized an artifical zeolite from the PS ash by the “Si-added method” to exclude the effect of excess calcium present in the ash. Furthermore, we studied the reaction conditions such as temperature, time and the alkali used, and found optimal synthesis conditions. Chemical and mineralogical characteristics of the synthesized zeolite were then investigated. It was found that an NaP 1-type zeolite was synthesized in an autoclave by processing at 120°C for 2 hours using a 3.5M meta sodium silicate (Na2SiO3) solution.The characteristic of Si and Al dissolved in a diluted NaOH solution shows a characteristic property of zeolite. The PS ash, coal fly ash and Shirasu were classified to S type (Si/Al 2), respectively, in terms of the characteristic solubility of Si and Al in diluted NaOH solutions. For zeolite synthesis, the PS ash was found to require more Si to meet the synthesis condition because the PS ash had a low Si and a high Ca content. As it was, Ca silicate (CSH) was generated and zeolite synthesis was prevented. Shirasu was chosen as a material providing complementary Si. Ca in the PS ash reacted successfully with the Si in the added Shirasu to generate zeolite.

Paper sludge (PS) discharged from the paper recycling process is one of the wastes requiring active development of novel technology for their complete recycling. The PS is mainly consists of organic (cellulose) and inorganic (calcite, talc. kaolinite) matters which are originally present in paper. The present study has been concerned with reaction conditions such as reaction time. solid/liquid ratio and NaOH concentration for the synthesis of zeolite from the inorganic matters by successive alkali treatment following carbonization of the organic matters. intending to develop a new use of PS. Chemical and mineralogical characteristics of the Synthesized zeolite were investigated. and the results are as follows:(1) It is ascribable to decomposition of calcite scarcely occurred in the processing carbonization due to a high partial pressure of CO2. Therefore, carbonization process is found to be effective for the synthesis of zeolite from the PS.(l2) Carbonized matter in PS was activated in the alkaline treatment. The metakaolinite in carbonized PS was converted to zeolite faster than pure metakaolinite alone by the alkaline treatment. The zeolite formed in carbonized PS, showed fine grain in crystal morphology. We found that careful control of solid/liquid ratio, NaOH concentration and reaction time in the alkali treatment process for carbonized PS could give a new composite material of active carbon and zeolite.