Conversion treatment of waste coal ash to zeolite and its utilization as materials for agriculture

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A lot of waste coal ash has been produced by the plants such as thermal powerstation which are using coal and/or pulverized coal for fue. There are about 45 big thermal power stations in Japan, and they are discharging approximately 4 million tons of coal ash a yer. It is expected that the amount of the useless article will increase because of the further waste ash which will be released from coal thermal power plant to be constructed in the near future. So far, more than half of the coal ash has been disposed of as solid wastes for reclamation materials. It becomes, however, difficult to make sure constantly of the reclamed site for the disposal of the wastes, and such reckless disposal is a serious problem recently. Therefore, development of technique for the utilization of coal ash is indispensable to the means of solving the problem and to recycling waste matters. Coal fly ash was treated with 3.5 M NaOH water solution by heating to 80-90 C for 24h. The alkali treatment caused an increase in cation exchange capacity (CEC) from 12-20me/100g to 158-360me/100g for the fly ash. X-ray powder diffraction analysis showed that hydroxy-sodalite, faujasite and phillipsite formed in theash after the treatment. The formation of such zeolite was most likely responsible for the increase of CEC.The zeolitized coal ash was shown to have preferable efficaciousness for soil conditioner. It was possible to apply the zeolotized ash to materials for removal of toxic heavy metal ions from soils, deodrization of excrement of domestic animals such as poultry manure. The outcome of the study is promising in further development of a tecnology for the utilization or recycling of waste coal ash which is an unwelcome by-product inevitably formed through human activities using coal as raw material and energy source. Thus, the present result is useful in opening the way for disposal of industrial solid waste products to control the pollution for environmental protection.