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

火力发电厂等以煤和/或煤粉为燃料的电厂产生了大量的废煤灰。日本大约有45座大型火力发电站，它们每年排放大约400万吨煤灰。预计在不久的将来，由于即将建设的火电厂将排放更多的废灰，废品量将会增加。到目前为止，超过一半的煤灰已作为固体废物处理为回收材料。然而，很难持续地确保废物的回收处置地点，这种不顾后果的处置是最近的一个严重问题。因此，发展粉煤灰资源化利用技术是解决这一问题和实现废弃物资源化利用的必要手段。采用3.5 M NaOH水溶液对粉煤灰进行处理，加热至80-90℃，处理24h。碱处理使粉煤灰的阳离子交换容量（CEC）由12 ~ 20me/100g提高到158 ~ 360me/100g。x射线粉末衍射分析表明，处理后的灰分中形成了羟基钠石、faujasite和phillisite。这种沸石的形成很可能是导致CEC升高的原因。沸石粉煤灰具有较好的土壤改良剂效果。沸石灰可用于土壤中有毒重金属离子的去除、禽畜粪便等家畜粪便的脱臭。废煤灰是人类以煤为原料和能源的活动中不可避免地产生的一种不受欢迎的副产品，研究结果对进一步开发利用或回收废煤灰的技术具有重要意义。因此，本研究结果为工业固体废物的处理开辟了道路，控制污染，保护环境。

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.