不同活化条件下粉煤灰中锂的酸碱溶出特性

粉煤灰提取氧化铝作为其资源高值利用的重要途径之一引起广泛关注.由于粉煤灰中还含有一定丰度Li（锂）元素，在提取氧化铝的同时实现Li的协同提取对于进一步提高粉煤灰的资源利用效益意义重大.为认识粉煤灰中Li的溶出特性，分别考察了原粉煤灰、CaO煅烧活化粉煤灰和Na₂CO₃煅烧活化粉煤灰中Li在酸性溶液和碱性溶液中的溶出特性，并采用XRD（X-射线衍射）分析了粉煤灰浸取前后的物相变化，结合Li溶出率的变化，阐释了Li在不同浸出条件下溶出率差异的原因.结果表明:在相同浸出温度（100℃）下粉煤灰直接在酸性溶液和碱性溶液中的溶出率相对较低，分别仅为28%和36%；而经CaO和Na₂CO₃活化后粉煤灰中Li的溶出率显著提高，活化后粉煤灰中Li在酸性溶液中的溶出率可达到98%和86%，均高于碱性溶液中Li的溶出率（86%和67%）.XRD的分析结果进一步表明，部分Li可能赋存于非晶相或晶相表面，这部分Li易于被酸或碱直接浸出；部分Li可能镶嵌在莫来石、石英等晶相内部，不易被溶出，经CaO和Na₂CO₃助剂活化后，部分Li又重新嵌入到钙黄长石、霞石等新生成物相的晶格中，而这些物相更易于与酸反应，因而酸性溶液中Li的溶出率普遍高于碱性溶液中的结果. 

Acid-Alkali Dissolution Characteristics of Lithium in Fly Ash under Different Activation Conditions

The extraction of alumina from coal fly ash as one of the important value-added ways causes wide concerns. The extraction of alumina and lithium simultaneously is of great significance to the improvement of the utilization efficiency since the coal fly ash contains a certain amount of lithium. To clear understand the dissolution characteristics of lithium (Li) in fly ash, the dissolution characteristics of Li in acidic solution and alkaline solution from the original fly ash, activated by CaO and Na₂CO₃ were investigated respectively, and the phase transformations of fly ash before and after leaching were analyzed by X-Ray diffraction. The results show that the fly ash directly leached by acidic solution and alkaline solution presented a relatively lower dissolution of Li (28% and 36%, respectively) at 100℃. The dissolutions of lithium, however, were significantly improved after coal fly ash activated by CaO and Na₂CO₃. The dissolutions of Li in acidic solution reached 98% and 86% after the fly ash activated by CaO and Na₂CO₃, which were higher than those in alkaline solution (86% and 67%). The XRD analysis results demonstrate that some Li is easier to be leached by acid or alkali which might be deposited in the amorphous or the surfaces of crystalline minerals. Some Li might be embedded in mullite, quartz and other crystalline phase and leached hardly. However, they were again embedded in calcium melilite and nepheline after CaO and Na₂CO₃ activation and the dissolution of Li were increased. The dissolution of Li in acidic solution was generally higher than that in alkaline solution owing to the reaction between calcium melilite and nepheline with acid is easier than those with alkali.