粉煤灰中稀有金属镓-铌-稀土的联合提取

 采用碱法烧结-分步浸出法, 对重庆安稳电厂循环流化床粉煤灰中Ga、Nb、REE 等稀有金属进行了联合提取实验。结果表明, 粉煤灰加无水碳酸钠在860℃下烧结30 min, 采用水浸法提取Ga, 采用酸浸法提取REE, Ga、REE 的提取率分别达到84.70%和80.07%;Nb 在两步浸出实验中的浸出率均低于1%, 但在酸浸滤渣中得到富集。采用D201 离子交换树脂和NH₄Cl(0.5 mol/L)溶液在40℃下对富Ga 水浸滤液中的Ga 进行吸附与解吸附, Ga 的吸附率(27.99%)、解吸附率(37.33%)偏低, 可能与解吸附液用量不足和水浸滤液中Al 离子竞争吸附有关, 后续将通过改进实验条件提升Ga 的分离提取效果;酸浸液中REE 及酸浸渣中Nb 的分离提取工艺尚需进一步研究。通过上述稀有金属Ga、Nb、REE 的联合提取及后续工作, 可实现安稳电厂粉煤灰的高附加值利用, 有效缓解粉煤灰造成的环境污染。

Combined extraction of rare metals Ga-Nb-REE from the fly ash

Alkali sintering-multistep leaching experiments are carried out to extract the rare metals Ga, Nb and REE (rare earth elements) from the fly ash in the circulating fluidized bed (CFB) generated from the Anwen Coal-fired Power Plant in Chongqing, Southwest China. It is shown that, the roasting of the CFB fly ash with 1.5 times Na₂CO₃ under 860℃ for 30 minutes, followed by the water leaching (Solid/Liquid (S/L)=1:10; 90℃; 2 hours) extraction of Ga and the acid leaching (HCl solution, 6 mol/L; S/L= 1:20; 60℃; 2 hours) extraction of REE, can achieve extraction rates of 84.70% and 80.07% for Ga and REE, respectively. The leaching rate of Niobium (Nb) enriched in the acid leaching residue, is lower than 1% in the above two steps. Adsorption and desorption experiments of Gallium from the Ga-rich water leaching filtrate using the D201 ion exchange resin and NH₄Cl solution (0.5 mol/L) are carried out both under a temperature of 40℃. The adsorption rate (27.99%) and the desorption rate (37.33%) of Ga are unsatisfactory. The conditions of the follow-up experiments would be adjusted in order to enhance the separation and extraction effect of Ga. The extraction process of Nb from the acid leaching residue and the separation of REE from the acid leaching solution also need to be further studied. With the above combined extraction technology for Ga, Nb, REE and subsequent studies, a high value-added fly ash product is expected. The environmental pollution pressure caused by the Anwen fly ash might be alleviated.