重庆中梁山煤田凝灰岩中战略性金属的浸出试验

Leaching test of strategic metals in the tuff from the ZhongliangshanCoalfield,Chongqing

西南地区晚二叠世含煤岩系底部广泛分布一层由基性火山灰经热液流体蚀变的凝灰岩。凝灰岩中富集稀土元素(REY),Nb和Ga等战略性金属,称之为一种新型的煤型战略性金属矿床。然而,凝灰岩中战略性金属的可提取性如何,尚不清楚,制约了这些金属的开发利用。为此,以重庆中梁山煤田晚二叠世凝灰岩为对象,采用(NH4)2SO4,H2SO4,NaOH,HCl和HF等试剂对凝灰岩中REY,Nb,Ga,Al2O3和SiO2进行分步连续浸出。结果表明,(NH4)2SO4能浸出约30%的REY,表明凝灰岩中离子吸附型REY占比大于30%,其余的战略性金属均以矿物相形式存在。(NH4)2SO4—H2SO4—NaOH—HCl—HF分步连续浸出可有效提取凝灰岩中的REY,Ga,Nb等战略性金属。REY,Ga,Nb,Al2O3,SiO2的总浸出率分别为86.52%,67.32%,54.70%,87.87%和98.97%。浸出后的残渣以硫铁矿为主,也可以被综合利用。整个分步连续浸出的较优条件为:①(NH4)2SO4质量浓度为15 g/L,浸出温度为20℃,浸出时间为12 h,液固比为1;②H2SO4质量分数为60%,浸出温度为130℃,浸出时间为3 h,液固比为3;③NaOH质量分数为45%,浸出温度为130℃,浸出时间为2.5 h,液固比为3;④HCl质量浓度为150 g/L,浸出温度为90℃,浸出时间为2 h,液固比为3;⑤HF质量分数为15%,浸出温度为75℃,浸出时间为2 h,液固比为4。

The tuff layer,a product of mafic volcanic ash altered by hydrothermal solutions,is distributed widely in the late Permian lowermost coal-bearing strata,southwestern China.The tuff is enriched in rare earth elements(REY),Nb,Ga,etc.,and is considered as new coal-bearing strata hosted strategic metal deposits.However,the extractability of strategic metals in the tuff is unclear,which restricts the development and utilization of these metals.In this study,REY,Nb,Ga,Al2O3,and SiO2 of the tuff in the Zhongliangshan Coalfield,Chongqing,southwestern China were leached out using step-by-step continuous leaching reagents including(NH4)2SO4,H2SO4,NaOH,HCl and HF.The results show that approximately 30%of REY were leached out by(NH4)2SO4,indicating that ion-adsorbed type REY accounts for more than 30%of the total REY and the remaining strategic metals are associated with minerals.The step-by-step continuous leaching reagents can extract strategic metals including REY,Nb,and Ga effectively.The total leaching efficiencies of REY,Ga,Nb,Al2O3,and SiO2 are up to 86.52%,67.32%,54.70%,87.87%,and 98.97%,respectively.The dominant constituent of residues is pyrite,which could be utilized comprehensively as well.The relative optimal conditions of step-by-step continuous leaching reagents are as follows:①(NH4)2SO4 concentration is15 g/L,temperature is 20℃,leaching time is 12 h,liquid/solid ratio(L/S)is 1;②H2SO4 concentration is 60%,temperature is 130℃,leaching time is 3 h,L/S is 3;③NaOH concentration is 45%,temperature is 130℃,leaching time is2.5 h,L/S is 3;④HCl concentration is 150 g/L,temperature is 90℃,leaching time is 2 h,L/S is 3;⑤HF concentration is 15%,temperature is 75℃,leaching time is 2 h,L/S is 4.