Diehl Lisarb O, Gatiboni Thais L, Mello Paola A, Muller Edson I, Duarte Fabio A, Flores Erico M M
Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
Ultrason Sonochem. 2018 Jan;40(Pt B):24-29. doi: 10.1016/j.ultsonch.2017.04.012. Epub 2017 Apr 12.
In view of the increasing demand for rare-earth elements (REE) in many areas of high technology, alternative methods for the extraction of these elements have been developed. In this work, a process based on the use of ultrasound for the extraction of REE from carbonatite (an igneous rock) is proposed to avoid the use of concentrated reagents, high temperature and excessive extraction time. In this pioneer work for REE extraction from carbonatite rocks in a preliminary investigation, ultrasonic baths, cup horn systems or ultrasound probes operating at different frequencies and power were evaluated. In addition, the power released to the extraction medium and the ultrasound amplitude were also investigated and the temperature and carbonatite mass/volume of extraction solution ratio were optimized to 70°C and 20mg/mL, respectively. Better extraction efficiencies (82%) were obtained employing an ultrasound probe operating at 20kHz for 15min, ultrasound amplitude of 40% (692Wdm) and using a diluted extraction solution (3% v/v HNO+2% v/v HCl). It is important to mention that high extraction efficiency was obtained even using a diluted acid mixture and relatively low temperature in comparison to conventional extraction methods for REE. A comparison of results with those obtained by mechanical stirring (500rpm) using the same conditions (time, temperature and extraction solution) was carried out, showing that the use of ultrasound increased the extraction efficiency up to 35%. Therefore, the proposed ultrasound-assisted procedure can be considered as a suitable alternative for high efficiency extraction of REE from carbonatite rocks.
鉴于许多高科技领域对稀土元素（REE）的需求不断增加，人们开发了提取这些元素的替代方法。在这项工作中，提出了一种基于超声从碳酸盐岩（一种火成岩）中提取稀土元素的工艺，以避免使用浓试剂、高温和过长的提取时间。在这项从碳酸盐岩中提取稀土元素的开创性初步研究中，对不同频率和功率下运行的超声浴、杯形换能器系统或超声探头进行了评估。此外，还研究了释放到提取介质中的功率和超声振幅，并将温度和碳酸盐岩质量/提取溶液体积比分别优化至70°C和20mg/mL。使用频率为20kHz的超声探头运行15分钟、超声振幅为40%（692Wdm）并使用稀释的提取溶液（体积分数3%的HNO+体积分数%的HCl）时，获得了更好的提取效率（82%）。需要指出的是，与传统的稀土元素提取方法相比，即使使用稀释的酸混合物和相对较低的温度，也能获得较高的提取效率。将结果与在相同条件（时间、温度和提取溶液）下通过机械搅拌（500rpm）获得的结果进行了比较，结果表明使用超声可使提取效率提高35%。因此，可以认为所提出的超声辅助方法是从碳酸盐岩中高效提取稀土元素的合适替代方法。
