Microextractors are known to provide high mass transfer rates for the extraction and separation of rare-earth elements (REEs). High-throughput microextractors are essential for industrial-scale production of REEs, but few practical studies have been conducted to date. In this work, a chaotic advection microextractor, i.e., a three-stage microextractor, was designed and demonstrated to extract Pr(III) and Ce(III) efficiently from nitric acid media at high throughputs by using 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) and sulfonated kerosene as an extraction agent and a diluent, respectively. Flow visualization experiments showed that the dispersed phase could be effectively broken into small droplets owing to vortex and recirculation flows. Microextraction experiments performed under optimal extraction conditions indicated that at low throughputs, the concentration ratio D , extraction efficiency E , and separation factor β decreased with an increase in the throughput, whereas at high throughputs, D , E , and β increased with an increase in the throughput. An extraction efficiency close to that of co-current balanced extraction was successfully achieved, even at a high total throughput of 100 mL/min and a rather short residence time of 0.029 s. Thus, the chaotic advection microextractor features a high throughput and high extraction efficiency, which are appropriate for the high-efficiency extraction and separation of REEs.
Wei Zhang,Fengzhen Zhang,Liping Ma,Jing Yang,Yi Wei,Deqi Kong
In this work, we propose a novel, effective, energy efficient technology to reduce CO 2 emissions and fully use the calcium in the solid waste by-product phosphogypsum (PG), by capturing CO 2 from the PG decomposition product’s hydrolysis solution. Experiments were conducted to investigate the technical feasibility and the influence of temperature and CO 2 partial pressure on CO 2 capture, as well as CO 2 loading on CO 2 sorption capacity. The results showed that > 90 % of the total calcium ions in the solution were converted into calcium carbonate (CaCO 3 ). Furthermore, a decrease in temperature and an increase in CO 2 partial pressure improved CO 2 uptake, with the latter having a greater effect on CO 2 capture capacity than the former. Moreover, kinetic analysis demonstrated that a higher temperature and CO 2 partial pressure increased the absorption rate; and showed that the CO 2 absorption rate is highly affected by the CO 2 loading levels. The thermodynamic analysis indicated that CO 2 absorption heat significantly declined as a function of increasing CO 2 loading. CaO from the calcination of carbonate was added to the hydrolysis solution and significantly enhanced its CO 2 capture ability. Thus, the hydrolyate of PG decomposition products in combination with CaO reinforcement may be a promising method for CO 2 capture.
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