Licheng Zhang,Lijuan Li,Dong Shi,Jinfeng Li,Xiaowu Peng,Feng Nie
Innovative application of Synergistic extraction system benzoyltrifluoroacetone(HBTA) and tri-n-octyl phosphine oxide(TOPO) for the extraction of lithium from alkaline brine were investigated. The extraction efficiencies of this extraction system were measured as a function of various extraction parameters, including pH value of aqueous phase, extraction temperature, and composition of organic phase. The extraction complex was determined by slope analysis method, which indicated that HBTA, TOPO and lithium formed a 2:1:1 complex. With this system, separation factor between lithium and sodium could be over 2100 by two stages countercurrent extraction according to McCabe Thiele diagram, and lithium extraction could be 95%. Co-extracted or restrained sodium in organic phase could be fully scrubbed by 0.5 M HCl at O/A = 10:1 and equilibrium pH = 4.68. Lithium reserved in organic phase was stripped completely into aqueous phase using 2.5 M HCl at O/A = 10:1 subsequently. Blank organic after stripping was regenerated by 2 M NaOH at R = 70% for next extraction circle. Stability test of organic phase was conducted with five-stage extraction process containing two stages extraction, single stage scrubbing, stripping and regeneration. Lithium yield reached 95.5% with high purity through the process, neither emulsification nor third phase was found during whole process.
The process of recycling lithium (Li) from common coal fly ash using strong acids can release substantial quantities of hazardous low-value residues, and the complex ionic composition of the acidic leaching solution hinders the selective extraction of Li. Accordingly, a green and economical approach was developed for the selective recovery of Li and extraction of valuable Al-rich residues from high-alumina fly ash (HAFA). In HAFA, the glass phase (the main Li-bearing phase) can be selectively dissolved in the mild NaOH solution at 95 °C for 2 h, and valuable mullite phase (the main Al-bearing phase) was retained in the leaching residue (Al 2 O 3 content 49.00 wt%). The leaching efficiencies of Li, Si, and Al were 91.60%, 43.19%, and 3.56%, respectively. Among the primary metallic elements present in HAFA, only Li, Na, K, and Al in the glass phase were readily dissolved in the alkaline solution. Meanwhile, the synergistic extraction system of HBTA and TOPO has good complexing ability with Li + compared to Al 3+ , K + , and Na + . Therefore, Li + can be selectively extracted from alkaline leaching solutions using HBTA and TOPO. The Li extraction efficiency reached 99.68% after three consecutive extractions under the optimal conditions. Finally, the used alkali leaching solution and synergistic extractants can be regenerated via Ca(OH) 2 precipitation and HCl reverse extraction. These findings can provide new strategies for the green and overall utilization of HAFA.
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