Gallium is one of the most important metals used in advanced and strategic industries, which is found in very low grades in various resources such as bauxite, lead, zinc and coal. In this study, the extraction of gallium from aqueous solutions, especially leaching solutions of high potential coal resources was investigated using the emulsion liquid membrane method and it was tried to investigate the mechanisms governing this process for the separation of gallium from dilute aqueous solutions. For this purpose, the key parameters of emulsion liquid membrane and ultrasonics on gallium extraction kinetics in synthetic and real leaching solutions were investigated. The selectivity of gallium in real gallium leaching solutions was also eva‎luated. The effect of chemical and operational parameters such as solution pH, concentration and the type of extractant (TOPO and TBP), surfactant concentration, gallium concentration, ratio of internal phase to membrane, ratio of external phase to emulsion, internal phase concentration and the speed of stirring, both as a single factor and with Box Behenken method was examined. The results showed that the highest gallium recovery (96.6%) was obtained at 6% extractant concentration, 3% surfactant concentration, 5 min extraction time and 0.1 M internal phase concentration and 250 rpm stirring speed. The results showed that at high concentrations of chemicals in the organic phase, the recovery of gallium was very low and reached about 1% due to membrane failure as a result of the low mass transfer rates and the membrane instability. Increasing the stirring speed of the emulsion system, in values ​​higher than 250 rpm, caused the failure of the two-phase emulsion and no metal extraction. Also, by increasing the concentration of acid in the internal phase, the stability of the membrane was significantly reduced. The effect of ultrasonic waves on gallium extraction efficiency and membrane stability was investigated. The results showed that The use of the ultrasonic system caused a more stable emulsion due to the formation of finer particles and increase of the gallium recovery up to 97.3%. In the following, the selectivity of gallium recovery process from leaching solutions containing different ions under optimal conditions was investigated by ultrasonic method. Gallium recovery in the emulsion liquid membrane process in the presence of different ions decreased from 97.3% to 14.8%. Using two stages of gallium extraction by emulsion liquid membrane method, the addition of iron powder as the cementation agent and the use of DTPA extractant for selective separation of zinc, gallium recovery was increased to 96.6%. For investigating surface and interfacial phenomena on the emulsion liquid membrane system in aqueous and organic phases, the effect of different factors on surface and interface tension was eva‎luated. The results showed that the surface tension of the organic phase did not change significantly with increasing the extractant concentration, but with increasing the surfactant concentration, the surface tension was decreased. By reducing the surface tension, particles with larger diameters formed and this phenomenon led to the increasing of emulsion particles. The results showed that the emulsion liquid membrane method has a good potential in extracting gallium from dilute chloride solutions obtained from low-grade ores. The most important advantages of which are high aqueous to organic phase ratio, high metal recovery, high selectivity, easy operating conditions and the low capital cost.

علي احمدي عامله

مرتضي صادقي

ضياءالدين شفاهي، احمد محب،مهدي نصيري سروي