Recovery of gallium from Bayer liquor: A review

Bayer liquor is the biggest raw material resource for gallium production. Four kinds of methods have been developed to recover gallium from Bayer solutions, including fractional precipitation, electrochemical deposition, solvent extraction, and ion exchange. The fractional precipitation method is based on Al–Ga precipitation with CO2 and subsequent separation of Al and Ga with lime milk or sodium aluminate solutions. This approach is more environmentally friendly and with low cost, but the process is complicated. The electrochemical method includes both mercury cathode electrolysis and cementation. The electrolysis with mercury cathode has been prohibited in most countries because of high toxicity of mercury. Cementation is an electrochemical process realized by a displacement reaction between gallium and reductants, such as sodium amalgam, aluminum and aluminum–gallium alloy. Solvent extraction is an efficient method and by using Kelex 100 system about 80% of the gallium in Bayer liquor can be extracted. However, the kinetics of the extraction process has been proved to be very slow, which generally requires several hours. Ion exchange is the main method applied in industry for gallium recovery from Bayer liquor. Duolite ES-346 and DHG586 exhibit good extracting properties for gallium, and are used as industrial resins. Unfortunately, the co-extraction of vanadium and the degradation of the amidoxime groups still remain as the main problems during industrial application. In order to recover gallium from Bayer liquor efficiently, further research and development are necessary.

► Fractional precipitation method is complex and difficult for process integration.
► Electrochemistry method is prone to environmental pollution.
► Solvent extraction is efficient for Ga recovery, but the reaction rate is slow.
► Ion exchange is a widely used, compact and efficient method for Ga recovery.
► V co-extraction and amidoxime group degradation are issues for ion exchange.