Determination of Gallium in Coal Ash Samples by Photometry after Separation and Pre-concentration with Polyurethane Foam Adsorption-Solvent Extraction

The adsorption and separation performances of polyurethane foam for gallium in HCl medium and the application for the sample pretreatment in rhodamine B solvent extraction photometric determination of gallium in coal ash samples were studied. The results showed that the polyurethane foam provided the excellent adsorption features for gallium in 6 mol/L HCl medium at room temperature. The adsorption equilibrium could be reached after 90 minutes with saturated adsorptive capacity of 42 mg Ga per gram of polyurethane foam. The gallium adsorbed could be quantitatively eluted with 0.5 mol/L NH₄Cl solution. Beer's law was obeyed in the concentration range of 0~1.0 μg/mL for gallium with the detection limit of 0.008 mg/L. Recovery of the method for gallium was 103%~107% with precision of 1.5%RSD(n=20). The method has been applied to the determination of gallium in coal ash samples with advantage of high selectivity.