Adsorption-Spectrophotometric Determination of Bismuth(III) in Ores and Ore Сoncentrates

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Using the mathematical planning of the experiment by the method of Latin squares, we optimize the adsorption conditions for Bi(III) from dilute aqueous solutions and its desorption from the surface of silica gel L100/250. It is found that the maximum degree of adsorption (95–98%) is reached at pH 4.5, near the zero-charge point of silica gel and under the domination of the Bi(OH)3 monomeric hydroxyl species in solution. The adsorption time does not exceed 30 min with an adsorbent weight of 0.4 g, and the maximum desorption is observed when Bi(III) is eluted with a 0.5 M nitric acid solution for 20 min. An adsorption-spectroscopic procedure for the determination of Bi(III) with Xylenol Orange is developed. The calibration dependence is linear in the concentration range of 0.25 to 6.0 μg/mL, and the detection and determination limits are, respectively, 0.09 and 0.28 μg/mL. The procedure is tested using standard reference samples of tungsten ores and molybdenum concentrate; the relative standard deviation does not exceed 4%.