Feasibility of pilot-scale disc-donut column for continuous cadmium extraction with the perspective of droplet size distribution

Heavy metal removal is a significant problem in various industries. Liquid-liquid extraction is a practical process in recovering these elements. In this study, the behavior of pilot-scale disc-donut column in the extraction of cadmium ions was evaluated. The effects of droplets with the variation size distributions are significant in describing performance and characteristics of an extractor for removing the substrate from aqueous or organic phases. The size distribution of droplets is relative to the interfacial area under steady conditions. To match the size distribution of droplets, the experiments are carried out in reaction and non-reaction conditions. In emulsion regime (pulsing intensity (Af), inlet organic and aqueous phase flow rate (V-c, V-d) equal to 3.3 cm/s, 2.22 mm/s, and 2.22 mm/s, respectively) and under the optimized conditions, 99.7% of the cadmium can be recovered from the aqueous solution. It was found that Weibull distribution gives the best fit at each operation mode while inverse Gaussian distribution gives the most inferior fit. According to a series of statistical analyses, it is shown that the pulsation intensity imposed more influence on drop sizes, and superficial flow rates of both phases are less able to the successful prediction of size distribution of droplets.