Determination of single droplet sizes, velocities and concentrations with image analysis for reactive extraction of copper

Abstract

The proposed image analysis method allows the measurement of organic phase droplet sizes, velocities, and copper concentrations in single droplet column copper extraction using hydroxyoxime complexation. The method uses image acquisition sequences from video, detection of moving droplets, binarization of background subtracted images, and noise reduction from images. The image analysis method enabled characterizing the shape of droplets, by determining the droplet minor and major axis lengths. The method can detect droplet concentration directly inside the column wherever the droplet is visible. Image based method was validated against reference samples which were analyzed using spectrophotometry. The traditional concentration measurement using the spectrophotometric analysis of column outlet sample collection was performed for comparison purposes. The direct image analysis showed smaller variation in mass transfer results because of longer and non-uniform residence times when using sample collection. However, separately collected sample analysis together with the image analysis enables determination of the copper mass transfer during all the three steps of column experiment. Image analysis can also be used to reveal concentration profiles inside the droplet. This method is not limited to extractants, but it can be applied to systems where a suitable color change is present depending on camera sensor technology.