Effect of Collector Dosage on Metal Removal by Precipitation/Flotation

Abstract

This study examined the effects of various dosages of chemical collectors on the removal in a combined metal hydroxide precipitation and air‐flotation of heavy metals from industrial wastevvaters. The residual metal concentrations were sensitive to pH, collector dosage, and air‐injection rate. The optimum pH for treatment of the industrial wastewaters was 9.18, determined from jar tests. Although this pH does not necessarily represent the maximum removal of any one metal, it represented the optimal removal of the combined metals system. A single collector dosage did not maximize the removal of each metal from the industrial wastewaters used in the study. Metal removals were slightly greater using the nozzle air flotation system as compared to the induced air flotation system. The study also found that a single collector dosage is not effective for all metals, although removals of more than 80% were consistently achieved. The removal of heavy metals and oil appears to occur through a coprecipitation‐adsorption mechanism.