Foaming behavior of surfactants for acid mist control in zinc electrolysis processes

Acid mist generation is a major concern in zinc, copper and nickel electrowinning industries and there is a strong environmental drive to control its emission into the work environment. Foaming reagents are typically added to the electrolyte to alleviate this problem. In zinc electrowinning, licorice and saponin are examples of foaming agents used for this purpose. In order for the foaming agent to be effective, its foaming behavior must be determined. In this work, a test procedure was developed to study the foaming characteristics of various surfactants for use as foaming agents to control acid mist in aqueous metal electrowinning. This new test was termed as "mini-flotation test" and it was used to study the foaming behavior of a large number of reagents in an industrial zinc sulfate electrolyte under simulated zinc electrowinning conditions (as sparging). In addition, the influence of important process parameters such as current density, electrolyte temperature, reagent addition level and sulfuric acid concentration on the foaming characteristics of the electrolyte for each surfactant was investigated. The results of this study have identified the most important factors that influence foam formation, growth and stability. This method could be used as a process control procedure for reagent addition in the cellhouse by generating a calibration curve for the optimum electrolyte conditions.