The application of freezing technology for zinc removal from Faro pit mine-impacted water, Yukon, Canada

Abstract

The application of freezing technology (cryopurification) could be a viable water treatment solution to the environmental industry, especially in northern climates as it holds several advantages, including high energy efficiency, the absence of chemical pre-treatment and cost-efficiency. The use of cryopurificiation in Northern Canada is of interest, considering three of the five largest federal contaminated mine sites where water treatment is typically required are located within Yukon and Northwest Territories. The current research aims to address the problem of elevated zinc concentrations in mine-impacted water (Faro Mine, Yukon, Canada) by applying cryopurification. The paper scope includes laboratory testing to quantitatively describe zinc removal from Faro Mine's water using cryopurification under various initial and boundary conditions. Based on laboratory testing results, zinc could be removed with an efficiency of above 75% and 95% using single-stage freezing under no mixing and constant mixing conditions, respectively and up to 97% in freezing-melting tests. The results reveal the purest ice production at freezing temperature range from −0.5 to −5 °C. Ice is purer with each subsequent melt fraction according to the results of freezing-melting laboratory tests. The addition of seed ice crystals enhances the purity of ice up to 10–14% and ice block shape has an effect on the purification process, as the results of laboratory testing show. The effect of mixing shows 23–72% improvement in overall removal efficiency depending on freezing temperature. The outcomes of current research form a foundation toward the development of an exceptional water treatment process utilizing northern climates' cold temperature conditions and having a potential to be scaled up.