Development of dissolved air flotation for mining wastewaters purification

Abstract

Modern mining uses vast amounts of water for the recovery of valuable metals. As the associated costs associated to fresh water price and wastewater treatment continue to increase, there has been a prolonged interest in reusing the mine effluents for the extraction processes. However, wastewater reclamation is challenging as many of the pollutants in the effluents decrease the efficiency of the recovery. Moreover, the huge volume of the effluents greatly reduces the number of suitable purification processes.

The present study tested the feasibility of using dissolved air flotation (DAF) for removing one of the most common pollutants in mining wastewaters: xanthates. The removal capability was evaluated using a general statistical factorial experiment design over two sets of jar tests. The experiments evaluated xanthate reduction with pH, flocculant type, and origin of wastewater (process water and thickener overflows from two different flotation circuits) as independent variables. The best performing conditions were scaled up and further examined using DAF over of settling.

Results demonstrate that it is possible to remove xanthate from the effluents of the thickener overflow using DAF, with average reductions of approximately 50%. It was also observed that the source of wastewater has the largest impact on the process and exhibits an important interaction with the type of flocculant. Overall, DAF has the potential to increase water recirculation in mining operations.