The potential arsenic retention role of Ca-Fe(III)-AsO₄ compounds in lime neutralized co-precipitation tailings

Arsenic is a major contaminant in a number of high grade uranium ores mined in Northern Saskatchewan. Upon processing of these ores by hydrometallurgical processes, arsenic reports to aqueous waste solutions from which arsenic(V) is removed by co-precipitation with iron(III). This process results in the generation of a mixture of poorly crystalline arsenate-bearing phases and gypsum. Based on laboratory investigations there exists the potential upon reaction of the disposed iron(III)-arsenate phases and gypsum to lead to Ca-Fe(III)-AsO₄ association resembling the mineral yukonite. In this paper the laboratory synthesis, characterization and solubility investigation of yukonite is reviewed and the implications of its formation in U-mill tailings as an arsenic control phase are discussed. (author)