Separation of arsenic and tin from Cu–As alloy based on phase transformation in a vacuum to form Cu–Fe–S compounds

•A cleaner process was proposed to separate As and Sn from Cu–As alloy.•96.29% of As and 88.70% of Sn were separated from Cu-As alloy.•Cu and Sn in alloy was sulfurized by FeS2 to form Cu5.433Fe1.087S4 and SnS.•As was freely volatilized after destruction of Cu–As alloy structure.•Excessive sulfur will interact with elemental arsenic to form As4S3.