Environmental Guidelines for Nickel Smelting and Refining
process used for nickel. Chloride electrolytes are used although sulfuric acid solutions are used more often. Waste Characteristics Air emissions Sulfur dioxide (SO2) is a major air pollutant emitted in the roasting, smelting and converting of sulfide ores (nickel sulfide concentrates contain 6-20% nickel and up to 30% sulfur).