Removal of Hg, As and Se ions from gold cyanide leach solutions by dissolved air flotation

The removal of Hg, As and Se ions from processing streams of gold cyanidation circuits was studied by dissolved air flotation (DAF) at laboratory scale. Two different methods were applied. The first was based on the separation by flotation of the aggregates (AF) formed between the ions and NaDTC (precipitant), LaCl3 or FeCl3 (coagulants) and Bufloc (a flocculant). The second was adsorptive particulate flotation (APF), using solid sorbing materials for the ions (chabazite and La2O3) and microbubbles in the solid/liquid separation stage. Results showed that removal was efficient in both cases and followed the order: (AF) >APF-chabazite >APF-La2O3. Almost complete removal (>98%) of the metal ions from solution was obtained. Process efficiency depended on the system solution and interfacial chemistry, aggregation phenomena and DAF operating parameters.