Evaluation of green synthetic depressants for sulfide flotation: Synthesis, characterization and floatation performance to pyrite and chalcopyrite.

• Study sheds new light on development and optimization of green depressants for flotation technology. • Research offers new low cost green depressants for sulfide minerals flotation separation. • Synthetic molecules depress pyrite flotation more strongly and selectively than chalcopyrite. • Costs and environmental impacts can be minimized by the use of synthetic depressants. Native starch has a complex molecular structure that limits its ability as a selective depressant in sulfide flotation separations. This research study was conducted primarily to develop a series of starch-based molecules of different molecular weights with the aim of obtaining the most selective depressant of pyrite in chalcopyrite flotation. Five low molecular weight molecules were produced by the oxidative treatment of starch using H 2 O 2 as the oxidant and FeSO 4 ·7H 2 O as the catalyst. Oxidation treatment resulted in molecular modification of starch, producing low molecular weight molecules of grafted polar groups with increased reaction time. The molecules developed were investigated by microflotation to obtain the most selective and effective depressant for pyrite than chalcopyrite. The optimal and most selective depressant was named tricarboxystarch (sodium salt), also known as TCSS, based on the results of characterization measurements. The inhibitory effect of tricarboxystarch on pyrite was far more selective and effective than native starch. Good selective separation between pyrite and chalcopyrite was achieved by adding tricarboxystarch to a low pH solution. Tricarboxystarch contained three –COOH and several –OH groups in the skeleton, providing excellent depression of pyrite. This study is a basic research that sheds new light on the development and optimization of organic polymers for flotation technology. [ABSTRACT FROM AUTHOR]