Abstract:Four modified starches with selected charge characteristics including cationic starch (CAS), carboxymethyl starch (CMS), amphoteric starch (AMS) and soluble starch (SS) were investigated as depressants for diaspore in reverse flotation test using cationic collector (dodecylamine). Adsorption examination, Zeta potential measurement and Fourier transform infrared (FTIR) spectroscopy were used to clarify the role of the surface charge characteristics of starches in determining the adsorption behavior and depression performance as well as the mineral−starch interaction. Results show that the positively charged starches (CAS and AMS) display higher adsorption amounts and also better depression performance compared with the non-ionic (SS) and anionic starch (CMS), benefiting from the favorable electrostatic attraction with diaspore and also electrostatic repulsion with collector. FTIR spectroscopy proves the presence of hydrogen bonds and chemical complexation between mineral and starches in an integrated manner.

Key words: starch; diaspore; reverse flotation; depressant