Carrageenan xanthate as an environmental-friendly depressant in the flotation of Pb–Zn sulfide and its underlying mechanism

Carrageenan xanthate, a new reagent, produced by reacting carrageenan with NaOH and CS2, was used for the first time as a flotation separation depressant for sphalerite and galena. A variety of techniques were used to investigate the depressive effectiveness and mechanism of carrageenan xanthate, including micro-flotation tests, zeta potential, adsorption measurements, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopic (XPS) analysis, and time of flight secondary ion mass spectrometry (ToF-SIMS). The flotation results demonstrated that galena could be effectively separated from sphalerite by using 40 mg/L carrageenan xanthate as a depressant. Studies of zeta potential and adsorption revealed that carrageenan xanthate adsorbed on both mineral surfaces, however, the adsorption on the galena surface was less than that on sphalerite, and may have been replaced by xanthate. The FTIR and XPS results confirmed that carrageenan xanthate formed new chemical bonds by adsorbing on the surface of sphalerite. According to the surface analysis of high-precision ToF-SIMS, –CSS– in the structure of carrageenan xanthate can interact with active zinc atoms to adsorb onto the surface of sphalerite.