Investigation of the adsorption mechanism of an eco-friendly surfactant LMAC on rutile surface: A novel insight

Abstract

In this paper, an eco-friendly surfactant sodium lauroamphoacetate(LMAC) was firstly studied as a collector for rutile flotation. The role and adsorption mechanism of LMAC on rutile surface was fully investigated by micro-flotation tests, zeta potential tests, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the density functional theory (DFT) calculation. The result of micro-flotation tests showed that the flotation recovery of rutile with 120 mg/L LMAC treatment is stable at around 92 % in pH=7. Under the condition of the same collector amount, LMAC has a stronger collecting capacity for rutile than styrene phosphonic acid (SPA), benzohydroxamic acid (BHA) and sodium oleate (NaOL) in acidic and neutral pulp condition. And the effective flotation separation of rutile and quartz was accomplished at pH=7 by employing inhibitor modified water glass and the collector LMAC. Zeta potential tests and FTIR analysis demonstrated that LMAC could chemically adsorb onto the positively charged atoms of rutile surface. XPS analysis further confirmed that Ti atoms on the surface of rutile reacted with O atoms in LMAC during the adsorption process. DFT calculation results directly show that the adsorption process of LMAC on rutile (110) surface is spontaneous, and forms two Ti − O bonds and a H−O bond. Mulliken population analysis and differential charge density analysis showed that during the adsorption process, electrons were transferred between the O atoms of LMAC and the Ti atoms on the rutile surface, forming the new Ti − O bonds.