Efficient flotation of sodium lauroyl sarcosinate on Pb2+-modified rutile surface: experimental study and DFT calculation

Abstract

This work explored the application of sodium lauroyl sarcosinate (SLAS) as a green surfactant in rutile flotation systems. A detailed examination of the flotation behavior and adsorption characteristics of rutile was conducted, particularly under Pb²⁺ ion-modified conditions. The experimental methodology incorporated multiple analytical techniques: micro-flotation experiments, surface potential analysis, adsorption quantification, FTIR spectroscopy, SEM-EDS characterization, XPS surface analysis, and computational DFT simulations. Micro-flotation experiments demonstrated that under the optimal conditions (SLAS concentration of 2.8 × 10⁻⁴ mol/L, pH 3), a rutile recovery of 81.49% was obtained. Notably, as the pH increased, the recovery of rutile exhibited a decreasing trend. Following Pb²⁺ modification (8.0 × 10⁻⁵ mol/L) combined with SLAS treatment (2.8 × 10⁻⁴ mol/L), the rutile demonstrated consistent flotation recovery exceeding 90.02% across a broad pH range (3∼7). The adsorption capacity experiments and SEM-EDS results indicated that multiple SLAS layers were adsorbed on the rutile. Moreover, Pb²⁺ modification improved the favorability of SLAS adsorption. A combination of surface potential measurements and infrared spectroscopy confirmed the chemical adsorption mechanism of SLAS on positively charged rutile surface atoms. XPS characterization confirmed that the SLAS oxygen atoms chemically bonded with the rutile surface Ti/Pb atoms. DFT simulations demonstrated that the adsorption processes were spontaneous, with Pb²⁺ and SLAS respectively, forming O−Pb and Ti−O bonds on the (110) surface. This mechanism explains how Pb²⁺ enhances the SLAS adsorption capacity and subsequent flotation efficiency of the rutile. These studies proved the industrial potential of environmentally friendly collector SLAS in rutile flotation.