Résumé
• In-depth characterization of surface properties of lepidolite was conducted;• Colloidal and surface properties are different since IEP = 2.5 and PZC = 8.5;• Derivative of the pH-titration curve exhibited 3 surface pKa at 4.8, 6.2, and 7.8;• These pKas were attributed to aluminol and silanol surface adsorption sites;• This will have a strong impact for the beneficiation of lepidolite by flotation.AbstractThis study proposes an in-depth exploration of the surface properties of lepidolite, a lithium-bearing phyllosi-licate mineral, using nitrogen and argon adsorption isotherms, electrophoretic mobility measurements, andsurface titration experiments. The solid-gas and solid-liquid interfaces analyses allow characterizing the surfaceheterogeneity of lepidolite, highlighting the dominance (~ 80%) of the basal surfaces over the lateral surfaces (~20%) in the total specific surface area. The N2 adsorption isotherm exhibited various adsorption sites, includingthe exposed interfoliar cations and the empty hexagonal cavities related to the cleavage process, on the basalplanes, or the exposed oxygen and fluorine atoms on the lateral surfaces. Besides, the solid-liquid interfacesanalyses highlighted a significant difference between the isoelectric point and point of zero charge of lepidolite,with pH values of 2–3 and 8.5–9, respectively, which demonstrated the importance of monitoring surface ob-servables such as the surface potential rather than the zeta potential. Noteworthily, surface titration experimentsallowed to identify distinct surface sites with specific pKa values that were discussed and demonstrated that thepotassium interfoliar cations are exchanged with protons when the pH is decreased. These findings allow to gainunderstanding in the lepidolite’s surface properties and will provide valuable implications for lithium extractionby the froth flotation method, a mineral beneficiation process based on the surface properties of minerals. Also,this research will pave the road to the in-depth investigation of physicochemical properties of surfaces in order tofinely tune the metal extraction in the current energy transition context.