Exploring the acid‐base surface properties of vivianite crystals in aqueous solution

The acid–base surface properties of vivianite crystals highly affect the adsorption capacity of vivianite for heavy metals and organic matters in aqueous solution. Therefore, the aim of the study was to innovatively explore and quantify the acid–base surface characterization of vivianite crystals in aqueous solution. It was found that the two surface active adsorption sites (≡POH and ≡FeOH) and five surface species thereof (i.e., ≡PO, ≡POH, ≡FeOH, ≡FeO−, and ≡FeOH2+) underwent surface reaction on vivianite crystals. Moreover, the active surface site and point of zero charge of vivianite crystals were 18 sites/nm2 and pH 5.9. Importantly, constant capacitance model was successfully employed to model the titration data, from which the distribution of surface species as function of pH and surface reaction constants were also accurately derived. The finding herein can be applied for plausible modeling molecular‐scale adsorption of the impurities on vivianite surface.