Dissolution and surface study of phlogopite in the presence of ethylenediamine at pH 4–13

• Ethylenediamine and nitric acid increase phlogopite dissolution at pH 4. • At pH 4 and 7, protonated ethylenediamine interacts with phlogopite surface. • Ethylenediamine does not significantly affect the dissolution at alkaline pH. • Ethylenediamine does not interact with phlogopite surface at pH 10 and 13. • The solution pH, ligand, and surface interactions highly affect the dissolution. Phyllosilicate minerals are relevant in several environmental applications, such as supplementary cementitious materials, carbon capture and storage, and nuclear waste disposal. Therefore, it is important to understand how phyllosilicates react with aqueous solutions and the components within the solutions. In this study, the interaction between ethylenediamine and the surface of milled phlogopite was investigated within a pH range of 4–13. X-ray diffraction analysis of raw and milled phlogopite sample was conducted prior to the experiments. Solution compositions after batch titration experiments were determined using inductively coupled plasma optical emission spectrometry, and the remaining phlogopite was analyzed using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, zeta potential, and thermogravimetry/differential thermal analysis. The results indicate that the combined effect of HNO 3 —used to control the pH—and the presence of ethylenediamine improves phlogopite dissolution at pH 4. Conversely, the maximum accumulation of ethylenediamine at pH 7 inhibits the dissolution and blocks the phlogopite surface. At pH 10 and 13, ethylenediamine exhibits predominantly neutral and negative charges, respectively. This charge distribution indicates a lack of significant interaction with the negatively charged phlogopite surface, however despite that, ethylenediamine accumulated Al, Mg, and Fe on the surface.