Dissolution of zinc silicate (hemimorphite) with ammonia-ammonium chloride solution

XRD, IR, SEM and XPS analysis were carried out to study the dissolution behavior of hemimorphite in ammonia-ammonium chloride solution at 25 +/- 0.5 degrees C. The results indicate that hemimorphite is soluble until its framework disintegrates. The residue possesses the characteristics of SiO2 center dot nH(2)O, which forms an amorphous SiO2 layer on the hemimorphite surface. After ammonia-ammonium chloride dissolution, the relative abundance of zinc on the residue surface decreases with an increase of total ammonia concentration. XPS data shows that the Si 2p3/2 and O 1s spectra of the dissolved hemimorphite are broadened and shifted to higher binding energies during ammonia-ammonium chloride dissolution and that their binding energies are closer to SiO2 (silica) with an increase of total ammonia and time. (C) 2010 Elsevier B.V. All rights reserved.