Exchange reactions of zinc hydroxide-sulfate minerals in halide solutions

摘要: Abstract The possibilities of exchange reactions in two types layer Zn-hydroxy sulfate minerals with neutral and negatively charged hydroxide – namuwite (Zn4(OH)6(SO4)·4H2O) gordaite (NaZn4(OH)6(SO4)Cl·6H2O) were studied. As starting materials, synthetic analogs these are used. Through direct synthesis, besides the known namuwite, gordaite, its Ca2+ form, a series new cationic (K+, NH4+) anionic (Cl− Br−) forms synthesized. K+, NH4+ content is respectively about 1/3 2/3 nominal compositions. determined characteristics Br-forms showed similarity corresponding chloride forms. results experimental study interaction between gordaites various halide solutions realization three solid-state reactions: cation exchange, simultaneous cation-anion water molecule-halide anion exchange. All samples characterized by powder XRD EDS chemical analysis, transformation mechanism was monitored SEM investigation. By all formed, addition, Sr2+-form also obtained. Mutual conversions isovalent cations Na+-K+, Ca2+-Sr2+, possible combinations heterovalent pairs established. Regardless charge (namuwite) or (gordaites), due to stronger interlayer than that layer's tetrahedral Zn2+ cation, exit together leaving observed, causing mutual substitution H2O molecules anions. In first case, from one formed. However, under treatment iodide solutions, no observed. big size I− probably prevents occupation apical position Zn-tetrahedron provokes formation pure zinc-hydroxy-sulfate-hydrate phase unknown specific structure. second anions apex resulted different zinc hydroxy hydrates, depending on treating amount. reversible reaction caused Na+, NH4+, Ca2+, Sr2+. some other alkaline earth metals Li+, Mg2+, Ba2+ dissolution subsequent pseudomorphic simonkolleite crystallization. geometric difficulties for Li+ Mg2+ incorporation their great hydration capability ability form insoluble barite.