Influence of synthesis conditions over simonkolleite/ZnO precipitation

Simonkolleite is a zinc-layered hydroxide salt with the formula Zn₅(OH)₈Cl₂·H₂O. It has a platelet morphology and can be used for many applications, owing to both its layered structure and its nature as a hydroxide salt. It can be prepared via a simple precipitation from ZnCl₂ and NaOH in water thermostated at 50 °C. Depending on the synthesis conditions, we could obtain different sizes and a hybrid containing parts of ZnO. We studied the influence of the OH:Zn molar ratio, the addition order, and the maturation time after the reaction was completed. With the support of pH profiles, kinetic studies, and thermodynamic equilibrium data, we were able to propose a global synthesis mechanism explaining the influence of those three parameters and identify the range of conditions in which simonkolleite can be formed. Depending on the desired application, we were able to synthesize bigger or smaller layered crystals of simonkolleite, in the presence of absence of ZnO.