Controlled synthesis of octahedral jarosite

Octahedral jarosite was successfully prepared without extra template using a novel hydrothermal route based on the redox reaction between KMnO4 and (NH4)2Fe(SO4)2·6H2O. The objective of this study was to explore the controlled synthesis of octahedral jarosite crystals and understand the key factors affecting their formation. Methodologically, the synthesis involved varying the mass ratio of (NH4)2Fe(SO4)2·6H2O to KMnO4, as well as adjusting the reaction time and temperature, to examine their influence on crystal morphology. Characterization techniques, including X-ray diffraction, scanning electron microscopy, energy dispersive spectrum, high-resolution transmission electron microscopy, and selective area electron diffraction, were employed to analyze the chemical composition and microstructure of the as-prepared octahedral jarosite. Results indicated that the mass ratio, reaction time, and temperature were critical in determining the formation of octahedral crystals, thereby enhancing our understanding of the mechanisms involved in the synthesis of jarosite. Furthermore, preliminary discussions on the formation mechanism of octahedral jarosite were provided.