Formation mechanism of a series of trigonal antiprismatic jarosite-type compounds

•A series of jarosite-type compounds was prepared.•The as-prepared samples exhibit a novel trigonal antiprismatic shape.•The formation mechanism of trigonal antiprismatic jarosite-type compounds was investigated.

Trigonal antiprismatic jarosite-type compounds were prepared by a simple, rapid and template-free synthetic route. The as-prepared samples were characterized by various techniques. The results indicate that the formation of jarosite-type particle with trigonal antiprismatic morphology strongly depends on pH of the system. Trace of Fe2+ ions enter jarosite-type crystal and play a role in the development of the trigonal antiprismatic morphology. Based on the characterization data and experimental observation, the possible formation mechanism was clarified. Fe3+ ions firstly transformed to schwertmannite in the presence of SO42− ions. When Na+ (K+ or NH4+) ions coexist in the system, schwertmannite is preferable to transforming jarosite-type compounds instead of other iron oxides.