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, schvvertmannite is preferable to transforming jarosite-type compounds instead of other iron oxides. (c) 2015 Elsevier By. All rights reserved,