Abstract
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► Birnessite type manganese oxides nanotubes and nanorods were prepared by calcination route. ► The transition from tube to rod structure is described by an oriented attachment-thermodynamical (OA-TD) process. ► The catalytic degradation efficiency of safranin O by as-prepared products was compared.
Birnessite-type manganese oxide nanotubes and nanorods were synthesized via a calcination process using manganese acetate and potassium hydroxide as precursors in presence of polyethylene glycol–melamine–formaldehyde. As-prepared products were characterized by XRD, FT-IR, FE-SEM, TEM, SA-ED, HR-TEM, Brunauer–Emmett–Teller (BET) and TGA analyses. The influences of reaction temperature and time on the morphology of manganese oxide nanocrystals were investigated. The oriented attachment-thermodynamical (OA-TD) process is suggested to describe the transition from tube to rod structure. Their capability of catalytic degradation of safranin O was compared. The results indicate that birnessite-type manganese oxide nanotube has higher catalytic activity for than nanorod crystal in aqueous solution, because it has a larger surface area. The decomposition of safranin O follows pseudo-first order kinetics and is markedly affected by pH.