Synthesis and characterization of a series of novel perovskite-type LaMnO/Keggin-type polyoxometalate hybrid nanomaterials for fast and selective removal of cationic dyes from aqueous solutions.

In this paper, Keggin-type heteropoly acids HPMoO (PMo), HPWO (PW) and HSiWO (SiW) were successfully supported on silica-coated perovskite type LaMnO nanoparticles by a simple acid-base reaction. These novel hybrid nanomaterials (denoted as LaMnO@SiO/PMo (1), LaMnO@SiO/PW (2), and LaMnO@SiO/SiW (3)) were characterized by means of FT-IR, PXRD, inductively coupled plasma (ICP) spectrometry, SEM, EDX, TEM and BET surface area analysis. Furthermore, the adsorption abilities of 1-3 were tested towards cationic methylene blue (MB) and anionic methyl orange (MO) dyes. The results revealed that the MB dye can be removed almost completely (≥98%) by adsorbents 1-3 in 1, 30 and 0.5 minutes, respectively. For the most efficient adsorbent 3, the effects of the initial concentration and the initial pH values of MB solution on its adsorption ability were examined. Furthermore, the selective adsorption of the hybrid materials towards mixed MB & MO solution was investigated. The nanomaterials 1-3 could be easily separated from the aqueous solution and reused several times without any impact on their adsorption abilities and structures.