Synthesis and characterization of a series of novel perovskite-type LaMnO3/Keggin-type polyoxometalate hybrid nanomaterials for fast and selective removal of cationic dyes from aqueous solutions

Abstract

In this paper, Keggin-type heteropoly acids H₃PMo₁₂O₄₀ (PMo₁₂), H₃PW₁₂O₄₀ (PW₁₂) and H₄SiW₁₂O₄₀ (SiW₁₂) were successfully supported on silica-coated perovskite type LaMnO₃ nanoparticles by a simple acid–base reaction. These novel hybrid nanomaterials (denoted as LaMnO₃@SiO₂/PMo₁₂ (1), LaMnO₃@SiO₂/PW₁₂ (2), and LaMnO₃@SiO₂/SiW₁₂ (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.