Efficient Removal of Methylene Blue by Novel Magnetic Hydrogel Nanocomposites of Poly(acrylic acid)

Abstract

ABSTRACTIn the current research, the sonochemically prepared magnetite nanoparticles (MNPs) were silylated with triethoxyvinylsilane to produce a core–shell structure containing vinyl moieties on the surface. The radical polymerization of the silylated product with acrylic acid in the presence of N,N‐methylenebisacrylamide, as the cross‐linker, led to the formation of novel magnetic hydrogel nanocomposites (MHNCs) in which some of polyacrylic acid (PAA) chains were chemically grafted onto MNPs (PAA‐grafted MNPs). Vibrating sample magnetometry showed the unique phenomenon of superparamagnetism for the prepared MNPs, silylated MNPs, and PAA‐grafted MNPs. Batch adsorption experiments were carried out for the removal of methylene blue (MB) using pure hydrogel and MHNCs as an adsorbent. The effects of contact time, PAA‐grafted MNP content, adsorbent mass, and initial pH value of the dye solution on adsorption were investigated. Results showed the MHNC containing 10 wt% of PAA‐grafted MNP (MHNC 10 wt%) had the maximum adsorption capacity. It was observed that the adsorption kinetics of MB followed pseudo–second‐order kinetics. The adsorption equilibrium data obeyed Langmuir isotherm, and the maximum adsorption amount of MB reached 507.7 mg g–1 for MHNC 10 wt%. It was shown that the adsorbed MB could be desorbed from the MHNCs by using methanol solution containing acetic acid and the nanoadsorbents could be recycled.