Poly(acrylic acid) functionalized magnetic graphene oxide nanocomposite for removal of methylene blue

Abstract

A polyacrylic acid (PAA) functionalized magnetic Fe₃O₄ nanoparticle-graphene oxide nanocomposite (PAA/MGO) was synthesized by a facile method. The structure and surface properties of MGO and PAA/MGO composites were characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA) and zeta potential measurements. The adsorption of a model dye pollutant, methylene blue (MB), on MGO and PAA/MGO was investigated in batch tests. The functionalization of PAA to MGO significantly enhances the maximum adsorption capacity of MB (at pH = 7) from ∼70 mg g⁻¹ (on MGO) to ∼291 mg g⁻¹ (PAA/MGO). The adsorption of MB on MGO and PAA/MGO was mainly driven by the electrostatic attraction between positively charged MB molecules and negatively charged nanocomposite surfaces, and the higher adsorption capacity of PAA/MGO is mainly attributed to the functionalization of PAA and its higher content of charged carboxyl groups than MGO. The adsorption capacity of MB on both MGO and PAA/MGO adsorbents also increases with increasing solution pH from 3 to 11, due to enhanced electrostatic attraction at high pH conditions. The limited adsorption capacity of MB on MGO and PAA/MGO at pH 3, when electrostatic attraction is almost negligible, indicates that π–π interaction between the GO surface and MB also plays a role in the adsorption process. The PAA/MGO shows a rapid adsorption rate and high adsorption capacity of MB with magnetic properties for easy separation and excellent recyclability, which endows the nanocomposite with great potential for the removal of cationic organic pollutants in wastewater treatment.