ZnO Nanoparticles Modified by Magnetic Carboxymethyl Starch for Effective Photocatalysis of Organic Dye Degradation

Abstract

Effective and sustainable methods are crucial for dealing with organic pollutants in wastewater. This study investigates modifying ZnO nanoparticles (ZnO NPs) with magnetic carboxymethyl starch (mCMS) to improve their photocatalytic performance for the removal of organic dye. The resulting nanocomposite (ZnO/mCMS NC) was characterized by FTIR, XRD, FESEM, VSM, and DRS analyses. The band gaps of the ZnO NPs and ZnO/mCMS NCs were calculated as 3.13 eV, and 2.87 eV, respectively. Magnetic measurement indicated the fabricated NCs had an excellent superparamagnetic property with a saturation magnetization value of 43.11 emu g⁻¹. In addition, the modified NC exhibited a higher adsorption ability to bromocresol green dye molecules compared with ZnO NPs, which would contribute to its use for photocatalytic degradation. According to the results of photocatalytic experiments, the ZnO NPs and ZnO/mCMS NCs removed 38.3% and 95.1%, of bromocresol green dye respectively, under UV light in 60 min. The effect of solution pH on the removal efficiency of the synthesized NCs was investigated. The Langmuir–Hinshelwood model was applied to describe the kinetics of photodegradation. Moreover, the ZnO/mCMS catalyst could be easily separated from the reaction system by using an external magnet and recycled up to four times without any loss of activity. Benefiting from the combined merits of ZnO NPs, magnetic NPs, and carboxymethyl starch, the ZnO/mCMS NCs simultaneously showed remarkable performance in organic dye removal and convenient magnetic separation capability.