Graphene Oxide as a Highly Efficient and Reusable Adsorbent for Simultaneous Removal of Parabens: Optimization by Response Surface Methodology, Adsorption Isotherms and Reusability Studies

Abstract

Paraben contamination in aquatic systems, primarily from personal care products, pharmaceuticals and industrial effluents, is an increasing environmental concern due to their widespread use as preservatives. The removal of parabens through conventional wastewater treatment processes is challenging and requires the development of innovative water treatment methods. In this study, graphene oxide nanoflakes were produced by Improved Hummers’ method and their adsorption characteristics were investigated for simultaneous removal of five parabens. Fourier transform infrared spectroscopy, Raman Spectroscopy, X-Ray Powder Diffraction, Scanning Electron Microscope and Transmission Electron Microscope were used and the nanoflakes were successfully characterized. A chromatographic method was developed for the simultaneous quantification of parabens. Process optimization for overall removal efficiency of parabens was achieved using Response Surface Methodology by a multiple response function. Nonlinear regression was used to fit the equilibrium data and the Freundlich model described the adsorption isotherm data accurately with R² values between 0.9807 and 0.9957. Factors such as mass of adsorbent, pH of solution and their interaction have the most significant impact on the adsorption process, while contact time shows low significance on the response. The adsorption behaviors of parabens were closely correlated with their hydrophobicity. Along with hydrophobic interactions, other mechanisms such as π–π stacking, hydrogen bonding and electrostatic forces, likely played significant role in the strong adsorption of parabens onto the GO surface. The reusability experiment showed that graphene oxide nanoflakes had a high potential present as a reusable adsorbent for the removal of parabens.