Graphene Oxide-Magnetite Hybrid Nanoadsorbents For Toxin Removal in Aqueous System

Abstract

Rapid industrialization has led to massive environmental pollution, resulting in damage to the ecosystem and human health. Dyes and heavy metals are non-biodegradable toxins that possess carcinogenic and mutagenic properties. With the rising scarcity of water, these toxins need to be removed from water bodies economically and efficiently. Among all the classical wastewater treatment techniques, including complexation, chemical oxidation or reduction, solvent extraction, chemical precipitation, adsorption is the most promising separation method. However, it is a challenge to design adsorbent materials with high specific surface area and appropriate chemical functionality to selectively adsorb toxins.
The present work demonstrates one of the new types of adsorbent materials, which is a hybrid of graphene oxide (GO) and magnetite. Nanostructured two dimensional sheets, such as GO, can act as anchor points where the ceramic magnetic oxide can be precipitated, thus reducing the latter’s agglomeration tendency and expose active sites effectively. A facile sonication assisted synthesis was adopted to prepare the hybrids, and tested for their toxin adsorption properties against three distinctly different materials. The adsorption characteristics of Cr(VI) (toxic heavy metal contaminant), malachite green (a toxic cationic dye), and phenol red (a neutral dye) on to the GO-Fe3O4 hybrids was systematically investigated. The hybrids exhibited better adsorption properties than that of bare Fe3O4 nanoparticles. In addition, the hybrids were proved to be an excellent material for the separation of malachite green, with efficiency as high as 97%, with faster kinetics. The removal efficiency of phenol red was moderate, owing to the lack of charge on the dye; upto 68% removal was observed due to the interaction of the zwitterions with the adsorbents.
The presentation aims to discuss the effects of time, pH, and concentration on adsorption. The experimental results will be analyzed based on various kinetic models, including pseuo-first order, pseudo-second order, intraparticle diffusion, Bangham model. Equilibrium adsorption isotherms of these toxins on the GO-Fe3O4 hybrids will be discussed in the context of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models.