A thiourea cross-linked three-dimensional graphene aerogel as a broad-spectrum adsorbent for dye and heavy metal ion removal

Abstract

Herein, a thiourea cross-linked three-dimensional graphene aerogel (TCGA-1) was successfully prepared via a ring-opening reaction between the amino groups of thiourea molecules and the epoxy groups of graphene oxide (GO) sheets. Honeycomb-like three-dimensional porous morphology was confirmed by SEM, TEM, TGA, FT-IR, XPS, RS and XRD. The removal of heavy metal ions (Cu²⁺, Pb²⁺, Cr³⁺ and Cd²⁺) onto TCGA-1 was investigated with respect to solution pH, metal ion concentration and cycle time. In addition, it was also developed for the removal of anionic dyes (acid orange II and methyl orange) and cationic dyes (rhodamine B, methylene blue, and malachite green) from water. The results indicate that the removal of heavy metal ions onto TCGA-1 was greatly influence by pH. The sample can be regenerated more than twenty times based on their adsorption/desorption cycles, with a slight loss in the removal capacity. Malachite green or methylene blue (100 mg L⁻¹) was completely removed using TCGA-1 within six hours and the removal behavior was described well using a pseudo-second-order kinetic model. It is also effective for removing other organic dyes used in this work. Therefore, the prepared broad-spectrum adsorbent exhibits satisfactory performance for many kinds of contaminants, suggesting its potential applications in the environmental cleanup.