Performance Differences of Hexavalent Chromium Adsorbents Caused by Graphene Oxide Drying Process

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Graphene oxide (GO) is a promising material for environmental remediation.
• Amine functionalization enhances the adsorption capacity of GO for heavy metals.
• Drying methods can significantly alter the properties of functionalized GO.

Purpose of the Study:

• To investigate the effect of different drying conditions on amine functionalization of GO.
• To compare the hexavalent chromium (Cr(VI)) adsorption efficiency of GO functionalized under various drying methods.
• To identify optimal conditions for preparing amine-functionalized GO for Cr(VI) removal.

Main Methods:

• Amine functionalization of graphene oxide (GO) using 3-[2-(2-aminoehtylamino) ethylamino]propyl-trimethoxysilane (3N).
• Preparation of solution-processed GO (SGO), freeze-dried GO (FDGO), and oven-dried GO (ODGO).
• Characterization using Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, Thermogravimetric Analysis (TGA), X-ray Photoelectron Spectroscopy (XPS), and Elemental Analysis (EA).
• Adsorption experiments to determine Cr(VI) removal efficiency.

Main Results:

• Thermogravimetric analysis (TGA) indicated higher 3N functionalization on solution-processed GO (SGO) compared to freeze-dried GO (FDGO) and oven-dried GO (ODGO).
• X-ray Photoelectron Spectroscopy (XPS) confirmed higher nitrogen (N/C) and silicon (Si/C) ratios in SGO, indicating more effective amine functionalization.
• SGO exhibited the highest maximum adsorption capacity for Cr(VI) (258.48 mg g⁻¹), followed by FDGO (212.46 mg g⁻¹) and ODGO (173.45 mg g⁻¹).

Conclusions:

• Solution-processed GO (SGO) without drying demonstrates superior amine functionalization and Cr(VI) adsorption efficiency.
• Freeze-drying is a preferable method over oven-drying when drying of functionalized GO is necessary.
• The findings highlight the critical role of processing conditions in optimizing GO-based adsorbents for environmental applications.