(639h) Metal Organic Framework Derived Nanoporous Carbon  As a Novel Adsorbent for Water Treatment

Metal organic framework derived nanoporous carbon

 as a novel adsorbent for water treatment

Zahra Abbasi^a, Ezzatollah Shamsaei^a, Soo Kwan Leong^a, Bradley Ladewig^a,b, Xiwang Zhang^a, Huanting Wang^a*

 ^aDepartment of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia

^bDepartment of Chemical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ,

United Kingdom

Phone: +61 3 9905 3449, Email: Huanting.wang@monash.edu

Nanoporous carbon materials have attracted a great deal of attention because of their potential application in many areas such as adsorption and catalysis. These materials have desirable properties such as high surface area, good chemical and thermal stabilities as well as fast kinetics, which make them suitable for adsorption applications. Porous metal organic frameworks (MOFs) consist of crystalline structures that provide high internal surface areas and tunable porosities which could be considered as starting materials for developing novel carbon based nano composite adsorbents.

Different types of adsorbents have been studied for the removal of organic pollutants from water and wastewater such as activated carbon, fly ash waste materials and different kind of MOFs. However, their adsorption capacity is low in comparison with nanoporous carbons. Therefore, developing novel carbon based materials with simple synthesis methods for adsorption of pollutants from water is of great importance.  

Zeolitic immidazolate frameworks (ZIFs) are a class of MOFs that exhibit remarkable features like high thermal and chemical stability and demonstrate similar pore topologies to zeolites. Among various ZIFs reported, ZIF-8 with the formula of Zn(2-methylimidazolate)₂ and with a sodalite-related zeolitic structure has been used for many applications such as adsorption and catalysis. The surface and bulk properties of ZIF-8 can be modified to make it a more competent adsorbent for water treatment purposes. Carbonization of ZIF-8 could be the easiest and most practical modification approach to amend this metal organic frame work’s characteristics.

The adsorption capabilities and characteristics of nanoporous carbon particles derived from ZIF-8 were investigated in this study. Direct carbonization of ZIF-8 was used to synthesize carbon nano particles. SEM and TEM images revealed that the ZIF-8 derived carbon carbonized at several temperatures retained the original structure and morphology of ZIF-8. These carbon nano-particles exhibited significantly greater adsorption capacities for the removal of dye from water compared to the ZIF-8. The high adsorption capacity is attributed to the change in surface charge and pore size. The surface functionality and hydrophobicity of the materials were investigated by Raman Spectroscopy, N₂ adsorption-desorption, FTIR, TGA and contact angle measurements. The change in the surface charge of the carbon particles was confirmed by zeta potential of the samples. The dye uptake followed pseudo-second order kinetics and the equilibrium data was best fit to the Langmuir model for the carbon nano-particles. Intra-particle diffusion studies showed that the adsorption process was governed by both the diffusion step and external mass transfer. The ZIF-8 derived nano porous carbons were found to be highly efficient adsorbents for water and waste water treatment.