Hybrid Reverse Monte Carlo Simulations of Activated Carbons Used as Adsorbents for Chemical and Biological Warfare Agents
Jeremy C. Palmer, Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Engineering Building I, Box 7905, Raleigh, NC 27695-7905, John K. Brennan, Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Building 4600, Aberdeen Proving Ground, MD 21005, Keith E. Gubbins, Chemical and Biomolecular Engineering and Center for High Performance Simulation (CHiPS), North Carolina State University, Raleigh, NC 27695-7905, Margaret Hurley, US Army Research Laboratory, Aberdeen, MD 21005, and Alex Balboa, Research and Technology Directorate, U.S. Army Edgewood Chemical Biological Research Center, 5183 Black Hawk RD, Aberdeen Proving Ground, MD 21010-5424.
Activated carbons are amorphous, microporous materials synthesized by pyrolysis of organic precursors such as nut shells, woods, and charcoals. Their excellent surface activity and low cost of production make them ideal materials for many industrial applications such as gas and liquid filtration, gas storage, and catalytic processes. As a result of their amorphous nature, little is know about how the structural features of these carbons influence their adsorptive characteristics. We have used an atomistic simulation technique known has hybrid reverse Monte Carlo (HRMC) to develop geometrically realistic models form experimental x-ray diffraction data for two activated carbons (BPL and ASZM-TEDA) that have shown promise as efficient adsorbents for chemical and biological warfare agents. Through a detailed structural analysis of our model structures, we have found that our models produce key structural features, such as the carbon-carbon radial distribution function, that are in excellent agreement with experimental measurements. We also performed grand canonical Monte Carlo simulations (GCMC) of argon and nitrogen gas at 77 K in order to calculate adsorption isotherms and isosteric heats of adsorption for our model structures. The results from these simulations indicate that our models for activate carbons are both geometrically realistic and have adsorptive properties that are consistent with those of real activated carbons.