Experimental and simulation studies for carbon dioxide (CO2) adsorption on porous silica glass were performed to reveal how surface heterogeneity can affect the adsorption mechanism of CO2. In performing the simulation, the structure of porous silica glass was modeled as a slit pore consisting of parallel walls of connected SiO4 units. The adsorption isotherms of CO2 at 283 K were generated for a series of pore widths using a Monte Carlo ensemble. The defective surfaces created by random removal of surface atoms and the surfaces containing hydroxyl functional groups were chosen to represent the surface heterogeneity for the simulation tasks. The isotherms derived for the defective surfaces showed a rapid adsorption at low pressures because of the stronger interaction between the rough nonuniform surfaces and CO2 molecules. For the role of surface functional groups, the adsorption isotherms dramatically increased with an increasing number of functional groups. The amount of CO2 adsorbed for randomly placed functional groups was greater than that for the presence of functional groups at the pore edges. The proper control of surface heterogeneity by manipulating both the amounts of hydroxyl surface groups and surface defects should help enhance the efficient capture of CO2 in porous silica glass.

Wet cassava pulp is generated in large quantity during a production of cassava starch. Major utilization of the pulp is in animal feed manufacturing. During a period of low demand, this material could accumulate and decompose causing air pollution in areas surround the starch factories. This research used biomass desiccant prepared from cassava pulp in a bench-scale packed-bed adsorption system to study the dehydration of ethanol and n-propanol vapor at concentration near their azeotropic points. The sorption capacity was found to be 0.053 and 0.119 gwater/gdesiccant for ethanol and iso-propanol at concentration of 80 %(w/w) and 0.109 gwater/gdesiccant for n-propanol at concentration of 65 %(w/w). Alcoholic solutions with concentration higher than their aqueous azeotropic points, which could not be achieved by normal fractional distillation, were obtained in all the experiments. This study elucidates that cassava pulp could be value-added, and water adsorption using cassava-derived desiccant could be an alternative technique for production of high purity alcohols.

In this paper, adsorption of methane on porous silica glass was investigated to see whether functional groups can affect the adsorption behavior. Adsorption isotherms for pores having widths between 7 and 40Å at 283 and 298 K were investigated using a Monte Carlo simulation (MC) method. The model of porous silica glass proposed in this study was assumed to be a finite-length slit pore which consisted of two parallel walls. The tetrahedral structure of SiO4 was used as atomic structure for the wall surface. Hydroxyl was assumed as the surface functional group which allocated either at pore mouth or random with concentration of 5 and 10%. It was found that the concentration of functional group has less significant effect on the adsorption of methane. The adsorption isotherm decreased a bit with an increase of functional group concentration. Effects of functional group position on adsorption isotherm were also investigated, the adsorption isotherm obtained for the random topology was greater than that for the pore mouth topology, due to the pore blocking effects. At the same pore width, the adsorption isotherm at 283K was greater than that at 293K, and this was due to that the adsorption of methane on porous silica glass was a physical adsorption. The initial adsorption of methane shifted to the higher pressure by increasing pore width, and the maximum adsorption capacity decreased with an increase of pore size, because of the pore packing effect.

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