Hydrodechlorination of Perchloroethylene with Swellable Organically-Modified Silica (SOMS)
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Date
2016-05
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The Ohio State University
Abstract
Groundwater is an important resource to residential, industrial, and agricultural sectors. Unfortunately, chlorinated compounds such as perchloroethylene and trichloroethylene can contaminate groundwater sources due to heavy industrial use. Current methods of groundwater treatment are costly and slow. In this paper, it is suggested that hydrodechlorination be used as a means to remove chlorinated compounds from groundwater. Current hydrodechlorination efforts, however, are hindered by the deactivating effects of ionic species inherent in groundwater on metal catalysts usually used for hydrodechlorination. It is suggested that if a different support were used for the catalyst rather than the traditional Al2O3 support, the catalyst could be better protected. The suggested material is Swellable Organically-Modified Silica (SOMS). It is expected that the swellable nature of SOMS will increase the number of available sites and the hydrophobic quality of SOMS will help to repel groundwater ionic species. Therefore, in this paper, the hydrodechlorination activity, quantified by percentage of conversion of perchloroethylene, was compared between both fresh and poisoned commercial (1%Pd/Al2O3) and synthesized (1%Pd/SOMS) catalysts. It was determined that when poisoning effects are not considered, the commercial catalyst achieves better conversion, with 95% conversion of perchloroethylene in four hours. When the poisoning effects of NaCl and NaHS are considered, however, the drop in hydrodechlorination activity is significantly more for the commercial catalyst versus the synthesized catalyst. These findings suggest that the SOMS support better protects the Pd when in the presence of poisoning ionic species. IR transmission spectra were also collected for the poisoned catalysts, in order to better understand the effect of the poisons on the surface functional groups. It was determined that sulfur containing species greatly impact the functional group, while the SOMS material better repels the water in the poisoning solutions.
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Keywords
Hydrodechlorination, Perchloroethylene, Groundwater Treatment, Pd Catalyst