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Catalytic Water Treatment

Contamination of groundwater by chlorinated compounds such as trichloroethylene (TCE) is an environmental concern due to their high level of toxicity and potential impact on drinking water.  It is estimated that TCE is present above permissible levels in 9-34% of drinking water sources in the U.S. Thus, development of a remediation system to remove chlorinated compounds from groundwater has become imperative. Existing remediation techniques for treatment of contaminated water are not efficient or feasible due to low rates of remediation, high energy inputs, and media regeneration/replacement cost. Although hydrodechlorination (HDC) appears to be an efficient way of groundwater remediation, it suffers kinetically due to low concentration of contaminants, catalyst deactivation due to anionic groundwater constituents, and catalyst inhibition due to HCl, unavoidable reaction product.

The focus of this study, which is conducted in collaboration with Professor Paul Edmiston of Wooster College and ABSmaterials, is the use of a new class of materials, namely swellable organically-modified silica (SOMS) as a catalyst scaffold for HDC reactions. SOMS is absorptive, swellable when contacted with organics and extremely hydrophobic (1-3). Organometallic precursors used for catalyst synthesis facilitate deposition of the active metal inside the pores, and therefore, a layer of protection is formed. The absorptive and hydrophobic nature of SOMS will guide the organics toward the active sites and repel water, anionic poisons as well as HCl. Our recent studies point out that when used as catalyst scaffolds, SOMS can have potential to resolve the issues involved in HDC of TCE(4).

Swelling of SOMS induced by drop-wise addition of acetone (2).

We are investigating the catalytic activity and poison resistance of Pd-incorporated SOMS for HDC of TCE. TCE reaction over the Pd/SOMS catalyst is being studied in a high-pressure batch reactor and in continuous flow reactor systems; both in the liquid and the gas phase. A wide variety of characterization techniques are being used for a better understanding of the nature of these materials.

References

(1) Burkett, C. M., Underwood, L. A., Volzer, R. S., Baughman, J. A., Edmiston, P. L. Chemistry of Materials 2008, 20, 1312.

(2) Edmiston, P. L., Underwood, L. A. Separation and Purification Technology 2009, 66, 532.

(3) Burkett, C. M., Edmiston, P. L. Journal of Non-Crystalline Solids 2005, 351, 3174.

(4) Sohn, H., Celik, G.,  Gunduz, S., Dean, S.L., Painting, E., Paul L. Edmiston, P.L., and Ozkan, U.S. Applied Catalysis, B 2016.