Bioremediation of hydrocarbon-contaminated soils is an attractive process for treating contaminated soils because it converts contaminants into harmless byproducts at low cost. However, the process is slow and typically requires months to years to reach regulated end points. In laboratory studies, we have been able to improve the process by adding selected guanidinium fatty acids to the contaminated soils. One of these materials, guanidinium cocoate, was synthesized from coconut acid and guanidine carbonate in a facile one-step process. Rates of biodegradation enhancement of nonvolatile hydrocarbons were evaluated using either oxygen and carbon dioxide respirometry in soil slurries or periodic measurements of extractable hydrocarbon residues in unsaturated soil microcosms. Results show rate enhancements in both soil slurries and unsaturated soil microcosms when these systems were treated with 500−1500 ppm of the surfactant. Adding small amounts of CGS to a silty clay soil containing aged lubricant-type hydrocarbons increased rates of hydrocarbon disappearance, mineralization, and oxygen utilization in unsaturated soil and soil slurry systems. Based on these initial investigations, doses of approximately 2 lb of CGS/t of soil appear effective at increasing rates of biodegradation.

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