Potential of activated carbon to recover randomly-methylated-β-cyclodextrin solution from washing water originating from in situ soil flushing.

Despite the overall high efficacy of cyclodextrins to accelerate the treatment of soil aquifer remediation by in-situ soil flushing, the use in practice remains limited because of the high costs of cyclodextrin and high concentrations needed to significantly reduce the treatment time. The current study tested the potential of activated carbon to treat washing water originating from soil flushing in order to selectively separate hydrocarbon contaminants from washing water containing cyclodextrin and subsequently reuse the cyclodextrin solution for reinfiltration. A high recovery of the cyclodextrin from the washing water would reduce the costs and would make the technique economically feasible for soil remediation. This study aimed to investigate whether cyclodextrin can pass through the activated carbon filter without reducing the cyclodextrin concentration when the contaminated washing water is treated and whether the presence of cyclodextrin negatively affects the purification potential of activated carbon to remove the organic pollutants from the pumped soil water. Lab-scale column experiments showed that with the appropriate activated carbon 100% of cyclodextrin (randomly-methylated-β-cyclodextrin) can be recovered from the washing water and that the effect on the efficiency of activated carbon to remove the hydrocarbon contaminants remains limited. These results show that additional field tests are useful to make in-situ soil flushing with cyclodextrin both a technical and an economical interesting technique. These results might stimulate the application of cyclodextrin in soil treatment technology.