Soil clogging during surfactant-enhanced flushing of naphthalene-contaminated sand-kaolinite

Abstract

The removal of naphthalene from soils using a surfactant-enhanced flushing process was studied. Column tests were conducted on sand-kaolinite specimens (0, 5, and 20% kaolinite content) with water and sodium dodecylsulfate (SDS) surfactant used as permeants. Upon the introduction of surfactant, the hydraulic conductivity (k) of the various test specimens containing kaolinite decreased by up to two orders of magnitude but then recovered gradually to its initial value upon further flushing. Although more than 90% of the naphthalene contaminant was removed from the test soils, excessively long periods of flushing were needed due to the clogging phenomenon. Upon varying the concentration of the liquid constituents (SDS, naphthalene, and NaCl), the micellar solutions were observed to convert into phases including liquid crystals and gel. The viscosity of these phases was measured to range from 10 to 1000 cP. Several hydraulic conductivity tests conducted with SDS amended with NaCl indicated the alleviation of the reduction in k when sufficient NaCl concentration was used.Key words: surfactant, hydraulic conductivity, kaolinite, sand, naphthalene, SDS, contaminant, remediation, viscosity.