Remediation of groundwater contaminated simultaneously with organic and inorganic pollutants using micellar-enhanced ultrafiltration

Abstract

The removal characteristics of nitrate, chromate, and ferriccyanide were investigated using micellar-enhanced ultrafiltration with a cationic surfactant, cetylpyridinium chloride (CPC). At the same concentration of the surfactant, the removal of each anionic pollutant increased with the valence of the pollutant: ferriccyanide with -3 as valence > chromate with -2 as valence > nitrate with -1 as valence. In the co-presence of nitrate, chromate, and ferriccyanide, ferriccyanide bound to CPC micelles preferentially to nitrate and chromate. After the removal of ferriccyanide reached saturation, nitrate and chromate bound competitively to CPC micelles. The solubilization characteristics of 1-chlorobenzene and 1,2-dichlorobenzene were investigated in the ionic surfactants solutions, sodium dodecyl sulfate (SDS), CPC, and dodecyltrimethylammonium chloride (DMAC). CPC showed the highest solubilization capacity for chlorobenzenes because CPC has the largest hydrophobic interior volume. At the same concentration of surfactants, extent of 1,2-dichlorobenzene was higher than that for 1-chlorobenzene because 1,2-dichlorobenzene is more hydrophobic. Most of chlorobenzenes were solubilized at the hydrophobic interior of micelles due to hydrophobic interactions, and some of those were solubilized at the water-micelle interface due to attractive interactions of between positive charges of cationic surfactant and pi-electrons of chlorobenzene. In the co-presence of chlorobenzenes, the solubilization of each chlorobenzene was inhibited by the other because two chlorobenzene were solubilized at the same locus in the micelles. The presence of nitrate and chromate inhibited the solubilization of chlorobenzene in CPC solution because the nitrate and chromate bound to outer shell of the CPC micelles, which reduced slightly the attractive interactions between positive charges of cationic surfactant and pi-electrons of chlorobenzene. However, the effect of nitrate and chromate on the...