Removal of Perchlorate from Contaminated Waters Using Surfactant-Modified Zeolite
- Pengfei Zhang *a,
- David M. Avudzegaa and
- Robert S. Bowmanb
We investigated the potential of using surfactant (hexadecyltrimethylammonium)-modified zeolite (SMZ) as an inexpensive sorbent for removing perchlorate (ClO4 −) from contaminated waters in the presence of competing anions. In batch systems, the presence of 10 mM OH− (i.e., pH 12), CO3 2−, Cl−, or SO4 2− had little effect on the sorption of ClO4 − by SMZ, indicating that the sorption of ClO4 − by SMZ was very selective. The presence of 10 mM NO3 −, however, reduced the sorption of ClO4 − at low initial concentrations. The maximum sorption capacity for ClO4 − by the SMZ remained relatively constant (40–47 mmol kg−1), in the absence or presence of the competing ions. In flow-through systems, ClO4 − broke through the SMZ columns much later than other anions present in an artificial ground water. The affinity of the anions for SMZ followed the sequence of ClO4 − > > NO3 − > SO4 2− > Cl− Perchlorate loading under dynamic flow-through conditions was 34 mmol kg−1, somewhat less than the maximum loading of 40 to 47 mmol kg−1 determined by the batch method. Less than 1% of previously sorbed ClO4 − was leached out by ultra-pure water, by extraction fluid #1 of the standard toxicity characteristic leaching procedure (TCLP), or by a solution of 0.28 M Na2CO3/0.5 M NaOH. About 40% of the previously sorbed ClO4 − was leached out from SMZ by a 0.5 M NO3 − solution. The exchange of ClO4 − with NO3 − corroborated results of the batch tests where NO3 − was shown to compete with ClO4 − sorption.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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