Removal of Perchlorate from Contaminated Waters Using Surfactant-Modified Zeolite
2007
Zhang, Pengfei | Avudzega, David M. | Bowman, Robert S.
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.
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