Removal of Perchlorate from Contaminated Waters Using Surfactant‐Modified Zeolite

Abstract

We investigated the potential of using surfactant (hexadecyltrimethylammonium)-modified zeolite (SMZ) as an inexpensive sorbent for removing perchlorate (ClO(4)(-)) from contaminated waters in the presence of competing anions. In batch systems, the presence of 10 mM OH(-) (i.e., pH 12), CO(3)(2-), Cl(-), or SO(4)(2-) had little effect on the sorption of ClO(4)(-) by SMZ, indicating that the sorption of ClO(4)(-) by SMZ was very selective. The presence of 10 mM NO(3)(-), however, reduced the sorption of ClO(4)(-) at low initial concentrations. The maximum sorption capacity for ClO(4)(-) by the SMZ remained relatively constant (40-47 mmol kg(-1)), in the absence or presence of the competing ions. In flow-through systems, ClO(4)(-) 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 ClO(4)(-) > > NO(3)(-) > SO(4)(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 ClO(4)(-) 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 Na(2)CO(3)/0.5 M NaOH. About 40% of the previously sorbed ClO(4)(-) was leached out from SMZ by a 0.5 M NO(3)(-) solution. The exchange of ClO(4)(-) with NO(3)(-) corroborated results of the batch tests where NO(3)(-) was shown to compete with ClO(4)(-) sorption.

Application of natural zeolites in environmental remediation: A short review

“…arsenates, chromates, iodides, nitrates, perchlorates, antimonates) (e.g. [62][63][64][65][66][67]. Similar sorption properties and capacity show the polymer-modified zeolites (e.g.…”

Influences of clinoptilolite and surfactant-modified clinoptilolite zeolite on nitrate leaching and plant growth

“…At the HDTMA sorption maximum, the surfactant molecules form bilayers on zeolite surfaces with the lower layer held by electrostatic interactions between the negatively charged zeolite surface and the positively charged surfactant head groups, while the upper layer is bound to the lower layer by hydrophobic forces between the surfactant tail groups in both layers [16]. Under the surfactant bilayer configuration, the zeolite reverses its surface charge, resulting in a higher affinity, sorption, and retention of negatively charged anionic contaminants that is attributed to surface anion exchange [16][17][18]. The use of surfactant-modified zeolite (SMZ), which represents a type of inexpensive anion exchanger, to remove anionic contaminants from water has been studied extensively [18][19][20].…”

“…Under the surfactant bilayer configuration, the zeolite reverses its surface charge, resulting in a higher affinity, sorption, and retention of negatively charged anionic contaminants that is attributed to surface anion exchange [16][17][18]. The use of surfactant-modified zeolite (SMZ), which represents a type of inexpensive anion exchanger, to remove anionic contaminants from water has been studied extensively [18][19][20].…”

Variation in performance of surfactant loading and resulting nitrate removal among four selected natural zeolites

“…The target contaminants include heavy metals [13][14][15], organic pollutants [16][17][18][19], organic dyes in waste water [20], nutrients [21], and microbial pathogens [22]. To widely apply the use of SMZs for water treatment, knowledge of the surfactant loading performance of selected zeolites is very important.…”