Adsorption of perchlorate and other oxyanions onto magnetic permanently confined micelle arrays (Mag-PCMAs)

The removal of oxyanions found in drinking water sources -perchlorate, nitrate, phosphate, and sulfate- onto magnetic permanently confined micelle arrays (Mag-PCMAs) was studied. We determined the removal efficiency in both competitive and non-competitive environments, as many of these anions are present in these sources. Mag-PCMA removed over 98% of the aqueous perchlorate anions across a concentration range of 60–500 μg/L. Nitrate was absorbed 100% over a concentration range of 10–35 mg/L as nitrate. Removal of phosphate was 95.7% for 0.2–2.45 mg/L as phosphate. Sulfate was 100% absorbed across a concentration range of 5–20 mg/L and an average 75.7% for 5–50 mg/L. The sorption isotherms followed a Freundlich relationship with Kf values of 2.00, 2.05, 1.9, and 3.86 mg/g for nitrate, perchlorate, phosphate, and sulfate respectively. Perchlorate and nitrate did not compete significantly for binding on Mag-PCMAs, with almost equal sorption, greater than 90%, for both anions in elevated concentrations. This is a distinguishing feature from ion exchange resins or activated carbon with cationic surfactants, where these anions have been shown to compete for sorption sites. At the concentrations studied, phosphate and sulfate also do not exhibit significant competition. Desorption for reuse was successful at pH 10. This reusable magnetic sorbent can thus be used to rapidly remove target anions such as perchlorate from water in the presence or absence of other oxyanions.

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► Mag-PCMAs remove 98% perchlorate, 96% phosphate, nearly 100% nitrate and sulfate.
► Mag-PCMAs have high free energy of adsorption for perchlorate.
► Little competition for sorption sites among oxyanions at most concentrations.
► Magnetic core allows fast, effective separation with low energy and no clogging.
► Mag-PCMAs can be reused several times to remove oxyanions from water.