Excess oxyanions in surface and drinking water such as nitrate, phosphate and arsenate produce negative effects on human health and the environment. Hence, research of methods to remove oxyanions is of great importance. Numerous studies have captured oxyanions using silica functionalized with amine groups because they have an affinity for anions. Additional studies suggest that electron-deficient aromatics have demonstrated a preference for nitrate due to anion-π interactions. Amine and electron-deficient aromatic functionalizations have been applied to silica materials in an attempt to selectively bind nitrate as well as other oxyanions in aqueous solutions. These silica adsorbents were synthesized by functionalizing fumed silica CAB-O-SIL® (cab) with terminal amine groups using 3-aminopropyltrimethoxysilane. Further functionalization with electron deficient aromatic rings was used to produce five materials: 3,5-disulfobenzamide cab, 4-(sulfo)benzamide cab, 4-(methylsulfonyl)benzamide cab, 4-dinitrobenzamide cab, and 4(trifluoromethyl)benzamide cab. The materials were characterized using thermogravimetric analysis, powder x-ray diffraction, elemental analysis, and infrared spectroscopy. Performance testing with nitrate, phosphate and arsenate is ongoing, initial results are promising.

Functionalized silica adsorbents for trace collections oxyanions

ACS Spring 2022

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