Network of Polyaniline Nanotubes for Wastewater Treatment and Oil/Water Separation

Polyaniline (PANI) nanofibers have been developed by an in situ polymerization technique using three different aromatic carboxylic acids as dopant. All dopants have the same aromatic core containing different numbers of carboxylic acid groups. Four (B4CA), three (B3CA), and two (B2CA) carboxylic acid functionalized organic acids have been selected as a dopant for polymerization of aniline in the presence of ammonium persulfate and the corresponding polyaniline composites are named as B4CAP, B3CAP, and B2CAP respectively. With increasing number of -COOH groups in the dopant, the aspect ratio of the fiber increases. Interestingly, all composites revealing nanotubes have shown very good adsorbing behavior toward water-soluble anionic dyes and dye uptake capacity varies with the aspect ratio of the nanofibers. The maximum dye adsorption efficiency achieved for the B4CAP matrix is similar to 300 mg/g toward indigo carmine dye in aqueous solution. The dye uptake ability also depends on the size as well as the charge of the dye molecule. Interestingly, PANI hollow nanotubes show good recyclability with several times by simple washing with diluted ammonia and acid solution. By taking advantage of hydrophilicity, polyaniline composites are subsequently employed to the oil/water separation. Polyaniline composites are able to separate different oil/water mixtures in a single-unit operation with >98% separation efficiency.