Polypyrrole@polyHIPE Composites for Hexavalent Chromium Removal from Water

In the present study, polymerized high internal phase emulsions, known as polyHIPEs, are used as a template for the synthesis of polypyrrole (PPy) monolithic composites. The unique properties of polyHIPEs such as a highly interconnected porous structure and a high surface area along with a simple preparation method have enhanced their use in variety of applications particularly as a support to produce monolithic composites. The resulting monolithic composites with an increased surface area and effective functional groups can be utilized for chromium (Cr) VI removal from contaminated water. Cr(VI) is a highly toxic carcinogenic chemical targeting eyes, skin, kidneys, and liver. PPy is a Cr(VI) adsorbent, but is usually in the powder form and cannot be separated from the effluent easily. In this work, we address this issue by preparing stable PPy monolithic composites. Scanning electron microscopy, Fourier transform infrared spectroscopy, and thermal gravimetric analysis confirm the PPy incorporation in the porous polymeric supports, particularly in the support based on a hydrophilic monomer (acrylic acid). The attraction between Cr(VI) ions and positively charged nitrogen atoms in the PPy chain and Cr(VI) reduction on the composite surface are possible mechanisms for Cr(VI) removal using PPy@polyHIPE composites. The adsorption results show that Cr(VI) removal increases from the neutral pH 7 to acidic pH 2, where the presence of sulfate anions in the solution does not have significant effects on Cr(VI) removal.