Preparation of hierarchical porous polypyrrole nanoclusters and their application for removal of Cr(vi) ions in aqueous solution

Hierarchical porous polypyrrole (PPy) nanoclusters composed of small PPy nanospheres were successfully prepared in one-step by a reactive-template method without any surfactants. The Fe₃O₄ nanoclusters acted as both the template for shaping PPy structure and oxidant source simultaneously. The dosage of pyrrole monomer, the concentration of HCl acid had significant influence on the structures and conductivities of the resulting PPy nanoclusters. By carefully controlling the experimental conditions, hierarchical porous PPy nanoclusters with the surface area as high as 104 m² g^-1 were obtained. The value was about 3.5 times larger than that of traditional PPy nanoparticles. Based on the transmission electron microscope (TEM) images and Fourier-transform infrared (FT-IR) spectra, a possible formation mechanism was proposed and investigated in detail. To test the feasibility of using the PPy nanoclusters in real applications, the capacity of nanoclusters as a heavy metal ion remover was explored. The resulting PPy nanoclusters showed an excellent ability to remove Cr(vi) ions in aqueous solution.