Sepiolite Fiber Oriented-Polypyrrole Nanofibers for Efficient Chromium(VI) Removal from Aqueous Solution

Polypyrrole-sepiolite nanofibers were prepared by in situ chemical oxidation polymerization in the presence of sepiolite. The nanostructure of PPy-sepiolite nanofibers was confirmed by field-emission scanning electron microscopy. The adsorption of Cr(VI) onto the PPy-sepiolite nanofibers was highly pH dependent and the adsorption kinetics followed the pseudo-second-order model. The Langmuir isothermal model well described the adsorption isotherm data and the maximum adsorption capacity increased with the increase of temperature. The maximum adsorption capacity of the PPy-sepiolite nanofibers for Cr(VI) was up to 302 mg·g–1 at 25 °C. Thermodynamic investigation indicated that the adsorption process is spontaneous and endothermic. Desorption experiment showed PPy-sepiolite can be regenerated and reused for four consecutive cycles without obvious loss of its removal efficiency. The excellent adsorption characteristic of PPy-sepiolite will render it a highly efficient and economically viable adsorbent for Cr(VI) removal.