Polypyrrole/bacterial cellulose nanofiber composites for hexavalent chromium removal

Polypyrrole/bacterial cellulose (PPy/BC) composites with nanofiber structure were prepared by a facile in situ oxidative polymerization for the efficient removal of hexavalent chromium (Cr(VI)) from aqueous solution. The characteristics of the adsorbent were analysed by SEM, TEM, BET, EDX, FT-IR, and XPS and PPy found to be evenly wrapped on cellulose surfaces to form a core–shell structure and the specific surface area calculated at 95.9 m2 g−1. Benefiting from high surface area, PPy/BC efficiently removed Cr(VI) and possessed a maximum adsorption capacity of 555.6 mg g−1 at 298 K and pH 2. Adsorption data was determined to conform to the Langmuir isotherm model and pseudo-second-order model. Cr(VI) adsorption on PPy/BC was involved in ion exchange and electrostatic attractions. Meanwhile, a portion of Cr(VI) was reduced to trivalent chromium (Cr(III)) by pyrrolic nitrogen and then retained on PPy/BC surfaces by chelation. In addition, PPy/BC maintained 70.5% of its initial adsorption capacity after five adsorption and desorption cycles. This study demonstrated that PPy/BC can be a cost-effective, reusable, and highly efficient adsorbent for Cr(VI) removal.