Enhanced removal of hexavalent chromium from aqueous media using a highly stable and magnetically separable rosin-biochar-coated TiO2@C nanocomposite

Recently, nanosized metal-oxides have been extensively investigated for their ability to remove metal ions from aqueous media. However, the activity and capacity of these nanosized metal-oxides for removing metal ions decrease owing to their agglomeration in aqueous media. Herein, we synthesized a highly stable and magnetically separable rosin-biochar-coated (RBC) TiO₂@C nanocomposite through a facile and environment-friendly wet chemical coating process, followed by a one-step heating route (pyrolysis) for efficient removal of Cr(vi) from aqueous solution. An array of techniques, namely, TEM, HRTEM, TEM-EDS, XRD, FTIR, VSM, BET and TGA, were used to characterize the prepared nanocomposite. The pyrolysis of rosin into biochar and the fabrication of Fe onto the RBC-TiO₂@C nanocomposite were confirmed by FTIR and XRD examination, respectively. Moreover, TEM and HRTEM images and elemental mapping using TEM-EDS showed good dispersion of iron and carbon on the surface of the RBC-TiO₂@C nanocomposite. Sorption of Cr(vi) ions on the surface of the RBC-TiO₂@C nanocomposite was very fast and efficient, having a removal efficiency of ∼95% within the 1^st minute of reaction. Furthermore, thermodynamic analysis showed negative values of Gibb''s free energy at all five temperatures, indicating that the adsorption of Cr(vi) ions on the RBC-TiO₂@C nanocomposite was favorable and spontaneous. Conclusively, our results indicate that the RBC-TiO₂@C nanocomposite can be used for efficient removal of Cr(vi) from aqueous media due to its novel synthesis and extraordinary adsorption efficacy during a short time period.

A biochar-coated RBC-TiO₂@C nanocomposite was synthesized using a wet chemical coating followed by a one-step heating route (pyrolysis) for the efficient removal of Cr(vi).