Facile synthesis of tea waste/Fe3O4 nanoparticle composite for hexavalent chromium removal from aqueous solution

Abstract

The modification of biomass waste, as a multifunctional composite, has received tremendous attention for resource utilization and recycling. In this study, tea waste, which is a high level generator of biomass waste, was loaded with nano-Fe3O4 particles to prepare a magnetic tea waste/Fe3O4 (TW/Fe3O4) composite through a facile chemical co-precipitation approach. BET, SEM, TEM, XRD, magnetic properties, FTIR, XPS were used to characterize the TW/Fe3O4 composite. A superparamagnetic TW/Fe3O4 composite (Fe3O4: about 20 nm) was successfully synthesized and possessed the advantages of tea waste and nano-Fe3O4 particles. A chromium(vi) adsorption experiment showed that this material has a strong adsorption capacity for aqueous chromium ions, which reached 75.76 mg g−1 based on the Langmuir model. The adsorption process could be well fitted by a pseudo-second-order kinetic model and Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models, and was spontaneous and endothermic according to the thermodynamic analysis. The TW/Fe3O4 composite revealed good reusability and the removal rate was more than 70% after five recycling cycles. The mechanism of Cr(vi) removal involved electrostatic attraction, reduction process, ion exchange, surface complexation, etc. 70% of Cr(vi) was reduced to Cr(iii) in this investigation. This study indicated that a TW/Fe3O4 composite could be an attractive option for heavy metal treatment.