Preparation of a quinoa straw-derived porous carbon material and a Fe3O4-contained composite material for removal of rhodamine B from water

In this work, quinoa straw (QS) is considered as a sustainable biomass resource to produce adsorbent materials for wastewater treatment. Two materials, a porous carbon material derived from QS (PCQS) and a Fe3O4-containing composite material based on the PCPS (Fe3O4@PCQS), were prepared. PCQS was prepared via carbonization and subsequent chemical activation of the QS using NaOH. Thereafter, PCQS was characterized by SEM, TEM, XRD, IR, XPS, and N2 adsorption-desorption analysis. As a carbon material with heterogeneous pores, PCQS has a BET specific surface area of 3435.21 m2 g−1, which is about 175 times higher than that of the precursor QS (19.60 m2 g−1). The PCQS had an adsorption capacity of 1778.1 mg g−1 toward rhodamine B (RhB), and the adsorption followed pseudo-second-order kinetics and the Freundlich isotherm model. The PCQS was further modified by synthesizing Fe3O4 magnetic nanoparticles on the surface of PCQS to give Fe3O4@PCQS. The adsorption capacity of Fe3O4@PCQS toward RhB reached 1156.2 mg g−1, and it could be rapidly separated from water by applying an external magnetic field. The PCQS and Fe3O4@PCQS exhibited acceptable reusability which was evaluated through ten successive adsorption/desorption cycles. In summary, the adsorption capacities of PCQS and Fe3O4@PCQS toward RhB are comparable with most current adsorbents, including the graphene-based materials, which shows that QS is a promising biomass feedstock to prepare carbon-based materials and composites.