A phytic acid modified CoFe2O4 magnetic adsorbent with controllable morphology, excellent selective adsorption for dyes and ultra-strong adsorption ability for metal ions

Phytic acid (PA) modified magnetic CoFe2O4 (PA/CFO) composites were successfully synthesized by a facile one-pot microwave hydrothermal method. The coating of PA onto the CFO NPs is clearly confirmed by FTIR, SEM and TEM. The characterization of the crystallinity, morphology and magnetic property reveals the effect of PA addition on the physical properties of the samples. XRD patterns indicate that, due to the addition of PA, crystal growth of the samples is inhibited, and, degree of crystallinity decreases. Interestingly, from SEM and TEM images, when the additive amount of PA increases from 0 to 1.2 g, the heterogeneous particles become smaller and tend to form uniform size. Then, through the self-assembly of the particle, the nanorods and nanosheets appear, and finally coral-like structure forms. In comparison with pure CFO, the PA/CFO composites show lower Ms and superparamagnetic behavior. Owing to the negatively charged surface of PA/CFO, a marked selective adsorption for cationic methylene blue (MB) and anionic Congo red (CR) is observed in PA/CFO nanocomposites. Meanwhile, PA/CFO exhibits excellent adsorption behavior for the metal ions (Mg2+, Cu2+, Zn2+ and Pb2+), where the equilibrium adsorption capacity is 227.3, 156.9, 126.4, 666 mg g−1, respectively. The corresponding adsorption kinetics and isotherms are analyzed. From Langmuir model, the maximum adsorption capacity for Pb2+ ion of the sample S5 is 833.8 mg g−1. It is worthy to note that the excellent adsorption property for Pb2+ attributes to the synergistic effect of ion exchange, chelate effect and electrostatic interaction. The present work gives a new route to develop ferrite-based composites as magnetic adsorbents for the removal of dyes and metal ions in the aqueous water.