Preparation of Carbon–Iron Composites Materials and Studies of Its Adsorption Properties for the Methylene Blue

A green, non-polluting magnetic iron–carbon composite material FCH with humic acid as a raw material was synthesized by high-temperature oxidation–reduction method, and was first applied to the adsorption and removal of methylene blue in water. And it has lower synthesis cost. The morphology and microstructure of the samples were characterized by scanning electron microscopy, X-ray diffractometer, Thermal analysis, and Fourier transforms infrared spectroscopy was used to analyze the composition and structure of materials, and the magnetic strength of the samples was analyzed by using a vibrating sample magnetometer. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and the Langmuir and Freundlich models were applied to describe the adsorption isotherms. The results showed that the equilibrium adsorption data were found to fit better to the Langmuir adsorption model and the kinetic process of adsorption could be described by the pseudo-first-order model. Compared with humic acid, iron–carbon composite materials can effectively improve the adsorption rate and adsorption capacity of methylene blue, and the adsorption capacity is as high as 34.45 mg/g within 30 min. Moreover, the material has super paramagnetic strength, and the composite material can be quickly separated from the aqueous solution in the presence of an external magnetic field. It finds that the material had good reusability through regeneration experiments.