A novel red mud@sucrose based carbon composite: Preparation, characterization and its adsorption performance toward methylene blue in aqueous solution

A novel carbonaceous composite material containing red mud and sucrose based carbon spheres, named as RM@ C composite, has been prepared via one-step hydrothermal carbonization (HTC) process. The prepared RM@ C composite is an environmentally friendly material because it utilized the red mud, a waste emerged from aluminium manufacturing, and sucrose, a renewable carbon precursor, in the one-step HTC process. After characterization of the composite material by XRD, FT-IR, TGA and SEM-EDX techniques, and specific surface area, pore size distribution and pH of zero point of charge (pHzpc) measurements, its batch adsorption performance was examined on the methylene blue in aqueous solution. The effective adsorption was achieved at pH = 11. At pH 11, the adsorption performance of RM@ C was superior to both red mud and naked carbon spheres. Kinetic analysis revealed that adsorption equilibrium is attained in 60 min and it is governed by the pseudo-second-order kinetic model together with intra-particle diffusion model. On the basis of isotherm analysis, Langmuir isotherm model better expressed the experimental data than Freundlich model. The Langmuir adsorption capacity of the composite material toward methylene blue was determined as 76.92 mg/g. The adsorption of methylene blue gradually decreased with increasing the ionic strength of the solution. The RM@ C composite can be reused at least five cycles of adsorption-desorption without significant changes in the adsorption efficiency.