Red mud derived facile hydrothermal synthesis of hierarchical porous α-Fe2O3 microspheres as efficient adsorbents for removal of Congo red

Towards the malignant impact of red mud on the environment and water pollution caused by organic dyes, affluent residual iron ions in red mud are recovered and converted into functional hierarchical porous alpha-Fe2O3 microspheres (HP alpha-Fe2O3 MSs) comprising nanosheets (S-BET: 78.75 m(2) g(-1), pore volume: 0.35 cm(3) g(-1), mean pore diameter: 15.92 nm) via a facile hydrothermal route (180 degrees C, 12.0 h), with the presence of urea and CTAB. When employed as the adsorbents for Congo red (CR) in simulated wastewater, the adsorption isotherm is well fitted with Langmuir isotherm model, and the corresponding maximum adsorption capacity is determined as 342.57 mg g(-1), superior to that of most referred adsorbents in literatures. Meanwhile, the adsorption kinetic data can be well interpretated via the pseudo-second-order and intra-particle diffusion models. Moreover, the red mud derived HP alpha-Fe2O3 MSs can be easily regenerated and reused with satisfactory chemical, morphological and structural stability.