Highly adsorptive removal of Congo red from aqueous solution using TiO doped with Fe nanoparticles

Fe-doped TiO nanoparticles (NPs) were synthesized via the solvothermal method to develop a cost-effective adsorbent for Congo red (CR) removal from aqueous solutions. The synthesized NPs were characterized by XRD, FTIR, FE-SEM, EDXS, and nitrogen adsorption isotherms. Results confirmed that the incorporation of Fe into the TiO lattice effectively decreased the particle size, increased the Brunauer–Emmett–Teller (BET) surface area, and therefore improved the adsorption capacity of TiO doped with Fe. The anatase nanocrystalline phase with spherical-shaped particles of a mean diameter of 14.8 nm was produced for Fe-doped TiO. The analysis of nitrogen adsorption isotherms revealed that the BET surface area of TiO doped with Fe was as high as 194.82 m.g, which was larger than that of pure TiO (161.36 m.g). The equilibrium adsorption data were compatible with the Langmuir isotherm model; the maximum adsorption capacity of CR by TiO doped with Fe reached 400 mg.g at 30 °C, which was considerably higher than that of pure TiO (238 mg.g). Moreover, the equilibrium adsorption time of as-synthesized Fe-doped TiO NPs was significantly shorter than that of other metal oxides nanostructures in previous works, making them excellent candidates for wastewater treatment. Further studies demonstrated that the adsorption of CR onto the TiO doped with Fe followed a pseudo-second-order kinetic model; the negative values of ∆G° and positive values of ∆H° indicated that the adsorption of CR by TiO doped with Fe was spontaneous and endothermic in nature. Graphical Abstract: [Figure not available: see fulltext.]