Evaluation of Mechanism on Selective, Rapid, and Superior Adsorption of Congo Red by Reusable Mesoporous α-Fe₂O₃ Nanorods

Abstract

A large scale synthesis of mesoporous hematite (α-Fe2O3) nanorods with a high surface area of 98 m2/g and an average pore size of ∼26 nm was used for adsorption studies for pollutant dye removal. The nanorods exhibited rapid, superior, and selective adsorption efficiency toward Congo red, an organic dye present in wastewater. Highly selective adsorption capability of the mesoporous α-Fe2O3 nanorods has been attributed to the presence of abundant surface active sites with porous networks which make it highly water dispersible facilitating the formation of H-bonding and coordination effect between the -NH2 group of Congo red with its surface -OH groups and Fe3+, respectively. Adsorption studies concerning the effect of contact time, initial dye concentration, dosage of adsorbent, and effect of pH on adsorption kinetics were explored in addition to the desorption process investigation regarding the effect of solution pH from acidic to alkaline. To unravel the unresolved phenomenon toward selective adsorption of Congo red by mesoporous α-Fe2O3 nanorods beyond conventional factors (viz., surface area/porosity, electrostatic interaction, and so on), investigation was also carried out by varying the nature of the different dye molecules as well as the phase and morphology of the α-Fe2O3 nanomaterials.

Three hierarchical porous magnesium borate microspheres: a serial preparation strategy, growth mechanism and excellent adsorption behavior for Congo red

“…If the intercept (c) in the internal diffusion model is 0, it means that the internal diffusion is the only speed control step. 20 Obviously, it can be seen that c is not zero from Table S2, † indicating that this adsorption process is mainly controlled by internal diffusion control. It is also found that K d is decreasing while intercept c is increasing, indicating that the thickness of the boundary gradually increases and the adsorption rate decreases during the adsorption process.…”

“…In order to determine the interaction between the adsorbent and CR molecules, zeta potential analysis was used to investigate the surface charge of the sample particles in aqueous solution. 20 The results of zeta potential analysis are shown in Fig. S5.…”

“…7 that the model was not linear over the entire time range, but it existed a certain degree of linearity in stages, indicating that the entire adsorption process could be divided into several stages. 20 The rst linear segment was the steepest, driven by the initial high concentration of CR difference, which could be regarded as the transfer of dye molecules from bulk solution to the microsphere surface or instantaneous adsorption. The second linear segment was the gradual adsorption phase, in which the intraparticle diffusion was the rate limiting steps.…”

Adsorption Mechanism of Congo Red on Mg–Al-layered Double Hydroxide Nanocompound

“…17 Moreover, due to its complex structure, it is very stable to biological degradation and remains in the environment for a long period of time. 18 For removing CR from effluents, different types of adsorbents like activated carbon, 19 shrimp shell powder, 20 mesoporous α-Fe 2 O 3 nanorods, 21 nano-Fe 3 O 4 , 22 kaolin, 23 hydroxyapatite 24 and biogas waste slurry 25 have been used.…”

α-Fe2O3 hollow meso–microspheres grown on graphene sheets function as a promising counter electrode in dye-sensitized solar cells

“…[6][7][8][9][10] Currently, mesoporous a-Fe 2 O 3 with regular morphologies, such as nanoparticles, nanorods, mesoporous lms, mesoporous (hollow) microspheres, and mesoporous walls, have been successfully obtained by chemical and physical routes. [11][12][13] The investigation for mesoporous a-Fe 2 O 3 microspheres revealed that these microspheres with sufficient thickness increase the reactive surface together with many active surface sites, effectually accommodating the volume expansion and enhancing the electronic conductivity. [14][15][16] These favorable structure features of the mesoporous a-Fe 2 O 3 microspheres lead to promising properties for electrochemical applications.…”