Statistical modeling and optimization of dexamethasone adsorption from aqueous solution by Fe3O4@NH2-MIL88B nanorods: Isotherm, Kinetics, and Thermodynamic

The presence of pharmaceutical compounds in the environment poses a significant threat to human and aquatic animal health. Dexamethasone (DEX), a synthetic steroid hormone with endocrine-disrupting effects, is one such compound that needs to be effectively removed before discharging into the environment. This research presents a novel approach utilizing magnetically recyclable Fe3O4@NH2-MIL88B NRs as an efficient adsorbent for the treatment of DEX from aqueous solutions. The synthesized adsorbent was characterized by X-ray diffraction (XRD), scanning microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), diffuse reflectance spectra (DRS), and Fourier transform infrared spectroscopy (FTIR). Response surface methodology based on central composite design (RSM-CCD) was employed to optimize DEX removal efficiency by determining the optimal conditions, including pH, adsorbent dose, time, and DEX concentration. Under the optimized conditions (pH: 5.53, adsorbent dose: 0.185 g/L, time: 16.068 min, and DEX concentration: 33.491 mg/L), Fe3O4@NH2-MIL88B NRs revealed remarkable DEX adsorption efficiency of 91 ± 1.34% and adsorption capacity of 180.01 mg/g. The Langmuir isotherm and pseudo-second-order kinetic model were found to fit well with the experimental data, indicating a monolayer and chemical adsorption process. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The study also investigated the inhibitory effect of background ions on DEX removal by Fe3O4@NH2-MIL88B NRs. Magnesium exhibited superior competitive ability with dexamethasone to occupy the active sites of the adsorbent compared to other background ions. The reuse of the adsorbent over ten consecutive cycles resulted in a 39.46% decrease in removal efficiency. The Fe3O4@NH2-MIL88B NRs are surrounded by abundant amounts of functional groups and π-electrons bands that can play a key role in the adsorption and separation of DEX from aqueous environments. The promising results obtained under real conditions highlight the potential of Fe3O4@NH2-MIL88B NRs as a practical and efficient adsorbent for the removal of DEX and other similar corticosteroids from aqueous solutions.

Adsorptive mercaptan removal of liquid phase using nanoporous graphene: Equilibrium, kinetic study and DFT calculations

This research investigated the adsorption of tertiary butyl mercaptan (TBM) from liquid phases by using nanoporous graphene. Nanoporous graphene synthesized through chemical vapor deposition method was characterized using Brunauer-Emmett-Teller method, transmission electron microscopy, field-emission scanning microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. The TBM adsorption equilibrium was investigated by using Langmuir, Freundlich, and Tempkin models. The obtained results were in good agreement with the Freundlich isotherm. The adsorption kinetics of this process was modeled by the pseudo-first-order, pseudo-second-order, and intraparticle models. The adsorption rate was obtained according to the pseudo-second-order model. The satisfactory results indicated that nanoporous graphene can be used as a good carbon nanostructure sorbent in mercaptan removal. The process reduced the sulfur content from 300 ppm to less than 10 ppm which was the standard level in environmental regulations. The capacity for TBM removal was achieved at 4.4 gr S/gr adsorbent. The desulfurization efficiency was revealed about 96.3% for nanoporous graphene at 298 K and 24 h. Moreover, density functional theory calculations were used to determine the stable configuration, adsorption energy, and electronic structure of different configurations of TBM adsorbed onto a graphene surface. TBM physically adsorbed onto the graphene surface with adsorption energies of approximately - 25 kJ/mol was indicated from DFT calculations.

Surface modification of banana stem fibers via radiation induced grafting of poly(methacrylic acid) as an effective cation exchanger for Hg(ii)

A low cost adsorbent, banana stem fibers (BSFs), was used for modification by grafting with methacrylic acid via three free radical generation methods.