Aseel Mushtaq Aljeboree

This study presents a comprehensive density functional theory (DFT) investigation into the stepwise reduction of nitrobenzene to aniline via nitroso and hydroxylamine intermediates. Two mechanistic pathways were explored: a non-catalyzed route in both gas and ethanol phases and a surface-catalyzed route facilitated by a palladium (Pd) catalyst. Geometry optimizations, thermodynamic parameters, frontier molecular orbital (FMO) analysis, and vibrational frequency (IR) simulations were carried out for all key species involved: nitrobenzene (Ph-NO₂), nitrosobenzene (Ph-NO), phenylhydroxylamine (Ph-NHOH), and aniline (Ph-NH₂). A comparison of gas-phase and solvent-phase geometries revealed solvent-induced elongation of N–O and N–H bonds, particularly in polar intermediates, consistent with ethanol’s stabilizing effect. FMO analysis showed a notable decrease in HOMO–LUMO energy gaps in the solvent phase, indicating enhanced reactivity. IR spectra further supported these findings, with observable shifts in characteristic stretching frequencies upon solvation. In the Pd-catalyzed pathway, adsorption of reactants and intermediates on the Pd surface significantly altered molecular geometries and lowered reaction energy barriers. Calculated adsorption energies and bond elongations suggest strong Pd–O and Pd–N interactions that facilitate bond activation. The overall energy profile indicates a smoother and more favorable reduction pathway on the Pd surface compared to the noncatalyzed routes. These results provide mechanistic insight into the catalytic role of Pd in hydrogenation reactions and highlight the importance of solvent effects in modulating electronic and structural properties. This comparative approach enhances our understanding of nitroarene reductions and offers valuable guidance for catalyst design and process optimization.

This study reports the preparation of potassium hydroxide-impregnated corn-cob-derived activated carbon (AC₅₀₀-K_1.1) as an efficient adsorbent for the rapid removal of the azo dye tartrazine (TZ) from aqueous solutions. The raw corn-cob (CC) powder was chemically activated at various KOH-to-biomass ratios and activation temperatures to optimise surface chemistry and porosity. Under optimal conditions (1.1 ratio at 500 °C), the prepared activated carbon exhibited an amorphous structure, a BET surface area of 276.34 m² g⁻¹, and a well-developed porous morphology. FTIR, XRD, FESEM-EDX, TEM, TGA, and BET characterisation confirmed the formation of abundant oxygen-containing acidic functional groups (which can also significantly enhance dye adsorption through electrostatic attraction and hydrogen-bond interactions). The batch adsorption studies revealed that the optimum adsorbent dosage was 0.04 g, with a contact time of 60 min, an initial dye concentration of 100 mg L⁻¹, a pH of 7, and a temperature range of 15–40 °C. The adsorption of TZ onto AC₅₀₀-K_1.1 was best represented by the Freundlich isotherm model (R² ≈ 0.9986), suggesting heterogeneous and multilayer adsorption, whereas the kinetic behavior was adequately described by the pseudo-first-order model. Thermodynamic parameters demonstrated that the adsorption process was spontaneous and exothermic (ΔH° = − 8.157 kJ mol⁻¹). Moreover, the prepared adsorbent exhibited excellent performance, achieving a maximum experimental adsorption capacity of 675.88 mg g⁻¹ and a removal efficiency of 95.07% under the optimized conditions. All of them were shown to exhibit much higher stability in regeneration experiments with up to 10 adsorption–desorption cycles and in recycling experiments. For the TZ-spiked real water samples (distilled water, tap water, and river water), significant dye uptake (> 73%) was observed with AC₅₀₀-K_1.1 and was marginally affected by ionic strength. This process establishes its practical applicability for actual real effluent decontamination. Molecular dynamics simulations performed using BIOVIA Materials Studio indicated that van der Waals interactions play a major role in the adsorption of TZ on activated carbon, with additional contributions from electrostatic interactions, hydrogen bonding, and π–π stacking. RDF and adsorption energy analyses further supported the spontaneous and stable adsorption configuration of TZ molecules on the carbon surface. These results provide molecular-level evidence supporting the experimentally observed adsorption behavior.

This study introduces a novel hydrogel design in which the combined incorporation of itaconic acid and Titanium dioxide (TiO₂) nanoparticles into an alginate–acrylic matrix creates a synergistic structure with enhanced functional groups, improved stability, and superior adsorption performance. This dual organic–inorganic modification distinguishes the material from conventional hydrogels and represents a meaningful advancement in dye-removal hydrogel systems. A Sodium Alginate (SA) based hydrogel was synthesized through free-radical copolymerization of Acrylic Acid (AA) and Itaconic Acid (IA), followed by incorporation of TiO₂ nanoparticles as functional and reinforcing additives. The structure of the SA-g-(AA-co-IA)/TiO₂ hydrogel was confirmed by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Thermogravimetric Analysis (TGA). SEM revealed a porous network with uniformly distributed TiO₂ nanoparticles, while XRD indicated a semi-crystalline matrix retaining TiO₂ crystalline phases. TGA showed improved thermal stability in TiO₂-loaded hydrogels. The material exhibited strong swelling behavior, reaching up to 800% of its dry weight, and demonstrated clear pH-responsive properties. In dye-removal tests, pristine TiO₂ showed low adsorption, whereas the composite hydrogel achieved a 91.2% removal efficiency for Brilliant Green (BG), significantly outperforming the unloaded hydrogel (73.4%). Isotherm analysis indicated that the adsorption followed the Freundlich model, indicating multilayer adsorption. The maximum adsorption capacity (Qₘ = 162.22 mg/g) indicated strong interactions between BG molecules and the hydrogel surface. These results highlight the synergistic role of TiO₂ NPs and the copolymer network in enhancing adsorption performance. The developed hydrogel represents a promising multifunctional material for wastewater treatment and other stimuli-responsive applications.

This study employed nanoclay as a low-cost, environmentally friendly adsorbent for the effective removal of malachite green (MG) dye from aqueous solutions. The nanoclay was characterized using XRD, FESEM, TEM, TGA, and FTIR. Structural and morphological analyses confirmed a porous, multilayered structure that was enhanced after adsorption. Batch experiments were conducted to evaluate the impact of key parameters, including dye concentration (10–100 mg/L), adsorbent dosage (0.02–0.15 g), contact time (5–60 min), temperature (10–40 °C), and pH (2–11). Adsorption equilibrium was reached within 60 minutes, and the highest removal efficiency (92.84%) was achieved under optimal conditions: 0.1 g of adsorbent, pH 7, 80 mg/L dye concentration, 60 minutes of contact time, and 30 °C. FTIR analysis confirmed the interaction of MG dye with hydroxyl and Si–O–Si functional groups through observed spectral shifts. FESEM and TEM images revealed increased surface porosity and dye–particle interaction. XRD analysis confirmed the crystalline nature of the nanoclay and minimal structural disruption after adsorption. Isotherm studies showed that the adsorption process followed the Freundlich model, indicating heterogeneous surface adsorption. Kinetic modelling revealed that the data fitted well with the pseudosecond-order model, suggesting chemisorption as the dominant mechanism. Thermodynamic parameters (∆G°, ∆H°, and ∆S°) indicated that the adsorption was spontaneous and exothermic. Regeneration tests over five cycles using ethanol and distilled water demonstrated that nanoclay retained over 90% of its initial efficiency, confirming its excellent reusability and structural stability. Overall, nanoclay proved to be a promising and sustainable adsorbent for treating dye-contaminated wastewater