In this study, polypyrrole-based activated carbon was prepared by the carbonization of polypyrrole at 650 °C for 2 h in the presence of four-times the mass of KOH as a chemical activator. The structural and morphological properties of the product (polypyrrole-based activated carbon (PPyAC4)), analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis, support its applicability as an adsorbent. The adsorption characteristics of PPyAC4 were examined through the adsorption of lead ions from aqueous solutions. The influence of various factors, including initial ion concentration, pH, contact time, and adsorbent dose, on the adsorption of Pb²⁺ was investigated to identify the optimum adsorption conditions. The experimental data fit well to the pseudo-second-order kinetic model (R² = 0.9997) and the Freundlich isotherm equation (R² = 0.9950), suggesting a chemisorption pathway. The adsorption capacity was found to increase with increases in time and initial concentration, while it decreased with an increase in adsorbent dose. Additionally, the highest adsorption was attained at pH 5.5. The calculated maximum capacity, q_m, determined from the Langmuir model was 50 mg/g.

The adsorption of methyl orange (MO) from aqueous solutions onto a KOH-activated polypyrrole-based adsorbent (PACK) was investigated using batch and fixed-bed column techniques. The structural, thermal, and morphological properties of the PACK, analyzed by various methods, support its applicability as an adsorbent. An adsorption kinetic study revealed a preferably pseudo-second-order (R² = 0.9996) and rate-limiting step controlled by both film and intra-particle diffusions. The thermodynamic adsorption tests resulted in negative ΔG°, ΔH°, and ΔS° values, which decreased as the temperature and concentration increased, indicating the spontaneous and exothermic adsorption over 25–45 °C. The adsorption isotherms fit the experimental data in the order of Langmuir ≈ Freundlich > Temkin, with evidence of adsorption operating well via the monolayer physical adsorption process, and maximum monolayer adsorption ranging from 520.8 to 497.5 mg/g. The breakthrough curve of the fixed-bed column experiment was modeled using the Thomas, Yoon–Nelson, and Hill models, resulting in an equilibrium capacity of 57.21 mg/g. A 73% MO recovery was achieved, indicating the possibility of column regeneration. Compared to other adsorbents reported, PACK had comparable or even superior capacity toward MO. For cost-effectiveness, similar nitrogen-containing polymeric wastes could be exploited to obtain such excellent materials for various applications.

Plant-based nanoparticles (NPs) have many advantages over physical and chemical methods and featured with several medicinal and biological applications. In this study, zinc oxide NPs (ZnO-NPs) were synthesized using pomegranate peel aqueous extract, under mild and ecofriendly conditions. The ZnO-NPs structure, morphology, and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and ultraviolet-visible (UV-Vis). Antibacterial activity against Gram-positive and Gram-negative strains were evaluated using the disk diffusion method. The effect of extract concentration (20, 30, and 40mL) on the final properties of NPs, as well as the NPs concentration used for antibacterial test (50, 100, and 200mg/mL), were also studied. The results indicate a hexagonal structure with particle size increases as extract concentration increase (D =18.53, 29.88, and 30.34nm), while the optical bandgap was decreased (E_g=2.87, 2.80, and 1.92eV). The antibacterial activity of ZnO-NPs indicated high efficiency, similar or even higher than that of the control azithromycin, more against S. aureus, increased with NPs concentration, and preferred when NPs prepared from high extract concentration. Such promising physicochemical properties support the usefulness and efficacy of the reported bio-route for production of ZnO-NPs and may encourage its application for large-scale production.

In the present work, a nitrogen-rich activated carbon (PAnAC) was prepared using polyaniline (PAn) as a precursor to represent one possible conversion of nitrogen-containing polymeric waste into a valuable adsorbent. PAnAC was fabricated under the chemical activation of KOH and a PAn precursor (in a 4:1 ratio) at 650 °C and was characterized using FTIR, SEM, BET, TGA, and CHN elemental composition. The structural characteristics support its applicability as an adsorbent material. The adsorption performance was assessed in terms of adsorption kinetics for contact time (0–180 min), methyl orange (MO) concentration (C₀ = 50, 100, and 200 ppm), and adsorbent dosages (20, 40, and 80 mg per 250 mL batch). The kinetic results revealed a better fit to a pseudo-second-order, specifically nonlinear equation compared to pseudo-first-order and Elovich equations, which suggests multilayer coverage and a chemical sorption process. The adsorption capacity (q_e) was optimal (405.6 mg/g) at MO C₀ with PAnAC dosages of 200 ppm and 40 mg and increased as MO C₀ increased but decreased as the adsorbent dosage increased. The adsorption mechanism assumes that chemisorption and the rate-controlling step are governed by mass transfer and intraparticle diffusion processes.

The aim of this study was to investigate the potential advantage of ZnFe₂O₄-incorporated activated carbon (ZFAC), fabricated via a simple wet homogenization, on the removal of cationic dye crystal violet (CV) from its aqueous solutions. The as-prepared ZFAC nanocomposite was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and ultraviolet–visible (UV–Vis). Batch adsorption operating conditions such as the pH (3–11), CV concentration (25–200 ppm), ZFAC dose (10–50 mg), temperature (23–45 °C), and contact time were evaluated. The results indicate pH-dependent uptake (optimum at pH 7.2) increased with temperature and CV concentration increase and decreased as adsorbent dose increased. Modeling of experimental data revealed better fit to the Langmuir than Freundlich and Temkin isotherms, with maximum monolayer capacities (Q_m) of 208.29, 234.03, and 246.19 mg/g at 23, 35, and 45 °C, respectively. Kinetic studies suggest pseudo-second order; however, the intra-particle diffusion model indicates a rate-limiting step controlled by film diffusion mechanism. Based on the thermodynamic parameters, the sorption is spontaneous (−ΔG°), endothermic (+ΔH°), and random process (+ΔS°), and their values support the physical adsorption mechanism. In addition to the ease of preparation, the results confirm the potential of ZFAC as a purifier for dye removal from polluted water.

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C₀) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (q_e, mg/g) was found to have increased as MO C₀ increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C₀ (200 ppm) and adsorbent dose (40 mg), the calculated q_e values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor’s importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route’s usefulness in converting nitrogenous-species waste into valuable materials.