A novel composite of poly(3-aminobenzoic acid) (PABA) and a cobalt zeolitic benzimidazolate framework (CoZIF) has been studied for the production of hydrogen through the hydrogen evolution reaction (HER). The structural characteristics and successful synthesis of PABA, CoZIF and the PABA/CoZIF composite were confirmed and investigated using different techniques. Probing-ray diffraction for phase analysis revealed that the composite showed a decrease and shift in peak intensities, confirming the incorporation of CoZIF on the PABA backbone via in situ polymerization, with an improvement in the crystalline phase of the polymer. The thermal stability of PABA was enhanced upon composite formation. Both scanning electron microscopy and transmission electron microscopy showed that the composite had a rough surface, owing to an interaction between the CoZIF and the external surface of the PABA. The electrochemical hydrogen evolution reaction (HER) performance of the synthesized samples was evaluated using cyclic voltammetry and Tafel analysis. The composite possessed a Tafel slope value of 156 mV/dec and an α of 0.38, suggesting that the Volmer reaction coupled with either the Heyrovsky or Tafel reaction as the rate determining step. The fabricated composite showed high thermal stability and excellent tolerance as well as high electroactivity towards the HER, showing it to be a promising non-noble electrocatalyst to replace Pt-based catalysts for hydrogen generation.

Carbon-based adsorbents were produced from onion skin waste for the adsorption of methylparaben from contaminated water. The biomass-derived carbon was characterized using various established analytical techniques. The microscopic examinations revealed micro- and mesoporous structures with a partially disordered network of the graphenic carbon-like multilayer structure, confirmed by XPS and Raman spectra. XRD analysis revealed that the biomass-derived carbon is largely amorphous with the graphitic phase also confirmed. Aside from the prominence of sp² hybridized carbon, FTIR analysis shows the existence of moieties and functional groups that may facilitate the sorption of methylparaben or other organic pollutants if explored. The adsorption isotherm revealed that the multilayer adsorption model (Freundlich) best fits experimental data with an SSE value of 0.454. A complex adsorption process is suspected between methylparaben and OSDC, and the physicochemical properties of the sorbate and sorbent played a huge role in the sorption process. The plausible interactions include van der Waals, hydrophobic bonding, hydrogen bonding, π-π stacking, and pore-filling mechanisms, leading to a hysteretic sorption process. The optimal removal efficiency and adsorption maxima of ~ 100% and ~ 8200 mg/g are obtainable at optimum process conditions. Therefore, waste valorization and adsorption performance achieved in this study suggest a sustainable and cost-effective pathway for pollution remediation.

Rapid advances in industries and agricultural practices have recently released various toxic pollutants into aquatic systems. Among other pollutants, pharmaceuticals, have been detected in environmental aquatic systems at levels that have negative health impacts on both humans and animals. This study employed an in situ chemical co-precipitation method to fabricate a magnetic amine-based metal organic framework nanocomposite. This nanocomposite was successfully synthesised and applied as a photocatalytic material for the mineralization of acebutolol (ACE) in water. The prepared materials, including the nanocomposite (Fe₃O₄@NH₂-MIL-101(Cr)) were characterised using transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The optoelectronic properties were determined using photoluminescence (PL), electrochemical impedance spectroscopy, diffuse reflectance spectroscopy (UV-Vis DRS) and ultraviolet–visible spectroscopy. The photocatalytic efficacy of the nanocomposite was assessed via the degradation of acebutolol under visible light illumination. The results indicate that adsorption–desorption equilibrium was attained after 60 min in the dark, and 98.3% degradation efficiency was achieved after 180 min with the light on. According to scavenging experiments, superoxide radicals (·O₂ ⁻) were the main reactive oxygen species (ROS) during photodegradation. The Nyquist plot obtained from electrochemical impedance spectroscopy (EIS) showed that the Fe₃O₄@NH₂-MIL-101(Cr) nanocomposite had a reduced charge transfer resistance (R_ct), indicating separation and accelerated transfer of charges at the interface. The obtained electron lifespan (τ_e) supported the results, and was found to be higher for Fe₃O₄@NH₂-MIL-101(Cr) compared to NH₂-MIL-101(Cr) and pure Fe₃O₄. The photocatalytic mechanism revealed that the formed heterojunction followed a Z-scheme mechanism.

The ubiquity of diclofenac (DCF) in the environment has raised significant concerns. Diclofenac is a non-steroidal anti-inflammatory drug that has been found in various environmental matrices at minimum concentrations that are harmful to aquatic and terrestrial organisms. Traditional wastewater treatment plants (WWTPs) are not fully equipped to remove a range of pharmaceuticals, and that explains the continued ubiquity of DCF in surface waters. In this study, an Fe₃O₄/SiO₂ nanocomposite prepared from acid mine drainage and coal fly ash was applied for the removal of DCF from wastewater. Major functional groups (Si–O–Si and Fe–O) were discovered from FTIR. TEM revealed uniform SiO₂ nanoparticle rod-like structures with embedded dark spherical nanoparticles. SEM-EDS analysis discovered a sponge-like structure fused with Fe₃O₄ nanoparticles that had significant Si, O, and Fe content. XRD demonstrated the crystalline nature of the nanocomposite. The surface properties of the nanocomposite were evaluated using BET and were 67.8 m²/g, 0.39 cm³/g, and 23.2 nm for surface area, pore volume, and pore size, respectively. Parameters that were suspected to be affecting the removal process were evaluated, including pH, nanocomposite dosage, and sample volume. The detection of DCF was conducted on high-performance liquid chromatography with diode-array detection (HPLC-DAD). Under optimum conditions, the adsorption process was monolayer, and physisorption was described using the Langmuir and Dubinin-Radushkevich (D-R) isotherm models. The kinetic data best fitted the pseudo-first order kinetic model, indicating a physisorption adsorption process. The thermodynamic experimental data confirmed that the adsorption process was spontaneous. The results obtained from real water samples showed 95.28% and 97.44% removal efficiencies from influent and effluent: 94.83% and 88.61% from raw sewage and final sewage, respectively. Overall, this work demonstrated that an Fe₃O₄/SiO₂ nanocomposite could be successfully prepared from coal fly ash and acid mine drainage and could be used to remove DCF in wastewater.