Dyes are classified as one of the major pollutants of water. They have negative impacts not only on environment but also on human health. In fact, wastewater that contains these harmful substances requires many types of treatments. Therefore, alternative methods and adsorption agents are needed. Herein, we propose to evaluate the decolorization of methylene blue (MB) and methyl orange (MO) as two models of soluble dyes from water using chitin and chitosan-graft-polyacrylamide. Furthermore, the applicability of these biomacromolecules as alternative adsorption agents, their sticking probability and desorption were also examined. Experimental parameters such as dye concentration, contact time, pH solution, adsorbent dosage and temperature were thoroughly examined for the grafted chitosan and chitin. The activation energy ( $E_a$ ) and the thermodynamic variables (i.e., standard Gibb’s free energy ( $\Delta G^0$ ), standard enthalpy ( $\Delta H^0$ ), and standard entropy ( $\Delta S^0$ )) were determined using the Van’t Hoff and Arrhenius equations. The sticking probability ( $S$ *) model for MB and MO removal by chitin and the chitosan derivative demonstrated that both dyes were successfully removed under the proposed conditions. Desorption studies of MB and MO showed the reusability of both materials, suggesting their application for removing dyes from aqueous solution.

Over the past few years, population growth, industrial progress and climate change have led to water scarcity. Thus, water pollution caused by hazardous soluble and insoluble pollutants, such as toxic metals and phenolic compounds, has become an important problem that should be dealt with urgently. For instance, new methods have been introduced to convert low-cost raw materials (i.e. coal fly ash and coal bottom ash “wastes-to-resource”) into suitable materials for new cleaner production to achieve sustainability goals in wastewater-containing toxic metals and phenolic compounds purification. Obviously, the functionalization of coal fly ash and bottom ash enhances the ability of coal ash-based entities as potential materials in wastewater remediation technologies. Here, we review the application of coal ashes, including coal bottom ash and fly ash-based materials for toxic metals and phenolic compounds removal. We also examine their structural properties and functionalization to enhance their affinities toward these pollutants in aqueous environment. Even though each process has its own benefits and limitations, coal ash-based materials appear promising for the removal of toxic metals and phenolic compounds using adsorption, membrane filtration, and photocatalysis. Overall, the study on the availability of coal fly ash and bottom ash for wastewater treatment have resulted in high removal efficiencies for toxic metals and phenolic compounds. In the future, new recycling methods for coal ashes as new water purification agents should be further studied and advanced processes should be investigated in order to achieve wastewater remediation purposes. Graphical Abstract

Photocatalytic NO removal is usually accompanied by the generation of NO₂, an intermediate with a higher toxicity than NO. Therefore, it is critically important to develop new photocatalysts capable of NO selective conversion. Herein, we report on the synergistic roles of cyano and hydroxyl functional groups in photocatalytic NO removal. According to the results, the NO₂ production efficiencies on cyano/hydroxyl-group-modified g-C₃N₄ (DCN-O-R) was limited to 4.8%, which was lower than that of cyano-group-modified g-C₃N₄ (DCN, 38.6%) and pure g-C₃N₄ (CN, 50.0%). Meanwhile, the photocatalytic NO conversion efficiency over DCN-O-R was higher than that of DCN and g-C₃N₄. It was found that the insertion of cyano groups favorably changes the energy band of g-C₃N₄ towards the generation of •O₂⁻. NO can only be oxidized to NO₂ by the photogenerated holes. When NO₂ is adsorbed on the surface of hydroxyl groups, it can be further oxidized to the product NO₃⁻ by •O₂⁻. The synergistic effect of bifunctional groups regulates the conversion pathway from NO→NO₂ to NO→NO₂→NO₃⁻. This work provides a strategy to abate toxic intermediates during the NO removal process, underlining the importance of surface/interface molecular engineering in regulating catalytic reaction pathways.

A novel (E)-1-(4-methylbenzylidene)-4-(3-isopropylphenyl) thiosemicarbazone was synthesized in a one-pot four-step synthetic route. Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonances (NMR), single-crystal X-ray diffraction, and UV-visible absorption spectroscopy were utilized to confirm the successful preparation of the title compound. Single-crystal data indicated that the intramolecular hydrogen bond N(3)-H(3)···N(1) and intermolecular hydrogen bond N(2)-H(2)···S(1) (1 − x, 1 − y, 1 − z) existed in the crystal structure and packing of the title compound. Besides the covalent interaction, the non-covalent weak intramolecular hydrogen bond N(3)-H(3)···N(1) discussed by atoms in molecules (AIM) theory also functioned in maintaining the title compound’s crystal structure. The strong intermolecular hydrogen bond N(2)-H(2)···S(1) (1 − x, 1 − y, 1 − z) discussed by Hirshfeld surface analysis played a major role in maintaining the title compound’s crystal packing. The local maximum and minimum electrostatic potential of the title compound was predicted by electrostatic potential (ESP) analysis. The UV-visible spectra and HOMO-LUMO analysis revealed that the title compound has a low ΔE_HOMO–LUMO energy gap (3.86 eV), which implied its high chemical reactivity due to the easy occurrence of charge transfer interactions within the molecule. Molecular docking and in vitro antifungal assays evidenced that its antifungal activity is comparable to the reported pyrimethanil, indicating its usage as a potential candidate for future antifungal drugs.