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In low- to middle-income communities, the lack of affordability of conventional sanitary products during menstrual cycles can cause psychological and health issues, ultimately affecting their quality of life. It is crucial to develop alternative products that are affordable and accessible to all while also promoting menstrual health and hygiene. Super absorbent polymers (SAPs) are a vital component in current disposable sanitary pads and nappies. However, these SAPs are often non-biodegradable and non-biocompatible. Therefore, the use of eco-friendly materials for the production of SAPs is gaining popularity in the hygiene industry, as it offers a means to reduce the carbon footprint and environmental impact associated with traditional SAPs made from non-renewable petroleum-based materials. SAPs made from polysaccharides often have naturally occurring antibacterial properties, making them appealing for commercial applications in sanitary products such as sanitary pads. In addition, the move toward reusable sanitary pads with antibacterial properties can significantly reduce waste generated by single-use products and prevent the growth of bacteria, improving the safety and hygiene of the product. Furthermore, computational modeling and artificial intelligence are now important tools in SAP synthesis, providing advantages such as predicting polymer properties, rationalizing synthesis pathways, and improving quality control. These tools can reduce synthesis costs by eliminating the need for trial-and-error approaches in polymer synthesis, ultimately promoting more affordable products for end users. Overall, these advancements in polymer synthesis and material design can help to create a more sustainable industry and promote menstrual hygiene and product accessibility to those who need it most. [ABSTRACT FROM AUTHOR]

Malachite green (MG) dye and cadmium metal ion are toxic pollutants that should be removed from aqueous environment. The recent study aimed to examine the adsorption behavior of MG dye and Cd (II) from wastewater onto low-cost adsorbent prepared by activating corn silk with nitric acid (ACS) and characterized by SEM, FTIR, XRD, BET and TGA. The optimum MG and Cd (II) adsorption was observed at pH 7 and pH 9 and maximum uptake of both pollutants was at 0.5 g dosage, 60 mins contact time and 20 mg/L initial concentration. The retention of dye and metal ion by the studied adsorbent was best fit to Langmuir isotherm and Pseudo-second order kinetics. The maximum monolayer coverage capacity of ACS for MG dye and Cd (II) ion was 18.38 mg/g and 25.53 mg/g, respectively. Thermodynamic studies predicted a spontaneous reaction with exothermic process for MG dye whereas an endothermic and spontaneous process was confirmed for Cd ion based on estimated parameters. The adsorption mechanism of MG dye and Cd (II) uptake was by combination of electrostatic interaction, pore diffusion, ion exchange, pie-pie attraction, hydrogen bonding, and complexation. The adsorbed pollutants were effectively desorbed with significant regeneration efficiency after successive five cycles that proved the potential of low-cost biosorbent for selective sequestration of cationic dye and divalent metal ion from effluents. The use of nitric acid-modified corn silk has been reported to enhance its adsorption performance over the unmodified cob for pollutants such as cadmium ions and malachite green. Although there may be no recorded data on the adsorption efficiency of acid-treated corn silk for selected pollutants, it can be considered as a prospective bio-sorbent owing to its chemical composition and functional groups for exchange of hydrogen ions for other cations. [ABSTRACT FROM AUTHOR]

• A series of deep eutectic solvents (DESs) catalysts with varying ratios were successfully synthesized. • The DES with a composition of [TEA-12][OH]:[Q-COOH]- 0.9: 0.1 had the lowest melting point of 100.17 °C. • The efficiency of the catalysts for CO 2 fixation was evaluated and [TEA-12][OH]:[Q-COOH]−0.9:0.1 proved to be the most effective catalyst with a TOF of 1466 h−1. • Exceptional conversions were observed for epoxides with electron-withdrawing function groups, while electron-donating functional groups showed lower activity. The accumulation of greenhouse gases (GHG) in the atmosphere, with carbon dioxide being the most significant contributor, is a major environmental problem as it impacts significantly on climate change. The development of new catalysts and chemical reactions that incorporate CO 2 are needed to reduce its further emission significantly. Deep eutectic solvents (DES) have garnered increasing attention as environmentally friendly catalysts in the cycloaddition of carbon dioxide (CO 2) with epoxide substrates to produce cyclic carbonates. Their appeal stems from their facile synthesis, cost-effectiveness, low vapour pressure, and thermal stability. In this study, we present a convenient solvent-free synthesis method for nine deep eutectic solvents (DES), utilizing varying compositions of quaternary amine salts (N,N,N -triethyldodecan-1-aminium hydroxide, [TEA-12][OH]) and quinaldic acid [Q-COOH]. These deep eutectic solvents were thoroughly characterized using several techniques, including FTIR, NMR, DSC, and TGA. Moreover, their efficacy for the solvent-free fixation of CO 2 to cyclic carbonates were evaluated. Among the tested compositions, [TEA-12]:[Q-COOH] (0.9:0.1) exhibited the lowest melting point (100.17 °C) and highest catalytic activity, showcasing an optimized Turn-Over Frequency (TOF) of 1466 h−1. This remarkable result represents a significant advancement in the application of DES for CO 2 fixation, exceeding the previous highest catalytic activity observed with TBAB:Citric acid (2.5:1) by more than tenfold. [Display omitted] [ABSTRACT FROM AUTHOR]

• Two isoreticular aluminum-based MOFs with azobenzene (Al-AZB) and stilbene (Al-STB) organic linkers, respectively, were synthesized. • Nitrogen functionalization (Al-AZB) enhanced the thermal stability and surface area of the MOFs. • Celestine blue dye adsorption by the MOFs followed the Freundlich isotherm model. • The pseudo-second-order model provided the best fit to the adsorption data and involves a film diffusion mechanism. • The MOFs were successfully regenerated using DMF and effectively reused for dye adsorption. Nitrogen functionalized metal-organic-frameworks (MOFs) exhibit enhanced dye adsorption capacity compared to their counterparts without nitrogen functionalization. Typically, this functionalization is in the form of nitrogen side groups on the benzene/imidazole ring. Research on the effect of nitrogen atoms included within the rigid MOF structure on adsorption is lacking. In this work, two isoreticular aluminum-based MOFs were synthesized, functionalized with azobenzene (Al-AZB) and stilbene (Al-STB) organic linkers, respectively, with the former having nitrogen atoms within its rigid MOF structure. The effect of these nitrogen atoms on the physical properties and dye adsorption of the MOFs was tested. The MOFs were characterized and analyzed by NMR, FTIR, TGA, PXRD, SEM, BET, and UV/Vis. The characterizations confirmed the successful synthesis of the isoreticular MOFs, with Al-AZB exhibiting photoresponsive properties. The nitrogen functionalization enhanced the thermal stability and surface area of the MOFs as Al-AZB exhibited higher thermal stability (380 °C) and surface area (2500 m2/g) than Al-STB (345 °C; 1500 m2/g). The celestine blue dye adsorption by the MOFs followed the Freundlich isotherm model. A maximum monolayer adsorption capacity of 5224 mg/g and 5604 mg/g was obtained for Al-AZB and Al-STB, respectively, as predicted by the Langmuir model. Kinetic analysis showed that the pseudo-second-order model provided the best fit to the adsorption data and involves a film diffusion mechanism. The MOFs were successfully regenerated using dimethylformamide and effectively reused for dye adsorption. The evaluation of the mode of adsorption revealed the participation of van der Waals interactions and H-bonding in which the latter played a major role. The results showed that the nitrogen functionalization within the MOF's structure influenced the physical properties of the MOF as well as its dye adsorption characteristics. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) are porous hybrid crystalline materials that consist of organic linkers coordinated to metal centres. The trans–cis isomerisation kinetics of the azobenzene-4,4′-dicarboxylic acid (AZB(COOH)2) precursor, as well as the Al3+ (Al-AZB)- and Zr4+ (Zr-AZB)-based MOFs with azobenzene-4,4′-dicarboxylate linkers, are presented. The photo-isomerization in the MOFs originates from singly bound azobenzene moieties on the surface of the MOF. The type of solvent used had a slight effect on the rate of isomerization and half-life, while the band gap energies were not significantly affected by the solvents. Photo-responsive MOFs can be classified as smart materials with possible applications in sensing, drug delivery, magnetism, and molecular recognition. In this study, the MOFs were applied in the dye adsorption of congo red (CR) in contaminated water. For both MOFs, the UV-irradiated cis isomer exhibited a slightly higher CR uptake than the ambient-light exposed trans isomer. Al-AZB displayed a dye adsorption capacity of over 95% for both the UV-irradiated and ambient light samples. The ambient light exposed Zr-AZB, and the UV irradiated Zr-AZB had 39.1% and 44.6% dye removal, respectively. [ABSTRACT FROM AUTHOR]

The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al3+ (Al-AZB) and Zr4+ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 ° C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m2/g) than the Zr-AZB (1098 m2/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm3/g and 0.35 cm3/g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption. [Display omitted] • Syntheses of Zr- and Al-based MOFs with Azobenzene dicarboxylate linkers. • Trans-cis photo-isomerization of the MOFs in suspension. • Al-based MOF has higher dye adsorption capacity than the Zr-based MOF. • Dye adsorption by the MOFs is a pseudo-second order kinetic process. • Both MOFs were successfully regenerated and reused for dye adsorption. [ABSTRACT FROM AUTHOR]