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Abstract: Global consumption and discharge of palladium (Pd) have raised environmental concerns but also present an opportunity for the sustainable recovery and reuse of this precious metal. Adsorption has proven to be an efficient method for the selective recovery of Pd from industrial wastewater. This study investigated a hydrazone-linked covalent organic framework (Tfpa-Od COF) as a potential material for the high-affinity adsorption of Pd2+ ions from wastewater, achieving a Kd value of 3.62 × 106 mL g–1. The electron-rich backbone of the COF contributes to its excellent selective removal efficiency (up to 100%) and adsorption capacity of 372.59 mg g–1. Furthermore, the Pd-adsorbed COF was evaluated as a sustainable catalyst for the Suzuki–Miyaura coupling reaction, demonstrating good catalytic conversion and recyclability. This work attempts to showcase a protocol for reusing waste palladium generated in water to fabricate heterogeneous catalysts and, thereby, promote the circular economy concept.
Keywords: covalent organic frameworks, sustainability, catalysis, palladium adsorption, water purification
Published in RUNG: 22.08.2024; Views: 747; Downloads: 6
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Abstract: The aimof this study was to develop composite films from cellulose, chitosan and polyvinyl alcohol to obtain environmentally friendly materials. Toughness, burst strength, distance to burst and water adsorption properties weremeasured and analysed as a function ofcellulose (3–5%), chitosan (0–1%) andpolyvinyl alcohol (0–4%) con- tents. Polynomial modelswere obtained. Light-barrier properties, transparency, morphology, structural and ther- mal analyses were assessed. Results showed that chitosan and polyvinyl alcohol enhanced the mechanical properties of cellulose-based films. Toughness values ranged from 0.47 to 8.01 MJ/m3, burst strength values ranged from 929 to 6291 g, distance to burst ranged from 1.25 to 2.52 mm and water adsorption values ranged from52.30 to 143.56%. Cellulose and chitosan improved the UV light protection effect ofthe films. However, PVA increased the transmittance meanwhile improved the film transparency. FT-IR and DSC showed an interaction between the components ofthe films. Results showed that it is feasible to obtain cellulose-chitosan-polyvinyl alcohol composite films with improvedmechanical properties, high capacity to adsorbwater, good barrier properties against UV radiations and adequate transparency value. These properties could be useful for potential packaging applications in the food industry or as a partial alternative to synthetic films
Keywords: Regenerated cellulose, Puncture test, Water adsorption
Published in RUNG: 14.12.2020; Views: 2884; Downloads: 0
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Abstract: Regenerated cellulose-based films combined with glycerol and polyvinyl alcohol (PVOH) show interesting UV- light barrier properties, with potential application in food packaging to prevent oxidative deterioration. How- ever, these materials are sensitive to moisture, and their properties could be modified as a function of the relative humidity. Hence, the objective of the present work was to evaluate the changes in the main properties of re- generated cellulose-glycerol-PVOH films depending on the relative humidity. Using the GAB adsorption iso- therms, the moisture content was related with the water activity of the films at several relative humidity conditions. According to the obtained results, water molecules manifested a plasticizing effect modifying the mechanical, water vapour permeability and optical properties of the developed films. Tensile strength and Young’s modulus values ranged from 92.65 to 17.57 MPa and from 3639.09 to 227.89 MPa, respectively. Both of them decreased when the moisture content increased. The mechanical resistance to deformation of films enhanced at high moisture content, changing from 5.88 to 15.97% and from 0.59 to 2.97 mm in the tensile and puncture test, respectively. This effect was also observed for the burst strength. Water vapour permeability increased from 5.15⋅10?10 to 5.44⋅10?9 g/ms Pa when the moisture content increased, being more significative at higher values. No significant variations were observed in the UV-VIS transmittance at different moisture contents. The obtained results allow expanding the knowledge of the behavior of films based on regenerated cellulose.
Keywords: Adsorption isotherms, Plasticization, Regenerated cellulose, Water vapour permeability, Moisture content
Published in RUNG: 09.12.2020; Views: 3368; Downloads: 0
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Keywords: bromate, covalent organic frameworks, Zincke reaction, adsorption, water purification
Published in RUNG: 03.09.2020; Views: 3805; Downloads: 0
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