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A process for dewatering spent ion exchange resins (gel and porous) used in nuclear power plants by supercritical CO2 (sCO2) is described. The amount of water removed by sCO2 is much higher than that expected from solubility considerations alone. Water from gel-type resins is both dissolved by and emulsified in sCO2. Emulsification also occurs in the absence of solids when water alone is contacted by sCO2. It is not a factor for microporous resins where an additional mechanism, viscous fingering, is involved. It appears that bulk water is emulsifiable but not if it is held in pores. Dewatering via viscous fingering has been previously invoked for matrices such as wood and sludge. The resins can be dewatered and dried with sequential batches of sCO2 at sub-boiling temperatures. The CO2 can then be potentially reused after expansion and separation from the entrained water. Partial decompression of the water-laden sCO2 would lead to cooling, which would drop the water solubility substantially. A reduction of temperature from 90 oC to 65oC reduces the solubility of water in sCO2 by a factor of five. The condensed water could then be separated with a hydrocyclone. The footprint of sCO2 is much smaller than the conventional drying process. The energy costs are also much lower because evaporation of water is avoided. [ABSTRACT FROM AUTHOR]

Interactions at the molecular and surface chemistry are some of the key factors that determine the adsorption capacity of pollutants and emerging contaminants in porous materials. As filtration-based purification of water sources expands, the generation of green materials, such as biopolymers, is the priority. However, to increase the removal capacity, modification of natural polymers appears necessary. Nanomaterials, especially bio-based materials like cellulose nanofibrils, inherently have large surface areas as a consequence of their high aspect ratios. Their capacity to modulate the interactions with contaminants present in water can be modulated by incorporating selective active points, such as hydrophobic cavities, that can further improve their overall adsorption capability. A bio-based material that can fulfil this requirement is β-cyclodextrin, a cyclic oligosaccharide with seven glucose units, which provides an easy grafting strategy onto cellulose due to structural affinity. Another advantage of using cellulose nanofibril is their film formability, aerogels, and hydrogels without the need of harsh chemicals or processes. In this work, an oligosaccharide with a hydrophobic centre – β-cyclodextrin – was immobilized onto bleached softwood cellulose nanofibrils, and then used to generate high surface area aerogels with a density of 175 kg/m3 and porosities above 88%. Charge density titration, Fourier transform infrared with attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and atomic force microscopy (AFM) characterization techniques were used to assess the successful modification of the fibrils. Inductive coupled plasma mass spectroscopy (ICP-MS) was used to determine the lack of trace chlorine in the material from the grafting process while scanning electron microscopy (SEM) and dynamic vapor sorption (DVS) were used to determine porosity and surface area of the aerogels. The adsorption capacity was tested with two molecules of different natures: a cyanotoxin (microcystin-LR) and a dye (methylene blue), using high-performance liquid chromatography with a UV detector (HPLC–UV) and UV–vis spectroscopy, respectively. The adsorption in equilibrium for CNF-CD aerogels was calculated to be 0.078 mg/g of microcystin-LR and 3.46 mg/g of methylene blue, enlightening its possible use to improve water quality. [ABSTRACT FROM AUTHOR]

With the increasing need for bio‐based materials developed by environmentally friendly procedures, this work shows a green method to develop shape‐controlled structures from cellulose dissolving pulp coated by chitosan. This material was then tested to adsorb a common and widespread pollutant, 2,4‐dichlorophenol under different pH conditions (5.5 and 9). Herein it was noticed that the adsorption only occurred in acidic pH (5.5) where electrostatic interaction drove the adsorption, demonstrating the potential to tune the response under desired conditions only. The adsorption was successful in the hydrogel structure with an adsorption capacity of 905 ± 71 mg/g from a solution with 16.6 ppm; furthermore, adsorption was also possible with dried hydrogel structures, presenting a maximum of adsorption of 646 ± 50 mg/g in a similar 16.6 ppm solution. Finally, adsorbent regeneration was successfully tested for both, dry (rewetted) and never‐dried states, showing improved adsorption after regeneration in the case of the never dried hydrogel structures. [ABSTRACT FROM AUTHOR]

Gelatin and chitosan polysaccharides were chemically modified to get methacrylate functionality to obtain biocompatible hydrogels for use as tissue engineering scaffolds. The methacrylation reaction was verified by 1H‐NMR. The degree of methacrylation was varied from 7% to 40% by changing the molar ratio of polysaccharide to methacrylic anhydride and the type of polysaccharide utilized. After the modification, polysaccharide‐based hydrogels were prepared by free‐radical polymerization in the presence of UV light and Irgacure 184 as a photoinitiator. The physical, chemical, and mechanical performances of the hydrogels were further characterized. Also, the biodegradability and the viability of the polysaccharide hydrogels were investigated using fibroblast cells. These cells were seeded directly onto the hydrogel surface, populated the entirety of the hydrogel, and remained viable for up to 1 week. Altogether, the modified polysaccharides exhibit the properties which make them crucial for applications in the field of regenerative medicine. [ABSTRACT FROM AUTHOR]

With increasing global water temperatures and nutrient runoff in recent decades, the blooming season of algae lasts longer, resulting in toxin concentrations that exceed safe limits for human consumption and for recreational use. From the different toxins, microcystin-LR has been reported as the main cyanotoxin related to liver cancer, and consequently its abundance in water is constantly monitored. In this work, we report a methodology for decorating cellulose nanofibrils with β-cyclodextrin or with poly(β-cyclodextrin) which were tested for the recovery of microcystin from synthetic water. The adsorption was followed by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), allowing for real-time monitoring of the adsorption behavior. A maximum recovery of 196 mg/g was obtained with the modified by cyclodextrin. Characterization of the modified substrate was confirmed with Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), and Atomic Force Microscopy (AFM). [ABSTRACT FROM AUTHOR]