Cryogels: Morphological, structural and adsorption characterisation

Abstract Experimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4100μm) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water — free unbound, weakly bound (changes in the Gibbs free energy−ΔG0.8kJ/mol), and weakly associated (chemical shift of the proton resonance δH=1–2ppm) and strongly associated (δH=3–6ppm) waters can be distinguished in hydrated cryogels using 1H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers filled with solid nano- or microparticles

Application of silica–alumina oxides of different compositions for removal of C.I. Reactive Black 5 dye from wastewaters

In this paper adsorptive removal of hazardous dye C.I. Reactive Black 5 from aqueous solutions was investigated using the mixed silica–alumina oxides including of 4% SiO 2 and 96% Al 2 O 3 as well as 97% SiO 2 and 3% Al 2 O 3 . The kinetic studies revealed that with the increasing initial dye concentration from 10 to 30 mg/l and contact time from 1 to 240 min, the sorption capacities ( q t ) increased and the equilibrium was observed after 240 min. Sorption of C.I. Reactive Black 5 on 4% SiO 2 and 96% Al 2 O 3 and 97% SiO 2 and 3% Al 2 O 3 takes place through the pseudo-second-order mechanism rather than the pseudo-first-order one. The experimental data were fitted using the Langmuir and Freundlich isotherm models. The effect of the auxiliaries such as anionic surfactant (sodium dodecyl sulphate) and sodium chloride on C.I. Reactive Black 5 removal was investigated in the 10 mg/l C.I. Reactive Black 5–0.1–1 g/l sodium dodecyl sulphate or 5–20 g/l NaCl systems. The potentiometric titrations indicated that the presence of C.I. Reactive Black 5 changed the surface charge density of silica–alumina mixed oxides, especially in the case of 4% SiO 2 and 96% Al 2 O 3 system

Textural Characteristics of Resorcinol—Formaldehyde Resin and Temperature Behavior of Bound Water Affected by Co-Adsorbed Trifluoroacetic Acid or Pyridine in Weakly Polar Organic Media

Resorcinol–formaldehyde resin (RFR) was synthesized as a porous material characterized by specific surface area of 140 m 2 /g and pore volume of 0.59 cm 3 /g with major proportions of broad mesopores and macropores. The interfacial behavior of water at low (h = 0.05 g of water/gram of dry RFR) and high (h = 2 g/g) hydration degrees depends on temperature and pore size filled by unfrozen water because its freezing-point depression increases in narrower pores. When water is mixed with co-adsorbates, the effects of such co-adsorbates as non-polar, weakly polar and polar organics depend on the amounts and the pore sizes. Even at a low hydration degree (h = 0.05 g/g), a portion of water can be displaced from pores by organic co-adsorbates because water has a relatively weak interaction with the RFR surface

Magneto-Sensitive Ni/C Adsorbents: Synthesis, Properties and Applications

A series of microporous carbons (chars) containing various amounts of magnetic Ni nanoparticles were prepared using a simple procedure. The resorcinol–formaldehyde polymers containing nickel(II) acetate was carbonized to produce chars (labelled as Ni/C-20, Ni/C-35 and Ni/C-50). All chars were characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption and scanning electron microscopy methods. The formation of Ni crystallites (18 nm in size) occurs in carbon spheres measuring 1–2 μm in diameter. The Raman spectra show that the content of Ni influences the carbon structure. Dye-separation performance by Ni/C was investigated using methylene blue. The adsorption capacity was 26.6, 20.8 and 15.1 mg/g for Ni/C-20, Ni/C-35 and Ni/C-50, respectively

Single-layer graphenes functionalized with polyurea: architectural control and biomolecule reactivity

The nondestructive, covalent reactivity of single-layer graphene oxide (SLGO) and hydrazine-reduced graphene oxide (rGO) in relation to its 3-dimensional geometry has been previously considered for various chemical reactions. However, the capability of the modified system to undergo additional chemistry is now demonstrated through an in-situ polycondensation reaction resulting in various linear or hyperbranched condensed polymers [e.g., polyureas, polyurethanes, and poly(urea–urethane)-bonded graphenes]. The use of aliphatic diisocyanates as the anchor molecule initially forms star-like clusters of SLGO and rGO, and on in-situ polycondensation reaction with aliphatic diamines, the underlying graphene architecture is further modified into scroll-like domains with extensive intersheet bridging. The use of aromatic isocyanates as bridging molecules keeps the graphene structure flat and is maintained throughout the polycondensation reaction with aromatic diamines. Critical point drying of the graphene–polymer composites shows that changes to the architecture of the composite occur in the solution phase and not through surface tension effects on drying. According to TGA analysis, the aliphatic systems have higher grafted polymer weight proportions of polyurea than the aromatic counterparts and the rGO systems are found to be greater than the SLGO composites. In all experiments, the external surface of the graphene–polyurea macrostructure is demonstrated to be reactive toward biomolecules such as ferritin and is therefore useful toward a solution chemistry development of morphology-controlled graphene-based bio-nano applications

pH driven physicochemical conformational changes of single-layer graphene oxide

Single-layer graphene oxides (SLGOs) undergo morphological changes depending on the pH of the system and may account for restricted chemical reactivity. Herein, SLGO may also capture nanoparticles through layering and enveloping when the pH is changed, demonstrating potential usefulness in drug delivery or waste material capture