Stability of Alum-Containing Paper under Alkaline Conditions.

The present contribution evaluates the methods of degradation and stabilization of alum-containing paper with a focus on the alkaline environment achieved by deacidification procedures. In terms of reviewed subjects, the contribution focuses on alum-rosin sized paper, which is still used as a carrier of knowledge and information; however, it also mentions cellulose itself and other brands of paper. The contribution summarizes the results on the homogeneity of the distribution of alum and rosin in the paper mass and on the paper surface. It provides the knowledge gained in the field of alkaline hydrolysis and oxidation with special regard to transition metal species. It shows the values of alkaline reserves achieved in the main mass-deacidification processes. On the basis of the acquired knowledge, the contribution emphasizes the procedures of paper stabilization. Criteria of "increased mechanical permanence and lifetime prolongation" adopted to evaluate and compare the efficacy of individual mass-deacidification processes were applied and corresponding data are introduced. The contribution also draws attention to the existence of open issues in the area of paper degradation and stabilization.

Considerations on factors influencing the degradation of cellulose in alum-rosin sized paper.

In Europe, the use of aluminium(III) compounds, namely AlK(SO4)2·12H2O and later on Al2(SO4)3·18H2O for hardening gelatin sizes was recorded as early as the 16th century. This review is focused on the critical assessment of published data concerning the following chemical aspects of paper degradation: direct influence of H3O+ ions formed during hydrolysis of aluminium(III) species; influence of low-molecular organic acids formed within degradation processes; influence of pH variation on the redox potential of reactive oxygen species acting as oxidizing agent; consequences of the absorption of gaseous NO2 and SO2 present in the air for paper degradation; involvement of aluminium species in redox radical oxidation catalytic processes; possible effect of the coordination of Al(III) with small radius and high charge on oxygen atoms of cellulose carboxyl or hydroxyl groups. It is indicated how the understanding of the above mentioned effects can help slow down paper degradation.

Use of Deep Eutectic Solvents in Polymer Chemistry-A Review.

This review deals with two overlapping issues, namely polymer chemistry and deep eutectic solvents (DESs). With regard to polymers, specific aspects of synthetic polymers, polymerization processes producing such polymers, and natural cellulose-based nanopolymers are evaluated. As for DESs, their compliance with green chemistry requirements, their basic properties and involvement in polymer chemistry are discussed. In addition to reviewing the state-of-the-art for selected kinds of polymers, the paper reveals further possibilities in the employment of DESs in polymer chemistry. As an example, the significance of DES polarity and polymer polarity to control polymerization processes, modify polymer properties, and synthesize polymers with a specific structure and behavior, is emphasized.

Extraction of value-added components from food industry based and agro-forest biowastes by deep eutectic solvents.

The scientific community, experts in technology and marketing have been seeking cost-competitive and green solvents with good dissolving capacity for the valorisation of biomass and biowaste. Along with traditional solvents and techniques, deep eutectic solvents (DESs) and their bio-analogues, natural deep eutectic solvents (NADESs) are currently emerging as a new class of promising liquid media. In this review, a comprehensive summary of recent contribution of DESs to the processing and valorisation of various kinds of plant and animal based biomass and biowaste is provided. In the field of food industry based and agro-forest waste valorisation, through treatment of the waste, by-products, and natural materials by DESs, several types of compounds, such as flavonoids and other plant phenolics, phenolic acids, stilbenes, tannins, lignans, and lignin were obtained. Extraction of algae by DESs led to isolation mainly of proteins, carbohydrates, lipids and nucleic acids. Vegetable oils, spent oils, residues and by-products of their processing are a rich source of phenolic compounds such as phenolic acids and phenolic alcohols, secoiridoid derivatives (aglycone and ligstroside), lignans (pino and acetoxypinoresinol), flavones (luteolin and apigein), tocopherols and tocotrienols. Dietary fibre serves as a source of lignin, pectic substances, gums, resistant starch, inulin, as well as non-carbohydrate components, e.g., polyphenols, waxes, saponins, cutin, phytates, resistant proteins. Valorisation of wastes originated from animal processing by DESs means obtaining high-value chemicals including amino acids, proteins, bioactive peptides, collagen peptides, albumin etc. Through the valorisation of the mentioned waste types value-added products with potential applications in the pharmaceutical, food and cosmetic industries are produced. The paper gathered data on the used DESs, treated substances and obtained products, together with treatment conditions and the products yields. The evaluation of the state-of-the-art in the field of biowaste valorisation using DESs and NADESs led to conclusions and indication of future prospects and predicted development in this field.

Effect of fluorine position on the coordinating ability of fluorosalicylic acids--an experimental study complemented with computations.

The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH(-1)] and [CuL(2)H(-2)](2-) of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu(2)L(2)H(-3)](-). Further species were also identified by the two-dimensional ESR simulation method: [CuL](+) in the acidic region, the minor dimer [Cu(2)L(2)H(-2)], and the cis and the trans isomers for [CuL(2)H(-2)](2-). The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH(-1)] and [CuL(2)H(-2)](2-), while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.

Equilibria of 3-pyridylmethanol with copper(II). A comparative electron spin resonance study by the decomposition of spectra in liquid and frozen solutions.

The copper(II)-3-pyridylmethanol (L) system was investigated in aqueous solution by two-dimensional ESR evaluation at 298 K, and computer simulation of the individual anisotropic spectra at 77 K. The data revealed that the paramagnetic copper(II) complexes [CuL] (2+), [CuL 2] (2+), [CuL 3] (2+), and [CuL 4] (2+) are formed up to pH approximately 7 at a moderate or high excess of ligand. As compared with chelating ligands, two differences were observed for the complexation of 3-pyridylmethanol with copper(II): (1) In contrast with the well-resolved spectra in frozen solution, considerable line-broadening and distortion of the spectral shapes were seen at 298 K, which was interpreted in terms of isomeric equilibria and the medium-rate interconversion of various complexes on the ESR time-scale. (2) At low temperature, there were dramatic changes in the concentration distribution, the minor complexes with higher numbers of coordinating ligands ([CuL 3] (2+) and in particular [CuL 4] (2+)) becoming strongly favored. This phenomenon is explained by the significant differences in the formation enthalpy values of various species, shifting the equilibria according to the van't Hoff equation, and a significant undercooling in the course of fast freezing of the solution, which enhances the changes of the concentration distribution.

Complexation of 5-fluorosalicylic acid with copper(II): a pH-potentiometric, UV-vis spectroscopic, and electron spin resonance study by the two-dimensional simulation of spectra.

The copper(II)-5-fluorosalicylic acid system was investigated in water and 50 v/v% water-methanol mixture by pH potentiometry combined with UV-vis spectrophotometry, and by the two-dimensional ESR simulation method, respectively. The data revealed that the stable paramagnetic mono- and bis(salicylato) copper(II) complexes [CuLH(-1)] and [CuL2H(-2)](2-) are formed, and at low excess of ligand, the ESR-silent mixed hydroxo complex [Cu2L2H(-3)](-) is also a major species. By the two-dimensional ESR simulation method, the species [CuL]+ in the acidic region, and the minor dimer [Cu2L2H(-2)] were also identified, and the cis and trans isomers of [CuL2H(-2)](2-) were characterized. In frozen solutions, the ESR analysis revealed a slight rhombic distortion of coordination polyhedra for the latter three species.