N. A. Mamleeva

The oxidative destruction of lignin in the ozonation of wood

The oxidative destruction of lignin in the ozonation of aspen wood was studied. The kinetic curves of ozone consumption for samples with different contents of water were obtained. The consumption of ozone increased as the content of water grew. The second derivatives of the UV absorption spectra of lignin were obtained to show that the principal direction of lignin transformations under the action of ozone was the destruction of its aromatic constituents with the formation of carboxyl- and carbonyl-containing compounds. Measurements of the UV diffuse reflectance and EPR spectra of wood showed that the ozonation of wood caused the destruction of lignin quinoid structures. Part of lignin remained unchanged under the action of ozone. A key role in the destruction of wood lignin was played by ozone dissolved in water. Varying the content of water in wood samples allows various lignin transformation products to be obtained through ozonation.

Adsorption of phenol on wood surfaces

Adsorption of phenol on aspen and pine wood is investigated. It is shown that adsorption isotherms are described by the Langmuir model. The woods’ specific surface areas and adsorption interaction constants are determined. It is found that the sorption of phenol on surfaces of aspen and pine is due to Van der Waals interactions (Ssp = 45 m2/godw for aspen and 85 m2/godw for pine). The difference between the adsorption characteristics is explained by properties of the wood samples’ microstructures.

Transformation of wood during ozonization in the presence of hydrogen peroxide

Samples of ozonized aspen wood pretreated with hydrogen peroxide solutions of various concentrations are investigated by UV diffuse reflectance spectroscopy, IR spectroscopy, and X-ray structural analysis. The general course of wood transformation under the action of the O3/H2O2 system is associated with the destruction of lignin and oxidation of carbohydrates, raising the fraction of the crystalline phase in a lignocarbohydrate material. The possibility of varying the depth of the chemical and structural transformation of the substrate upon changing the hydrogen peroxide concentration in the O3/H2O2 system is demonstrated.

Delignification of deciduous wood under the action of hydrogen peroxide and ozone

AbstractKinetic curves of the dependence of ozone specific absorption (Qr, sp) upon the ozonation of aspen wood pretreated with solutions of hydrogen peroxide of various concentrations (from 5 × 10−4 to 2 × 10−1 mol/L) are obtained. The water content in the samples being 56 ± 3%. The initial rate of ozone absorption and total ozone consumption (Qinlet) are determined. Wood samples are investigated by IR and UV diffuse reflection spectroscopy. Based on the kinetics and spectral data, it is concluded that pretreating wood with a H2O2 solution allows the degree of delignification (DD) to be increased at a constant Qinlet value. The DD is maximal at

Ozonation of deciduous wood in the presence of hydrogen peroxide

C_{H_2 O_2 } = 5 \times 10^{ - 3}

Degradation of polysaccharides and lignin in wood ozonation

mol/L and is 88% in contrast to a sample ozonated without H2O2 (DD = 85%). The role of pretreatment with hydrogen peroxide and the subsequent action of the O3/H2O2 system in the process of delignification of wood is analyzed.

Physicochemical patterns of ozone absorption by wood

The kinetic curves of ozone absorption by aspen wood were obtained. Processing of wood with peracetic acid gave cellulose samples. The yields of ozonated wood, water-soluble compounds, and cellulose were determined for the samples corresponding to different consumptions of ozone. The IR absorption spectra of wood and cellulose isolated from ozonated wood were analyzed. The supramolecular structure of cellulose can be changed by varying the conditions of wood ozonation.

Oxidation of sodium lignosulfonate by ozone in aqueous solutions

The kinetic curves of the dependence of ozone specific absorption (Qr, sp) upon aspen wood ozonation in the presence and absence of hydrogen peroxide are obtained. It is established that the rate of ozone and Qr, sp absorption increase in the O3/H2O2 system. It is demonstrated by ESR, IR, and UV spectroscopy of diffuse reflection that wood ozonation in the O3/H2O2 system results in the destruction of lignin aromatic and quinoid structures. The ozonation process in the presence of H2O2 is accompanied by destruction of the carbohydrate component of the lignocarbohydrate complex. We conclude that O3/H2O2 can be used in the deep delignification of wood. It is shown that the presence of hydrogen peroxide upon ozonation increases the efficiency of the process, allowing its duration and total ozone consumption to be reduced.