A. L. Bychkov

Mechanochemical modification of the structure of brown coal humic acids for preparing a sorbent for heavy metals

Mechanochemical modification of the structure of brown coal humic acids with classical base (NaOH) and oxidizing base (Na2CO3·1.5H2O2) reagents was studied. Treatment of brown coal under these conditions leads to an increase in the degree of recovery of humic acids without breaking the macrostructure of the molecules. The reaction with the base reagent leads to an increase in the content of carboxy groups at hydrocarbon chains, whereas the action of the oxidizing base reagent leads to an increase in the content of phenolic and carboxy groups at aromatic rings, with the formation of chelating structures. The samples obtained show high performance as sorbents for heavy metals.

Prediction of higher heating values of plant biomass from ultimate analysis data

For natural plant raw materials and for artificial mixture samples with different lignin content, a comparison between empirical equations for the calculation of higher heating values was carried out relying on the data of ultimate analysis. Selection of tested equations from already known was carried out according to the criteria: equations should be intended for work with plant raw materials; the range of used materials should be rather wide; the data on element content (C, H, N, S) obtained experimentally and in routine mode, as well as ash value of the material, should be variables; ambiguous equations should be excluded. Only 8 from more than 150 published equations were chosen for testing, and 3 of these provide calculation of higher heating values with a less than 5–6% deviation from reference values obtained by means of combustion in an adiabatic calorimeter.

Pretreatment of rice husk in a pilot scale mill for further enzymatic hydrolysis

The effect of the mechanical activation of rice husk on the reactivity of its carbohydrates was studied. The activation was performed in a pilot-scale centrifugal roller mill. The mechanical treatment of the raw material led to an increase in its reactivity due to the increase in the specific surface area and amorphization of the crystalline regions of cellulose. The optimum process conditions of activation, leading to the preparation of a reactive product from rice husk, were determined: rotor frequency 1500 rpm, raw material feed rate 30 kg/h. The rice husk particles were ground to 45–50 μm under these conditions. These changes led to a sevenfold increase of the yield of low-molecular carbohydrates in the complete enzymatic hydrolysis of the material.

Sorption capacity of lignocellulosic materials toward humic acids

Sorption capacity toward humic acids was studied for a number of lignocellulosic materials with different structures and chemical compositions. The values of sorption capacity of the materials toward humic acids were determined taking into account the desorption process. In addition to physical sorption due to porosity, a more considerable contribution to humic acid binding is made by chemical sorption provided by the lignin component of the plant cell wall structure.

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L−1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.

Disordering of the Crystal Structure of Cellulose Under Mechanical Activation

The present paper describes the study of the effect of mechanochemical activation on the amorphization process of individual α-cellulose and native cellulose being a constituent part of the lignocellulosic material in the form of partially crystalline fibrils. In processing the powder X-ray diffraction data the following methods are used to determine the degree of crystallinity of cellulose: Segal’s, Rietveld’s, and Lorentzian deconvolution. It is demonstrated that mechanical activation of individual α-cellulose in an AGO-2 laboratory planetary ball mill with a shock-shear action results only in grinding and amorphization, while the degree of amorphization increases propotionally to the duration of the power supply. When α-cellulose is treated in an RM-20 flow-through centrifugal roller mill with a shear action, particle agglomeration is observed together with amorphization. When a lignocellulosic material (wheat straw) is treated in a centrifugal roller mill, considerable amorphization occurs only at high energies, and no particle agglomeration is observed.

The role of mechanical action in the process of the thermomechanical isolation of lignin

Transmission electron microscopy of ultrathin sections of reed straw samples subjected to thermomechanical treatment revealed changes in the ultrastructure due to lignin isolation. It is assumed that the lignin in cell walls melts under the influence of high temperature and forms accumulations localized in the depth of the cell walls. Mechanical action exerted on the material presses the lignin with a damaged structure out of the cell walls. Pores 10–20xa0nm in diameter are observed in cell walls; lignin is localized on the surface of the particles in formations that are approximately 200xa0nm in size.

Changes in the structure of cell wall polymers in thermomechanical treatment of highly lignified plant feedstock

The effect of mechanical treatment at various temperatures on structural changes in polymers contained in highly lignified plant feedstock was studied by the example of reed stems. The optimal conditions (about 10°C) of mechanical activation of plant feedstock were determined, under which its structure is disordered enough for subsequent enzymatic hydrolysis, but the lignin decomposition is prevented, and so is the formation of a layer of substances inhibiting enzymes on the surface of particles.