To decrease climate changes, more research focuses on decreasing waste wood biomass (WWB) burning and increasing its conversion into value-added products. The WWB was isolated from model wood processing wastewater with a new hybrid coagulant by the coagulation/flocculation method. This study is aimed to characterize the WWB and to investigate its effect in the composition of a hybrid lignocellulosic filler on the properties of recycled polypropylene (rPP)-based wood–plastic composites (WPCs). The waste biomass contained high-molecular lignin and hemicelluloses substances and represented a finely dispersed powder. It was hydrophobic and was characterized by enhanced thermal stability. To minimize the negative effect of polymer wastes on the environment, recycled polypropylene as a polymer matrix was used with the hybrid filler in fabricating WPC samples. The presence of the coagulated WWB in the hybrid filler composition positively affects the mechanical properties, water uptake and dimensional stability of the composite samples. Such a behavior of the waste biomass showed its function as a compatibilizer, which promoted the interfacial adhesion in the composite system.

A wood residuesawdust of the mechanical processing of aspen (Populus tremula) woodwas used to obtain a short fibre filler in the form of the modified microparticles < 250 µm for polymeric composite materials. To reduce energy input for wood size reduction and the activation of the lignocellulosic matrix for modification, low temperature acid hydrolysis of the residue under mild conditions was carried out. The effect of the pre-treatment parameters (acid concentration, hydrolysis duration, hydromodulus) on the fractional and chemical composition as well as on the zeta potential and contact angle of the obtained filler were studied. A comparison of the mechanical properties (tensile, bending) of the composites filled with initial sawdust and hydrolysed microparticles modified with a non-stoichiometric polyelectrolyte complex showed a pronounced improvement of the mechanical properties of the composites filled with modified wood microparticles.

The production of veneer in Latvia and many countries of East Europe is accomplished by the hydrothermal treatment of hardwood in special water basins. As a result, formed effluents contain wood-originated pollutants, which are responsible for the enhanced chemical oxygen demand and the intensive colour of the wastewater. Keeping in mind the volume of the polluted effluents formed annually at the Latvian plywood plants, it is very important to extract qualitatively and quantitatively the formed biomass from the effluent. The choose of an effective method of the waste biomass extraction depends on chemical characterisation of the effluent. In this work, for imitating woodworking wastewater, birch sawdust was hydrothermally treated in mild alkaline conditions at 90 o C. The yield of the solid biomass did not exceed 7% and contained, mainly, hemicelluloses in the polysaccharide form and lignin. The applied instrumental analysis (FTIR-, UV-, Raman spectroscopy) testify the dominant content of hemicelluloses in the obtained biomass. The fractionation of the biomass was performed using concentrated sulphuric acid and ethanol. As the obtained results have shown, the content of lignin, hemicelluloses and water-soluble degraded wood products in the solid biomass corresponded to the following mass ratio: 1.2 /6.7 /1.0, respectively.

The aim was to compare the chemical composition and some properties of three industrial lignosulfonates produced as a by-product at three pulp and paper mills (Russia). Using the classical methods of lignin chemistry, it was found that there were differences in the elemental composition and the content of functional groups of the industrial lignosulfonates, but in general, they were not very significant. The Kondopoga lignosulfonates contained the highest content of methoxy, aliphatic hydroxyl groups and carbonyl groups. The Vyborg lignosulfonates had the highest degree of sulfonation and the lowest content of carbonyl groups. The content of the functional groups in the chemical composition of the Syassky lignosulfonates was intermediate between the functional composition of the Vyborg and Kondopoga lignosulfonates. The Vyborg lignosulfonates had the lowest values of the viscosity average molecular mass, dynamic viscosity and surface tension at the air-water interface in comparison with these parameters of the Kondopoga and Syassky lignosulfonates.

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