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Wpływ warunków termicznych procesu pirolizy na jakość biowęgli otrzymanych z odpadów roślinnychAn effective way of managing natural waste, including waste from the agri-food industry or products that are economically useful can be offered by production of biochar. Biochar is used not only as an energy product, but also as a sorption material for e.g. groundwater treatment, sewage treatment, as well as biogas valorization. Therefore, the aim of the study was to determine the effect of the conditions of cascade heating of selected types of vegetable waste in carbon dioxide on the microstructure and chemical composition of the obtained biochar. Wheat straw, corn waste in the form of dried leaves and stems, as well as flax shives and cherry stones were subjected to pyrolysis. Cascading temperature conditions were programmed for a total time of 100 minutes, including 15 minutes of final heating at 500°C in one variant and at 700°C in the other. After final heating, the products were left in the pyrolytic chamber to cool down spontaneously to room temperature. The biochar samples were next subjected to microscopic examinations coupled with X-ray microanalysis (SEM/EDS) and infrared spectral examination (FTIR). It was found that the pyrolysis yielded biochar in the amount from 26 to 32.3% of the initial charge mass, depending on the conditions of the process and the type of waste. Furthermore, the differences observed in the chemical structure of the surface of the biochar concerned mainly the occurrence of organic oxygen functional groups whose type depends on the pyrolysis temperature. An increase in the temperature of pyrolysis leads to a decrease in the oxygen content of the products obtained, which results in a relative increase in the proportion of char in the product. Biochar obtained at temperatures of up to 500°C contains aromatic rings and quinone groups, whereas those obtained at higher temperatures (up to 700°C) have ether groups embedded mainly in aliphatic cyclic groups.

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Tribochemical behaviour of the selected mesogenic compound (4-butylcyclohexanoic acid p-hexaoxyphenyl ester) was investigated by means of ball-on-disk machine at ambient and elevated temperatures. To selection of the thermal conditions of tribological tests DSC technique was used and to analyse tribochemical products layered on the wear tracks-SEM/EDS, FTIRM and XPS ones. Obtained results show that the mesogen dissolved in n-hexadecane is an effective antiwear additive which decreases temperature of the lubricant. This is favoured mainly by tribochemical processes.

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