Morphology, pore size distribution, and nutrient characteristics in biochars under different pyrolysis temperatures and atmospheres
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To evaluate the agronomic potential of biochar, we prepared a series of biochars using rice straw waste under the limited oxygen cracking condition (CO2 or N2) and the different pyrolysis temperatures including 300, 400, 600, and 800 °C. The results showed that morphology structure, specific surface area, pore size distribution, and element contents of the biochars were superior to the biochars prepared under traditional inert atmosphere (N2) and the same four pyrolysis temperatures. In comparison with the rice straw, pore structure of biochars was mainly mesoporous and more developed, average pore size decreased, and BET-specific surface area increased with the increase of temperature from 300 to 800 °C. Biochars distributed abundant mesopores and macropores under 400 and 600 °C; the maximum macropores of the biochar were shaped under 600 °C. Concentration of phosphorus (P) and potassium (K) increased significantly with increasing temperature, while that of nitrogen (N) first increased and then decreased and reached a maximum at 400 °C. In addition, taking these physiochemical properties into consideration, we drew a conclusion that the optimum quality biochar could acquire under the work conditions of 400 °C and CO2 atmosphere, which was supposed to provide theoretical guidance for biochar returning to soil.
KeywordsCO2 atmosphere Biochars Nutrient content Pore structure
This study was supported by the National Natural Science Foundation of China (No. 41571283) and National Key Research and Development Program of China (2016YFD0800702).
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