Effects of different preparation methods on physicochemical properties of buckwheat straw biochar
In order to understand the physicochemical properties of buckwheat straw biochar,the effect of different temperatures and heating rates on the pyrolysis characteristics of buckwheat straw was investigated,and the physicochemical characteristics of buckwheat straw biochar were revealed by differential scanning calorimetry,specific surface area and pore size and Fourier infrared spectroscopy.The results showed that the differential heat curves of buckwheat straw at different heating rates had a similar change curve,the pyrolysis reaction shifted to the right with the increase in the heating rate;The yield of biochar was negatively correlated with pyrolysis temperature;pH and conductivity gradually increased(9.16-12.27 and 2.56-4.96 mS/cm);With the increase of pyrolysis temperature,the types of surface functional groups of buckwheat straw biochar gradually was decreased,and the stretching vibration was increased with the increase of heating rate.The specific surface area and pore volume of biochar increased with the increase in pyrolysis temperature and then decreased,but there was no correlation with the rate of heating,at lower temperatures,with the increase in the rate of heating,pore structure gradually transitioned from mesoporous to macroporous;The fractal dimension range of buckwheat straw biochar prepared at different pyrolysis temperatures was[2.3709,2.9368].In summary,the buckwheat straw biochar prepared under the conditions of pyrolysis temperature of 700℃and heating rate of 12.5℃/min had the best comprehensive properties in terms of its stable structure,maximum specific surface area and high biochar yield.
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