基于灰度的生物炭pH值与N和K离子吸附研究

通过固定床石英管热解装置将稻壳、木薯秸秆及玉米秸秆在350、450、500、550、600℃进行充分热解制备生物炭，利用图像识别技术获得生物炭的RGB值（红、绿、蓝三个通道的颜色）及相应的灰度值，研究了生物炭灰度值与其水溶液中的pH值及阳离子（NH₄⁺-N及K⁺-K）吸附性能的关系.结果表明：3种生物炭的pH值随着灰度值的增加呈现“S”型增长趋势，并符合DoseResp模型，回归方程的决定系数（R²）分别为0.9766、0.9592和0.9219，残差平方和（RSS）均小于0.01；除玉米秸秆炭的K⁺-K吸附量与灰度值的关系为线性负相关外，3种生物炭的NH₄⁺-N和K⁺-K吸附量与灰度值之间满足一元高次非线性模型，R²范围在0.8595~0.9999.本研究为快速预测生物炭在水溶液中的pH值和阳离子吸附性能提供了理论基础.

Research on pH and adsorption properties of N and K cations of biochar based on gray value

According to statistics of the past 40years, average fertilizer use efficiency is only about 50%. The low fertilizer efficiency not only causes energy loss but also causes environmental pollution and ground and surface water contamination. A new fertilizer using biochar as carrier has a great potential to solve this issue. In this research, the biochars made from rice husk, cassava straw and corn stover were obtained by a horizontal fixed bed quartz tube pyrolysis reactor with varied temperatures (350, 450, 500, 550, and 600℃). The RGB values and corresponding gray value of these biochars were analyzed by image recognition technology. The relationship between pH and gray value and the relationship between adsorption capacities of N and K cations (NH₄⁺-N and K⁺-K,) and gray value were studied. In general, the pH value of biochar increased as gray value increased with R² of 0.9766, 0.9592, and 0.9219, respectively, and the trend fitted well with the DoseResp model. NH₄⁺-N and K⁺-K adsorption capacity of those three biochars followed the one-dimensional high-order nonlinear models with R² ranged from 0.8595 to 0.9999, except the negative linear correlation between K⁺-K adsorption capacity and gray value for corn stover. This study provides theoretical basis for development of rapid method to predict pH and cation adsorption properties of biochar, and also has a potential to develop portable equipment for online testing.