Changzhou Key Laboratory of Biomass Green, Safe & High Value Utilization Technology, Institute of Urban and Rural Mines, Changzhou University, Changzhou 213164, China.
Department of Chemical Engineering for Energy Resources, East China University of Science and Technology, Shanghai 200237, China.
Int J Environ Res Public Health. 2022 Dec 15;19(24):16875. doi: 10.3390/ijerph192416875.
In this study, Baoqing lignite (BL) and rice straw (RS), which were the representatives of low-rank coal and biomass, were co-thermally oxidized to produce composite humic substances (HS), including humic acid (HA) and fulvic acid (FA). Taking HS content as the output response, the co-thermally oxidizing conditions were optimized through single factor experiment and response surface methodology (RSM). The structures of HA and FA prepared under optimized conditions were analyzed by SEM, UV, and FTIR. Results showed that HS content was clearly influenced by the material ratio, oxidation time, and oxidation temperature, as well as their interactions. The optimized co-thermal oxidization condition was as follows: BL and RS pretreated with a material ratio of 0.53, oxidation time of 59.50 min, and oxidation temperature of 75.63 °C. Through verification, the experimental value (62.37%) had a small relative error compared to the predicted value (62.27%), which indicated that the developed models were fit and accurate. The obtained HA had a tightly packed block structure; FA had a loosely spherical shape. The molecular weight of FA was 2487 Da and HA was 20,904 Da; both had a smaller molecular weight than that reported in other literature. FA showed strong bands at 1720 cm, thus confirming the presence of more oxygen-containing functional groups. The appearance of double peaks at 2900~2980 cm indicated that HA contains more aliphatic chains. The co-thermal oxidation of BL and RS gives a new method for the synthesis of HS, and the optimization of co-thermal oxidation conditions will provide fundamental information for the industrialization of composite HS.
在这项研究中，选取了低阶煤代表——保庆褐煤（BL）和生物质代表——稻草（RS），通过共热氧化法制备了复合腐殖质（HS），包括腐殖酸（HA）和富里酸（FA）。以 HS 含量为输出响应，通过单因素实验和响应面法（RSM）对共热氧化条件进行了优化。采用 SEM、UV 和 FTIR 对最佳条件下制备的 HA 和 FA 的结构进行了分析。结果表明，HS 含量明显受到物料比、氧化时间和氧化温度以及它们相互作用的影响。最佳共热氧化条件为：预处理的 BL 和 RS 物料比为 0.53，氧化时间 59.50 min，氧化温度 75.63℃。通过验证，实验值（62.37%）与预测值（62.27%）的相对误差较小，表明所建立的模型拟合准确。得到的 HA 具有紧密堆积的块状结构；FA 具有松散的球形形状。FA 的分子量为 2487 Da，HA 的分子量为 20904 Da；两者的分子量均小于其他文献报道的值。FA 在 1720 cm 处显示出强带，因此证实了存在更多的含氧官能团。2900~2980 cm 处出现双峰表明 HA 含有更多的脂肪链。BL 和 RS 的共热氧化为 HS 的合成提供了一种新方法，共热氧化条件的优化将为复合 HS 的工业化提供基础信息。
