炭化温度对沙蒿生物炭K、Ca、Mg含量和pH值的影响

 以沙蒿(Artemisia arenaria)为材料,通过无氧炭化法制取生物炭,研究炭化温度对沙蒿生物炭全K、全Ca、全Mg 元素含量及富集效应和pH 值的影响。结果表明,生物炭中K、Ca、Mg 元素含量均随着炭化温度的升高而升高,K 含量的升高幅度最大,K、Ca、Mg 元素含量在900℃较300℃分别提高了52.47%、25.76%和86.32%,元素含量的提高与沙蒿生物质中可挥发和分解的组分在不同的炭化温度下逐渐去除有关;升温炭化过程中对K、Ca、Mg 等元素均得到了不同程度的富集(相对富集系数RE>1),低温有利于K 元素和Ca 元素的富集,中温有利于Mg 元素的富集,K、Ca、Mg 等元素的RE 值分别在300、300、500℃时取得最大值,分别为1.17、1.15 和1.22;pH 值随炭化温度的升高而增大,生物炭的碱性与K、Ca、Mg 元素的富集及生物炭表面含氧官能团的种类和数量均有关,与生物炭表面的总碱性官能团有较好的相关性(相关系数为0.8665)。

Effects of carbonization temperature on the pH and of K,Ca and Mg cocentrations in Artemisia ordosica biochar

Artmisia ordosica was used as the experimental material for making biochar in this study. The effects of carbonization temperature on the pH and total K, Ca, and Mg of Artmisia ordosica biochar were investigated. The results showed that the concentrations of K, Ca, and Mg in the biochar increased with the increase of carbonization temperature. Compared with those at 300℃, the K, Ca, and Mg concentrations increased by 52.47%, 25.76%, and 86.32% at 900℃, respectively. The increase of element concentration is due to gradual removal of the volatile and decomposable components in Artmisia ordosica under different carbonization temperature. The heating process of carbonization enriches K, Ca, Mg, and other elements (relative enrichment coefficient RE>1). Low temperature contributes to the enrichment of K and Ca, while medium temperature is favorable for Mg. The RE of the three elements reached their maximum values at 300, 300 and 500℃, being 1.17, 1.15, and 1.22, respectively. The pH increased with the increase of carbonization temperature. The alkalinity of the biochar was correlated to the enrichment of the three elements, and the number and types of oxygen-containing functional groups at the biochar surface, and it had good correlation with the total alkaline functional groups at the surface of the biochar (with correlation coefficient of 0.8665).