Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, NMBU, 1430 Ås, Norway; Norwegian Institute of Bioeconomy Research (NIBIO), Division of Environment and Natural Resources, Høgskoleveien 7, 1432 Ås, Norway.
Norwegian Institute of Bioeconomy Research (NIBIO), Division Food Production and Society, Høgskoleveien 7, 1432 Ås, Norway.
Chemosphere. 2022 Aug;301:134662. doi: 10.1016/j.chemosphere.2022.134662. Epub 2022 Apr 18.
Sorption of nutrients such as NH is often quoted as a critical property of biochar, explaining its value as a soil amendment and a filter material. However, published values for NH sorption to biochar vary by more than 3 orders of magnitude, without consensus as to the source of this variability. This lack of understanding greatly limits our ability to use quantitative sorption measurements towards product design. Here, our objective was to conduct a quantitative analysis of the sources of variability, and infer which biochar traits are more favourable to high sorption capacity. To do so, we conducted a standardized remodelling exercise of published batch sorption studies using Langmuir sorption isotherm. We excluded studies presenting datasets that either could not be reconciled with the standard Langmuir sorption isotherm or generated clear outliers. Our analysis indicates that the magnitude of sorption capacity of unmodified biochar for NH is lower than previously reported, with a median of 4.2 mg NH g and a maximum reported sorption capacity of 22.8 mg NH g. Activation resulted in a significant relative improvement in sorption capacity, but absolute improvements remain modest, with a maximum reported sorption of 27.56 mg NH g for an activated biochar. Methodology appeared to substantially impact sorption estimates, especially practices such as pH control of batch sorption solution and ash removal. Our results highlight some significant challenges in the quantification of NH sorption by biochar and our curated data set provides a potentially valuable scale against which future estimates can be assessed.
对营养物质（如 NH）的吸附通常被认为是生物炭的一项关键特性，这解释了其作为土壤改良剂和过滤材料的价值。然而，生物炭对 NH 的吸附的已发表值相差超过 3 个数量级，而且对于这种可变性的来源也没有达成共识。这种缺乏了解极大地限制了我们利用定量吸附测量来进行产品设计的能力。在这里，我们的目标是对变异性的来源进行定量分析，并推断出哪些生物炭特性更有利于高吸附能力。为此，我们使用 Langmuir 吸附等温线对已发表的批量吸附研究进行了标准化的重新建模。我们排除了那些数据集无法与标准 Langmuir 吸附等温线相协调或产生明显异常值的研究。我们的分析表明，未经修饰的生物炭对 NH 的吸附容量比以前报告的要小，中位数为 4.2 mg NH g，最大报告的吸附容量为 22.8 mg NH g。活化导致吸附容量显著提高，但绝对提高仍然较小，最大报告的活化生物炭的吸附容量为 27.56 mg NH g。方法学似乎对吸附估计值有很大的影响，特别是批量吸附溶液的 pH 控制和灰分去除等做法。我们的结果强调了生物炭对 NH 吸附进行定量的一些重大挑战，并且我们的经过编目的数据集提供了一个潜在有价值的基准，可用于评估未来的估计值。
