Laboratory of Environment-Enhancing Energy (E2E), College of Water Resources and Civil Engineering, China Agricultural University, Beijing, 100083, China.
College of Ecology, Taiyuan University of Technology, Taiyuan, 030024, PR China.
Chemosphere. 2022 Dec;308(Pt 1):136153. doi: 10.1016/j.chemosphere.2022.136153. Epub 2022 Aug 24.
Controversy exists to quantify the fate and speciation of Arsenic (As). We investigated its characteristics by As-containing algae in various pH hydrothermal liquefaction (HTL) system, specifically via two classical methods, i.e. the European Community Bureau of Reference (BCR) and Wenzel's method. Solid residue immobilized 11.23-16.55% of As, and 88.07-82.44% was in aqueous by the pH regulators (e.g., CHCOOH, HCl, and KOH). ICP-MS and XRD analysis revealed that As (V) was converted into As (III) and As (0) in the solid residue, while the As (V) was mainly converted into As (III) in the aqueous phase during HTL. When the classified forms of As in solid residue are compared, Wenzel's method was more appropriate for dividing the bio-availability forms of As, whereas BCR was better for estimating the toxic-potential forms of As. Subsequently, pH regulators raised the risk of As in solid residue associated with the increasing of unstable forms. The amide was hydrolyzed to carboxylic acid with acidic additives, which weakened the reducing environment in the HTL process. In contrast, the amide was hydrolyzed to ammonia with the alkaline additives, which enhanced the reducing environment and increased the risk of As in products. This work provided a new insight in systematically evaluating the risk and speciation of As in HTL.
砷（As）的归宿和形态一直存在争议。我们通过在不同 pH 值的水热液化（HTL）系统中含砷藻类来研究其特性，具体采用了两种经典方法，即欧洲共同体参考局（BCR）和 Wenzel 法。pH 调节剂（如 CHCOOH、HCl 和 KOH）将固体残渣中的 11.23-16.55%的砷固定，而 88.07-82.44%的砷存在于水溶液中。ICP-MS 和 XRD 分析表明，砷（V）在固体残渣中转化为砷（III）和砷（0），而在 HTL 过程中，砷（V）主要转化为砷（III）。当比较固体残渣中砷的分类形式时，Wenzel 法更适合划分砷的生物可利用形式，而 BCR 更适合估计砷的毒性形式。随后，pH 调节剂增加了与不稳定形式增加相关的固体残渣中砷的风险。酸性添加剂将酰胺水解为羧酸，这削弱了 HTL 过程中的还原环境。相比之下，碱性添加剂将酰胺水解为氨，增强了还原环境，增加了产品中砷的风险。这项工作为系统评估 HTL 中砷的风险和形态提供了新的见解。
