Cu is one of the dominant heavy metals toxic to human health and environmental ecosystems. Understanding its fate and chemical speciation is of great importance for hydrothermal liquefaction (HTL) of Cu-rich hazardous streams. Herein, we investigated its evolution during the HTL of wastewater algae through ICP-MS, XRD, XANES, and EXAFS. Cu-cysteine complexes (51.5%) and Cu₂S (40.4%) were the main components of Cu in algae, whereas the predominant form was CuS (70.9%) in 220^oC-hydrochar. Model compound experiments indicated that Cu-cysteine could be converted into CuS, while Cu₂S was stable during HTL. However, Cu₂S was partially converted into CuS in the hydrochar. Subsequently, the positive Gibbs free energy (36.8KJ/mol) indicates that the oxidation from Cu⁺ to Cu²⁺ can’t occur spontaneously. Furthermore, cyclic voltammograms demonstrated that hydrochar facilitated the oxidation of Cu₂S due to its higher capability of electron acceptance. All these results prove that hydrochar serves as a catalyst for the conversion of Cu₂S to CuS during HTL. This study firstly elucidated that Cu₂S was oxidized into CuS in the presence of hydrochar, and Cu-cysteine was converted into CuS under HTL. This study provides a critical insight into the transformation mechanism of Cu during the HTL of hazardous streams.

铜是对人体健康和环境生态系统有毒的主要重金属之一。了解其命运和化学形态对于富含铜的危险物流的水热液化（HTL）至关重要。在这里，我们通过ICP-MS，XRD，XANES和EXAFS研究了废水藻类HTL期间其演变。铜-半胱氨酸配合物（51.5％）和铜₂ S（40.4％）是藻类中铜的主要成分，而主要形式是在220 ^o C的碳氢盐中的铜（CuS）（70.9％）。模型化合物实验表明，Cu半胱氨酸可转化为CuS，而HTL期间Cu ₂ S稳定。但是，Cu ₂S在水焦中部分转化为CuS。随后，正吉布斯自由能（36.8KJ / mol）表明不能自发发生从Cu ⁺到Cu ²⁺的氧化。此外，循环伏安图表明，水煤由于其较高的电子接受能力而促进了Cu ₂ S的氧化。所有这些结果证明，在HTL期间，水焦炭可作为Cu ₂ S转化为CuS的催化剂。该研究首先阐明了在水煤油存在下Cu ₂ S被氧化为CuS，而HTL催化下Cu-半胱氨酸被转化为CuS。这项研究提供了对有害流HTL过程中Cu转化机理的重要见解。