TY - JOUR
T1 - In Situ hydrochar regulates Cu fate and speciation
T2 - Insights into transformation mechanism
AU - Li, Hugang
AU - Cao, Maojiong
AU - Watson, Jamison
AU - Zhang, Yuanhui
AU - Liu, Zhidan
N1 - Funding Information:
This work was financially supported by through the National Key Research and Development Program of China ( 2016YFD0501402 ) and the National Natural Science Foundation of China [ U1562107 ]. The author also thanks Mr. Jian Wu for their assistance in the experiments.
PY - 2021/5/15
Y1 - 2021/5/15
N2 - 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 °C-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 (36.8 KJ/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.
AB - 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 °C-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 (36.8 KJ/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.
KW - Algae
KW - Heavy metal
KW - Hydrochar
KW - Hydrothermal liquefaction
KW - Transformation
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U2 - 10.1016/j.jhazmat.2020.124616
DO - 10.1016/j.jhazmat.2020.124616
M3 - Article
C2 - 33248821
SN - 0304-3894
VL - 410
SP - 124616
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
M1 - 124616
ER -