Multiple roles of ferric chloride in preparing efficient magnetic hydrochar for sorption of methylene blue from water solutions

• Published in: Bioresource technology Vol. 373; p. 128715
• Main Authors: Sun, Xiao-Na, Yu, Kun, He, Jiong-Hua, Chen, Yan, Guo, Jian-Zhong, Li, Bing
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2023
• Subjects: Adsorption; Fe3O4; Ferric Compounds - chemistry; Hydrochar; Magnetic Phenomena; Magnetism; Methylene blue; Methylene Blue - chemistry; Water; Water Pollutants, Chemical - chemistry; Fe3O4; Hydrochar; Magnetism; Adsorption; Methylene blue; FeO
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2023.128715

•Fe3O4-loaded hydrochar was prepared by HTC and precipitation.•FeCl3 plays at least two roles as a catalyst and an oxidant in HTC.•Electrostatic interaction was the primary mechanism of MB sorption by HC-Fe3O4.•Fe3O4-loaded hydrochar can be stably recycled for at least 5 consecutive cycles.•Adsorption follows Langmuir isotherm and pseudo-second-order kinetics. Highly efficient and cheap magnetic materials have application prospects in wastewater treatment. Herein, Fe3O4-loaded hydrochar (HC-Fe3O4) was obtained from hydrothermal carbonization (HTC) of bamboo with FeCl3 and then added with FeCl3 to form a magnetic sorbent via simple precipitation. The HC-Fe3O4 was characterized with various instruments. The characterizations show FeCl3 plays at least two roles as a catalyst and an oxidant in HTC. The specific surface area of hydrochar enlarged from 39.9731 to 60.9887 m2·g−1 after the addition of FeCl3 during HTC, which showed FeCl3 acted as a catalyst in HTC. XRD indicated Fe3O4 was formed by the structure of HC-Fe3O4, which indicated Fe(III) was reduced to Fe(II) during HTC. Sorption of methylene blue (MB) onto HC-Fe3O4 was better fitted by the Langmuir isotherm and pseudo-second-order kinetic models. Sorption is a spontaneous thermodynamic endothermic process and HC-Fe3O4 is easily separated by an applied magnetic field and reused.