Superefficient Removal of Heavy Metals from Wastewater by Mg-Loaded Biochars: Adsorption Characteristics and Removal Mechanisms

• Published in: Langmuir Vol. 36; no. 31; pp. 9160 - 9174
• Main Authors: Li, An Yu, Deng, Hua, Jiang, Yan Hong, Ye, Cheng Hui, Yu, Bi Ge, Zhou, Xin Lan, Ma, Ai Ying
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.08.2020
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.0c01454

Six types of biochar (BSB, CSB, FSB, CFSB, MSB, and TSB) were prepared from different raw materials by loading magnesium ions (Mg2+) via an impregnation process. The adsorption kinetics and thermodynamics of heavy metals at high concentrations were analyzed. The adsorption mechanisms were investigated by zeta potential, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma–atomic absorption spectroscopy analyses. The adsorption of heavy metals by BSB, CSB, FSB, CFSB, MSB, and TSB conformed to the Langmuir model and PS-order. The maximum theoretical saturation adsorption capacities for Cd­(II), Cu­(II), and Pb­(II) were 333.33, 238.10, 75.19, 96.15, 66.23, and 185.19 mg·g–1; 370.37, 294.12, 111.11, 169.49, 84.75, and 217.39 mg·g–1; and 302.58, 200.00, 61.73, 90.91, 54.47, and 166.67 mg·g–1, respectively. According to the analysis of the contribution of adsorption, the adsorption process was mainly controlled by cation−π interactions, ion exchange, mineral precipitation, and functional group interactions. Biochars contain ash, functional groups and load a large number of Mg2+, which can form complexes with metal ions and perform strong ion exchange; therefore, mineral precipitation and cation exchange played dominant roles in the adsorption process. The prepared Mg-loaded biochars presented in this research showed excellent adsorption properties for heavy metals and have great potential for practical application; in particular, BSB had the strongest adsorption capacity for the three heavy metal ions.