Effects of pyrolysis temperature and aging treatment on the adsorption of Cd2+ and Zn2+ by coffee grounds biochar. (June 2022)

• Record Type: Journal Article
• Authors: Ke, Yuxin; Cui, Song; Fu, Qiang; Hough, Rupert; Zhang, Zulin; Li, Yi-Fan
• Is Part Of: Chemosphere. Volume 296(2022)
• Publication Date: 2022-06
• Subjects: Coffee grounds biochar -- Aging treatment -- Cadmium -- Zinc -- Adsorption mechanism; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.134051
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: As an in-situ immobilization material for heavy metals, biochar can exist in the environment for thousands of years, while whether the natural aging would affect its heavy metals adsorption performance still remains unclear. Therefore, the coffee grounds biochar (CGB) was prepared under different pyrolysis temperatures (300, 500 and 700 °C) in this study, and the simulated artificial aging treatment was carried out to investigate the effects of pyrolysis temperature and aging treatment on Cd 2+ and Zn 2+ (both separate and combined conditions) adsorption performance of CGB. The result revealed that Fresh-CGB adsorption performance increased with increasing pyrolysis temperature, while the relationship was not so clear with Aged-CGB where adsorption performance peaked at medium pyrolysis temperature (500 °C) but reduced again as pyrolysis temperature increased to 700 °C. The changes of Aged-CGB adsorption performance for Cd 2+ and Zn 2+ represented the long-term performance of naturally aging biochar in environment, and a mid-range pyrolysis temperature would seem most appropriate for long-term application of biochar. The X-ray Diffraction (XRD) result revealed that the degree of graphitization of CGB increased with increasing pyrolysis temperature, which represents a stronger environmental stability as the weight loss of CGB300, CGB500 and CGB700 after aging treatment was 2.38%, 0.66%, and 0%, respectively. The EDS and FTIR results suggested that ion-exchange and complexation between CGB/Aged-CGB with Cd 2+ /Zn 2+ played a dominant role in adsorption processes. In addition, the selectivity for Cd 2+ was significantly improved after the aging treatment. This is desirable given the stronger toxicity of Cd 2+ relative to Zn 2+ . In general, this study provides new insights into the practical application of biochar from the perspective of long-term effects. Graphical abstract: Image 1 Highlights: Pyrolysis temperature is independedt with aging treatment in long-term adsorption. A mid-range pyrolysis temperature was more appropriate for long-term adsorption. Aged-biochar has a stronger selective adsorption for Cd 2+ than Zn 2+ . Ion-exchange and complexation play a dominant role in adsorption processes.