Adsorption behaviors of Cu2+, Zn2+ and Cd2+ onto proteins, humic acid, and polysaccharides extracted from sludge EPS: Sorption properties and mechanisms

• Published in: Bioresource technology Vol. 291; p. 121868
• Main Authors: Wei, Liangliang, Li, Jianju, Xue, Mao, Wang, Sheng, Li, Qiaoyang, Qin, Kena, Jiang, Junqiu, Ding, Jing, Zhao, Qingliang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2019
• Subjects: Adsorption; EPS components; Mechanisms; Metal ions; Structural changes; Structural changes; EPS components; Mechanisms; Adsorption; Metal ions
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.121868

[Display omitted] •Protein/humic acid were more efficient in Zn2+ and Cd2+ sorption than polysaccharides.•Noticeable electrostatic interaction occurred for proteins/humic acid adsorption.•Freundlich model for Cu2+/Cd2+ sorption while Langmuir for Zn2+ on polysaccharide/HA.•Metals sorption on EPS was exothermic process, especially for humic acid and proteins. To clarify the adsorption behaviors of typical heavy metals onto sludge extracellular polymeric substances (EPS), the adsorption capacities and mechanisms, as well as the contributions of the different EPS components (proteins, humic acids and polysaccharides), to the adsorption of Zn2+, Cu2+ and Cd2+ were separately explored. Overall, proteins exhibited a relatively high adsorption capacity for the three metals ions, followed by humic acid, whereas least for polysaccharides. The adsorption of Cu2+ and Cd2+ onto proteins, humic acid and polysaccharides fit well to the Freundlich isotherm, whereas Langmuir model was the best fit for Zn2+ bindings onto polysaccharides/humic acid. The binding of Cu2+, Zn2+ and Cd2+ onto the three EPS components was exothermically favorable, and significant electrostatic interactions were observed for the heavy metals sorption onto humic acid and proteins. In addition, the effect of metal ions sorption on the spectrum of the proteins, polysaccharides and humic acid was also explored.