Enhanced removal of metal-cyanide complexes from wastewater by Fe-impregnated biochar: Adsorption performance and removal mechanism

Yunmei Wei; Lianying Chen; Gangzhen Jiao; Yi Wen; Qin Liao; Hongli Zhou; Shengjun Tang

doi:10.1016/j.chemosphere.2023.138719

Enhanced removal of metal-cyanide complexes from wastewater by Fe-impregnated biochar: Adsorption performance and removal mechanism

Chemosphere. 2023 Aug:331:138719. doi: 10.1016/j.chemosphere.2023.138719. Epub 2023 Apr 20.

Authors

Yunmei Wei¹, Lianying Chen², Gangzhen Jiao³, Yi Wen², Qin Liao², Hongli Zhou², Shengjun Tang⁴

Affiliations

¹ Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China. Electronic address: wym_1982@cqu.edu.cn.
² Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
³ Department of Environmental Science and Safety Engineering, Tianjin University of Technology, Tianjin, 300384, PR China.
⁴ Urban Planning and Design Institute of Shenzhen, Shenzhen, 518055, PR China.

PMID: 37086981
DOI: 10.1016/j.chemosphere.2023.138719

Abstract

Metal-cyanide complexes are common contaminants in industrial wastewater. Removal of these refractory contaminants is essential before their discharge into the environment. This study investigated a biochar (BC)-based sorbent material that could be applied for the efficient removal of metal-cyanide complexes from wastewater. In consideration of the strong electrostatic repulsion of the pristine BC toward anions, iron-modified BC (Fe-BC) composites were fabricated by a one-step co-pyrolysis of corn straw and FeCl₃ at 600-800 °C. The adsorption performance and corresponding sorption mechanisms of representative metal-cyanide complexes (ferricyanide [Fe(CN)₆]^3- and tetracyanonickelate [Ni(CN)₄]^2-) onto the Fe-BC composites were investigated. The results indicated that the Fe-BC composites had significantly high affinity toward the metal-cyanide complexes, reaching a maximum sorption capacity of 580.96 mg/g for [Fe(CN)₆]^3- and 588.86 mg/g for [Ni (CN)₄]^2-. A mechanistic study revealed that Fe-impregnation during BC fabrication could effectively alter the negatively charged BC surface, forming more functional groups that could interact with the metal-cyanide complexes. Moreover, the transformation of carbon structure promoted the carbothermal reduction process, leading to the formation of various reductive-Fe minerals in the resulting Fe-BC composites. These modification-induced alterations to the surface and structural characteristics of BC were expected to facilitate the adsorption/precipitation of target contaminants. Different sorption mechanisms were proposed for the two metal-cyanide complexes that were the focus of this study. For [Fe(CN)₆]^3-, precipitation by Fe-bearing species in the Fe-BC composites was the major factor controlling [Fe(CN)₆]^3- removal, while for [Ni(CN)₄]^2- hydrogen bonding interactions between surface functional groups (especially hydroxyl (-OH) and carboxyl (-COOH)) and [Ni(CN)₄]^2- were the main factors controlling removal.

Keywords: Adsorption; Biochar; Contaminant removal; Cyanide; Iron modification.

MeSH terms

Adsorption
Charcoal / chemistry
Coordination Complexes* / chemistry
Cyanides / chemistry
Wastewater
Water Pollutants, Chemical* / analysis

Substances

Wastewater
Coordination Complexes
biochar
Charcoal
Cyanides
Water Pollutants, Chemical