Simultaneous adsorption of Cd and As by a novel coal gasification slag based composite: Characterization and application in soil remediation

Changzhi Zhou; Junhuan Wang; Qian Wang; Zheng Leng; Yue Geng; Shurui Sun; Hong Hou

doi:10.1016/j.scitotenv.2023.163374

Simultaneous adsorption of Cd and As by a novel coal gasification slag based composite: Characterization and application in soil remediation

Sci Total Environ. 2023 Jul 15:882:163374. doi: 10.1016/j.scitotenv.2023.163374. Epub 2023 Apr 6.

Authors

Changzhi Zhou¹, Junhuan Wang², Qian Wang³, Zheng Leng², Yue Geng², Shurui Sun², Hong Hou⁴

Affiliations

¹ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Water Sciences, Beijing Normal University, Beijing 100875, China.
² State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
³ Technical Centre for Soil, Agricultural and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China.
⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: houhong@craes.org.cn.

PMID: 37030369
DOI: 10.1016/j.scitotenv.2023.163374

Abstract

Cadmium (Cd) and arsenic (As) co-contamination has become increasingly serious in China agricultural soil due to rapid industrialization and urbanization. The opposite geochemical behaviors of Cd and As pose huge challenges for developing a material for their simultaneous immobilization in soils. Coal gasification slag (CGS) as a by-product of coal gasification process, is always dumped into a local landfill, which has a negative impact on environment. Few reports have been available on applying CGS as a material to immobilize simultaneously multiple soil heavy metals. A series of iron-modified coal gasification slag (IGS) composites IGS3/5/7/9/11 (with different pH values) were synthesized by alkali fusion and iron impregnation. After modification, carboxyl groups were activated, and Fe was successfully loaded onto the surface of IGS in the form of FeO and Fe₂O₃. The IGS7 exhibited the best adsorption capacity with the maximum Cd and As adsorption capacity of 42.72 mg/g and 35.29 mg/g, respectively. The Cd was mainly adsorbed through electrostatic attraction and precipitation, while the As through complexation with iron (hydr)oxides. IGS7 significantly reduced the bioavailability of Cd and As in soil with Cd bioavailability reduced from 1.17 mg/kg to 0.69 mg/kg and As bioavailability reduced from 10.59 mg/kg to 6.86 mg/kg at 1 % IGS7 addition. The Cd and As were all transformed to more stable fractions after IGS7 addition. The acid soluble and reducible Cd fractions were transformed into oxidizable and residual Cd fractions, and the non-specifically and specifically adsorbed As fractions were transformed to amorphous iron oxide-bound As fraction. This study provides valuable references for the application of CGS to the remediation of Cd and As co-contaminated soil.

Keywords: Arsenic; Bioavailability; CGS; Cadmium; Iron modified.