Synthesis of Fe-N doped porous carbon/silicate composites regulated by minerals in coal gasification fine slag for synergistic electrocatalytic treatment of phenolic wastewater

Yanjie Niu; Qiqi Zhang; Li Wang; Fanhui Guo; Yixin Zhang; Jianjun Wu

doi:10.1016/j.envres.2024.118643

Synthesis of Fe-N doped porous carbon/silicate composites regulated by minerals in coal gasification fine slag for synergistic electrocatalytic treatment of phenolic wastewater

Environ Res. 2024 Mar 6;251(Pt 1):118643. doi: 10.1016/j.envres.2024.118643. Online ahead of print.

Authors

Yanjie Niu¹, Qiqi Zhang¹, Li Wang¹, Fanhui Guo¹, Yixin Zhang², Jianjun Wu³

Affiliations

¹ School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, 221116, PR China.
² Chinese National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou, 221116, PR China.
³ School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, 221116, PR China. Electronic address: jjuw@163.com.

PMID: 38458590
DOI: 10.1016/j.envres.2024.118643

Abstract

Coal gasification fine slag (CGFS), as a difficult-to-dispose solid waste in the coal chemical industry, consists of minerals and residual carbon. Due to the aggregate structure of minerals blocking pores and encapsulating active substances, the high-value utilization of CGFS still remains a challenge. Based on the intrinsic characteristics of CGFS, this study synthesized Fe-N doped porous carbon/silicate composites (Fe-NC) by alkali activation and pyrolysis for electrocatalytic degradation of phenolic wastewater. Meanwhile, minerals were utilized to regulate the surface chemical and pore structure, turning their disadvantages into advantages, which caused a sharp increase in m-cresol mineralization. The positive effect of minerals on composite properties was investigated by characterization techniques, electrochemical analyses and density functional theory (DFT) calculations. It was found that the mesoporous structure of the mineral-regulated composites was further developed, with more carbon defects and reactive substances on its surface. Most importantly, silicate mediated iron conversion through strong interaction with H₂O₂, high work function gradient with electroactive iron, and excellent superoxide radical (•O₂^-) production capacity. It effectively improved the reversibility and kinetics of the entire electrocatalytic reaction. Within the Fe-NC₃₁₁ electrocatalytic system, the m-cresol removal rate reached 99.55 ± 1.24%, surpassing most reported Fe-N-doped electrocatalysts. In addition, the adsorption and electrooxidation experiment confirmed that the synergistic effect of Fe-N doped porous carbon and silicate simultaneously promoted the capture of pollutants and the transformation of electroactive molecules, and hence effectively shortened the diffusion path of short-lived radicals, which was further supported by molecular dynamics simulation. Therefore, this research provides new insights into the problem of mineral limitations and opens an innovative approach for CGFS recycling and environmental remediation.

Keywords: Composite electrocatalyst; Electrochemical advanced oxidation; Gasification fine slag; Phenolic wastewater; Synergistic electrocatalysis.