Adsorption and reduction of Cr(VI) by N, S co-doped porous carbon from sewage sludge and low-rank coal: Combining experiments and theoretical calculations

Xiaoyang Yang; Baofeng Wang; Peng Zhang; Xutao Song; Fangqin Cheng

doi:10.1016/j.scitotenv.2023.169265

Adsorption and reduction of Cr(VI) by N, S co-doped porous carbon from sewage sludge and low-rank coal: Combining experiments and theoretical calculations

Sci Total Environ. 2024 Feb 20:912:169265. doi: 10.1016/j.scitotenv.2023.169265. Epub 2023 Dec 10.

Authors

Xiaoyang Yang¹, Baofeng Wang², Peng Zhang¹, Xutao Song¹, Fangqin Cheng³

Affiliations

¹ Engineering Research Center of CO(2) Emission Reduction and Resource Utilization - Ministry of Education of the People's Republic of China, Institute of Resources and Environment Engineering, Shanxi University, Taiyuan 030006, China.
² Engineering Research Center of CO(2) Emission Reduction and Resource Utilization - Ministry of Education of the People's Republic of China, Institute of Resources and Environment Engineering, Shanxi University, Taiyuan 030006, China. Electronic address: wangbaofeng@sxu.edu.cn.
³ Engineering Research Center of CO(2) Emission Reduction and Resource Utilization - Ministry of Education of the People's Republic of China, Institute of Resources and Environment Engineering, Shanxi University, Taiyuan 030006, China. Electronic address: cfangqin@sxu.edu.cn.

PMID: 38086485
DOI: 10.1016/j.scitotenv.2023.169265

Abstract

Herein, a novel N, S co-doped porous carbon (S5C5-AC) for Cr(VI) removal was prepared by co-hydrothermal carbonization (HTC) of sewage sludge (SS) and low-rank coal (LC) combining with KOH modification. The results showed that S5C5-AC had excellent adsorption performance on Cr(VI), and lower pH value, higher initial concentration and longer contact time were beneficial for Cr(VI) adsorption. The adsorption kinetics and isotherms revealed that Cr(VI) adsorption by S5C5-AC was homogeneous and dominated by chemisorption. The adsorption isotherm showed that the maximum equilibrium adsorption capacity of S5C5-AC for Cr(VI) was 382.04 mg/g at 25 °C. Furthermore, the results showed that the main mechanisms for Cr(VI) removal were the pore filling, electrostatic interaction and reduction. Moreover, the electron transfer mechanism during the adsorption and reduction process was further explored at the molecular and electronic levels by density functional theory (DFT) and front orbital theory (FOT) simulations. The analysis of DFT and FOT indicated that the synergistic effect between S and N functional groups was exhibited during the Cr(VI) removal process. Considering the existence of synergistic effects between N and S functional groups during adsorption, the S and N content and form were modified collaboratively. Increasing the relative content of pyrrolic N may be the most effective pathway for improving removal performance. Besides that, S5C5-AC exhibited excellent adsorption capacity over a high coexisting ion concentration range and various actual water bodies and regeneration performance, which indicated that S5C5-AC had promising potential for the remediation of wastewater in industrial applications.

Keywords: Cr(VI) removal; Hydrothermal carbonization; Low-rank coal; N, S co-doped porous carbon; Sewage sludge.