▎ 摘　　要

Biochar has recently been fascinating for research in many environment areas due to its potential applications. In this research, graphene, and nano zero-valent iron (nZVI) were integrated with biochar and used for copper immobilization in the soil. Initially, the biomass feedstock was pyrolyzed under N-2 atmosphere from 150 to 650 degrees C and immersed in an aqueous solution containing graphene, and then impregnated with nZVI. Laboratory characterization with different instruments (eg. SEM, TEM, XRD, UV-Vis, VSM, and XPS) showed that graphene sheets and reactive nZVI were loaded on the biochar surface during the development process. The 450 degrees C was considered as optimum pyrolysis temperature based on the effective surface properties of the obtain biochar material. Boehm titration and functional group analysis confirmed the presence of carboxylic groups, phenolic groups in the corn stack biochar supported graphene oxide/nZVI (CTBC-GO/nZVI). Thermogravimetric analysis showed that nZVI incorporation to biochar surface could improve thermal stability as compared to graphene oxide incorporated biochar and pristine biochar. The material was utilized for copper (Cu) immobilization in the soil and a comparative evaluation was established on the basis of efficiency. The soil experiment showed that the CTBC-GO/nZVI has a superior immobilization efficiency of copper than pristine biochar and GO@BC. The available Cu content decreased by > 65% in CTBC-GO/nZVI amended soil after 14 days. Sequential extraction procedure (SEP) results suggested that CTBC-GO/nZVI promoted the conversion of more accessible Cu into the less accessible and bioavailable forms to reduce the toxicity of Cu. Therefore, CTBC-GO/nZVI composite is a promising and effective amendment for immobilizing Cu in contaminated soils and improving soil properties. This work can put forward a strategy to develop magnetic biochar composites and an application towards toxic heavy metals immobilization in soil. (C) 2019 Elsevier Ltd. All rights reserved.