Assembling nanoscale zero-valent iron on magnetic Fe3O4/reduced graphene oxide composite for efficient reduction of hexanitrohexaazaisowurtzitane (CL-20)

To increase the hexanitrohexaazaisowurtzitane (CL-20) removal capacity of nanoscale zero-valent iron (nZVI), the present study explored a facile modification route based on the assembling of nZVI onto a magnetic Fe3O4/reduced graphene oxide (MG) composite. These nZVI particles were well dispersed and tightly attached on the basal plane of reduced graphene oxide (rGO) with Fe3O4 integration as the middle layer. These nZVI@MG composites showed better CL-20 removal efficiency, compared with commercial ZVI, nZVI, MG and nZVI assembled on rGO (nZVI@rGO). The rGO and Fe3O4 played a confirming role in alleviating the agglomeration and improving nZVI reducibility. The CL-20 removal process by nZVI@MG followed a pseudo-second-order kinetics model, indicating the involvement of hybrid adsorption and chemical reactions. Three intermediates during CL-20 reduction by nZVI@MG were identified through LC-MS or GC-MS. Based on these intermediates, two distinct pathways were proposed. This study demonstrated that nZVI@MG composites could be promisingly implemented as an environmentally friendly and inexpensive material for CL-20 removal from wastewater.