Preparation of Novel ALRCs/nZVI Composite and Its Removal of Cr(VI) from Aqueous

Abstract

To optimize carbon-based nanoscale-zero-valent iron (nZVI) material and remove hexavalent chromium [Cr(VI)] more effectively, activated low rank coals (ALRCs) and FeCl2 were used to prepare “activated low rank coals/nanoscale-zero-valent iron” (ALRCs/nZVI) composites by carbothermal reduction. The prepared ALRCs/nZVI was characterized by XRD, SEM, BET and XPS. Then the removal characteristics of Cr(VI) from solution by ALRCs/nZVI were studied. The results show that the BET specific surface area of ALRCs/nZVI is as high as 2908 m2 g−1. The nZVI microspheres are successfully loaded onto the surface of ALRCs with a diameter of about 500 nm. The low pH and high temperature is beneficial to the removal of Cr(VI) by ALRCs/nZVI. The adsorption of Cr(VI) by ALRCs/nZVI follows the Freundlich model and the pseudo-second-order kinetic model. Electrostatic attraction, reduction, and surface precipitation are main mechanisms for Cr(VI) removal. The maximum Cr(VI) removal amount fitted by Langmuir model was 159.7–196.5 mg g−1 which is higher than that of most reported carbon-based nZVI composites. The innovations of this work include (1) using low rank coal as raw material to reduce the cost, (2) the material pre-activation process improves the adsorption capacity of production, and (3) reduction and loading of nanoscale-zero-valent iron using carbothermal method (easy operation, high safety, strong combination of zero-valent iron and substrate, easy to large-scale application and continuous production, etc.).