The sorptive and reductive capacities of biochar supported nanoscaled zero-valent iron (nZVI) in relation to its crystallite size

In this work, nZVI was immobilized by bamboo derived biochars (nZVI/BB), hydrogen peroxide (H2O2) (nZVI/PBB) and nitric acid (HNO3) (nZVI/HBB) modified BB. H2O2 and HNO3 deceased surface area and pore volume of pristine biochars. Total iron (Fe) contents were 16.50, 24.40, and 13.08% for nZVI/BB, nZVI/PBB and nZVI/HBB, respectively. The X-ray diffraction revealed that nZVI in biochar matrix was dominantly metallic Fe coated with Fe oxides. The transmission electron microscopy indicated nZVI particle sizes were 41.5, 30.5 and 6.1 nm for nZVI/BB, nZVI/HBB and nZVI/PBB, respectively. The removal capacities of arsenate (AsV) and silver ions (Ag+) by nZVI nanocomposites were compared in a batch experiment. Greater reductive removal of Ag+ (1217 g kg−1 nZVI) and sorptive removal of AsV (109.1 g kg−1 nZVI) were achieved in nZVI/PBB, indicating smaller-sized nZVI was more reactive. Thus, particle size of nZVI affected the sorptive and reductive capacities for AsV and Ag+.