Probing the fast transformation mechanism of Cr (VI) on carbon dots with structural defects and surface oxygen functional groups

Abstract

Carbon dots (CDs) with dimensional size less than 10 nm have similar constitutional units to black carbon (BC) in natural environment. Herein, we investigated the fast transformation mechanism of Cr (VI) oxyanions on CDs with structural defects and surface oxygen functional groups. The electrons transferred from CDs to reduce Cr (VI) were calculated to be 0.07–0.1 mmol g−1 in 20 min The reduction kinetics rate driven by carbon defects is of approximately 3–5 times faster than that driven by surface oxygen-containing functional groups. Metal cations (K+, Na+, Ca2+, Mg2+) in water matrix showed negligible effect on the reduction of Cr (VI), while iron ions chelate with CDs to form a CD-COOFe complex structure, promoting diffusion and electron transfer simultaneously, enhancing the electron transfer rate constant from 6.94 × 10−3 to 10.00 × 10−3 cm s−1.