Enhanced heterogeneous and homogeneous Fenton-like degradation of carbamazepine by nano-Fe3O4/H2O2 with nitrilotriacetic acid

Abstract

The influence of a biodegradable agent, nitrilotriacetic acid (NTA), on the degradation of the model compound carbamazepine (CBZ) by the nano-Fe3O4/H2O2 system was investigated. The results showed that the presence of NTA can provide better performance of the nano-Fe3O4/H2O2 system for CBZ degradation at reduced usage of H2O2 and nano-Fe3O4. The optimal concentration of NTA was determined to be 0.5–1.0mM. The first-order rate constant, kapp, for CBZ degradation by 1.0gL−1 of nano-Fe3O4 and 100mM of H2O2 in the presence of 0.5mM of NTA at an initial neutral pH was determined to be 4.32×10−2min−1, which was 80 times larger than that in the absence of NTA. In addition, the kapp value increased with the increase in nano-Fe3O4 concentration from 0.1 to 3.0gL−1, and the H2O2 concentration increased from 5 to 600mM. The initial pH of CBZ solutions over a range of pH 5.0–9.0 did not affect the kapp value of CBZ (p=0.08). A decrease in the initial concentration of CBZ from 6.35×10−2 to 1.06×10−2 mM resulted in an increase of the kapp value from 4.32×10−2 to 1.51×10−1min−1. Moreover, the results indicated that the degradation intermediates were generated by the attack of OH. The degradation mechanism of CBZ included both an enhanced heterogeneous Fenton-like reaction on the Fe3O4 nanoparticle surface and an enhanced homogeneous Fenton-like reaction in the aqueous phase by Fe-NTA complexes.