The degradation of EDTA by the bimetallic Fe–Cu/O2 system

Abstract

• The Fe–Cu/O 2 process exhibited higher removal rate of EDTA than that of ZEA process. • It would not cause heavy new metal pollution in initial acidic condition. • Cu 0 may improve the generation of OH in acidic condition. • The degradation of EDTA may be attributed to OH in acidic condition. • It may be attributed to a mixture of OH and ferryl ion in alkalinity condition. The bimetallic Fe–Cu/O 2 process exhibited significantly higher reactivity than did the Fe/O 2 process for the degradation of ethylenediaminetetraacetic acid (EDTA). With the analysis of the soluble Cu 2+ in the solution and decomposition of H 2 O 2 catalyzed by Cu 0 , possible enhanced-pathways at different pHs were suggested. The degradation efficiency of EDTA increased with decreasing initial pH ranging 3–9, however, the reactions proceeded at a weakly-basic to basic condition in most of the reaction time. POD inhibition test showed that in situ generation of H 2 O 2 played a pivotal role in the EDTA degradation, however, the instant concentration analyzed by DPD–POD method was less than 4.5 μM due to rapid subsequent Fenton reaction. Furthermore, DMPO–ESR spectroscopy and BA-trapping experiments detected the in situ generation of OH. The mechanism of EDTA oxidative degraded by the bimetallic Fe–Cu/O 2 process was verified using control experiments of absorption, stripping, and coagulation sedimentation of EDTA in the system, analysis of solid residue, oxidation of O 2 and H 2 O 2 , as well as detection of H 2 O 2 and OH.