Ethanol enhanced carbon tetrachloride degradation in Fe(II) activated calcium peroxide system

The degradation of carbon tetrachloride (CT) by Fe(II) activated calcium peroxide (CaO2) in the presence of ethanol (CH3CH2OH, EtOH) was investigated. The results showed that CT could be completely degraded in 20 min with 3.90 mmol L-1 CaO2, 5.20 mmol L-1 Fe(II) and 1.30 mmol L-1 EtOH in CaO2/Fe(II)/EtOH system. Superoxide radical anion (O-2(center dot-)) and hydroxyethyl radical ((CHCH3OH)-C-center dot, HER) were demonstrated as the main radicals for CT degradation which were confirmed by scavenging tests and electron paramagnetic resonance (EPR) detection. The mechanism of CT degradation was mainly due to the split of C-Cl and CT degradation pathway was proposed accordingly. Further investigation suggested that the solution pH in range of 3-5 were favorable to CT degradation. Both Cl- and HCO3- had inhibitive effect on CT removal, while the influence of NO3- and SO42- could be negligible. Moreover, the results of experiments performed using actual groundwater demonstrated that an adverse impact occurred on CT degradation, but this drawback could be overcome by increasing reagent dosages. In summary, CT degradation in Fe(II) activated CaO2 system can be significantly promoted by EtOH addition, and this finding, for the first time, provides an innovative technology for degradation of the highly oxidized organic contaminants.