Photo-Fenton pretreatment of carbofuran – Analyses via experimental design, detoxification and biodegradability enhancement

The central composite design (CCD) and response surface methodology (RSM) were employed to evaluate the effect of H2O2 dosage rate (1–10 mg L−1 min−1) and Fe3+ dosage (1–100 mg L−1) in the photo-Fenton treatment of carbofuran and to develop the second-order polynomial equations in terms of carbofuran and dissolved organic carbon (DOC) removals and BOD5/DOC ratio with different reaction times. Both H2O2 dosage rate and Fe3+ dosage have significant effects on the dependable variables. Based on the results of carbofuran removal and BOD5/DOC ratio, H2O2 dosage rate of 5.4 mg L−1 min−1 and Fe3+ dosage of 59 mg L−1 were found to be the favorable reagent dosages for carbofuran degradation. Under these conditions, the toxicity unit measured by Microtox® test with 5 min exposure was decreased from 47 to 6 and the biodegradability evaluated by BOD5/COD ratio was increased from 0 to 0.76 after 60 min reaction. The results obtained in this study demonstrate that the photo-Fenton process is a promising pretreatment before the application of biological treatment for carbofuran removal from contaminated water/wastewater.

► H2O2 dosage rate and Fe3+ dosage have significant effects on dependent variables.
► Polynomial equations for dependent variables have been successfully developed.
► A 100 mg L−1 of carbofuran was completely removed after 60 min reaction.
► Toxicity decreased and biodegradability increased at the end of experiment.
► Oxidation degree of organic carbon contributes to enhancement of biodegradability.