A Fenton-like process with combination of
dye has been used to enhance the treatment of
carbofuran (2,3-dihydro-2,2-dimethylbenzofuran -7-yl methylcarbamate)
pesticide rinsate. Results showed that as compared to Fenton-like process, this
photosensitization Fenton-like process improved the degradation efficiency of
carbofuran rinsate significantly. Among the conditions studied, the optimum dosage for the complete destruction of
carbofuran molecular structure was found under a [H2O2]0/[Fe3+]0 ratio of 30-35 and a [
Dye]0/[Fe3+]0 ratio of 2%, respectively, after an irradiance of 500 W/m2 for 20 min. As a result, the COD degradation efficiency of rinsate could be promoted from 37.1 to 61.2% and 66.0% by an addition of
methylene blue (MB) and
alizarin red S (ARS), respectively. Nevertheless, ARS showed a much more effective acceleration effect on the mineralization and microtoxicity reduction of
carbofuran than MB. A mineralization efficiency of 57.2% and a microtoxicity reduction of 90% could be achieved with the addition of ARS. Because of its
quinone structure unit, the
dye ARS could play a role like
hydroquinone to recycle Fe2+ from Fe3+, resulting in one more catalytic effect on the reduction of Fe3+ and thus the mineralization and microtoxicity reduction of
carbofuran was greatly promoted in the presence of ARS. In addition, it was found that
carbofuran molecules could be decomposed quickly to lower-molecular-weight intermediates and even mineralized by attacking of
hydroxyl radicals.
Carbofuran was found to be decomposed to
carbofuran phenol, 3-oxo
carbofuran phenol, and 3-hydroxyl
carbofuran phenol initially, and then further be degraded to smaller molecules, such as NO3-, CH3COOH, (COOH)2 and CO2. Accordingly, it was believed that the Fenton-like process along with the aid of a
photosensitizer, such as ARS, under an appropriate ratio could be a feasible and potential technology for the treatment of
pesticide rinsate.