Application of Fenton-like oxidation as pre-treatment for carbamazepine biodegradation

• CBZ inhibits the microbial activity being essentially non-biodegradable.
• Fenton oxidation allowed complete conversion of CBZ under mild operating conditions.
• The mineralization efficiency was increased by increasing the temperature.
• Aromatic intermediates were converted into non-toxic short-chain organic acids.
• Fenton oxidation of CBZ enhanced the biodegradability and reduced the toxicity.

Degradation of carbamazepine (CBZ) upon Fenton-like oxidation has been investigated analyzing the effect of H2O2 dose and temperature at a very low catalyst concentration (2 mg L−1 of Fe3+). Fenton-like oxidation allowed complete conversion of CBZ, the oxidation rate depending on the amount of H2O2 used. The addition of the theoretical stoichiometric amount of H2O2 led to the complete conversion of CBZ in 1 h reaction time. The reduction of the H2O2 initial concentration down to 10% of the stoichiometric led to a significant increase of that time up to 3 h. The mineralization efficiency of H2O2 was considerably increased by increasing the temperature (from 21 to 131 mg TOC/g H2O2 at 35 and 50 °C, respectively). Beyond 50 °C no significant effect was observed in the extension of reaction although it proceeded at significantly higher rate. The toxicity and biodegradability of the resulting effluents from Fenton-like oxidation were evaluated by respirometric tests using non-acclimated activated sludge. CBZ strongly inhibits the microbial activity (EC50 = 1.8 mg L−1) being essentially non-biodegradable. Fenton-like oxidation of CBZ (10 mg L−1) at 50 °C with the theoretical stoichiometric H2O2 amount for complete mineralization (5.6 mg H2O2/mg CBZ) allowed obtaining an easily biodegradable effluent.

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