Thermally activated persulfate oxidation of ampicillin: Kinetics, transformation products and ecotoxicity

The heat-activated persulfate system showed encouraging results for the destruction of the widely used antibiotic Ampicillin (AMP). AMP removal follows exponential decay, and the observed kinetic constant was enhanced with persulfate (PS) dosage at the range 50-500 mg L-1 and temperature (40-60 ?), while AMP thermolysis at 60 ? was almost negligible. The apparent activation energy was estimated to 124.7 kJ mol(-1). Alkaline conditions, water matrix constituents like bicarbonates, humic acid, and real water matrices retarded AMP oxidation. Experiments performed with tert-butanol and methanol as scavengers demonstrated the contribution of sulfate radicals as the dominant reactive species. Seven transformation products (TPs) of AMP have been identified from AMP destruction. An EC50 value equal to 187 mg L-1 was calculated for 72 h of exposure of the microalgae Chlorella sorokiniana to AMP. According to the ecotoxicity experiments that conducted after treatment of AMP with PS for different reaction times, no important inhibition of microalgae was noticed for contact time of 72 h and 10 d. These results indicate the formation of no toxic AMP by-products for the applied experimental conditions.

Automated summary

The heat-activated persulfate system showed promising results in the destruction of the widely used antibiotic Ampicillin (AMP). The removal of AMP exhibited exponential decay and was enhanced by persulfate dosage and higher temperatures. The formation of sulfate radicals was identified as the main reactive species. The experiments also revealed the absence of significant inhibition of microalgae after treatment with persulfate.