Optimized water treatment by combining catalytic Fenton reaction using diamond supported gold and biological degradation

Abstract

Recently it has been reported that gold nanoparticles supported on Fenton treated diamond nanoparticles (Au/DNP) is a highly efficient catalyst to promote the generation of hydroxyl radicals from H2O2 [S. Navalon, R. Martin, M. Alvaro, H. Garcia, Angew. Chem. Int. Ed. 49 (2010) 8403–8407]. In the present work we have optimized a series of experimental parameters including initial pH, reaction temperature, H2O2 concentration, phenol to gold mol ratio and oxygen pressure to achieve biodegradability of aqueous phenol solutions with the minimum H2O2 concentration and attain a complete lack of toxicity (determined by the Vibrio fischeri bioluminescence assay). The results presented show how to combine mild Fenton degradation of bioreluctant phenol with consecutive biological treatment in such a way that the amount of H2O2 is kept to the minimum value. It was determined that the best conditions are pH 4, 50 ◦C, H2O2 to phenol molar ratio 4 and 320 mg L−1 (1 wt% Au) catalyst under oxygen atmosphere. Au/DNP exhibits a remarkable stability under these conditions and can be used up to four times without observing any loose of catalytic activity as determined by the temporal profiles of phenol degradation and H2O2 decomposition.