Strongly enhanced Fenton degradation of organic pollutants by cysteine: An aliphatic amino acid accelerator outweighs hydroquinone analogues.

Quinone-hydroquinone analogues have been proven to be efficient promoters of Fenton reactions by accelerating the Fe(III)/Fe(II) redox cycle along with self-destruction. However, so far there is little information on non-quinone-hydroquinone cocatalyst for Fenton reactions. This study found that cysteine, a common aliphatic amino acid, can strongly enhance Fenton degradation of organic pollutants by accelerating Fe(III)/Fe(II) redox cycle, as quinone-hydroquinone analogues do. Further, cysteine is superior to quinone-hydroquinone analogues in catalytic activity, H2O2 utilization and atmospheric limits. The cocatalysis mechanism based on the cycle of cysteine/cystine was proposed.