Bicarbonate-enhanced Removal of a Typical Amino Acid Using a Cobalt(ii)-Catalyzed Fenton-like Reaction in Aqueous Solution

Dissolved organic nitrogen (DON) has drawn more attention because of its potential to form nitrogenous disinfection by-products. Amino acids are important DON constituents in alkaline eutrophic water. Alkaline water interferes with advanced oxidation processing of target compounds. A new oxidation process using the H2O2-HCO3-system was used to remove the typical amino acid histidine from water. The rates of DON and histidine removal in the Co2+/H2O2-HCO3- system within 60 min were 54% and 72%, respectively. The optimum pH for histidine degradation was 8, and the optimal dosages of NaHCO3 and H2O2 were 35 and 20 mM, respectively. Co(II) complex with amino acids (Co(II)-Xaa complex), center dot OH, and HCO4- were involved in the degradation, and center dot O-2 formed via HCO4- decomposition, as evidenced by the previous study. The reaction products suggest that part of the histidine undergoes oxidation to ammonia nitrogen within 60 min. High-performance liquid chromatography-mass spectrometry results reveal that histidine degradation consists of two separate pathways involving the Co(II)-Xaa complex, center dot OH, and center dot O-2(-), with the two pathways gradually converting -NH2 into NH4+-N. Gas chromatography detection showed that the nitrogenated-disinfection by-products formation rate decreased in the Co2+/H2O2-HCO3-system.