Trichloronitromethane formation from amino acids by preozonation-chlorination: The effects of ozone dosage, reaction time, pH, and nitrite

The formation potentials of trichloronitromethane (TCNMFPs) of four natural amino acids (glycine, threonine, lysine and tryptophane) were investigated during chlorination and preozonation-chlorination. The effects of initial ozone dosage, reaction time, pH, and nitrite concentration on the TCNMFP of selected amino acid (AA) solutions were carried out in detail. During preozonation-chlorination, TCNMFPs of glycine- and lysine-containing solutions were more significant than that containing the other two AAs. Increasing the initial ozone concentration resulted in a considerable increase of TCNMFPs from glycine, lysine, and tryptophane. The concentration of trichloronitromethane (TCNM) of glycine, threonine, and lysine solutions increased during preozonation-chlorination with the ozonation time extended. The effect of pH on TCNMFPs of amino acid by preozonation was compound-specific. In addition, the presence of nitrite ions contributes greatly to TCNMFP for all four types of amino acids. However, as the concentration of NO2− increased to higher levels, there was no significant further enhancement of TCNMFP. For chlorination alone, TCNM formed in all four amino acid solutions, with tryptophane solution having the highest TCNMFP.