Chlorination of L-tyrosine and metal complex: degradation kinetics and disinfection by-products generation

ABSTRACT

The presence of metal ions in drinking water treatment and distribution systems may affect the disinfection process of organic matter, which had aroused people's concern. L-tyrosine can complex with metal ions through carboxyl, carbonyl, and amino groups and affect its chemical reactions. In this paper, the complexation of L-tyrosine with common metal ions was studied and the influence of complexation on chlorination with different experimental factors was investigated. It was inferred that L-tyrosine complexed with metal ions by single dentate ligand or double dentate chelation in a ratio of 2:1. The degradation of L-tyrosine-metal complex followed the pseudo-first-order reaction kinetic. TCM, DCAA, and TCAA were the main species DBPs in the chlorination of L-tyrosine. Compared with L-tyrosine, the reaction rate constants of complex increased by 5.6%, the formation of trihalomethane production decreased by 21.5% and the formation of haloacetic acids production increased by 26.9% at the state of metal complexation. The effect of metal complexation on chlorination was more obvious than that of metal coexistence. For different metal complexation, the order of inhibition on trihalomethane production was Ca²⁺> Fe³⁺> Mn²⁺ and the order of promotion on haloacetic acids production was Mn²⁺> Fe³⁺> Ca²⁺. Moreover, it was found that alkaline conditions were favorable for the formation of DBPs due to the hydroxyl radical. The combination of ultraviolet and chlorine disinfection promoted L-Tyrosine degradation and DBPs generation, and the promotion efficiency follow the order: UV/Cl₂> UV-Cl₂> Cl₂.

GRAPHICAL ABSTRACT

KEYWORDS:

• Amino acids
• metal ions
• complexation
• chlorine disinfection
• DBPs

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study was available from the corresponding author, upon reasonable request.

Additional information

Funding

This research was financially supported by the National Natural Science Foundation of China [grant number 51808489], the Fundamental Research Funds for the Central Universities of China [grant number 2020QNA4030], and the National Science and Technology Major Project for Water Pollution Control and Treatment of China [grant number 2017ZX07201003].