Effect of Metal Ions on the Formation of Trichloronitromethane during Chlorination of Catechol and Nitrite

Catechol, nitrite, and dissolved metals are ubiquitous in source drinking water. Catechol and nitrite have been identified as precursors for halonitromethanes (HNMs), but the effect of metal ions on HNM formation during chlorination remains unclear. The main objective of this study was to investigate the effect of metal ions (Fe 3+ , Ti 4+ , Al 3+ ) on the formation of trichloronitromethane (TCNM) (the most representative HNM species in disinfected water) on chlorinating catechol and nitrite. Trichloronitromethane was extracted by methyl tert-butyl ether and detected by gas chromatography. The results show that metal ions promoted the formation of TCNM and that the enhancement efficiency followed the order of Fe 3+ > Ti 4+ > Al 3+ . Trichloronitromethane formation increased greatly within 2 h, and a basic condition (pH 8–9) favored TCNM formation more than acidic or neutral conditions. The conjoint effect of the metal–ion mixtures was shown to be similar to that of the single metal ion having the highest promoting effect on TCNM formation. Our results strongly suggest that metal ions play a significant role in enhancing TCNM formation. Core Ideas Metal ions increased TCNM formation during chlorination of catechol and nitrite. Type and concentration of metal ions affected TCNM yield. Effect of metal ions on the formation of TCNM varied with pH. Conjoint effect of metal ions on TCNM formation was not obvious.