TMT only decreased by 1.3% and 27%, respectively, in the presence
of 50-mM bicarbonate at pH 8.8, while k0 of TMP and TMT
decreased by 50% and 74%, respectively, in the presence of 0.5-mM
t-butanol. 50-mM bicarbonate can scavenge ~90% HO and Cl from
TMP or TMT, but its scavenging effect on ClO is negligible (Eqs
(6)e(8)). The results confirmed the significant role of ClO in the
degradation of TMP and TMT in the UV/chlorine process (Details
see Text S3).
These results reveal the different target moieties attacked by
different reactive species during the TMP degradation in the UV/
chlorine process. RCS contributes >50% to the overall removal rate
of TMP, and they can attack both TMT and DAP in TMP. Interestingly,
ClO plays the most important role in TMT degradation and its
contribution increases with increasing pH, while Cl is expected to
contribute to DAP degradation and its contribution decreases with
increasing pH. The contribution of HO to the TMP degradation is
much lower than that of RCS, and it attacks on TMT more effectively
than DAP. Free chlorine is very reactive with DAP, but not with TMT.