Enhancive and inhibitory effects of copper complexation on triplet dissolved black carbon-sensitized photodegradation of organic micropollutants.

Excited-triplet dissolved black carbon (DBC) was deemed as a significant reactive intermediate in the phototransformation of environmental micropollutants, but the impacts of concomitant metal ions on photochemical behavior of excited-triplet DBC (3DBC*) are poorly understood. Here, the photolytic kinetics of sulfadiazine and carbamazepine induced by 3DBC* involving Cu2+ was explored. The presence of Cu2+ reduced the 3DBC*-induced photodegradation rate of sulfadiazine; whereas for carbamazepine, Cu2+ enhanced 3DBC*-induced photodegradation. Cu(II)-DBC complex was formed due to the decreasing fluorescence intensities of DBC in the presence of Cu2+. Cu2+ complexation caused the decrease of 3DBC* steady-state concentrations, which markedly reduced 3DBC*-induced photodegradation rate of sulfadiazine due to its high triplet reactivity. Kinetic model showed that 3DBC* quenching rate by Cu2+ was 7.98 × 109 M-1 s-1. Cu2+ complexation can also enhance the electron transfer ability, thereby producing more ∙OH in Cu(II)-DBC complex, which explains the promoting effect of Cu2+ complexation on carbamazepine photodegradation in view of its low triplet reaction rate. These indicate that 3DBC* reactivity differences of organic micropollutants may explain their photodegradation kinetics differences in DBC system with/without Cu2+, which was supported by the linearized relationship between the photodegradation rate ratios of ten micropollutants with/without Cu2+ and their triplet reaction activity.

[Photo-assisted Degradation of Sulfamethazine by Ferrocene-catalyzed Heterogeneous Fenton-like System].

Antibiotics are acknowledged micropollutants in wastewaters and surface waters. They are of particular concern because they can trigger an increase in resistant bacteria. Therefore, novel and efficient technology for the removal of antibiotics is urgently needed. In this study, heterogeneous Fenton-like reaction based on ferrocene (Fc) had been constructed, sulfamethazine (SMZ) was selected as target compound due to its abundance in water. The degradation kinetics, transformation pathway, and degradation products of SMZ in this system were investigated. The results showed that Fc+H2O2+UV had better degradation efficiency for SMZ than did Fc, Fc+UV, H2O2, and H2O2+UV, Fc+H2O2 systems. Radical scavenger experiments confirmed that the photogenerated OH was largely responsible for the photolytic enhancement of SMZ in the Fc+H2O2+UV system. Additionally, the electron spin resonance technique revealed that photogenerated O2- was found in the system, indicating that Fc can generate electrons under light conditions. H2O2 underwent electron disproportionation to produce OH, which promoted the degradation of SMZ. The degradation products of SMZ in the Fc+H2O2+UV system were identified by LC/LTQ-Orbitrap MS. The hydroxylation of SMZ, the removal of SO2, and the products of breaking C-S, S-N, and N-C bonds were observed. Common soluble components (such as DOM, Cl-, and Br-) in water can quench OH, thus inhibiting the photodegradation of SMZ. However, the ionic strength had no significant effect on the degradation of SMZ in the Fc+H2O2+UV system, which showed that this technique positively affected the treatment of wastewater containing high-salinity antibiotics.

Fluorescent pH Sensors for Broad-Range pH Measurement Based on a Single Fluorophore.

We constructed a series of novel optical sensors for determination of broad-range pH based on a single fluorophore and multi-ionophores with different pK(a) values. These optical sensors use photoinduced electron transfer (PET) as the signal transduction and follow the design concept of "fluorophore-spacer-receptor (ionophore)" which employs 4-amino-1,8-naphthalimide as the single fluorophore, ethyl moiety as the spacer, and a series of phenols and anilines as the receptors. Key to the successful development of this sensor system is that coupling the receptors with six different pK(a) values with a single fluorophore produces the correct optical properties. This rational design affords a series of optical pH sensors with unique fluorescence property and accurately tunable pH measurement ranging from 1 to 14 pH units. Because of covalent immobilization of the indicators, these sensors demonstrate excellent stability, adequate reversibility, and satisfactory dynamic range up to full pH ranges (pH 1-14).