By: Xiangliang Pan, Jing Liu, Daoyong Zhang, Xi Chen, Wenjuan Song, Fengchang Wu
Binding of dicamb at osoluble EPS(SEPS) and bound EPS(BEPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks(peak A with Ex/Em=225 nm/342–344 nm and peak B with Ex/Em=275/340–344 nm) were identified in SEPS and BEPS. Humic-like fluorescence peak C (Ex/Em=270–275nm/450–460nm) was only found in BEPS. Fluorescence of the peaks A and B for SEPS and peak A for B EPS were markedly quenched by dicamba at all temperatures where as fluorescence of peaks B and C for BEPS was quenched only at 298 K. A dynamic process dominated the fluorescence quenching of peak A of both SEPS and BEPS. Fluorescence quenching of peak B and C was governed a static process. The effective quenching constants (log Ka) were 4.725–5.293 for protein-like fluorophores of SEPS and 4.23–5.190 for protein-like fluorophores of BEPS, respectively. Log Ka for humic-like substances was 3.85. Generally, SEPS had greater binding capacity for dicamba than BEPS, and protein-like substances bound dicamba more strongly than humic-like substances. Binding of dicamba to SEPS and BEPS was spontaneous and exothermic. Electrostatic force and hydrophobic interaction forces play a crucial role in binding of dicamba to EPS.
Binding of dicamb at osoluble EPS(SEPS) and bound EPS(BEPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks(peak A with Ex/Em=225 nm/342–344 nm and peak B with Ex/Em=275/340–344 nm) were identified in SEPS and BEPS. Humic-like fluorescence peak C (Ex/Em=270–275nm/450–460nm) was only found in BEPS. Fluorescence of the peaks A and B for SEPS and peak A for B EPS were markedly quenched by dicamba at all temperatures where as fluorescence of peaks B and C for BEPS was quenched only at 298 K. A dynamic process dominated the fluorescence quenching of peak A of both SEPS and BEPS. Fluorescence quenching of peak B and C was governed a static process. The effective quenching constants (log Ka) were 4.725–5.293 for protein-like fluorophores of SEPS and 4.23–5.190 for protein-like fluorophores of BEPS, respectively. Log Ka for humic-like substances was 3.85. Generally, SEPS had greater binding capacity for dicamba than BEPS, and protein-like substances bound dicamba more strongly than humic-like substances. Binding of dicamba to SEPS and BEPS was spontaneous and exothermic. Electrostatic force and hydrophobic interaction forces play a crucial role in binding of dicamba to EPS.
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