RESUMEN
In this paper, the effects and mechanism of ciprofloxacin (CIP) degradation with peroxymonosulfate (PMS) catalyzed by solid waste red mud (RM) was firstly studied. The results indicated that RM has large specific surface area (10.96 m2·g-1) and complex pore structure, containing ferric, alumina and calcium oxide, which enhanced ciprofloxacin degradation by PMS effectively. Radical quenching experiments revealed that SO4-·and HO·were contributed to ciprofloxacin oxidation, and the reaction was mainly occurred on RM's surface. An increase in temperature could accelerate CIP degradation, and the corresponding reaction activation energy Ea was about 5.74 kJ·mol-1. Meanwhile, CIP degradation rate increased with PMS concentration and the optimal dosage of RM was 1.0 g·L-1. Eight degradation intermediates were identified using HPLC/MS/MS, and consequently, CIP was degraded mainly through two pathways; the piperazine groups were preferentially attacked by active free radicals. This study further indicated that RM is a cheap catalyst and can be potentially used in the treatment of antibiotic contaminated wastewater.
Asunto(s)
Ciprofloxacina , Contaminantes Químicos del Agua , Peróxidos , Espectrometría de Masas en TándemRESUMEN
High oxidative sulfate radicals can be produced by potassium persulfate (K2S2O8). The integrated effect of ultrasonic and K2S2O8, on norfloxacin degradation was investigated. The experimental parameters such as K2S2O8 concentration, norfloxacin initial concentration, initial pH value, free radicals quenching agents such as methanol and tert-butyl on norfloxacin degradation were discussed. The results indicated that ultrasonic/K2S2O8, system had an obvious degradation and mineralization effect on norfloxacin. Norfloxacin removal efficiencies were 3.2 and 8.9 times in ultrasonic/K2S2O8 system than those in single K252O8 and ultrasonic oxidation system, respectively. And the reaction followed the first-order kinetics. Norfloxacin removal efficiency varied gently with K2S2O8 concentration. Solution initial pH had a significant effect on norfloxacin degradation, which was attributed to the different oxidizing species under different pH values. The radicals were sulfate radicals under acidic and neutral conditions, and was the combination of sulfate and hydroxyl radicals under alkaline conditions. TOC and agar diffusion test with E. coli showed that 49.12% norfloxacin was mineralized and antibacterial activity was completely removed, with the diameter of E. coli inhibition zone decreased from 45 mm to 14 mm (filter paper diameter). The result implied that ultrasound/K2S2O8 showed promising results as a possible application for treatment of norfloxacin antibiotics wastewater.