Kinetics, Mechanism, and Toxicity of Amlodipine Degradation by the UV/Chlorine Process

Abstract

The UV/chlorine process, as a new type of AOP (Advanced Oxidation Process), was utilized to treat amlodipine (AML)-containing water. The influencing factors, including chlorine dose, UV intensity, solution initial pH value, and ammonia concentration, were investigated. The degradation of AML in real water and the relative contributions of OH• and Cl• were also studied. Finally, high-resolution mass spectrometry (HRMS) and GC-MS were used to identify the possible degradation products. The results demonstrated that the AML degradation process was fitted with apparent first-order kinetics. AML degradation had a positive correlation with UV intensity and chlorine dose, and a negative correlation with ammonia concentration. In the presence of ammonia nitrogen and DOM, the removal of AML from real water was reduced. OH• made a dominant percentage contribution of 55.7% to the degradation of AML. Sixteen intermediates were detected and identified. A possible degradation mechanism was also proposed. Acute toxicity tests and risk prediction both illustrated that the complete removal of AML does not guarantee the reduction of acute toxicity, but a prolonged degradation promoted the detoxification of toxic intermediates. The UV/chlorine process can be regarded to be an effective method to remove AML and reduce ecological risk.

Experimental study and quantum chemical calculation of free radical reactions in ciprofloxacin degradation during the UV/chlorine oxidation process

“…The phenomenon was also observed in a research study on the degradation of amlodipine using the UV/chlorine process. 24 OCl − + H 2 O ⇄ HOCl + OH − …”

“…Before analysis of intermediates, ciprofloxacin degradation samples were collected and pre-treated according to an SPE procedure published in our previous research. 17,24 High resolution mass spectrometry (Thermo Qe-plus, USA) was used to screen and identify the unknown reaction intermediates. The instrument parameters included the following: Waters HSS T3 column (2.1 mm × 50 mm, 2.6 μm), positive and negative scan modes, MS range of 100-500 m/z, higher energy collision dissociation (HCD) at 35%, mass resolution of 35 000 for MS 2 , and 70 000 for MS.…”

“…The other parameters were also described in our published paper. 24 Acute toxicity tests were carried out using Vibrio fischeri as an indicator bacterium. 25 1.5 mL of water samples was taken and balanced with 3% NaCl solvent and then exposed to Environmental Science: Water Research & Technology Paper reactivated luminous bacteria (100 μL).…”