Abstract
As an emerging light source, ultraviolet light emitting diodes (UV-LEDs) are adopted to overcome the shortcomings of the conventional mercury lamp, such as mercury pollution. The degradation of chloramphenicol (CAP) using three UV-LED-based advanced oxidation processes (AOPs)—UV-LED/persulfate (UV-LED/PS), UV-LED/peroxymonosulfate (UV-LED/PMS) and UV-LED/chlorine—was investigated. Results indicate that CAP can be more effectively degraded by the hybrid processes when compared to UV irradiation and oxidants alone. Degradation of CAP using the three UV-LED-based AOPs followed pseudo-first-order kinetics. The degradation rate constants (kobs) for UV-LED/PS, UV-LED/PMS, and UV-LED/chlorine were 0.0522, 0.0437 and 0.0523 min−1, and the CAP removal rates 99%, 98.1% and 96.3%, respectively. The degradation rate constant (kobs) increased with increasing oxidant dosage for UV-LED/chlorine, whereas overdosing reduced CAP degradation using UV-LED/PS and UV-LED/PMS. Ultraviolet wavelength influenced degradation efficiency of the UV-LED based AOPs with maximum CAP degradation observed at a wavelength of 280 nm. The application of UV-LED enhanced the formation DBPs during subsequent chlorination. uUV-LED/PMS produced more disinfection by-products than UV-LED/PS. Compared to UV-LED, UV-LED/PS reduced the formation of dichloroacetonitrile and trichloronitromethane during chlorination owing to its capacity to degrade the nitro group in CAP. The intermediates dichloroacetamide, 4-nitrobenzoic acid, 4-nitrophenol were produced during the degradation of CAP using each of UV-LED, UV-LED/PS and UV-LED/chlorine. The present study provides further evidence supporting the application of UV-LED in AOPs.
Highlights
IntroductionAntibiotics are a new environmental contaminant that have garnered a lot of attention recently [1]
Numerous chlorine free radicals in the system, resulting in the formation of 2,6-dichloro-pThe rate of CAP degradation increases with oxidant dosage for each ultraviolet light emitting diodes (UV-LEDs) advanced oxidation processes (AOPs), nitrobenzoic acid (TP3)
When UV-LED was introusing UV-LED and mercury indicated different degradation mechanisms for the two light duced, disinfection by-product (DBP) formation increased which indicates that UV-LED AOPs did not fully minersources
Summary
Antibiotics are a new environmental contaminant that have garnered a lot of attention recently [1]. Due to biological accumulation and transformation potential in the environment, antibiotics pose a significant risk to human health [2]. The presence of antibiotics in the aquatic environment negatively impacts the growth and reproduction of organisms [3]. Trace concentrations of antibiotics in water are typically difficult to remove using conventional water treatment methods [4]. The development of techniques that effectively remove antibiotics during drinking water treatment is a top priority. Chloramphenicol (CAP) is the most widely detected in water [5,6,7]. Evidence suggests that ingestion of CAP may result in negative human health impacts such as aplas-
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