Photodegradation of Sulfamethoxazole Applying UV- and VUV-Based Processes

Abstract

The efficiency of UV-and VUV-based processes (UV, VUV, UV/H 2 O 2 , and VUV/H 2 O 2 ) for removal of sulfamethoxazole (SMX) in Milli-Q water and sewage treatment plant (STP) effluent was investigated at 20°C. The investigated factors included initial pH, variety of inorganic anions (NO 3 − and HCO 3 − ), and humic acid (HA). The results showed that the degradation of SMX in Milli-Q water at both two pH (5.5 and 7.0) followed the order of VUV/H 2 O 2 > VUV > UV/H 2 O 2 > UV. All the experimental data well fitted the pseudo-first order kinetic model and the rate constant (k) and half-life time (t 1/2 ) were determined accordingly. Indirect oxidation of SMX by generated • OH was the main degradation mechanism in UV/H 2 O 2 and VUV/H 2 O 2 , while direct photolysis predominated in UV processes. The quenching tests showed that some other reactive species along with • OH radicals were responsible to the SMX degradation under VUV process. The addition of 20 mg L −1 HA significantly inhibited SMX degradation, whereas, the inhibitive effects of NO 3 − and HCO 3 − (0.1 mol L −1 )were observed as well in all processes except in UV irradiation for NO 3 − . The removal rate decreased 1.7-3.6 times when applying these processes to STP effluent due to the complex constituents, suggesting that from the application point of view the constituents of these complexes in real STP effluent should be considered carefully prior to the use of UV-based processes for SMX degradation.

Removal of Sulfamethoxazole, Sulfathiazole and Sulfamethazine in their Mixed Solution by UV/H2O2 Process

“…The pKa values of SMZ, STZ and SMT were shown in Table 1. They had a cationic form at pH < pKa 1 and an anionic form at pH > pKa 2 [16,21]. These different ionic states of sulfonamides might have a considerable impact on their reactivity and light absorbing properties.…”

“…Among these AOPs, the UV/H 2 O 2 process consists of a combination of two well-known processes, direct UV photolysis and peroxidation, that lead to the generation of hydroxyl radicals, which make this process simpler and more effective for the removal of organic contaminants compared to peroxidation or photolysis respectively [14,15]. It is reported that some sulfonamides, such as sulfaquinoxaline sodium [14], sulfamethoxazole [16], sulfamethazine and sulfapyridine [17], can be efficiently removed by the UV/H 2 O 2 process, and the photochemical oxidation of a single antibiotic with a high concentration (>10 mg L −1 ) was elucidated. However, other contaminations in the water may dramatically affect the removal of the target pollutant by competitively interacting with hydroxyl radicals and photons or with each other among these compounds.…”

A novel approach to interpret quasi-collimated beam results to support design and scale-up of vacuum UV based AOPs

“…Optimizing a reactor for both the short penetrating VUV and relatively longer penetrating UV is challenging. Most of the laboratory-scale configurations, like quasi -collimated beam apparatus ( q CB) ( Baeza and Knappe, 2011 ; Duca et al., 2017 ; Fang et al., 2014 ; Feng et al., 2007 ), annular reactors ( Ngouyap Mouamfon et al., 2011 ; Zhan et al., 2021 ; Zoschke et al., 2012 ) and micro-fluidic vacuum UV reactors ( Yang et al., 2018 ) employed in VUV research have small mean reactor pathlengths that favorably uses VUV over UV. Despite extensive research published using laboratory-scale VUV reactors, there are scarce applications of VUV reported at pilot-scale ( Krakko et al., 2021 ).…”

Resource recovery in self-driven bio-electrochemical systems

“…These materials have been applied in the removal of recalcitrant organic matters with the combination of other AOPs process. Ngouyap et al [58] investigated the removal of SMX under UV-and VUV-based processes, reporting that complete degradation of 10 mg/L SMX was obtained. Kim et al [59] demonstrated that different removal efficiencies of SMX were obtained under lowpressure lamp UV (352 nm, 254 nm) and vacuum -UV (185 nm, 254 nm).…”