Degradation of Pharmaceuticals and Metabolite in Synthetic Human Urine by UV, UV/H₂O₂, and UV/PDS

Abstract

To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09-8.53) × 10(9) M(-1)·s(-1) with hydroxyl radical, and (2.35-16.1) × 10(9) M(-1)·s(-1) with sulfate radical. In fresh urine matrix, the pharmaceuticals' indirect photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the indirect photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H2O2, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (k = 2.68 × 10(8) and 3.45 × 10(7) M(-1)·s(-1)) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals' degradation. Overall, the AOPs' performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H2O2, and varied significantly depending on pharmaceutical's structure.

Efficient degradation of sulfamethoxazole by the Fe(II)/HSO5− process enhanced by hydroxylamine: Efficiency and mechanism

“…Although a high concentration of chloride (6.7 mM) was detected in the pharmaceutical wastewater, the degradation of SMX was hardly influenced by the chloride (Fig. S13) as reported by Zhang et al (2015). Therefore, the other coexisting components (especially organic contaminants) in the real wastewater could be the dominant factor to result in the reduction of SMX removal rate.…”

Solar photo-Fenton and UV/H 2 O 2 processes against the antidepressant Venlafaxine in urban wastewaters and human urine. Intermediates formation and biodegradability assessment

“…The step-wise addition of H 2 O 2 (50 and 100 mg/L) was beneficial, reaching up to $30% degradation of VFA. Other researchers have also demonstrated the increase in PhACs' degradation by the addition of H 2 O 2 in the bulk [46]. The positive aspects of H 2 O 2 addition are found also in the COD removal, where up to 15% of COD and 13% of DOC were removed.…”

Ag+/S2O8 2– system for the degradation of aqueous flutriafol

“…Compared to • OH (E 0 = 2.80 V vs. NHE, t 1/2 = 10 -3 μs), • SO 4 − (E 0 = 2.43-2.80 V vs. NHE, t 1/2 = 1-10 μs) is similar in redox potential but more stable. There are • SO 4 − radicals in ground waters originating from atmospheric SO 2 , natural sulfur, and sulfur-based inorganic salts in industrial and household wastes [13].…”

“…However, the ecotoxicology, metabolic transformation and degradation products of flutriafol in the environment cannot be monitored easily because of the low concentration and interference from inorganic/organic matters. Zhang et al [13] selected the sulfate radical-advanced oxidation process (SR-AOP) to study the transformation of pharmaceuticals, which is a promising approach for soil and groundwater remediation [14]. Among various oxidants available, persulfate (S 2 O 8…”