Factors affecting formation of deethyl and deisopropyl products from atrazine degradation in UV/H₂O₂ and UV/PDS

Abstract

Formation of deethyl products (DEPs) (i.e., atrazine amide and deethylatrazine) and deisopropyl product (i.e., deisopropylatrazine (DIA)) from parent atrazine (ATZ) degraded in UV/H2O2 and UV/PDS processes under various conditions was monitored.

Impact of Chloride Ions on UV/H2O2 and UV/Persulfate Advanced Oxidation Processes

“…For a UV/PS process that destroys organic compounds that only react with SO 4 – ·, Cl – inhibits PFOA degradation . In the UV/PS reaction of organic compounds that react with SO 4 – ·, HO·, and Cl·, Cl – has been reported to inhibit the degradation of biphenyl, polychlorinated biphenyls, azathioprine, humic acid, sulfamethoxazole, propranolol, carbamazepine, acyclovir, lamivudine, chloramphenicol, acetaminophen, atrazine and atenolol, 1,4-dioxane, diclofenac, and diethyl phthalate . However, Cl – has less of an inhibitory effect on 2,4,6-trichloroanisole, monochlorophenols, and trichloroethylene .…”

“…This is because they have very high second-order rate constants with Cl· (e.g., TCE is 4.88 × 10 10 M –1 ·s –1 ) . In the UV/H 2 O 2 process, Cl – has a slight inhibitory effect for iodinated trihalomethanes, monensin, salinomycin, narasin, humic acid, acetyl-sulfamethoxazole, trimethoprim, sulfamethoxazole, propranolol, carbamazepine, atrazine, lamivudine, 4-nitrophenol, phenol (seawater conditions), and atenolol . These experimental observations are in general agreement with the conclusions reached in this study.…”

“…Cl – is one of the most common anions in water matrices; for example, Cl – is present at approximately 0.001 M in freshwater and 0.1 M in industrial wastewater. − Some experimental studies have been conducted that shed light on the impact of Cl – on only certain organic oxidization rates in the UV/H 2 O 2 and UV/PS processes (e.g., atenolol, atrazine, propranolol, chloramphenicol, etc.). However, a quantitative insight with the fundamental and comprehensive understanding of the impact of Cl – on the UV/H 2 O 2 and UV/PS processes remains challenging because (1) experimentally screening the impact of Cl – on all organic contaminants that may be present in the water matrix is time-consuming and cost prohibitive, − (2) the sophisticated radical chain reactions typically involved in AOPs limit most current experimental studies to only qualifying the effects of Cl – on a particular compound (rather than determining the intrinsic mechanism and quantifying Cl – impacts for any compound), and (3) Cl – can react with SO 4 – · in the UV/PS process or HO· in both the UV/H 2 O 2 and UV/PS processes to form chlorine radicals (Cl·), which are also strong oxidants ( E °(Cl·/Cl – ) = 2.4 V) and can oxidize organic contaminants .…”

“…•, HO•, and Cl•, Cl − has been reported to inhibit the degradation of biphenyl, 12 polychlorinated biphenyls, 12 azathioprine, 11 humic acid, 53 sulfamethoxazole, 20 propranolol, 20 carbamazepine, 20 acyclovir, 20 lamivudine, 20 chloramphenicol, 21 acetaminophen, 54 atrazine 55 and atenolol, 19 1,4-dioxane, 56 diclofenac, 57 and diethyl phthalate. 58 However, Cl − has less of an inhibitory effect on 2,4,6trichloroanisole, 10 monochlorophenols, 59 and trichloroethylene.…”

“…61 In the UV/H 2 O 2 process, Cl − has a slight inhibitory effect for iodinated trihalomethanes, 22 monensin, 23 salinomycin, 23 narasin, 23 humic acid, 53 acetyl-sulfamethoxazole, 24 trimethoprim, 24 sulfamethoxazole, 20 propranolol, 20 carbamazepine, 20 atrazine, 20 lamivudine, 20 4-nitrophenol, 62 phenol (seawater conditions), 47 and atenolol. 19 We further developed a user-friendly algorithm based on the mathematical model to quantify the effects of Cl − at the beginning stage of UV/PS and UV/H 2 O 2 processes, as engineers are likely to encounter situations in real applications that were not discussed in this manuscript (for example, different pH, different NOM in different water matrix, etc.). Users can input their specific feasible conditions and kinetic parameters to obtain the ratio of the organic destruction rate when Cl − is present to the rate when Cl − is not present.…”