“…The highest k obs in the pH range of 5-9 appeared at pH 7, which was consistent with that of UV/Cl 2 system. This might be ascribed to the homologous radicals of % OH and %Cl in both processes [32,[66][67][68]. k obs followed the order of pH7 > pH6 > pH5 > pH8 > pH9 and the tendency was slightly different from that in UV/Cl 2 .…”
Section: Degradation Of Iopamidol By Uv/nh 2 CL Processmentioning
Removal efficiency of iopamidol fol-• The pH behaviors of UV-based AOPs upon iopamidol in 5-9 exhibited quite differently.• UV/Cl 2 and UV/NH 2 Cl enhanced classical DBPs and I-THMs while UV/ClO 2 and UV/H 2 O 2 exhibited elimination effect.• The risk ranking of DBPs-related toxicity was UV/NH 2 Cl > UV/ Cl 2 > UV > UV/H 2 O 2 > UV/ClO 2 .
“…The highest k obs in the pH range of 5-9 appeared at pH 7, which was consistent with that of UV/Cl 2 system. This might be ascribed to the homologous radicals of % OH and %Cl in both processes [32,[66][67][68]. k obs followed the order of pH7 > pH6 > pH5 > pH8 > pH9 and the tendency was slightly different from that in UV/Cl 2 .…”
Section: Degradation Of Iopamidol By Uv/nh 2 CL Processmentioning
Removal efficiency of iopamidol fol-• The pH behaviors of UV-based AOPs upon iopamidol in 5-9 exhibited quite differently.• UV/Cl 2 and UV/NH 2 Cl enhanced classical DBPs and I-THMs while UV/ClO 2 and UV/H 2 O 2 exhibited elimination effect.• The risk ranking of DBPs-related toxicity was UV/NH 2 Cl > UV/ Cl 2 > UV > UV/H 2 O 2 > UV/ClO 2 .
“…This is similar to the research results of Dong et al that the acidic condition was more favorable for the generation of chloronitromethane (CNM) during UV/chlorine disinfection process 31 . The concentration of hydroxyl radical (HO·) and chlorine free radicals (Cl·) showed a decreased trend with the increase of pH, which might be the reason of the decrease of DCNM formation 42 . Figure 6 Effect of pH on the formation and photodegradation of DCNM from ( a ) MA, ( b ) DMA and ( c ) PolyDADMAC under UV/chlorine.…”
Investigations were conducted to examine the effects of amine type and initial concentration, free chlorine concentration, UV light intensity, pH and tert-butyl alcohol (TBA) on the formation of dichloronitromethane (DCNM) under UV/chlorine. Methylamine (MA), dimethylamine (DMA) and poly-dimethyl diallyl ammonium chloride (PolyDADMAC) were selected as the amine precursors of DCNM. And the reaction products of amines were explored through observing the contents of various nitrogen under UV/chlorine. Experimental results indicated that the higher of the intensity of UV light, the concentration of amines and free chlorine, the greater of the amount of DCNM formation; the amine substance with simple structure is more likely oxidized to form DCNM, so the potential of MA to form DCNM is the largest among three amines; the formation of DCNM decreased with increasing pH from 6.0 to 8.0; due to adding TBA into the reaction solution, halogen and hydroxyl radicals were restrained which resulted the DCNM formation decreased. In the reaction process, the formation of DCNM from amines increased at the beginning, then decreased and almost disappeared due to photodegradation. During the formation and photodegradation of DCNM, the dissolved organic nitrogen could be transformed into the ammonia-nitrogen (NH 3-N) and nitrate-nitrogen (NO 3 −-N).
“…On the surface of the Ti 4 O 7 anode, water and chloride ions were effectively oxidized under high potential (e.g., 2.8 V vs. Ag/AgCl) to generate OH• and free chlorine (e.g., HClO or ClO − ), respectively. The ClO• can be produced by the instantaneous adduct of OH• with free chlorine (Equations (4) and (5)) [33,34]. In particular, the ClO• can react selectively with NH 4 + (k ClO• = 3.1 × 10 9 M −1 s −1 ), compared with that of OH• (k OH• = 8.9 × 10 7 M −1 s −1 ) and Cl• (k Cl• = 1.1 × 10 9 M −1 s −1 ) [29].…”
“…)[33,34]. In particular, the ClO• can react selectively with NH4 + (kClO• = 3.1 × 10 9 M −1 s −1 ), compared with that of OH• (kOH• = 8.9 × 10 7 M −1 s −1 ) and Cl• (kCl• = 1.1 × 10 9 M −1 s −1 )…”
Herein, an electroactive filtration system, consisting of a Ti4O7 anode and a Pd-Cu co-modified nickel foam cathode, was developed and applied for the decontamination of ammonia from water. When assisted with an external electrical field, ClO• was generated on the surface of the Ti4O7 anode, which then reacted selectively with ammonia to generate N2. The anodic byproduct, NO3−, could also be reduced efficiently at the functional cathode to produce N2 as well. Electron paramagnetic resonance technique and radical scavenging tests synergistically verified the essential role of ClO• during the highly efficient ammonia conversion process. Relative to conventional batch systems, the developed flow-through design demonstrated enhanced ammonia conversion kinetics, thanks to the convection-enhanced mass transport. The proposed technology also showed desirable stability across a wide environmental matrix. This work provides new insights for the development of advanced and affordable continuous-flow systems towards effective decontamination of ammonia.
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