Impact of the Ultraviolet Photolysis of Monochloramine on 1,4-Dioxane Removal: New Insights into Potable Water Reuse

详细信息    查看全文

• 作者：Samuel Patton ; Wei Li ; Kylie D. Couch ; Stephen P. Mezyk ; Kenneth P. Ishida ; Haizhou Liu
• 刊名：Environmental Science & Technology Letters
• 出版年：2017
• 出版时间：January 10, 2017
• 年：2017
• 卷：4
• 期：1
• 页码：26-30
• 全文大小：366K

文摘

Although chloramines are ubiquitously present during ultraviolet-driven advanced oxidation processes (UV/AOP) that are becoming increasingly important for potable water reuse, the photochemistry of chloramines in treated wastewater, and the associated effects on trace chemical contaminant degradation, are unknown. This study investigated the fundamental radical chemistry involved in monochloramine (NH₂Cl) photolysis and its efficiency in degrading 1,4-dioxane using a low-pressure Hg lamp (λ = 254 nm). These results showed that the UV fluence-normalized rate of 1,4-dioxane degradation in UV/NH₂Cl ranged between 1.1 × 10^–4 and 2.9 × 10^–4 cm²·mJ^–1. The photolysis of NH₂Cl produced NH₂^• and Cl^•, which further transformed to a series of reactive radical species. An optimal NH₂Cl dosage for 1,4-dioxane degradation was observed at a NH₂Cl/1,4-dioxane concentration ratio of 8.0, while excess NH₂Cl scavenged reactive radicals and decreased the treatment efficiency. Scavenging experiments and probe compound calculations showed that both Cl₂^•– and HO^• contributed significantly to 1,4-dioxane removal, while the NH₂^• radical reacted slowly with 1,4-dioxane. The presence of dissolved oxygen further decreased NH₂^• reactivity. This study generated critical knowledge of the photochemistry of NH₂Cl and will allow for future optimization of the UV/AOP for more efficient water reuse treatments.