摘要
为了考察紫外光(λmax=365 nm)照射下三价砷(As(Ⅲ))在含有腐殖酸的水体中光氧化过程,该文研究了初始pH、HA浓度、外加铁离子以及不同分子量范围的HA组分等环境因子对As(Ⅲ)光氧化的影响。利用ESR检测和自由基猝灭实验以及不同气氛实验,量化不同活性物种对As(Ⅲ)光氧化的贡献率。结果表明,pH值对As(Ⅲ)在HA体系中的光氧化影响极大,低pH有利于As(Ⅲ)的光氧化。当pH为2.6,As(Ⅲ)浓度为100.0μg/L时,HA的最佳投加量为10.0 mg/L。Fe(Ⅲ)-HA络合物表现出低光活性,外加低浓度铁离子抑制As(Ⅲ)的光氧化,高浓度则促进As(Ⅲ)的光氧化。不同分子量范围的HA组分对As(Ⅲ)的光氧化贡献不同。As(Ⅲ)的形态转化是由于三重态腐殖酸(3HA*)的直接作用以及羟基自由基(HO·)直接氧化共同作用的结果。其中85%的As(Ⅲ)氧化是HO·直接氧化导致,HO·主要来自HO2·/O2·-;剩余15%依赖于3HA*对As(Ⅲ)的直接氧化。研究结果有助于了解As(Ⅲ)在含有溶解性有机质的酸性水体中光化学转化行为。
Photo-oxidation of arsenite(As(Ⅲ))in waters containing humic acid(HA)under the UVA-irradiation(λmax=365 nm)has been studied.The effects of initial pH,HA concentration,additional Fe(Ⅲ)and different molecular weight fractions of HA on As(Ⅲ)photo-oxidation were explored.The contribution efficiency of different reactive species to As(Ⅲ)photo-oxidation were also quantified by using electron spin resonance(ESR)and radical-quenching experiment and different gas-purging experiments.Results showed that the photo-oxidation of As(Ⅲ)was significantly affected by the pH value in waters containing HA and lower p H facilitated the photo-oxidation of As(Ⅲ).In addition,the optimal concentration of HA was 10.0 mg/L for 100.0μg/L As(Ⅲ)photo-oxidation at pH 2.6.Besides,the low addition of ferric ion retarded the photooxidation of As(Ⅲ)due to the poor photoactivity of Fe(Ⅲ)-HA complexes,high addition of ferric ion greatly accelerated As(Ⅲ)photo-oxidation.The fraction of HA with different molecular weight showed different capacities of oxidizing As(Ⅲ).HA induced the photo-oxidation of As(Ⅲ)by producing triple excited state of HA(3HA*)and hydroxyl radical(HO·).Approximately 85%of As(Ⅲ)oxidation was induced by HO·which was strongly dependent on HO2·/O2·-and the remaining 15%of As(Ⅲ)oxidation was attributed to the direct reaction between As(Ⅲ)and 3HA*.This study has important environmental implication for photo-transformation behavior of As(Ⅲ)in acidic waters containing dissolved organic matter(DOM).
作者
王雅洁
龚先河
董鑫
WANG Yajie;GONG Xianhe;DONG Xin(School of Eco-environmental Engineering,Guizhou Minzu University,Guiyang 550025,China)
出处
《环境科学与技术》
CAS
CSCD
北大核心
2021年第8期99-107,共9页
Environmental Science & Technology
基金
国家自然科学基金项目(21667011)
贵州省科技计划项目(黔科合基础[2018]1078)
贵州省高新技术产业化示范工程项目(黔发改高技[2020]896号)资助。
关键词
腐殖酸
三价砷
光氧化
三重态腐殖酸
羟基自由基
humic acid
arsenite(As(Ⅲ))
photo-oxidation
triple excited humic acid(3HA*)
hydroxyl radical(HO·)
