Comparison of UV/PDS and UV/H2O2 processes for the degradation of atenolol in water

UV/H2O2 and UV/peroxodisulfate (PDS) processes were adopted to degrade a typical β-blocker atenolol (ATL). The degradation efficiencies under various operational parameters (oxidant dosage, pH, HCO3-, humic acid (HA), NO3- , and Cl-) were compared. Principal factor analysis was also performed with a statistical method for the two processes. It was found that increasing the specific dosage of the two peroxides ([peroxide]0/[ATL]0 ) ranging from 1:1 to 8:1 led to a faster degradation rate but also higher peroxide residual. Within the pH range 3-11, the optimum pH was 7 for the UV/PDS process and elevating pH benefitted the UV/H 2O2 process. The presence of HCO3- , HA, and Cl adversely affected ATL oxidation in both processes. The NO3- concentration 1-3 mmol/L accelerated the destruction of ATL by the UV/PDS process, but further increase of NO3- concentration retarded the degradation process, contrary to the case in the UV/H2O2 process. The rank orders of effects caused by the six operational parameters were pH ≈ specific dosage > [HA]0 > [NO3-]0 > [HCO3-]0 > [Cl-]0 for the UV/H2O2 process and specific dosage > pH > [HA]0 > [NO3-]0 > [HCO3-]0 >[Cl-]0 for the UV/PDS process. The UV/PDS process was more sensitive to changes in operational parameters than the UV/H2O2 process but more efficient in ATL removal under the same conditions.     

广东省夏秋季光化学反应活性空间分布表征

于夏末秋初在深圳市城市和郊区开展了大气OH自由基观测,结果显示OH自由基日间峰值平均浓度分别为6.0×10⁶cm^-3和5.9×10⁶cm^-3,与国内外其他地区相比处于中等水平.基于实测数据构建了拟合效果较好的本地化OH自由基参数化公式,应用于广东省OH自由基空间分布的表征,并进一步利用日间OH和NO₂浓度之积反映光化学反应活性(AP).结果发现,2018年夏秋季广东省大气光化学反应活性总体上呈现珠江三角洲较高,AP达10.1×10⁷μg/(m³·cm³),粤东、粤西、粤北地区较低的分布态势,AP分别为5.4×10⁷, 5.9×10⁷和7.7×10⁷μg/(m³·cm³);同期的PM_2.5和O₃高值区域也集中在珠江三角洲,说明了调控光化学反应活性对珠江三角洲协同控...     

纳米核壳Co@NC催化剂活化过氧乙酸降解磺胺甲噁唑

过氧乙酸[PAA,CH₃C(O)OOH]作为一种新兴的氧化剂,在处理污水中难降解有机污染物中受到了越来越多的关注.通过蚀刻方法制备出纳米核壳Co@NC催化剂,并将其用于活化PAA降解污水中磺胺甲■唑(SMX).结果表明,当控制催化剂投加量为0.02 g·L^-1、PAA浓度为0.12mmol·L^-1和SMX浓度为10μmol·L^-1时,反应5 min时SMX的去除率即可达到98%,且降解SMX的速率常数为0.80 min^-1.SMX降解效率随催化剂添加量和PAA浓度提高而显著增加.结果发现核壳Co@NC/PAA体系在近中性条件下(pH为6.0～8.0)可获得最佳的SMX降解效果,酸性或碱性条件均不利于SMX去除.HCO^-₃和腐殖酸对该催化体系存在显著抑制,而Cl^-抑制作用较弱.此外,通过自由基淬灭实验和电子顺磁共振(EPR)研究发现,乙酰氧自由基(CH₃CO₂·)和乙酰过...     

HSO3-强化Fe3+/S2O82-降解水中双氯芬酸

采用HSO₃^-强化Fe³⁺/S₂O₈^2-降解水中双氯芬酸（DCF）,考察了溶液初始pH值,Fe³⁺、HSO₃^-和S₂O₈^2-用量,溶解氧对HSO₃^-/Fe³⁺/S₂O₈^2-体系降解DCF的影响;通过自由基淬灭实验,识别了体系中主要的活性物种;最后,探讨了DCF在该体系中的降解产物和转化路径.结果表明：HSO₃^-可以明显促进Fe³⁺/S₂O₈^2-对DCF的降解,初始pH 4.0时,DCF降解效果最佳.DCF的降解速率随Fe³⁺或S₂O₈^2-浓度的增大而增大;适量增加HSO₃^-浓度可提高DCF的降解,而过量的HSO₃^-对DCF降解有一定抑制作用.在通入氮气条件下,DCF去除率仅下降10.4%,无明显的抑制作用.自由基抑制实验表明,该体系含有SO₄^·-、HO^·和SO₅^·-3种活性自由基,其对DCF降解的贡献率分别为83.0%、12.8%和4.3%.在HSO₃^-/Fe³⁺/S₂O₈^2-降解DCF的反应中共检测出4种产物,据此提出DCF可能的转化路径为：羟基化、脱羧基、脱水和甲酰化反应.     

Nano Fe2O3 embedded in montmorillonite with citric acid enhanced photocatalytic activity of nanoparticles towards diethyl phthalate

Nano-Fe₂O₃ embedded in montmorillonite particles (Fe-Mt) were prepared to degrade diethyl phthalate (DEP) with citric acid (CA) under xenon light irradiation. Compared to pristine montmorillonite (Na-Mt), the embedding process increased 14.5-fold of iron content and 1.8-fold of specific surface area. The synthesized Fe-Mt have more oxygen vacancies than Fe₂O₃ nanoparticles (nFe₂O₃), which could induce more reactive oxygen species (ROSs) generation in the presence of CA under xenon lamp irradiation. Fe-Mt with CA enhanced photo-assisted degradation of DEP 2.5 times as compared to nFe₂O₃ with CA. Quenching experiments, electron paramagnetic resonance (EPR) spectroscopy and identification of products confirmed that surface-bound ?OH was the main radical to degrade DEP. Common anions (i.e., NO₃^?, CO₃^2?, Cl^?) and humic acid could compete ?OH with DEP and cause slower degradation of DEP. The removal efficiency of DEP was more than 56% with Fe-Mt after three recycles, and the dissolved Fe concentration from Fe-Mt was below 75 μmol/L, indicating Fe-Mt had a good stability as a catalyst. Fe-Mt together with CA appeared to be a promising strategy to remove organic pollutants in surface water, or topsoil under solar irradiation.     

Vertical distributions of wintertime atmospheric nitrogenous compounds and the corresponding OH radicals production in Leshan, southwest China

Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were operated from 02 to 21 December 2018 in Leshan, southwest China, to measure HONO, NO₂ and aerosol extinction vertical distributions, and these were the first MAX-DOAS measurement results in Sichuan Basin. During the measurement period, characteristic ranges for surface concentration were found to be 0.26–4.58 km^?1 and averaged at 0.93 km^?1 for aerosol extinction, 0.49 to 35.2 ppb and averaged at 4.57 ppb for NO₂ and 0.03 to 7.38 ppb and averaged at 1.05 ppb for HONO. Moreover, vertical profiles of aerosol, NO₂ and HONO were retrieved from MAX-DOAS measurements using the Heidelberg Profile (HEIPRO) algorithm. By analysing the vertical gradients of pollutants and meteorological information, we found that aerosol and HONO are strongly localised, while NO₂ is mainly transmitted from the north direction (city center direction). Nitrogen oxides such as HONO and NO₂ are important for the production of hydroxyl radical (OH) and oxidative capacity in the troposphere. In this study, the averaged value of OH production rate from HONO is about 0.63 ppb/hr and maximum value of ratio between OH production from HONO and from (HONO+O₃) is > 93% before12:00 in Leshan. In addition, combustion emission contributes to 26% for the source of HONO in Leshan, and we found that more NO₂ being converted to HONO under the conditions with high aerosol extinction coefficient and high relative humidity is also a dominant factor for the secondary produce of HONO.     

Fe (II)活化过硫酸盐处理喹啉工艺参数优化及生物毒性

以喹啉为处理目标物,采用Fe²⁺活化K₂S₂O₈（PS）的高级氧化体系在不同环境因素下降解喹啉.结果表明：与单一PS体系和Fe²⁺体系相比,Fe²⁺/PS体系可以有效降解喹啉.在初始喹啉浓度为250mg/L,喹啉/PS物质的量比为1：10,PS/Fe²⁺物质的量比为3,初始pH3,反应温度为45℃,反应时间为80min的条件下,喹啉降解率可达100%.提高PS和Fe²⁺浓度均能有效提高喹啉降解率,但超过一定限值后对喹啉去除效果不明显.Fe²⁺/PS去除喹啉的过程符合一级反应动力学.溶液初始pH值越高,喹啉去除率越低;反应温度越高,喹啉去除率越高.自由基淬灭实验证实,Fe²⁺活化PS体系中有SO₄^-·和OH·的存在,其中由SO₄^-·产生的OH·对喹啉的降解占主导地位.通过GC/MS检测到2种中间产物8-羟基喹啉和2（1H）-喹啉酮,据此推测基于硫酸根自由基强化喹啉降解的可能路径.大肠杆菌急性毒性实验结果证实,虽然Fe²⁺/PS体系去除喹啉过程中产生了毒性更强的中间产物,但酸性条件和较高的反应温度有利于体系脱毒.     

Fe(Ⅵ)/Na2SO3体系降解阿特拉津效能

利用高铁酸钾活化亚硫酸钠(Fe(Ⅵ)/Na₂SO₃体系),探究其对阿特拉津(ATZ)的降解效能;鉴别了反应体系主要活性组分,并考察了Na₂SO₃投加量、反应溶液pH值和水质背景成分对ATZ降解效能的影响.结果表明:当Fe(VI)和Na₂SO₃的投加量分别为50和200μmol/L时,反应10s后Fe(Ⅵ)/Na₂SO₃体系对ATZ的降解效能达到74.4%,单独Fe(VI)(50μmol/L)和单独Na₂SO₃(200μmol/L)对ATZ的去除率仅为10.2%和7.5%.探针化合物和溶解氧作用等实验证实体系中主要的活性基团为SO₄^·-.在pH=8,Fe(VI)投加量为50μmol/L时,随着Na₂SO₃投加量的增大,Fe(Ⅵ)/Na₂SO₃体系对ATZ的去除效率先增大后减小,其中最佳Na₂SO₃投加量为150~200μmol/L.Fe(Ⅵ)/Na₂SO₃体系在pH 7~10的范围内,均可以快速降解ATZ.在天然水体中,Fe(Ⅵ)/Na₂SO₃体系也可以高效降解ATZ,但是水质背景成分会竞争消耗SO₄^·-,导致Fe(Ⅵ)/Na₂SO₃体系对ATZ的降解效能降低.     

Mechanisms of photochemical release of dissolved organic matter and iron from resuspended sediments

Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter (DOM) and affect its ultimate fate in water ecosystems. In the present study, the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O₂ and NO₃^? concentration conditions to study the mechanisms of DOM and Fe photorelease. The amount of photoreleased Fe, which ranged from 0.22 to 0.70 μmol/L, was significantly linearly correlated with the amount of photoreleased DOM. O₂ and NO₃^? could promote the photochemical release of DOM and Fe, especially during the initial 4 h irradiation. In general, the order of the photorelease rates of DOM and Fe under different conditions was as follows: NO₃^?/aerobic > aerobic ≈ NO₃^?/anaerobic > anaerobic. The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation. The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes. The relative contributions of indirect processes (>60%) was much greater than that of direct photodissolution (<40%). The photoproduced H₂O₂ under aerobic and anaerobic conditions indicated that hydroxyl radicals (?OH) are involved in the photorelease of DOM. Using ?OH scavengers, it was found that 38.7%, 53.7%, and 77.6% of photoreleased DOM was attributed to ?OH under anaerobic, aerobic, and NO₃^?/aerobic conditions, respectively. Our findings provide insights for understanding the mechanisms and the important role of ?OH in the DOM and Fe photorelease from resuspended sediments.     

土壤铵氮在热活化过硫酸盐氧化过程中的转化

采用来自江苏和河北, 具有不同土壤有机质含量和NH₄⁺浓度的土壤样本, 系统地研究了NH₄⁺在热活化过硫酸盐(PS)氧化过程中的转化和归趋, 考察了反应时间、PS浓度和外加NH₄⁺对硝基副产物生成的影响.结果表明, 土壤中的NH₄⁺能够转化成3-硝基酚、4-硝基酚、2-羟基-5-硝基苯甲酸、4-羟基-3-硝基苯甲酸、2, 4-二硝基酚等副产物, 它们的生成量随着反应的进行先增加后降低.增大PS浓度可促进硝基副产物的生成.当PS浓度为30mmol/kg, 反应12h后一硝基酚和一硝基羟基苯甲酸的生成量达到最大.然而随着PS浓度进一步增大, 硝基副产物发生降解.硫酸根自由基(SO₄·^-)在硝化过程中起到了关键作用, 它能将NH₄⁺氧化生成氨基自由基(·NH₂), 随后经过一系列自由基链式反应生成二氧化氮自由基(NO₂·).同时, SO₄·^-进攻土壤有机质中的酚结构单元, 使其氧化生成苯氧自由基, 苯氧自由基进一步与NO₂·结合生成硝基副产物.天然有机质(NOM)在环境中无处不在, NH₄⁺在环境中也普遍存在, PS用于土壤和地下水污染修复时生成硝基副产物很可能是一个普遍现象.