臭氧深度氧化法处理2,4-二氯苯氧乙酸农药废水

对臭氧深度氧化法降解农药2,4-二氯苯氧乙酸(2,4-D)废水进行了研究。实验结果表明,紫外光催化臭氧化降解2,4-D成效显著,臭氧/紫外(UV)深度氧化法是最好的臭氧化处理方法。2,4-D200mg/L的水样,反应30min,2,4-D降解完全,75min时矿化率达75%以上。碱性反应氛围有利于臭氧化反应进行。自由基抑制剂(叔丁醇)的加入,显著降低臭氧化反应去除2,4-D的效果,自由基参与的反应历程对于2,4-D的降解十分重要。双氧水的引入对2,4-D降解无明显促进作用,这是因为双氧水分解消耗OH-,没有缓冲的反应体系pH降低,限制了双氧水的分解和.OH自由基链反应。总之,单独臭氧化对2,4-D降解有一定的反应效率,在有利于.OH产生的体系中,2,4-D降解效率进一步提高。     

臭氧/Mn2+催化降解水溶液中的2,4-二氯苯氧乙酸

以Mn2 为催化剂与臭氧联合降解除草剂2,4-二氯苯氧乙酸(2,4-D).考察了反应温度、pH、2,4-D初始浓度和臭氧气体流量等因素对2,4-D降解效果的影响.pH对2,4-D降解效果影响很大,当pH=2.0、反应5 min时,2,4-D的去除率达99.8%;当pH=10.1、反应20min时,2,4-D的去除率仅为50.0%.反应温度升高、臭氧气体流量增加、2,4-D初始浓度降低均有助于2,4-D降解速率的提高.单独臭氧氧化2,4-D的表观反应速率常数为0.170 min-1;催化臭氧氧化2,4-D的表观反应速率常数为0.295min-1,是单独臭氧氧化的1.74倍.2,4-D的Mn2 催化臭氧反应遵循拟一级反应动力学方程.     

Fe-MCM-41催化氧化2,4-二氯苯氧乙酸

采用水热法合成了Fe-MCM-41中孔分子筛,紫外、红外及XRD表征显示铁离子已进入中孔分子筛骨架。以H2O2为氧化剂形成类Fenton试剂,实验结果表明,在催化剂加入量为1 g/L、H2O2体积分数为6%、pH为4、反应时间为10h、反应温度为35℃的条件下,处理质量浓度为50 mg/L的2,4-D废水的降解率达94.95%。宏观动力学研究显示,该反应近似为一级反应,反应速率常数、表观活化能分别为0.21667 min-1和26.65 kJ/mol。     

臭氧氧化法处理焦化废水生化出水的反应动力学

对臭氧氧化去除焦化废水生化出水COD的反应动力学及其影响因素进行了实验研究,结果表明,在臭氧投加量为8．50mg／min,反应温度为20＇E和初始pH为10．61条件下,对COD的降解符合表观一级反应动力学模型,其相关系数R。=0．9991,表观反应速率常数k。。=1．01×10^-3s-1。该条件下,臭氧氧化对COD的降解主要来源于高活性羟基自由基的强氧化作用。在不同的臭氧投加量（4．25～12．75mg／min）、不同的反应温度（10～40℃）和不同的初始pH（3．76～12．53）下,COD的降解也同样遵循一级反应动力学规律。随着臭氧投加量的增大,COD降解的表观反应速率常数从（0．554×10^-3）s-1增加到（1．06×10＆-3）s-1;随着反应温度的升高,表观反应速率常数从（0．427×10^-3）s-1增加到（1．40×10-3）s-1,温度越高反应速率提高的幅度却越小;在初始pH3．76～10．61范围内,表观反应速率常数从（0．218×10^-3）s-1增加到（1．01×10^-3）s-1,在初始pH为12．53时表观反应速率常数下降到（0．857×10^-3）s-1。     

2-甲基-4-氯苯氧乙酸及其脱氯产物的光化学降解

紫外消毒工艺作为废水/给水处理的重要步骤,不仅可以有效控制水中的病原体,而且可使废水或水源水中存在的一些污染物发生化学降解作用,但目前对这一作用过程的研究尚不完善。本文针对一种典型的除草剂——2-甲基-4-氯苯氧乙酸（MCPA）及其脱氯产物二甲基苯氧乙酸（MPA）,研究了两者在紫外灯照射下的光化学行为,并进一步考察了波长、初始pH值、H2O2及水中其他共存物质对MCPA和MPA光降解效率的影响。研究结果表明,不同光源对MCPA的光降解速率大小为：254 nm波长紫外灯 > 365 nm波长紫外灯 > 可见光灯;低pH值不利于MCPA的光降解,但对MPA光降解的影响不大;在溶液中加入H2O2,会增大MCPA和MPA的光降解速率;MCPA的光降解过程符合一级动力学方程;腐殖酸（HA）会降低MCPA的光降解速率;MPA与MCPA呈现相似的光降解效应,但反应速率比MCPA略快,且在两者共存状态下会降低MCPA的光降解速率。     

好氧氨氧化菌混培物的氨氧化动力学研究

采用批式呼吸法求得好氧氨氧化菌产率系数为0.2119 mg COD/mg NH4 -NOD(或者0.7268 mg COD/mg NH4 -N)和氨氧化菌最大氨氮降解速率为0.1 mg NOD/(mg COD·h)(或者0.0292 mg N/(mg COD·h)).用间歇式批试验法,加入24 μmol/L NaN3抑制NO2--N氧化,建立氨氧化反应动力学方程,得到氨氮半饱和系数为18.38 mg NOD/L(或者5.36 mg NH4 -N/L),DO半饱和系数为0.494 mg/L.对比参数值表明,用一步硝化动力学来描述氨氧化反应动力学模型是错误的.     

臭氧氧化法处理焦化废水生化出水的反应动力学简

对臭氧氧化去除焦化废水生化出水COD的反应动力学及其影响因素进行了实验研究,结果表明,在臭氧投加量为8.50 mg/min,反应温度为20℃和初始pH为10.61条件下,对COD的降解符合表观一级反应动力学模型,其相关系数R²=0.9991,表观反应速率常数k_Abs=1.01×10^-3 s^-1。该条件下,臭氧氧化对COD的降解主要来源于高活性羟基自由基的强氧化作用。在不同的臭氧投加量（4.25~12.75 mg/min）、不同的反应温度（10~40℃）和不同的初始pH（3.76~12.53）下,COD的降解也同样遵循一级反应动力学规律。随着臭氧投加量的增大,COD降解的表观反应速率常数从（0.554×10^-3） s^-1增加到（1.06×10^-3） s^-1;随着反应温度的升高,表观反应速率常数从（0.427×10^-3） s^-1增加到（1.40×10^-3） s^-1,温度越高反应速率提高的幅度却越小;在初始pH3.76~10.61范围内,表观反应速率常数从（0.218×10^-3） s^-1增加到（1.01×10^-3） s^-1,在初始pH为12.53时表观反应速率常数下降到（0.857×10^-3） s^-1。     

微气泡臭氧化强化吸收-氧化处理高浓度乙酸乙酯气体

采用微气泡臭氧化处理模拟高浓度乙酸乙酯气体,考察了强化吸收与氧化去除体系的性能、反应动力学及氧化反应的过程。结果表明,微气泡臭氧化能明显提高易溶性乙酸乙酯气体吸收-氧化处理的效率,乙酸乙酯气体整体平均去除率高于96%,氧化矿化率可达到90.22%,高于普通气泡臭氧化过程的63.25%和47.15%。微气泡臭氧化可提高臭氧利用效率,累积臭氧利用率可达到85.5%,高于普通气泡中的58.6%;同时,还可强化·OH氧化反应,提高臭氧化反应效率,反应中臭氧消耗量与乙酸乙酯TOC去除量比值(R)仅为1.04 mg∙mg⁻¹,明显低于普通气泡臭氧化过程的1.53 mg∙mg⁻¹。微气泡臭氧化处理中,乙酸乙酯传质吸收和氧化矿化反应均符合表观零级动力学方程,氧化矿化速率与传质速率基本平衡。以上结果表明,微气泡臭氧化处理可实现长期稳定高效处理乙酸乙酯气体。     

臭氧氧化6-APA制药厂生化处理出水的特性及动力学

通过现场实验研究了6-APA制药厂生化处理出水的臭氧氧化特性及其动力学规律。结果表明,当臭氧浓度为27．5mg／L,气水接触时间为80min时,COD、UV254、NH3-N和色度的去除率分别可达72．95％、73．28％、72％和96．25％,达到《发酵类制药废水工业水污染物排放标准》（GB21903—2008）排放控制要求。拟合结果表明,在0～10、10～30和30～90min时段内,臭氧氧化过程遵循拟一级反应,但反应速率逐渐降低。当气水接触时间为30min时,废水可生化性可由0．1提高至0．35,采用臭氧／生物处理的联合工艺也有望使出水达到相同的排放控制要求。     

Catalytic ozonation of 2,4-Dichlorophenoxyacetic acid using alumina in the presence of a radical scavenger

Using a laboratory-scale mixed reactor, the performance of alumina in degrading 2,4-Dichlorophenoxyacetic acid with ozone in the presence of tert-butyl alcohol radical scavenger was studied. The operating variables investigated were the dose of alumina catalyst and solution pH. Results showed that using ozone and alumina leads to a significant increase in 2,4-D removal in comparison to non-catalytic ozonation and adsorption processes. The observed reaction rate constants (k_obs ) for 2,4-D during ozonation were found to increase linearly with increasing catalyst dose. At pH 5, the k_obs value increased from 19.3 to 26 M^?1 s^?1 and 67 M^?1 s^?1 when varying the alumina dose from 1 to 2 and 4 g L^?1, respectively. As pH was increased, higher reaction rates were observed for both non-catalytic ozonation and catalytic ozonation processes. Thus, at pH 3 and using a catalyst dose of 8 g L^?1, the k_obs values for non-catalytic ozonation and catalytic ozonation processes were 3.4 and 58.9 M^?1 s^?1, respectively, whereas at pH 5 reaction rate constants of 6.5 and 128.5 M^?1 s^?1 were observed, respectively. Analysis of total organic carbon suggested that catalytic ozonation with alumina achieved a considerable level of mineralization of 2,4-D. Adsorption of 2,4-D on alumina was found to play an important role in the catalytic ozonation process.     

2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.     

SMX degradation by ozonation and UV radiation: a kinetic study

The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV₂₅₄ radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV₂₅₄ radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8) × 10⁻³ and (1.7-18.9) × 10⁻³ s⁻¹, respectively. The second-order rate constants of SMX with ozone (k_O3), under varying operational parameters, were also determined and varied in the range of (0.60-3.38) ± 0.13 × 10⁵ M⁻¹ s⁻¹. In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.     

铜铈二元材料催化臭氧降解草酸的研究

采用水热/焙烧法合成了铜铈二元复合催化剂(CuO-CeO2),并通过X射线衍射、扫描电子显微镜和透射电子显微镜对其进行了表征.以草酸为模型化合物,应用CuO-CeO2为催化剂进行连续流催化臭氧降解动态试验.结果表明:25 min时草酸去除率达到97.66％,远高于臭氧(2.66％)、CuO/臭氧(7.38％)和CeO2...     

水溶液中甲基橙的超声化学降解动力学研究

研究了水溶液中甲基橙的超声化学降解动力学。结果表明 ,水溶液中甲基橙可通过超声化学方法降解 ,降解动力学为一级反应 ,降解速率常数为 -2 .2 5× 10 - 3m in- 1。甲基橙降解速率随初始浓度的升高而降低 ,随介质温度的下降而升高 ,随介质酸度的变化而变化。 H2 O2 、F e2 +和 I- 等自由基促进剂可有效加速甲基橙的降解     

无机阴离子对催化臭氧氧化邻苯二甲酸的影响

考察了重碳酸根离子（HCO3-）、磷酸根离子（PO43-）、硫酸根离子（SO42-）和硝酸根离子（NO3-）等自然水体中常见的无机阴离子对非均相催化臭氧氧化邻苯二甲酸（PA）的影响。结果表明,能够捕获羟基自由基（HO·）的HCO3-对羟基氧化铁催化臭氧氧化体系影响很大,会明显抑制该体系对PA的降解,而对氧化铈催化臭氧氧化体系基本没有影响。PO43-和SO42-对2个体系中PA的降解均有很大的抑制效果,而NO3-对此影响甚少。从这些无机阴离子的影响可以侧面证明羟基氧化铁催化臭氧氧化遵循羟基自由基机理,而氧化铈催化臭氧氧化PA主要依靠络合作用。     

Exposure of Florida airboat aquatic weed applicators to 2,4-Dichlorophenoxyacetic acid (2,4-D)

Florida airboat handgun applicators were monitored for exposure to 2,4-Dichlorophenoxyacetic acid (2,4-D). Four applicators were monitored with air samplers, α -cellulose patches, and 24 hr urine samples on 10 separate days. Estimated total body exposure averaged 15 ± 2 mg/hr, of which 74% was to the legs and feet with an additional 18% to the hands and arms. Estimated respiratory exposure was about 0.03% of the total body exposure. Twenty-four hr urinary 2,4-D ranged from 0.190–0.645 mg. The use of disposable coveralls and effective hand protection would markedly reduce this exposure.     

2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation on WO3-TiO2-SBA-15 nanostructured composite

Environmental Science and Pollution Research - A current environmental problem is the uncontrolled use of various pesticides that are harmful to the environment and public health. The herbicide...     

污泥减量过程中臭氧氧化对硝化和反硝化影响的试验研究

采用AO工艺,考察了在污泥减量过程中臭氧(O3)氧化对生物系统硝化和反硝化能力的影响.结果表明,在每克SS中O3投量为0.05 g时,氧化后污泥中的CODcr由37.5 mg/L增至700mg/L,TN由4.86 mg/L增至36.6 mg/L,NH4 -N由0.353mg/L增至7.49 mg/L,NO3--N由2.19 mg/L增至5.15 mg/L.虽然氧化系统出水NH4 -N浓度略高于对照系统,但氧化系统NH4 -N的去除率大于98%,硝化能力基本没有受到O3氧化的影响.O3氧化污泥后增加的有机物作为附加的碳源循环至缺氧段,提高了反硝化的效果,当污泥氧化比例分别为10%、20%、30%时,进入缺氧段的CODCr/TN分别平均增至11.21、11.56、11.88,氧化系统的反硝化效果也随之分别提高5%、25%、37%.