Aqueous S(IV) oxidation—I. Catalytic effects of some metal ions

Catalytic effect of metal ions [Fe(III), Mn(II), Cu(II), Pb(II) and Zn(II)] on the oxidation of S(IV) in aqueous solution at concentrations of metal ions and S(IV) as found in an urban atmosphere were studied under controlled experimental conditions (T, pH air flow rate, mixing, concentration of reactant, etc.). The following rate expressions were obtained: −r_S(IV) = k [Fe(III)] [S(IV)], −r_S(IV) = k [Mn(II)] [S(IV)]^0.65, −r_S(IV) = k [Cu(II)] [S(IV)]². The activation energy equals 104 kJ mol⁻¹ for Fe(III), 63.3 kJ mol⁻¹ for Mn(II), and 116.8 kJ mol⁻¹ for Cu(II) catalysed S(IV) oxidation.     

Electrolyte effects on aqueous atmospheric oxidation of sulphur dioxide by hydrogen peroxide

The rate of oxidation of sulphur dioxide by hydrogen peroxide in the presence of various supporting electrolytes has been determined by the stopped flow method. In a sodium perchlorate medium (chosen as reference electrolyte) first-order kinetics were observed with respect to HSO₃⁻, H₂O₂ and H⁺. The influence of the ionic strength was investigated and the third-order rate constant was calculated at infinite dilution. The rate constants of the reaction are shown to be far higher when chloride or ammonium ions are added to the solution.The effect of temperature and traces of metals ions (Mn²⁺, Fe²⁺, Fe³, Cu²⁺, Cr³⁺) was studied. The oxidation reaction is virtually insensitive to the effects of Mn²⁺, Fe³⁺, Cu²⁺ and Cr³⁺. Catalytic activity is observed with Fe²⁺.     

树脂负载草酸铁光助类芬顿降解水中孔雀石绿

为了强化多相类芬顿反应的速率,在可见光下采用以草酸盐为配体的三价铁草酸络合物(Fe~(3+)C_2O_4/R)为催化剂催化过氧化氢降解水中孔雀石绿.结果表明,与Fe~(3+)/R相比催化剂Fe~(3+)C_2O_4/R具有更强的催化活性,能强化羟基自由基(·OH)的产生. 过氧化氢的初始浓度越高,反应速率越快,反应遵循一级反应动力学,反应速率常数与过氧化氢浓度具有很好的相关性.在pH值3～9的范围内,催化剂Fe~(3+)C_2O_4/R都能有效地对MG进行降解,最佳pH值为6.随着催化剂投量的增加,MG的去除效率明显提高.随着MG初始浓度的增加,MG的去除也由吸附为主转化为以氧化为主,但总体影响不大.催化剂重复使用后仍然具有较好的催化活性,说明铁在树脂表面负载比较牢固,催化剂具有反复使用的能力.反应中的氧化活性物种是羟基自由基和高价态铁同时共存.     

Fe/Zn-TMS体系吸收去除催化裂化干气中H2S的性能

本研究采用FeCl3·6H2O、ZnCl2和环丁砜(TMS)复配形成的Fe/Zn-TMS体系脱除催化裂化(FCC)干气中的H2S,并用30%H2O2氧化再生Fe/Zn-TMS体系.同时,研究了各活性成分比例、吸收液体积浓度、吸收液pH值等对脱硫效率的影响,以及H2O2用量、吸收富液pH值对Fe2+氧化率的影响.结果表明,n(FeCl3·6H2O)∶n(ZnCl2)∶n(TMS)为0.45∶0.55∶1,吸收液pH为0.75,体积浓度(W)为50%的条件下能长时间高效脱硫,最高脱硫率达99.9%;在n(Fe2+)∶n(H2O2)为2∶1,吸收富液pH为0.65的条件下,Fe2+氧化率达96.7%.体系可循环使用3次,且能耗低、操作简单.     

Field studies of the SO2/aqueous S(IV) equilibrium in clouds

Concentrations of S(IV) were measured in cloudwater at Great Dun Fell and compared with theoretical HSO₃⁻ assuming equilibrium between aqueous and gaseous phases in cloud. Detectable concentrations of S(IV) in the range of 1 × 10⁻⁶ to 17.2 × 10⁻⁶ mol dm⁻³ were observed only in samples which contained low H₂O₂ concentrations, generally <1 × 10⁻⁶ mol dm⁻³. Concentrations of S(IV) were below the detection limit of 1 × 10⁻⁶ mol dm⁻³ in samples which contained hign H₂O₂ levels (1 × 10⁻⁶−80 × 10⁻⁶ mol dm⁻³) confirming that either SO₂ or H₂O₂ acts as the limiting reagent in the oxidation of SO₂ in cloudwater.Equilibrium HSO₃⁻ concentrations were estimated from the measured cloudwater pH, the gas phase SO₂ concentration and the ambient temperature and found to be on average about 5 times lower than the measured S(IV) concentrations. The possible role of formaldehyde in stabilizing S(IV) in cloudwater is discussed. The kinetic data available in the literature suggest that the complexation reaction between S(IV) and HCHO is too slow to account for the observed difference between measured and calculated S(IV) concentrations over the typical lifetime of clouds in our study.S(IV) accounted for up to 10% of the SO₄²⁻ measured in stored cloudwater samples.     

Ce3+与Cu2+协同强化芬顿体系氧化苯酚的效能与机制研究

研究了Ce~(3+)与Cu~(2+)协同强化芬顿体系在不同初始条件下对水中苯酚的氧化效能与机制.结果表明,在p H适用范围的宽度和H_2O_2浓度变化方面,Ce~(3+)/Cu~(2+)/Fe~(2+)/H_2O_2体系比传统的芬顿体系更具有优势,该体系在p H=5.0、H_2O_2浓度为2.0mmol·L-1的条件下,仍可以对苯酚保持相对较高的氧化效能;Cu~(2+)可能会借助反应过程中的中间产物(醌类物质)生成Cu+,Cu+催化H_2O_2分解生成·OH,Ce~(3+)可能促进体系内醌类物质的形成,加快Fe~(3+)与Fe~(2+)的循环效能,在一定程度上提高了芬顿体系中H_2O_2分解生成·OH的速率,说明Cu~(2+)与Ce~(3+)对芬顿体系的强化作用具有协同性;自由基终止剂依然可以抑制Ce~(3+)、Cu~(2+)强化的芬顿体系对苯酚的降解,由此说明体系中起到氧化作用的活性物种仍然是羟基自由基(·OH).     

Numerical modeling of long-range transport of acidic species in association with mesoβ-convective-clouds across the Japan sea resulting in acid snow over coastal Japan—II. Results and discussion

The acid snow/rain model [describedin Part I, Kitada et al., Atmospheric Environment27A, 1061–1076, 1993] was applied to investigate transport/transformation/deposition of acidic species in association with snow-precipitating cloud over the Japan Sea in winter. The model results showed: (1) The snow-precipitating clouds generated by relatively weak convective motions tend to trap aerosols of sulfate and nitrate and soluble gases such as SO₂ and HNO₃ below cloud levels, thus keeping their concentrations at higher levels than those for no-cloud situations. The mechanisms involved are: transfer of gas- and aerosol-phase species to cloud-phase through absorption and nucleation scavenging, then their transfer from cloud to snow through riming, and subsequent release from sublimating snow back to gas- and aerosol-phases below cloud base. (2) In-cloud oxidation enhanced the overall conversion of SO₂ to SO₄²⁻ by some 25% with respect to no-cloud situation after 12 h. Furthermore, contributions to the oxidation were 77.4%, 21.1% and 1.5% for S(IV)H₂O₂, S(IV)O₂ with catalysts of Fe³⁺ + Mn²⁺ and S(IV)O₃ reactions, respectively. (3) The sulfate wet deposited by precipitating snow for 12 h was due mostly to in-cloud scavenging and in-cloud oxidation, i.e. 66% by nucleation scavenging and the remaining by in-cloud oxidation of S(IV), while the contribution of below-cloud scavenging was negligible. (4) The adsorption process of HNO₃ onto the surface of falling snow was found to account for major below-cloud scavenging of snow, and thus in contrast to SO₄²⁻, the below-cloud scavenging contributed very significantly to the nitrate wet deposition. Throughout the stimulation, below-cloud scavenging was responsible for 75% of the snow-NO₃⁻ formation. Therefore, taking account of this process in acid snow models is important.     

Magnetically recoverable Fe3O4@polydopamine nanocomposite as an excellent co-catalyst for Fe3+ reduction in advanced oxidation processes

Advanced oxidation processes are widely applied to removal of persistent toxic substances from wastewater by hydroxyl radicals(·OH),which is generated from hydrogen peroxide(H_2O_2) decomposition.However,their practical applications have been hampered by many strict conditions,such as iron sludge,rigid pH condition,large doses of hydrogen peroxide and Fe~(2+),etc.Herein,a magnetically recyclable Fe_3O_4@polydopamine(Fe_3O_4@PDA) coreshell nanocomposite was fabricated.As an excellent reducing agent,it can convert Fe~(3+)to Fe~(2+).Combined with the coordination of polydopamine and ferric ions,the production of iron sludge is inhibited.The minimum concentration of hydrogen peroxide(0.2 mmol/L and Fe~(2+)(0.18 mmol/L)) is 150-fold and 100-fold lower than that of previous reports,respectively.It also exhibits excellent degradation performance over a wide pH range from 3.0 to 9.0.Even after the tenth recycling,it still achieves over 99% degradation efficiency with the total organic carbon degradation rate of 80%,which is environmentally benign and has a large economic advantage.This discovery paves a way for extensive practical application of advanced oxidation processes,especially in environmental remediation.     

常规金属离子对Fe3O4磁性纳米颗粒悬浮和沉降的影响

水体中的有机质、无机盐及酸碱度是影响纳米材料迁移转化的主要因素.考察了Na~+、Mg~(2+)、Ca~(2+)、Sr~(2+)和Ba~(2+)对Fe_3O_4磁性纳米材料(Magnetic Nanoparticles,MNPs)的沉降作用.结果表明,Fe_3O_4MNPs的沉降作用是水体pH、金属离子化合价、离子强度共同影响的结果.整体上,碱土金属离子较Na~+更能加速Fe_3O_4MNPs的沉降.当pH为5.0时,浓度低于1.0 mmol·L~(-1)的Na~+、Mg~(2+)和Ca~(2+)有助于Fe_3O_4MNPs的悬浮;当浓度大于1.0 mmol·L~(-1)时,较强的离子强度促使Fe_3O_4MNPs团聚,发生沉降.当pH为9.0时,碱土金属离子较Na~+更能促使Fe_3O_4MNPs聚沉.因此,纳米颗粒在水体中的扩散和聚沉需要综合考虑金属离子种类和浓度.     

Sulfur(IV) oxidation by hydrogen peroxide in aqueous suspensions of SiO2, Al2O3, TiO2 and zeolite

Normal and stopped-flow spectrophotometry were used to study the rate of oxidation of sulfur(IV) (SO₃²⁻/HSO₃⁻) by H₂O₂ in aqueous suspensions of finely divided SiO₂, Al₂O₃, TiO₂ and Na-A-zeolite buffered at pH 8.2 and 4.0. Within the limits of error, the rate constants obtained agree with those measured in the absence of suspended material, i.e. under the given conditions there is no surface catalytic effect to be observed.     

Decontamination of alachlor herbicide wastewater by a continuous dosing mode ultrasound/Fe2+/H2O2 process

We used a ultrasound/Fe2+/H2O2 process in continuous dosing mode to degrade the alachlor.Experimental results indicated that lower pH levels enhanced the degradation and mineralization of alachlor. The maximum alachlor degradation(initial alachlor concentration of 50 mg/L) was as high as 100% at pH 3 with ultrasound of 100 Watts, 20 mg/L of Fe2+, 2 mg/min of H2O2 and 20℃ within60 min reaction combined with 46.8% total organic carbon removal. Higher reaction temperatures inhibited the degradation of alachlor. Adequate dosages of Fe2+and H2O2 in ultrasound/Fe2+/H2O2process not only enhance the degradation efficiency of alachlor but also save the operational cost than the sole ultrasound or Fenton process. A continuous dosing mode ultrasound/Fe2+/H2O2 process was proven as an effective method to degrade the alachlor.     

UV/H2O2氧化降解克拉霉素的反应动力学及影响因素

克拉霉素用量大、检出频率高、生态风险大,已被欧盟列为优先监测污染物.针对传统污水处理厂难以完全去除克拉霉素的问题,主要研究了UV/H_2O_2降解克拉霉素的效果和反应动力学,探讨了pH、天然有机质(NOM)和水中共存阴、阳离子对UV/H_2O_2降解克拉霉素的影响.结果表明:单一UV对克拉霉素的光降解符合准一级反应动力学模型,其反应速率常数为0.0016 min~(-1).UV/H_2O_2对克拉霉素的降解符合准一级反应动力学模型,且克拉霉素的降解速率随H_2O_2浓度的增大而增大,在H_2O_2浓度为40 mmol·L~(-1)时,克拉霉素降解的反应速率常数为0.0284min~(-1).克拉霉素与·OH的二级反应速率常数为(2.36±0.20)×10~(10)L·mol~(-1)·s~(-1).碱性条件有利于克拉霉素的降解;NOM(2~10 mg·L~(-1))会抑制克拉霉素的降解,且随NOM浓度增大而增大;共存阴离子CO_3~(2-)对克拉霉素降解无影响,HCO_3~-、NO_3~-、Cl~-会抑制克拉霉素的降解,抑制程度的大小顺序为NO_3~-HCO_3~-Cl~-;共存阳离子Ca~(2+)、Mg2+、Cu~(2+)、Fe~(3+)会抑制克拉霉素的降解,抑制程度的大小顺序为Fe~(3+)Cu~(2+)Mg2+Ca~(2+).     

Fe2+-H2O2法处理DSD酸生产氧化母液的研究

为改善DSD酸氧化母液的可生化降解性,将废液先用有机絮凝剂TS-1(一种季胺盐)处理,TS-1的投加量为3g/L,其后用Fe²⁺-H₂O₂法氧化,Fe²⁺和H₂O₂的量分别为150mg/L,7g/L,废液COD和色度的去除率分别可达64%和62%。经处理后的废水,其BOD₅/COD≈0.3,可以认为已达到生化处理的要求。当H₂O₂的投量为2g/L,经Fe²⁺-H₂O₂氧化处理后的废液,再用FeCl₃进行两级混凝处理(FeCl₃的投加量分别为5g/L和2g/L),则COD和色度的去除率可达90%和95%。     

双极电化学氧化降解水中苯胺

采用钛基氧化物涂层材料（Ti/SnO2-Sb2O5）为阳极,石墨为阴极,在含Fe2＋和不含Fe2＋2种电解质条件下研究了苯胺的电化学氧化降解效率和机制.结果表明,Ti/SnO2-Sb2O5阳极氧化降解有机物的电位约2.0 V±0.1 V,而石墨阴极还原O2生成H2 O2的优化电位为-0.65 V.H2 O2单独作用不能...     

无机阴离子对CuO-H2O2氧化苯酚废水的影响

以苯酚为模型底物,研究了中性低温常压条件下无机阴离子对CuO-H₂O₂氧化苯酚废水的影响及机制.结果表明,CuO-H₂O₂能高效彻底氧化苯酚,10 min氧化率达94.7%,氧化遵循羟基自由基机制.无机阴离子对氧化效果有不同影响,浓度越高影响越显著.HCO^-₃加速H₂O₂的无效分解,当浓度从0增加到20 mmol·L^-1 时,H₂O₂分解速率常数由0.373 8 min^-1提高到0.534 7 min^-1,TOC去除速率常数由0.267 min^-1下降到0.019 4 min^-1.HPO^2-₄通过抑制H₂O₂分解实现对苯酚的氧化抑制,H₂O₂分解速率常数及TOC去除速率常数分别由0.373 8 min^-1、0.267 min^-1降低到0.033 8 min^-1、 0.033 8 min^-1.Cl^-能够促进H₂O₂有效分解,对苯酚氧化有利,H₂O₂分解速率常数及TOC去除速率常数分别由0.373 8 min^-1、0.267 min^-1提高到0.604 0 min^-1、0.387 9 min^-1.NO^-₃、SO^2-₄对H₂O₂的分解及苯酚的氧化影响不大.     

电-Fenton技术中H2O2积累强化的研究现状及展望

电-Fenton技术因原位电化学合成H₂O₂、电循环Fe²⁺/Fe³⁺而在水处理领域备受关注.阴极2电子氧还原（ORR）电合成H₂O₂反应决定着·OH形成速率及产量.本文首先从阴极电合成H₂O₂全过程角度阐明了阴极积累H₂O₂的原理,随后分别总结了近年来在电-Fenton体系强化2电子ORR前驱体氧传质策略、提高2电子ORR电合成H₂O₂的反应活性/选择性方法、减小/抑制H₂O₂无效分解的途径.在此基础上,进一步总结了电-Fenton技术在环境中的应用,最后对电-Fenton的发展趋势进行了阐述.     

超声-Fenton法对沼液中3种四环素类和3种磺胺类抗生素氧化去除的研究

近年来,各类抗生素被广泛用于畜禽养殖,并经动物代谢后随粪便和尿液排出体外.代谢物通过沼气工程处理后,得到的沼液又多用于灌溉,使得抗生素进入环境被农作物吸收,进而通过食物链的传递对人体产生危害,因此,沼液中抗生素的去除就显得尤为重要.本文选择畜禽养殖中使用较多的6种抗生素作为目标物质,采用超声-Fenton氧化技术进行去除.通过设置单因素实验考察了超声能量密度、H_2O_2浓度、pH值、n(H_2O_2)/n(Fe~(2+))对抗生素去除的影响,并利用响应曲面法研究了各个因素的交互性影响,拟合出去除抗生素的最优条件.结果表明,通过单因素试验筛选出的最佳反应条件为:pH=4,H_2O_2浓度为0.04 mol·L~(-1),n(H_2O_2)/n(Fe~(2+))=10,超声能量密度为0.050 kW·L~(-1),在此条件下四环素、土霉素、金霉素、磺胺甲恶唑、磺胺甲基嘧啶、磺胺嘧啶的去除率分别为91.90%、93.65%、86.09%、87.30%、77.54%、88.21%;再经由响应曲面法进一步优化实验方案得出优化条件为:pH=3.80,H_2O_2浓度为0.04 mol·L~(-1),n(H_2O_2)/n(Fe~(2+))=10.9,超声能量密度为0.055 kW·L~(-1),在此条件下四环素、土霉素、金霉素的去除率分别为92.04%、94.23%、88.46%,磺胺甲恶唑、磺胺甲基嘧啶、磺胺嘧啶的去除率分别为87.98%、80.78%、89.58%,养分TN、TP、TK的保留率分别为99.1%、98.6%、100.2%.可见,超声-Fenton氧化法对沼液中抗生素的去除效果良好,同时又可保留其养分.响应曲面法对优化超声-Fenton氧化去除沼液中的抗生素具有实际应用价值,这为沼液中抗生素的去除提供了一条可能的途径.     

Photodegradation of amoxicillin by catalyzed Fe3+/H2O2 process

Three oxidation processes of UV-Fe³⁺(EDTA)/H₂O₂ (UV: ultraviolet light; EDTA: ethylenediaminetetraacetic acid), UV-Fe³⁺/H₂O₂ and Fe³⁺/H₂O₂ were simultaneously investigated for the degradation of amoxicillin at pH 7.0. The results indicated that, 100% amoxicillin degradation and 81.9% chemical oxygen demand (COD_Cr) removal could be achieved in the UV-Fe³⁺ (EDTA)/H₂O₂ process. The treatment efficiency of amoxicillin and COD_Cr removal were found to decrease to 59.0% and 43.0% in the UV-Fe³⁺/H₂O₂ process; 39.6% and 31.3% in the Fe³⁺/H₂O₂ process. Moreover, the results of biodegradability (biological oxygen demand (BOD₅)/COD_Cr ratio) revealed that the UV-Fe³⁺ (EDTA)/H₂O₂ process was a promising strategy to degrade amoxicillin as the biodegradability of the effluent was improved to 0.45, compared with the cases of UV-Fe³⁺/H₂O₂ (0.25) and Fe³⁺/H₂O₂ (0.10) processes. Therefore, it could be deduced that EDTA and UV light performed synergetic catalytic effect on the Fe³⁺/H₂O₂ process, enhancing the treatment efficiency. The degradation mechanisms were also investigated via UV-Vis spectra, and high performance liquid chromatography-mass spectra. The degradation pathway of amoxicillin was further proposed.     

Fenton氧化去除制药企业活性污泥中AOX的效果研究

用Fenton氧化处理合成制药企业活性污泥混合液,考察了不同Fe~(2+)、H_2O_2投加量和不同反应时间下污泥与上清液中AOX(可吸附有机卤代物)的去除效果,优化了反应条件,探讨了氧化机制.结果表明,Fenton氧化的最佳条件为H_2O_2投加量0.90 mol·L~(-1),Fe~(2+)投加量0.045 mol·L~(-1)[物质的量比为:n(Fe~(2+))∶n(H_2O_2)=1∶20],反应2 h,污泥和上清液中AOX可分别去除70.7%和78.5%.GC-MS分析结果显示,污泥中含有11种有机卤代物,Fenton氧化后有8种不再检出;3种仍有检出,但浓度有所降低,去除率约为40%~50%.与此同时,污泥中对二甲苯、邻苯二甲酸二异丁酯等非有机卤代物类有毒有害有机物也得到有效去除.