紫外/TiO_2/芬顿复合工艺增强在近中性pH值下对布洛芬的降解能力（英文）

药品及个人护理品(PPCPs)造成的潜在环境污染已引起广泛关注.布洛芬(IBP,2-(4-异丁基苯基)丙酸)作为苯丙酸类非甾体抗炎药物,是一种在水环境中广泛检测到的PPCPs类物质.水环境中的IBP主要来自制药企业排放和人体代谢物,因IBP具有不易挥发、物理性质稳定、半衰期较长和不易被生物吸收等特点,其在环境的残留浓度较高且污染风险大.目前,传统的水处理工艺并不能有效治理水中的IBP,比如:混凝剂和絮凝剂对IBP的去除效率低,吸附和膜处理运行成本过高且不能矿化IBP.近年兴起的光催化技术利用OH和O2儃等强氧化性活性物种降解水中有机污染物,将其彻底矿化,实现污染物的无害处理.光催化技术适用于常温、常压和中性pH环境,该环境特点与污水环境十分匹配,适合应用.但异质光催化通常发生在催化剂表面,有效反应活性位少,反应速率不够高.相比而言,同质芬顿反应能够均匀、快速地在整个溶液中发生反应,但芬顿反应必须在酸性条件下才可以进行.本文整合了异相光催化和均相光-芬顿反应的优点,设计了紫外/TiO_2/芬顿(PCF)复合工艺,评估了在中性pH下对典型的PPCPs布洛芬的降解效果.对比实验结果表明,PCF复合工艺对IBP的降解速率比传统的UV,UV/H_2O_2,Fenton,光-Fenton和光催化快得多.动力学分析发现,IBP的降解遵循两阶段的一级反应动力学,且速率常数k_1k_2.本研究进一步优化了运行参数,确定IBP降解的最佳条件为:pH=4.2,[Fe~(2+)]_0=0.20 mmol/L,[Fe~(2+)]_0/[H_2O_2]_0=1/40,[TiO_2]_0=1.0 g/L.pH值的增加造成IBP降解速率略微降低,但在30 min反应时间内,中性pH(6.0–8.0)与最佳pH条件下的降解效率完全相同,证明PCF在中性pH下进行水处理切实可行.数据分析发现,lnk_1和lnk_2均与1/pH0,[IBP]0,[H_2O_2]_0,[H_2O_2]_0/[Fe~(2+)]_0和ln[TiO_2]_0线性相关,据此建立了IBP去除效率的数学预测模型,通过验证发现,动力学模型曲线与实验数据高度契合,表明模型的有效性高.     

新颖的PW11O39Fe(Ⅲ)(H2O)4-/H2O2类光-Fenton体系光催化降解苯胺

将Keggin型铁取代杂多阴离子PW11O39Fe(Ⅲ)(H2O)4-[PW11Fe(Ⅲ)(H2O)]构成的类光-芬顿体系用于水体生物难降解有机污染物苯胺(ArNH2)的降解。 研究了在紫外光照射和H2O2存在下,PW11Fe(Ⅲ)(H2O)对ArNH2降解的均相光催化作用。 考察了ArNH2、H2O2和PW11Fe(Ⅲ)(H2O)浓度对光催化降解反应速率的影响。 实验结果表明,0.1 mmol/L PW11Fe(Ⅲ)(H2O)+0.2 mmol/L H2O2+0.1 mmol/L ArNH2的中性溶液在300 W汞灯照射下反应60 min,ArNH2的降解率达100%,总有机碳(TOC)去除约52%。 同时讨论了PW11Fe(Ⅲ)(H2O)光催化H2O2产生羟基自由基的分子机制,并比较了酸性和中性条件下苯胺的光催化降解效果。     

Keggin型铁取代杂多阴离子PW_(11)O_(39)Fe(Ⅲ)(H_2O)~(4-)光催化降解硝基苯

以Keggin型铁取代杂多阴离子PW11O39Fe(Ⅲ)(H2O)4-[PW11Fe(Ⅲ)(H2O)]代替传统光芬顿方法中的Fe3+作为光催化剂,构成一个新颖的光催化体系并用于水体生物难降解有机污染物硝基苯(NB)的降解.详细研究了在紫外光照射和H2O2存在下,PW11Fe(Ⅲ)(H2O)对NB降解的均相光催化作用.考察了NB初始浓度、溶液pH、H2O2和PW11Fe(Ⅲ)(H2O)浓度对光催化降解反应速率的影响.实验结果表明,1.0mmol·L-1PW11Fe(Ⅲ)(H2O)+5.0mmol·L-1H2O2+1.0mmol·L-1NB的中性溶液在300W汞灯照射下反应120min,NB的降解率达93%,总有机碳(TOC)去除约31%,显示了该新颖体系对NB光催化降解的高效性和优越性.     

H2O2-Na2S2O3反应对pH和反应物起始浓度比的依赖性

在H2O2-Na2S2O3反应体系中，pH值和[H2O2]0/[Na2S2O3]0对反应产物的浓度大小起着关键作用.本文通过考察这两种因素对反应产物的影响，以及对反应机理的模拟，得出了pH值和氧化剂与还原剂浓度比影响反应产物浓度的一般规律.结果表明：pH< 3时，反应主要生成单质硫， 3< pH< 6时， 较为稳定，提高pH和[H2O2]0/[Na2S2O3]0有利于SO42-生成，在中性或弱碱性溶液中S(Ⅳ)(HSO42-或SO32-)物质浓度出现峰值.     

三元复合材料K8[Fe（H2O）W11MnO39]/PANI/TiO2的制备及光催化性能

采用静电自组装法制备出三元复合材料K8[Fe（H2O）W（11）MnO（39）]/PANI/TiO2.采用IR,UV,XRD,SEM,XPS和N2吸附-脱附的表征手段对K8[Fe（H2O）W（11）MnO（39）]/PANI/TiO2进行表征,并以龙胆紫为模型,在紫外光照射下,考察了K8[Fe（H2O）W（11）MnO（39）]/PANI/TiO2对龙胆紫染料的光催化性能,确定光催化最佳条件：龙胆紫溶液浓度为5mg/L,pH=3,K8[Fe（H2O）W11MnO39]/PANI/TiO2的用量为10mg,脱色率可达92.93%.     

气相苯在TiO2光催化剂上吸附常数和光催化反应常数测定

采用溶胶-凝胶法制备TiO2光催化剂以及掺杂Fe3 和Ce3 的TiO2光催化剂,进行间歇式光催化降解气相苯动力学实验,基于光催化Langmuir-Hinshelwood反应动力学模型(L-H模型),测定气相苯在3种光催化剂上的降解动力学常数和吸附平衡常数.根据光催化降解气相苯实验动力学曲线和L-H模型,估算出TiO2、Fe3 /TiO2和Ce3 /TiO2光催化剂光催化降解苯的反应速率常数k和Langmuir吸附常数K分别为0.5247g/m3·min、1.523g/m3·min、1.010g/m3·min和8.605×10-2m3/g、2.390×10-2m3/g、3.928×10-2m3/g.掺杂Fe3 和Ce3 可明显提高光催化剂光催化降解苯的反应速率常数k,其中Fe3 /TiO2,的反应速率常数k最大.     

Keggin型杂多阴离子PW11O39Fe(III)(H2O)4-电催化降解硝基苯

以Keggin型铁取代杂多阴离子PW11O39Fe(III)(H2O)4－ (PW11Fe)代替传统电芬顿(electro-Fenton)方法中的Fe3＋作为电催化剂, 构成一个新颖的电催化体系并用于中性水溶液中硝基苯的降解. 结果表明, 含有1.0 mmol•L－1硝基苯和1.0 mmol•L－1 PW11Fe的混合磷酸盐溶液(pH 6.86), 在－0.5 V电位和60 mL•min－1 O2流速下反应100 min, 硝基苯便完全降解. 降解的准一级表观速率常数与硝基苯的初始浓度有关, 当硝基苯的初始浓度为1.0, 2.0和5.0 mmol•L－1时, kobs分别为7.18×10－2, 3.57×10－2和1.47×10－2 min－1. 降解反应100 min的TOC(有机碳总量)去除率约为35%, 表明硝基苯的降解过程伴随着矿化.     

氟离子对TiO2/膨润土光催化降解酸性桃红的影响

研究了在紫外光照射下, 添加氟离子对P25(锐钛矿)和TiO2/膨润土光催化降解酸性桃红(SRB)的影响. 紫外可见光谱测定结果表明无氟的反应体系, pH值越小, 光降解速率越快; pH值固定, 添加氟离子越多, 反应速率越快, 在TiO2/膨润土催化剂上, 当氟离子浓度达到一定程度时, 反应速率不再变化. 在P25和TiO2/膨润土催化剂上, 添加氟离子对H2O2的产生量影响不同, 通过电子顺磁共振(EPR)技术探测到了超氧自由基和羟基自由基, 这两个体系添加氟离子对其产生强度影响不同, 这可能是因为TiO2/膨润土催化剂为层状结构, BET 比表面积较大, 经XRD和TEM测试表明其晶粒直径约为57.9 nm. TiO2/膨润土催化剂连续循环使用11次, 光催化活性基本不变, 这个现象说明TiO2/膨润土催化剂既易于从分散体系中分离出来, 而且其稳定性也好, 它是一个有应用前途的催化剂.     

层状纳米光催化复合材料H0.8Fe0.8Ti1.2O4/TiO2的合成及性质

用固相合成法制备出K0.8Fe0.8Ti1.2O4,并用离子交换反应制备出H0.8Fe0.8Ti1.2O4;通过C3H7NH2层间膨胀,TiO2粒子的插入和紫外光分解等反应,合成出一种新的层状光催化纳米复合材料-H0.8Fe0.8Ti1.2O4/TiO2.X射线衍射和漫反射等表征结果表明 该样品的层间高度为0.47nm,禁带能隙为2.18和2.88eV.用(>400 nm的光照射30 min,0.4 g样品可使甲基橙溶液(20 mg/L)的降解率达到22.1%.而同样条件下标准TiO2(P-25)仅为6.2%,表明所研制的层状纳米复合材料具有较高的光催化活性.     

添加剂对有机颜料光催化降解的影响

 研究了(NH4)2S2O8,H2O2和表面活性剂十二烷基苯磺酸钠(DBS)对TiO2光催化降解颜料艳红6B的影响. 结果表明,(NH4)2S2O8的加入可提高颜料艳红6B的降解速率,以酸性及近中性条件较为适宜; H2O2的加入也可提高颜料艳红6B的降解速率,并可提高TiO2的重复使用次数; DBS的加入可降低颜料艳红6B的降解速率,但颜料艳红6B在酸性和碱性条件下降解较中性条件下快. DBS在中性条件下降解较快. 颜料艳红6B与DBS二者之间存在密切的共降解关系. 随着DBS浓度的增加,颜料艳红6B和DBS的降解速率均逐渐降低.     

钛铝载体的合成及负载CuO对NO催化性能研究

以TiCl4为原料合成了TiO2/[[alpha]]-Al2O3载体. 在色谱-微反流动法反应装置上考察了CuO/15%(w, 下同)TiO2/[alpha]-Al2O3系列催化剂对NO+CO 的反应性能. 结果表明上述催化剂对NO+CO 反应表现出较好的活性, 其中12%CuO/15%TiO2/[alpha]-Al2O3反应活性最佳. 空气和H2 预处理后, NO 完全转化的温度分别为300C[[deg]]和275C[deg].通过H2-TPR、XRD 和FT-IR 等技术表征, 发现适量TiO2能促进CuO 在钛铝载体上的分散. TPR 结果显示12%CuO/15%TiO2/[alpha]-Al2O3在整个TPR 过程中出现四个还原峰, 琢和酌还原峰分别是钛铝载体表面裸露的TiO2上高度分散的CuO 和晶相CuO 的还原；茁和啄还原峰为钛铝载体上高度分散的CuO 和晶相CuO 的还原. FT-IR实验表明NO和CO 在经H2气氛预处理的催化剂表面上吸附较强, 且生成了N2O 和NO2等物种；NO+CO混合气在经空气和H2预处理的催化剂表面吸附时, 出现了N2O吸收峰, 峰温分别为200C[deg]和150C[deg].     

ESR and resonance Raman spectroscopic studies of peroxide intermediates derived from iron diazaoxacyclononane

A peroxide-Fe3+ intermediate generation during the Fenton reaction of iron chelate involving a ligating N,N'-di-2-picolyl-4, 7-diaza-1-oxacyclononane (DPC), H2O2/[Fe2+ DPC]2+, is reported. The identity of this peroxide complex is confirmed by resonance Raman (RR) and electron spin resonance (ESR) spectroscopies. The RR spectrum of [Fe2+ DPC]2+ treated with H2O2 shows a frequency at 854 cm(-1) ascribable to v(O-O) vibrational modes of the peroxide-Fe3+ complex with a side-on geometry. On the other hand, the ESR spectrum of H2O2/[Fe2+ DPC]2+ acquired at 77 K exhibits the resonance transition at g = 2.196 and 2.017 due to the peroxide-Fe3+ complex with an axial symmetry. It has been concluded that the H2O2/[Fe2+ DPC]2+ reaction proceeds by rapid bonding of H2O2 to an open coordination site on the central Fe2+ cation.     

Reactive sulfur species: kinetics and mechanism of the equilibrium between cysteine sulfenyl thiocyanate and cysteine thiosulfinate ester in acidic aqueous solution

The kinetics and mechanism of the hydrolysis of cysteine sulfenyl thiocyanate (CySSCN) to give cysteine thiosulfinate ester (CyS(=O)SCy) have been investigated between pH 0 and 4. The reaction is reversible. The hydrolysis of CySSCN is second-order in [CySSCN] and inverse first-order in [H+] and [SCN-]. The following mechanism is proposed for the hydrolysis of CySSCN (where the charge depends upon the pH): CySSCN0/+ + H2O <==>CySOH0/+ + SCN- + H+, CySOH0/+ + CySSCN0/+ --> CyS(=O)SCy0/+/2+ + SCN- + H+; k1 = 3.36 +/- 0.01 x 10-3 s-1, K1k2 = 0.13 +/- 0.05 Ms-1 (which yields k2/k-1 = 39 M). The observed rate law rules out alternative mechanisms for 1 0.4 M). The following mechanism is proposed: CyS(=O)SCy2+ + H+ <==> CyS(OH)=SCy3+, Ka; CyS(OH)SCy3+ + SCN- --> CySOH+ + CySSCN+, k-2 = 0.239 +/- 0.007 M-2s-1/Ka M-1. Since cysteine sulfenic acids are known to play an important function in many enzymes, and SCN- exists in abundance in physiologic fluids, we discuss the possible role of sulfenyl thiocyanates in vivo.     

Direct oxidation of L-cysteine by [FeIII(bpy)2(CN)2]+ and [FeIII(bpy)(CN)4]-

The oxidation of L-cysteine by the outer-sphere oxidants [Fe(bpy)2(CN)2]+ and [Fe(bpy)(CN)4]- in anaerobic aqueous solution is highly susceptible to catalysis by trace amounts of copper ions. This copper catalysis is effectively inhibited with the addition of 1.0 mM dipicolinic acid for the reduction of [Fe(bpy)2(CN)2]+ and is completely suppressed with the addition of 5.0 mM EDTA (pH<9.00), 10.0 mM EDTA (9.010.0) for the reduction of [Fe(bpy)(CN)4]-. 1H NMR and UV-vis spectra show that the products of the direct (uncatalyzed) reactions are the corresponding Fe(II) complexes and, when no radical scavengers are present, L-cystine, both being formed quantitatively. The two reactions display mild kinetic inhibition by Fe(II), and the inhibition can be suppressed by the free radical scavenger PBN (N-tert-butyl-alpha-phenylnitrone). At 25 degrees C and micro=0.1 M and under conditions where inhibition by Fe(II) is insignificant, the general rate law is -d[Fe(III)]/dt=k[cysteine]tot[Fe(III)], with k={k2Ka1[H+]2+k3Ka1Ka2[H+]+k4Ka1Ka2Ka3{/}[H+]3+Ka1[H+]2+Ka1Ka2[H+]+Ka1Ka2Ka3}, where Ka1, Ka2, and Ka3 are the successive acid dissociation constants of HSCH2CH(NH3+)CO2H. For [Fe(bpy)2(CN)2]+, the kinetics over the pH range of 3-7.9 yields k2=3.4+/-0.6 M(-1) s(-1) and k3=(1.18+/-0.02)x10(6) M(-1) s(-1) (k4 is insignificant in the fitting). For [Fe(bpy)(CN)4]- over the pH range of 6.1-11.9, the rate constants are k3=(2.13+/-0.08)x10(3) M(-1) s(-1) and k4=(1.01+/-0.06)x10(4) M(-1) s(-1) (k2 is insignificant in the fitting). All three terms in the rate law are assigned to rate-limiting electron-transfer reactions in which various thiolate forms of cysteine are reactive. Applying Marcus theory, the self-exchange rate constant of the *SCH2CH(NH2)CO2-/-SCH2CH(NH2)CO2- redox couple was obtained from the oxidation of L-cysteine by [Fe(bpy)(CN)4]-, with k11=4x10(5) M(-1) s(-1). The self-exchange rate constant of the *SCH2CH(NH3+)CO2-/-SCH2CH(NH3+)CO2- redox couple was similarly obtained from the rates with both Fe(III) oxidants, a value of 6x10(6) M(-1) s(-1) for k11 being derived. Both self-exchange rate constants are quite large as is to be expected from the minimal rearrangement that follows conversion of a thiolate to a thiyl radical, and the somewhat lower self-exchange rate constant for the dianionic form of cysteine is ascribed to electrostatic repulsion.     

Catalase-peroxidase activity of iron(III)-TAML activators of hydrogen peroxide

Exceptionally high peroxidase-like and catalase-like activities of iron(III)-TAML activators of H 2O 2 ( 1: Tetra-Amidato-Macrocyclic-Ligand Fe (III) complexes [ F e{1,2-X 2C 6H 2-4,5-( NCOCMe 2 NCO) 2CR 2}(OH 2)] (-)) are reported from pH 6-12.4 and 25-45 degrees C. Oxidation of the cyclometalated 2-phenylpyridine organometallic complex, [Ru (II)( o-C 6H 4py)(phen) 2]PF 6 ( 2) or "ruthenium dye", occurs via the equation [ Ru II ] + 1/2 H 2 O 2 + H +-->(Fe III - TAML) [ Ru III ] + H 2 O, following a simple rate law rate = k obs (per)[ 1][H 2O 2], that is, the rate is independent of the concentration of 2 at all pHs and temperatures studied. The kinetics of the catalase-like activity (H 2 O 2 -->(Fe III - TAML) H 2 O + 1/2 O 2) obeys a similar rate law: rate = k obs (cat)[ 1][H 2O 2]). The rate constants, k obs (per) and k obs (cat), are strongly and similarly pH dependent, with a maximum around pH 10. Both bell-shaped pH profiles are quantitatively accounted for in terms of a common mechanism based on the known speciation of 1 and H 2O 2 in this pH range. Complexes 1 exist as axial diaqua species [FeL(H 2O) 2] (-) ( 1 aqua) which are deprotonated to afford [FeL(OH)(H 2O)] (2-) ( 1 OH) at pH 9-10. The pathways 1 aqua + H 2O 2 ( k 1), 1 OH + H 2O 2 ( k 2), and 1 OH + HO 2 (-) ( k 4) afford one or more oxidized Fe-TAML species that further rapidly oxidize the dye (peroxidase-like activity) or a second H 2O 2 molecule (catalase-like activity). This mechanism is supported by the observations that (i) the catalase-like activity of 1 is controllably retarded by addition of reducing agents into solution and (ii) second order kinetics in H 2O 2 has been observed when the rate of O 2 evolution was monitored in the presence of added reducing agents. The performances of the 1 complexes in catalyzing H 2O 2 oxidations are shown to compare favorably with the peroxidases further establishing Fe (III)-TAML activators as miniaturized enzyme replicas with the potential to greatly expand the technological utility of hydrogen peroxide.     

H2O2/TiO2超声协同光降解活性艳橙的研究

以活性艳橙溶液为模拟废水,通过H₂O₂/TiO₂超声(US)协同作用光降解活性艳橙溶液,探讨了TiO₂催化剂用量、H₂O₂用量、活性艳橙溶液的初始浓度、pH值、TiO₂催化剂锻烧温度等对活性艳橙溶液降解率的影响,并比较了几种不同作用方式对活性艳橙溶液的降解效果.结果表明:UV/H₂O₂/TiO₂/US协同作用降解活性艳橙溶液的效果最好;当活性艳橙溶液的初始浓度为20 mg·L^-1,pH＝5,TiO₂用量为0.4 g·L^-1,H₂O₂用量为0.4 ml·L^-1时,降解率可达92.06%.     

Kinetics and mechanism of the comproportionation of hypothiocyanous acid and thiocyanate to give thiocyanogen in acidic aqueous solution

The kinetics of comproportionation of hypothiocyanous acid (HOSCN) and thiocyanate (SCN-) to give thiocyanogen ((SCN)2) in acidic aqueous solutions have been determined by double-mixing stopped-flow UV spectroscopy. Hypothiocyanite (OSCN-) was generated at pH 13 by oxidation of excess SCN- with hypobromite (OBr-), followed by a pH jump to acidic conditions ([H+] = 0.20-0.46 M). The observed pseudo-first-order rate constants exhibit first-order dependencies on [H+] and [SCN-] with overall third-order kinetics. The corresponding kinetics of hydrolysis of (SCN)2 have also been examined. Under conditions of high (and constant) [H+] and [SCN-], the kinetics exhibit second-order behavior with respect to [(SCN)2] and complex inverse dependences on [H+] and [SCN-]. Under conditions of low [H+] and [SCN-], the kinetics exhibit first-order behavior with respect to [(SCN)2] and independence with respect to [H+] and [SCN-]. We attribute this behavior to a shift in the rate-limiting step from disproportionation of HOSCN (second-order dependency on [(SCN)2]) to rate-limiting hydrolysis (first-order dependency on [(SCN)2]). Thus, we have determined the following equilibrium constant by the kinetic method: (SCN)2 + H2O HOSCN + SCN- + H+; Khyd = [HOSCN][SCN-][H+]/[(SCN)2] = khyd/kcomp = 19.8(+/-0.7) s-1/ 5.14(+/-0.07) x 103 M-2 s-1 = 3.9 x 10-3 M2.     

Investigations on the kinetics of electron transfer reactions in magnetic fields

There is a controversial debate if a magnetic field can influence the rate of electron transfer (ET) reactions. In this paper, we report kinetic measurements of the ET rate constants for the redox couples [IrCl6]2-/[IrCl6]3-, [Fe(CN)6]3-/[Fe(CN)6]4-, and [Fe(H2O)6]3+/[Fe(H2O)6]2+ in magnetic fields up to 1 T. To reduce effects arising from magnetically induced mass transport (magnetohydrodynamic effect), disk microelectrodes with a diameter of 50 microm were used in potentiodynamic (cyclic and linear sweep voltammetry) and in electrochemical impedance spectroscopy experiments. None of the investigated redox couples showed a magnetic field effect on the ET rate constant.     

Kinetics and mechanism of bromate-bromide reaction catalyzed by acetate

The initial rate of the bromate-bromide reaction, BrO3- + 5Br- + 6H+ --> 3Br2 + 3H2O, has been measured at constant ionic strength, I = 3.0 mol L(-1), and at several initial concentrations of acetate, bromate, bromide, and perchloric acid. The reaction was followed at the Br2/Br3- isosbestic point (lambda = 446 nm) by the stopped-flow technique. A very complex behavior was found such that the results could be fitted only by a six term rate law, nu = k1[BrO3-][Br-][H+]2 + k2[BrO3-][Br-]2[H+]2 + k3[BrO3-][H+]2[acetate]2 + k4[BrO3-][Br-]2[H+]2[acetate] + k5[BrO3-][Br-][H+]3[acetate]2 + k6[BrO3-][Br-][H+]2[acetate], where k1 = 4.12 L3 mol(-3) s(-1), k2 = 0.810 L4 mol(-4) s(-1), k3 = 2.80 x 10(3) L4 mol(-4) s(-1), k4 = 278 L5 mol(-5) s(-1), k5 = 5.45 x 10(7) L6 mol(-6) s(-1), and k6 = 850 L4 mol(-4) s(-1). A mechanism, based on elementary steps, is proposed to explain each term of the rate law. This mechanism considers that when acetate binds to bromate it facilitates its second protonation.