纳米Fe0降解2,4-二氯酚的影响因素及其机理

采用化学还原法制备了纳米Fe⁰, 并研究了不同条件下纳米Fe⁰对2,4-二氯酚(2,4-DCP)的降解情况, 探讨了纳米Fe⁰降解2,4-二氯酚的反应途径. 结果表明, 纳米Fe⁰对2,4-二氯酚的去除作用包括吸附、脱氯、开环三种机制. 其中脱氯作用是一种界面反应, 发生在氯酚分子被吸附到Fe原子表面之后. 2,4-二氯酚可以脱去一个氯原子生成2-氯酚或4-氯酚, 也可以脱去两个氯原子生成苯酚. 随着氯酚初始浓度的增大, 其相对去除率略有降低, 但绝对降解量有较大提高. 温度不仅影响脱氯速率, 而且影响氯酚的去除途径. 温度较高时脱氯作用占主导地位, 先脱氯后开环, 温度较低时吸附作用占主导地位, 较易发生先开环后脱氯的情况.     

金属钯纳米颗粒/氮化钛复合材料对水中2,4-二氯苯酚的电催化氢化脱氯（英文）

随着社会经济的快速发展,含氯有机物,特别是含氯苯系物,在农业、化工和医药等领域的使用量逐年增多,而使用过程中不合理的排放和控制致使含氯苯系物对生态环境,特别是水体环境的污染日趋严重.含氯苯系物具有高致毒致癌性,易生物富集,且很难被完全降解矿化,已被国家环保局认定为优先控制污染物.常规的废水处理工艺,如吸附、氧化及生物降解等,效率不高,且具有二次污染风险.电催化氢化脱氯技术是一种新型特别针对废水中含氯有机污染物的处理工艺,是通过在阴极电解还原水,原位生成原子态氢,以进攻苯环上C.Cl键,通过C.Cl键断裂H原子取代,使含氯苯系物完全转化为苯系物,达到去毒去害化的目的,近年来越来越受到研究者的关注.在整个电催化氢化脱氯技术中,高效稳定的电催化剂合成是关键,决定着脱氯效率、脱氯动力学、产物选择性及能量的利用率.本文报道了一种简易、无需添加任何表面活性剂的湿式还原法制备金属钯/氮化钛(Pd/TiN)和金属钯/碳(Pd/C)复合材料.在该复合材料中,金属钯颗粒具有均一的纳米尺寸(约5.0 nm)和球状形貌,且均匀分布在TiN和C载体上.作为针对水体中代表性含氯苯系物2,4-二氯苯酚的电催化氢化脱氯反应催化剂,Pd/TiN所展现的活性和稳定性均优于TiN和Pd/C,这源于TiN载体的促进作用.当TiN与Pd复合时,相应形成的Pd-TiN界面可改变Pd表面的电子结构,进一步优化Pd产活性氢及其吸附活化2,4-二氯苯酚的性能,因而其催化氢化脱氯活性增加.阴极工作电压是该催化反应中一个重要操作参数,决定了电催化氢化脱氯的效率和最终产物的构成.实验表明,.0.80 V vs Ag/AgCl是最佳操作电压,此时2,4-二氯苯酚的电催化氢化脱氯效率最高,可达到93.27%,且可实现最大程度的2,4-二氯苯酚向苯酚转化.脱氯反应路径研究发现,在Pd/TiN催化剂上2,4-二氯苯酚脱氯反应路径为2,4-二氯苯酚→对位一氯苯酚,邻位一氯苯酚→苯酚,但Pd/TiN对邻位和对位的C.Cl键断裂基本没有选择性.本文提供了一种新的有效调控Pd材料电催化氢化脱氯性能的方法,可望用于其他氢化反应体系的高效催化剂的设计合成,同时可推动电催化氢化脱氯技术在环境污染修复中的应用.     

银基负载的氧化石墨烯磁性纳米复合材料的合成、表征及其对2,4-二氯酚的吸附

以溶剂热法制备得到磁性Ag/AgCl@Fe₃O₄@GO纳米复合材料,利用透射电镜(TEM)、扫描电镜(SEM)、X射线能谱(EDX)和N₂吸附-脱附对样品的结构和形貌进行测试表征,研究了材料对水溶液中2,4-二氯酚(2,4-DCP)的吸附性能。此纳米复合材料由具有介孔结构的球形磁性纳米颗粒Ag/AgCl@Fe₃O₄负载在一层带褶皱的氧化石墨烯表面制备而成,平均孔径S_p为13.98 nm,比表面积为46.91 m²/g,孔体积为0.1791 cm³/g。Ag/AgCl@Fe₃O₄@GO复合材料对2,4-DCP的吸附实验表明,对于20 mg/L 2,4-DCP溶液,20 min基本达到吸附平衡,吸附量为13.74 mg/g;吸附以拟二级动力学模型为主导,相关系数为0.9995;吸附符合Langmuir模型,相关系数为0.9841～0.9972,为单分子层吸附;吸附热力学参数...     

TiO2的低温制备及其对有毒有机污染物的降解

溶胶水热法制备了TiO₂粉末,用X射线衍射仪(XRD)、比表面积及孔径分析仪(BET)和透射电镜(TEM)对TiO₂进行了初步表征,结果显示:纳米TiO₂主要为锐钛矿相(含板钛矿相(121)),比表面积为106.2 m²/g.在紫外光(λ≤387 nm)照射条件下,以有机染料罗丹明B(Rhodamine B,RhB)和无色小分子2,4-二氯苯酚(2,4-dichlorophenol,2,4-DCP)的紫外光(λ≤387 nm)光催化降解试验为探针反应,低温(50℃)下制备的TiO₂粉末具有较高光催化活性,对RhB和2,4-DCP有较好的降解效果.通过分析紫外-可见光谱(UV-Vis)、红外光谱(FTIR)和总有机碳(TOC)测定,发现TiO₂/UV体系能使RhB和2,4-DCP发生有效的降解,反应5 h后RhB和7 h后2,4-DCP的矿化率分别达到81.2%和86.8%.同时,采用辣根过氧化物酶(POD)、N,N-二乙基对苯二胺(DPD)分光光度法和苯甲酸荧光光度法分别测定了在降解过程中H₂O₂和羟基自由基(.OH)的变化,表明TiO₂光催化机理涉及到.OH历程.     

过氧化氢-2,4-二氯苯酚-4-氨基安替比林体系催化光度法测定血红细胞中的铁

基于在十二烷基硫酸钠存在下的弱碱性介质中Fe(Ⅲ)对H_2O_2氧化2,4-二氯苯酚(2,4-DCP)与4-氨基安替比林(4-AAP)偶联显色反应的催化作用,建立了检出限为7.90μg/L.线性范围为0～1.25mg/L的新催化光度分析法.方法用于血红细胞中铁的测定,相对标准偏差与回收率分别为2.6%与98.8%～101%,结果满意.     

聚邻氨基苯硫酚/纳米金复合膜分子印迹传感器测定2, 4-二氯苯酚

在2,4-二氯苯酚(2,4-DCP)存在下, 在金电极表面自组装邻氨基苯硫酚(oATP)并电聚合oATP/金纳米粒子, 制得2,4-DCP印迹复合膜电化学传感器.采用循环伏安法和交流阻抗技术对传感器制备过程进行了表征, 以K₃Fe(CN)₆为探针, 间接对2,4-DCP进行定量分析.结果表明, 2,4-DCP在5.0×10^-8~1.2×10^-4 mol/L 浓度范围内与K₃Fe(CN)₆示差脉冲伏安曲线的峰电流呈线性关系(R²=0.9964), 检出限为1.5×10^-8 mol/L(S/N=3).该印迹传感器可在几种氯代酚干扰下选择性测定2,4-DCP.利用该传感器对环境水样进行加标回收检测, 回收率为95.2%~109.3%.     

载体焙烧温度对Pd/Al_2O_3催化剂催化6-氯-3-硝基甲苯-4-磺酸液相加氢合成CLT酸的催化性能影响

以不同焙烧温度得到的氧化铝为载体,采用浸渍法制得负载型Pd/Al_2O_3催化剂,并将该催化剂应用于6-氯-3-硝基甲苯-4-磺酸液相加氢合成2-氨基-4-甲基-5-氯苯磺酸的反应中,结果表明,载体的焙烧温度为500℃,反应温度为100℃,反应压力为3 MPa,反应时间为2 h,Pd负载量为0.2%,催化剂用量为2 g时,6-氯-3-硝基甲苯-4-磺酸转化率最高,转化率为95.4%。此外,考察了不同脱氯抑制剂对Pd/Al_2O_3催化剂性能和脱氯反应的影响,发现在100℃时,吗啡啉能够有效抑制脱氯副反应的发生。通过XRD、BET、ICP技术对催化剂的物相组成、比表面积和贵金属含量进行了表征,发现Pd高度分散在γ-Al_2O_3载体上。     

拜耳赤泥改性用于含酚废水处理实验研究

以炼铝行业固体废弃物赤泥为原料,采用酸脱碱后改性再水热的方法制备了硫化镉/改性赤泥复合材料(CdS/ARM).通过XRD、SEM与TEM等表征方法分析了复合材料的晶体结构与微观形貌.研究其对2,4-二氯苯酚(2,4-DCP)的降解,探讨了不同比例复合材料的光催化活性,当中20％CdS/ARM对2,4-DCP的降解效果最...     

基于CS-GO/AgNPs氯酚分子印迹电化学传感器的构建

以2,4-二氯苯酚(2,4-DCP)为模板分子,吡咯(Py)为功能单体,协同壳聚糖-银纳米粒子氧化石墨烯(CS-GO/AgNPs)复合材料增强电导性,在玻碳电极(GCE)表面制备分子印迹膜,构建了2,4-DCP分子印迹电化学传感器(2,4-DCP-MIECS)并用于水环境中氯酚的特异性识别与检测。通过透射电子显微镜(TEM)、X射线衍射仪(XRD)对GO/AgNPs复合材料进行分析表征,采用循环伏安法(CV)、交流阻抗法(EIS)对电化学传感器进行性能表征。采用差分脉冲伏安法(DPV)对2,4-DCP进行检测,该电化学传感器的线性范围为1.0～1.0×10~3pmol/L,检出限为0.1 pmol/L,该传感器已用于水样品中2,4-DCP的检测。     

硼掺杂金刚石薄膜电极上二氯酚的电化学阻抗谱研究

以2,4-二氯酚(2,4-DCP)和2,6-二氯酚(2,6-DCP)为模型污染物,采用循环伏安法和电化学阻抗谱研究了硼掺杂金刚石(BDD)电极上2种氯酚的电催化氧化过程.结果表明,2,4-DCP和2,6-DCP的氧化电位分别为1.55和1.62 V.等效电路拟合结果表明,当极化电位由开路电位提高至1.5 V时,2种氯酚的电荷转移电阻均有明显下降,反应控制步骤为扩散控制步骤.与2,6-DCP相比,2,4-DCP在BDD电极上更容易发生直接电化学氧化.     

Reductive dechlorination of 2,4-dichlorophenol using nanoscale Fe~0: influencing factors and possible mechanism

Nanoscale Fe0 was synthesized through a reductive method in this paper. The experiments were per-formed to investigate the reduction of 2,4-dichlorophenol (2,4-DCP) by nanoscale Fe0 under different conditions. The pathways for the reduction of 2,4-DCP by nanoscale Fe0 were discussed. Batch studies demonstrated that the mechanism includes adsorption, dechlorination and cleavage of the benzene ring. Dechlorination, which occurs after 2,4-DCP molecule is adsorbed on the interface of Fe particle, is an interfacial reaction. One or two chlorine atom can be removed from 2,4-DCP to form 2-chlorophenol, 4-chlorophenol or phenol. As the concentration of 2,4-DCP increased, the relative dechlorination ratio decreased. However, the reduced quantities of 2,4-DCP increased. Temperature can influence dechlo-rination rate and pathway. Dechlorination is prior to cleavage of the benzene ring at a higher tempera-ture, but at a lower temperature, adsorption may be the main pathway, and cleavage of the benzene ring may be prior to dechlorination.     

Reductive dechlorination of 2,4-dichlorophenol using nanoscale Fe<Superscript>0</Superscript>: influencing factors and possible mechanism

Nanoscale Fe⁰ was synthesized through a reductive method in this paper. The experiments were performed to investigate the reduction of 2,4-dichlorophenol (2,4-DCP) by nanoscale Fe⁰ under different conditions. The pathways for the reduction of 2,4-DCP by nanoscale Fe⁰ were discussed. Batch studies demonstrated that the mechanism includes adsorption, dechlorination and cleavage of the benzene ring. Dechlorination, which occurs after 2,4-DCP molecule is adsorbed on the interface of Fe particle, is an interfacial reaction. One or two chlorine atom can be removed from 2,4-DCP to form 2-chlorophenol, 4-chlorophenol or phenol. As the concentration of 2,4-DCP increased, the relative dechlorination ratio decreased. However, the reduced quantities of 2,4-DCP increased. Temperature can influence dechlorination rate and pathway. Dechlorination is prior to cleavage of the benzene ring at a higher temperature, but at a lower temperature, adsorption may be the main pathway, and cleavage of the benzene ring may be prior to dechlorination. Supported by the National Natural Science Foundation of China (Grant Nos. 50325824, 50678089) and the Excellent Young Teacher Program of MOE.     

Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd／Fe

IntroductionTherehasbeenagrowinginterestintheuseofzero valentironforthetreatmentofchlorinatedor ganiccompounds(COCs)inwaterandgroundwater .Thestudieshavebeenfocusedonsuchcompoundsascarbontetrachloride ,trichloroethene ,pesticidesandtherelatedcompounds[1— 7] .Whenironisincontactwithalessreductivemetalsuchaspalladiumwhosecomplexhasbeenusedtohydrogenatenitroben zene[8] ,themetalcouplecanformgalvaniccells .ThisledtothediscoveryofaPd/Febimetalliccomplexofwhichpalladiumservesasacatalystandironasa…     

Adsorptive Stripping Voltammetric Determination of 2,4-Dichlorophenol by Laponite Modified Carbon Paste Electrode

A laponite modified carbon paste electrode was prepared, characterized and applied for the 2,4-dichlorophenol (2,4-DCP) voltammetric determination. It takes advantage of the ability of laponite to adsorb phenols, as well as of its availability and very low cost. Kinetic and equilibrium data for 2,4-DCP adsorption by laponite in aqueous dispersions demonstrated that the adsorption process obeyed a pseudo first order kinetic model and was consistent with the formation of adsorbed multilayers on a surface with heterogeneous pore distribution. The composite paste electrode exhibited a heterogeneous surface with 65 % increased surface area and 27 % enhanced catalytic activity compared to the unmodified one. The adsorptive stripping voltammetric determination of 2,4-DCP at an electrode with an optimized graphite:laponite ratio of 55 : 15 w% using a 3 min accumulation time at pH 5.5 was found to be suitable for its quantification in the linear concentration range extended up to 50 μmol L⁻¹ with a sensitivity of 0.56 μA L μmol⁻¹ and a LOD of 0.2 μmol L⁻¹ (S/N=3).The 2,4-DCP electrochemical response was not affected by the presence of some structurally similar phenols, like catechol and p-nitrophenol, while resorcinol, 2-chlorophenol, and 4-chlorophenol presented interferences. The results were validated by 2,4-DCP determination in spiked tap water.     

Dechlorination of 2,4-dichlorophenoxyacetic acid using biochar-supported nano-palladium/iron: Preparation,characterization, and influencing factors

In the present study, peanut shell, a green waste raw material, was used to prepare biochar (BC) and to obtain BC-supported nano-palladium/iron (BC-nPd/Fe) composites for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from water. Characterization analysis demonstrated that nPd/Fe particles were well dispersed on the BC surface with weakened magnetic properties. The average particle diameter and specific surface area of nPd/Fe were 101.3 nm and 6.7 m² g⁻¹, whereas the corresponding values of the BC-nPd/Fe materials were 88.8 nm and 14.8 m² g⁻¹, respectively. Several factors were found to influence the dechlorination of 2,4-D, including the weight ratio of BC to Fe, Pd loading ratio, initial solution pH, 2,4-D concentration, and reaction temperature. Dechlorination results indicated that the 2,4-D removal and phenoxyacetic acid (PA) generation rates were 44.1% and 20.1%, respectively, in the nPd/Fe system, and 100.0% and 92.1%, respectively, in the BC-nPd/Fe system. The dechlorination of 2,4-D was well described by the pseudo-first-order kinetic model (R² > 0.97), and the observed rate constants k_obs were 0.0042 min (nPd/Fe) and 0.0578 min (BC-nPd/Fe), respectively. The reaction mechanism indicated that the dechlorination hydrogenation was the main process to remove 2,4-D from water in the BC-nPd/Fe system. In addition, BC inhibited the formation of a passivation layer on the particle surface during the reaction, thus maintaining the high reactivity of BC-nPd/Fe. The easy preparation technique, high 2,4-D dechlorination capacity, and mild reaction conditions suggest that BC-nPd/Fe may be a promising alternative composite to remove 2,4-D from water.     

In situ encapsulation of laccase in nanofibers by electrospinning for development of enzyme biosensors for chlorophenol monitoring

A biosensor based on Trametes versicolor laccase (Lac) was developed for the determination of phenolic compounds. The biosensor was prepared by in situ electrospinning of a mixture of polyvinyl alcohol (PVA), Lac, PEO-PPO-PEO (F108) and gold nanoparticles (Au NPs), where F108 was used as an enzyme stabilizing additive and Au NPs was used to enhance the conductivity of the biosensor. Laser confocal scanning microscopy and electrochemical impedance spectroscopy proved that the enzyme was successfully encapsulated into the electrospun nanofibers. Under the optimal conditions, the lowest detection limit was found to be 0.04 μM (S/N = 3) for 2,4-DCP and the highest detection limit was found to be 12.10 μM for 4-CP. The sensitivity of the biosensor obtained in the linear range for chlorophenols followed the sequence 2,4-dichlorophenol (2,4-DCP) > 2,4,6-trichlorophenol (2,4,6-TCP) > 4-chlorophenol (4-CP). The sensing performance for chlorophenols was attributed to the suitable electrochemical interface of PVA/F108/Au NPs/Lac, resulting from biocompatibility, a high surface area-to-volume ratio (10.42 m(2) g(-1)) and superior mechanical properties of the electrospun nanofibers. The biosensor exhibited good repeatabilities of 7.6%, 2.8% and 9.0% (R.S.D.) and reproducibilities of 14.9%, 10.4% and 13.7% (R.S.D.) for 4-CP, 2,4-DCP and 2,4,6-TCP, respectively. Lac retained 65.8% of its initial activity after a 30-day storage period.     

Fabrication of bimetallic nanoparticles modified hollow nanoporous carbons derived from covalent organic framework for efficient degradation of 2,4-dichlorophenol

Bimetallic nanoparticles modified hollow-structured nanoporous carbons (NPCs) have been fabricated via a convenient one-step carbonizing strategy derived from covalent organic framework. The Pd/Fe/NPCs, Pt/Fe/NPCs and Rh/Fe/NPCs were obtained and can be used as Fenton-like catalysts with good stability and reusability. The catalytic activity was evaluated by the degradation of 2,4-dichlorophenl (2,4-DCP). These fabricated bimetallic catalysts exhibited much higher catalytic activity than Fe/NPCs at room temperature. The enhancement of catalytic ability was benefited from synergetic catalytic effect of bimetallic nanoparticles and accelerated mass transfer of hollow structure. Additionally, the enhanced catalytic mechanism of bimetallic catalysts was studied in detail and the reasonable reaction pathway was proposed. Besides, the bimetallic catalysts were successfully used for degradation of 2,4-DCP in actual industrial wastewater and the removal efficiency could reach 74.3% within 120 min, which demonstrated the promising potential application of bimetallic catalysts in the removal of pollutants in environment.     

Application of carbon nanotubes as solid-phase extraction sorbent for analysis of chlorophenols in water samples

The aim of this work was to investigate the efficiency of various MWCNTs as SPE materials for the preconcentration of chlorophenols. The COOH-functionalized MWCNTs and MWCNTs were used as SPE sorbents. To evaluate the capability of MWCNTs for the preconcentration of chlorophenols from water samples, 2,4-chlorophenol, 4-chlorophenol, 2,4,6-chlorophenol, 2,6-chlorophenol, 3,4-chlorophenol, and 2-chlorophenol were used as model compounds. Chlorophenols were extracted with acetone, methanol, ethanol, and dichloromethane, and determined by gas chromatography–mass spectrometry. COOH-functionalized MWCNTs <8 nm were found to be the best sorbent for the tested chlorophenols. For COOH-functionalized MWCNTs <8 nm, the recovery rates for all chlorophenols were higher than 50% when acetone or ethanol was used as eluents. In the case of dichloromethane elution, recovery rates for chlorophenols were from 62.0% for 2,6-DCP to 116.8% for 2,4-DCP; only for 2,4,6-TCP was the recovery rate 30.6%. Similar percentage recoveries were achieved with methanol as the eluent.     

担载CuO基催化剂上2,4-二氯酚的有效氧化降解

研究了2,4-二氯酚的催化氧化降解.结果表明,CuO/y-Al2O3催化剂表现出较高的活性,且碱土金属氧化物助剂的添加可进一步显著提高2,4-二氯酚氯离子的释放率,其中以SrO的促进作用最强,该催化剂循环使用3次,2,4-二氯酚转化率及氯离子的释放率均维持100％.X射线衍射和NH3程序升温脱附结果表明,催化剂上CuO...