Electroreductive dechlorination of chlorophenols with Pd catalyst supported on solid electrode

Electroreductive dechlorination of chlorophenols with Pd catalyst supported on solidelectrode was studied. As solid electrodes, carbon cloth (CC), carbon felt (CF) and titanium mesh were used, and palladium was plated on solid electrodes by either electrolytic or electroless method. On each electrode with Pd, chlorophenols were qualitatively dechlorinated to phenol, while they were entirely intact on electrodes without Pd. Moreover, neither base electrode nor plating method significantly affected the activity of Pd as far as it was sufficiently loaded on the electrode. Based on the results in the experiments using one electrode repeatedly, Pd catalyst proved to possess a satisfactory duarability under the present condition. It was suggested that the reactive species responsinble for the dechlorination of chlorophenols could be formed during preliminary electrolysis. Thus, (Pd)_x-H resulting from the adsorption of electrogenerated hydrogen on metallic Pd might be assumed most probable.     

Electrochemical dechlorination of chloroform in neutral aqueous solution on palladium/foam-nickel and palladium/polymeric pyrrole film/foam-nickel electrodes

Electrochemical dechlorination of chloroform in neutral aqueous solution was investigated using palladium-loaded electrodes at ambient temperature. Palladium/foam-nickel （Pd/foam-Ni） and palladium/polymeric pyrrole film/foam-nickel （Pd/PPy/foam-Ni） composite electrodes which provided catalytic surface for reductive dechlorination of chloroform in aqueous solution were prepared using an electrodepositing method. Scanning electron microscope （SEM） micrographs showed that polymeric pyrrole film modified the electrode-surface characteristics and resulted in the uniform dispersion of needle-shaped palladium particles on foam-Ni supporting electrode. The experimental results of dechlorination indicated that the removal efficiency of chloroform and current efficiency in neutral aqueous solution on Pd/PPy/foam-Ni electrode could be up to 36.8% and 33.0% at dechlorination current of 0.1 mA and dechlorination time of 180 min, which is much higher than that of Pd/foam-Ni electrode.     

Pd-MWCNTs-泡沫镍电极对2,4-二氯苯酚的电催化加氢脱氯研究

为发展废水中氯代酚的处理技术和保护水环境安全,采用"浸渍-干燥-电沉积"法制备钯-多壁碳纳米管-泡沫镍电极,研究电极对2,4-二氯苯酚（2,4-DCP）的去除能力和动力学特征,并探讨了2,4-DCP的脱氯机理.结果表明,在MWCNTs和Pd负载量分别为0.7 mg·cm^-2和0.01 mmol·cm^-2时制备的电极对2,4-DCP去除效果最好;掺入多壁碳纳米管（MWCNTs）可增大电极的表面积,提高Pd的分散性,增强电极的催化效率.当Na₂SO₄浓度为0.05 mol·L^-1,工作电压为-1 V,反应液初始pH为7时,50 mg·L^-1的2,4-DCP降解90 min的去除率达到99.74%,降解过程符合一级反应动力学模型,速率常数为0.0667 min^-1.采用高效液相色谱法监测2,4-DCP的降解产物,发现苯酚为2,4-DCP还原的最终产物,降解途径包括直接脱去2个氯原子转化为苯酚和分步脱去2个氯原子再转化为苯酚,但以直接脱去2个氯原子为主要途径.活性基淬灭实验证明,电极通过产生的吸附态氢原子（H_ads）对2,4-DCP进行加氢脱氯.     

Promotional effect of Si-doped V2O5/TiO2 for selective catalytic reduction of NOx by NH3

TiO2 supports doped with different amounts of Si were prepared by a sol-gel method, and 1 wt% vanadia (V2O5) loaded on Si-doped TiO2 was obtained by an impregnation method. The mole ratio of Si/Ti was 0.2, NOx conversion exceeds 94% at 300℃ and GHSV of 41,324 hr-1 , which is about 20% higher than pure V2O5/TiO2 . The catalysts were characterized by XRD, BET, TEM, FT-IR, NH3-TPD, XPS, H2-TPR, Raman and in situ DRIFTS. The results of FT-IR and XPS indicated that Si was doped into the TiO2 lattice successfully and a solid solution was obtained. V2O5 active component could be dispersed well on the support with the increasing of surface area of the catalyst, which was confirmed by Raman and XRD results. Above all, the numbers of acid sites (especially the Br nsted-acid) and oxidation properties were enhanced for Si-doped V2O5/TiO2 catalysts, which improved the deNOx catalytic activity.     

纳米级Pd/Fe@SiO2复合颗粒对2,4-DCP的还原脱氯研究

为有效抑制纳米级Pd/Fe颗粒的团聚和钝化及改善其表面特性,将纳米SiO_2包覆在Pd/Fe颗粒表面,超声波辐照下液相还原法制备纳米级Pd/Fe@SiO_2复合颗粒,采用TEM、SEM、XRD、EDX及BET表征其物性,以2,4-二氯苯酚(2,4-DCP)为目标污染物,探究其对2,4-DCP的还原脱氯影响因素、降解机理和动力学,结果表明:制备的纳米级颗粒粒径均匀、分散性好,比表面积大;体系中纳米级Pd/Fe投加量、钯化率、TEOS投加量、反应温度及溶液初始pH均会对2,4-DCP的降解效果产生明显影响;并推测出纳米级Pd/Fe@SiO_2复合颗粒对2,4-DCP的降解机理即快速吸附—逐步脱氯—最终脱附释放,其降解符合拟一级动力学关系.     

Dechlorination of chlorophenols by zero valent iron impregnated silica

Laboratory studies were conducted to find out the efficacy of uniquely prepared zero valent iron impregnated silica in transforming xenobiotic chlorophenols namely 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. Continuous mode column experiments were performed to investigate the transformation of chlorophenols by varying pH, column height, flow rate and initial chlorophenol concentration. Reusability study of the zero valent iron impregnated silica was studied as well as the morphological changes and the chemical composition of the catalyst medium were also investigated. Dechlorination kinetic studies were conducted and the order of dechlorination of chlorophenols was found to be 2,4,6-trichlorophenol > 2,4-dichlorophenol > 4-chlorophenol. The optimum pH, column height and flow rate were found to be 7, 20 cm and 0.75 L/hr respectively for all chlorophenols in the reaction duration of 4 hr. Intermediates formed during dechlorination study were identified by gas chromatography-mass spectroscopy analysis. This method was applied to real pulp and paper wastewater and was found satisfactory.     

Pd-Ni/GC电极电化学还原水中三氯甲烷的研究

通过电沉积法在玻碳板(GC)电极上负载钯镍双金属,并利用正交实验对其进行循环伏安(CV)研究. CV结果表明,钯镍双金属比钯、镍单金属具有更大的氢吸附峰值,可以在- 500 mV(以Hg/Hg2SO4 为参比电极)左右获得- 24.83 mA的氢吸附峰.扫描电镜分析(SEM)表明,镍的加入改变了钯颗粒在GC表面的分布形态,钯镍双金属颗粒形貌明显不同于钯、镍单金属颗粒,钯镍双金属颗粒粒径介于钯、镍单金属颗粒粒径之间.实验考察了脱氯电流、脱氯时间对三氯甲烷去除率的影响.三氯甲烷的去除率随脱氯电流的增大而增大,随脱氯时间的延长而提高.在优化条件下制备的Pd-Ni/GC电极在0.5 mA、180 min的脱氯条件下对三氯甲烷的去除率为42.53%.可以推测,随着脱氯时间的继续延长,三氯甲烷去除率可得到进一步提高.     

Pd/C气体扩散电极用于电化学降解4-氯酚的研究

采用氢气还原法制备Pd/C催化剂,利用XRD、TEM及XPS对该催化剂进行了表征,并利用此催化剂制备成新型的Pd/C气体扩散阴极;在隔膜电解体系中对4-氯酚进行降解,比较了不同通气方式下的去除效果.结果表明,所制备的催化剂中Pd以无定形态存在并高度分散在活性炭表面,形状比较规则,粒径在4.1 nm左右;制备的0.5%Pd/C催化剂表面的Pd摩尔分数达到1.29%;制备的Pd/C气体扩散阴极既对4-氯酚具有还原脱氯作用(通入H2时),又促进O2还原生成H2O2(通入O2时).采用先通氢气后通空气的方式对4-氯酚有很好的去除效果,反应60min后4-氯酚的转化率和脱氯率接近100%,120 min后阴极室COD去除率达到87.4%.因此,采用Pd/C气体扩散阴极可通过还原.氧化相结合的方法对氯酚类有机物进行降解.     

生物电催化方法处理三氯乙酸的研究

利用吸附法将血红蛋白(Hb)固定在碳纳米管修饰电极表面,研究了Hb在碳纳米管修饰电极的直接电化学行为.固载Hb碳纳米管修饰电极在pH=7.0的PBS缓冲溶液中于-0.300V(vsSCE)处有一对相当可逆的循环伏安还原氧化峰,为Hb血红素辅基Fe(Ⅲ)/Fe(Ⅱ)电对的特征峰.利用循环伏安法和恒电位电解法研究了固载Hb的碳纳米管修饰电极对有机氯模型污染物三氯乙酸的电催化还原脱氯,并通过鉴定中间产物探讨了其催化还原机理.结果表明,固载Hb的碳纳米管修饰电极对三氯乙酸的还原具有很高的催化活性,三氯乙酸是按照三氯乙酸→二氯乙酸→一氯乙酸→乙酸的途径分布还原脱氯.将固载Hb的碳纳米管修饰电极组装成三维填充床电解反应器,进行了三氯乙酸连续流动电解还原的初步研究.-0.6V(vs.SCE)电解180min,三氯乙酸去除率为40.13%.     

用于降解4-氯酚的载钯碳纳米管催化电极研究

采用不同体积分数的硝酸溶液（8%、15%、20%、68%）对多壁碳纳米管（MWNTs）进行预处理,使用甲醛还原方法制备出Pd/MWNTs催化剂,利用Boehm滴定法、红外光谱分析、X射线衍射（XRD）、扫描电子显微镜（SEM）及循环伏安曲线（CV）对催化剂进行表征分析,并制备成Pd/MWNTs催化阴极,在隔膜电解体系中...     

Pd/Ti电极上2,4,6-三氯酚还原脱氯:条件优化及降解途径

利用电沉积法制备了Pd/Ti电极,用于2,4,6-三氯酚(2,4,6-TCP)的电还原脱氯.采用单因素实验和响应面分析法,探讨了2,4,6-TCP脱氯试验条件;根据实验结果,拟合出了脱氯中各步骤的反应速率常数.结果表明,2,4,6-TCP初始浓度为80mg/L时,优化的脱氯参数为电流为5mA,支持电解质Na2SO4浓度为0.05mol/L,阴极电解液初始pH值为2.40.在优化条件下, 2,4,6-TCP在80min内完全脱氯; 2,4,6-TCP的还原脱氯符合准一级反应动力学,主要脱氯途径为2,4,6-TCP→2,6-DCP→2-CP→苯酚.     

双信号细胞电化学法检测氯酚类的毒性

以多壁碳纳米管和离子液体复合修饰电极(MWCNTs-IL/GCE)为工作电极,运用线性扫描伏安法(LSV)研究了人乳腺癌(MCF-7)细胞的电化学行为,检测到了2个明显的氧化峰,其氧化峰电位分别为0.725 V和1.038 V.结合4种嘌呤碱基与模型细胞的电化学行为比较与高效液相色谱分析,确定细胞的电化学响应来源分别为细胞质中黄嘌呤与鸟嘌呤、次黄嘌呤与腺嘌呤的电化学氧化.基于2个响应信号峰电流的变化,研究了五氯酚(PCP)、2,4,6-三氯酚(TCP)和2,4-二氯酚(DCP)对MCF-7细胞的毒性效应,根据剂量-效应关系曲线计算半数抑制效应浓度(IC50)值,并与四甲基偶氮唑盐(MTT)比色法进行比较.结果发现,氯酚类污染物对MCF-7细胞活性有明显抑制作用,细胞电化学法与MTT法测得细胞毒性顺序均为:PCPTCPDCP,表明细胞电化学法可以快速、准确地评价氯酚类污染物的细胞毒性.该研究结果可从核苷酸代谢角度为危害化学品的安全无标记、准确客观的毒性评价方法建立提供新思路.     

钯/泡沫镍阴极对水中微量氯贝酸的电催化氢化还原脱氯研究

氯贝酸（Clofibric acid, CA）是一种常见药品和个人护理品（PPCPs）类物质,在环境中具有持久性和稳定性.常规的水处理技术难以去除微量的CA,采用电催化氢化脱氯的方法可有效实现脱氯.本研究考察了CA初始浓度、工作电位、阴极液初始pH、反应温度、钯载量和电解质Na₂SO₄的浓度等多种因素对氯贝酸降解的影响.结果表明,CA的脱氯降解符合一级动力学方程,在工作电位为-0.85 V vs Ag/AgCl,钯负载量为0.20 mg·cm^-2,Na₂SO₄浓度为10 mmol·L^-1,初始阴极液pH为4.6,反应温度控制在303 K时,经过120 min的反应后,初始浓度为5 mg·L^-1的CA降解率达98%.因此利用钯/泡沫镍电极电催化还原降解废水中的CA具有很大的应用潜力.     

Pd/C气体扩散电极用于电化学降解五氯酚钠的研究

采用氢气还原法制备出Pd/C催化剂,利用循环伏安曲线（CV）对氧在Pd/C催化剂上的电化学还原行为进行了分析,并由催化剂制备成Pd/C气体扩散阴极,采用先通H₂后通空气的方式在隔膜电解体系中对五氯酚钠进行降解,比较了不同电极体系下五氯酚钠的去除效果.结果表明,在阴极室,Pd/C气体扩散电极通过外界曝气提供的O₂在阴极还原产生H₂O₂,电解100 min后H₂O₂的稳定浓度达到9.8 mg/L.实验制备的Pd/C气体扩散阴极既对五氯酚钠具有还原脱氯作用（通入H₂时）,又促进O₂还原生成H₂O₂（通入O₂时）,它对五氯酚钠的去除效果要好于不掺杂Pd的气体扩散阴极.反应120 min后,五氯酚钠平均转化率和脱氯率均超过80%,反应200 min后TOC平均去除率分别超过75%.采用高效液相色谱（HPLC）等手段分析出五氯酚钠在阴极室还原脱氯的中间产物主要是苯酚,Pd/C气体扩散阴极利用电化学还原脱氯和阴阳极同时氧化相结合对氯酚类有机物的降解是可行的.     

三维Pd/OMC粒子电极体系电催化泛影酸盐还原脱碘研究

以泛影酸盐(DTZ)的高效还原脱碘为目标,通过硼氢化钠还原法制备钯负载有序介孔碳(Pd/OMC)作为粒子电极,以碳纤维(CFP)电极作为主阴极,建立了三维电极电催化还原体系.该体系在低阴极电位下(-0.6～-0.8 V)可实现电化学/感应电化学的耦合还原,其脱碘速率是单独阴极体系的2.38～3.65倍;在阴极电位高于析氢电位(-1.5 V)时,可实现电化学/感应电化学/化学催化加氢多还原过程协同去除碘代有机物,其反应速率为单独阴极体系的1.27～4.69倍.进一步研究了DTZ初始浓度、Pd/OMC投加量及Pd的负载量对DTZ还原去除的影响.电化学测试结果表明三维电化学体系具有良好的电子传递能力与电还原性能.利用自由基淬灭实验与ESR自由基捕获对活性还原物种分析,表明原子H~*在三维电化学还原脱碘过程中起重要作用.     

载钛活性炭电极电吸附除盐性能的研究

采用sol-gel法制备载钛活性炭(Ti-AC),并用此活性炭制取了Ti-AC电极,利用扫描电子显微镜(SEM)、X射线荧光光谱(XRF)、X射线衍射仪(XRD)和电化学工作站等对活性炭电极的表面形貌、元素组成、化合物形态以及电极的电化学性能进行分析,并考察载钛前后活性炭电极的除盐能力,而且对Ti-AC电极与碳纳米管电极和活性炭纤维电极的实用性进行比较.结果表明,Ti-AC电极含有一定量的Ti元素,其形态为金红石型TiO2,并在电极表面积聚为很多的絮状结构,载钛后双电层形成速率更快,电吸附容量显著提高.对NaCl的吸附试验表明,Ti-AC电极物理吸附降低,电吸附明显提高,除盐率提高了62.7%.实用性分析表明,Ti-AC电极更适宜应用于电吸附除盐.     

Catalytic dechlorination of chlorobenzene in water by Pd/Fe bimetallic system

IntroductionChlorinatedorganiccompoundshavebeenusedonalargescaleinthechemical,petrochemical,andelectronicindustries.Inrecentyears ,worldwideattentionhasbeengiventotheenvironmentalandhealthimpactofthemasaclassofcontaminants .Severalareknowntocauseozonedepletion ,whileothersproduceadverseeffectsonthehumancentralnervoussystemandhavebeenlinkedtodiseasessuchascancer.Almostallofthechlorinatedaromaticcompoundsaretoxicandthermallystable .Oncereleasedintoenvironment,theywillaccumulateinthesurroundings…     

钯/泡沫镍对水体中4-氯酚的氢解脱氯研究

采用置换沉积法制备泡沫镍负载钯(Pd/Ni)催化剂,研究了其在H2作为供氢体时对水相中4-氯酚(4-CP)的催化氢解脱氯作用.考察了Pd负载量、H2流量和反应液pH值对4-CP转化率的影响.结果表明,在相对较低的Pd负载量和H2流量下即可实现4-CP的快速高效去除,且反应液pH值在3.04~10.97的范围对反应影响不显著.当Pd负载量为0.1%、H2流量为10mL/min、pH值为6.80时,反应1h,4-CP转化率达92.6%.Pd/Ni具有较高的稳定性,重复实验表明,该催化剂使用3次后,催化活性仅下降了2.0%.     

A high activity of Ti/SnO2-Sb electrode in the electrochemical degradation of 2,4-dichlorophenol in aqueous solution

Electrochemical degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was investigated over Ti/SnO₂-Sb anode. The factors influencing the degradation rate, such as applied current density (2-40 mA/cm²), pH (3-11) and initial concentration (5-200 mg/L) were evaluated. The degradation of 2,4-DCP followed apparent pseudo first-order kinetics. The degradation ratio on Ti/SnO₂-Sb anode attained > 99.9% after 20 min of electrolysis at initial 5-200 mg/L concentrations at a constant current density of 30 mA/cm² with a 10 mmol/L sodium sulphate (Na2SO4) supporting electrolyte solution. The results showed that 2,4-DCP (100 mg/L) degradation and total organic carbon (TOC) removal ratio achieved 99.9% and 92.8%, respectively, at the optimal conditions after 30 min electrolysis. Under this condition, the degradation rate constant (k) and the degradation half-life (t_1/2) were 0.21 min^-1 and (2.8±0.2) min, respectively. Mainly carboxylic acids (propanoic acid, maleic acid, propanedioic acid, acetic acid and oxalic acid) were detected as intermediates. The energy efficiencies for 2,4-DCP degradation (5-200 mg/L) with Ti/SnO₂-Sb anode ranged from 0.672 to 1.602 g/kWh. The Ti/SnO₂-Sb anode with a high activity to rapid organic oxidation could be employed to degrade chlorophenols, particularly 2,4-DCP in wastewater.     

Pd/CMK-3的合成、表征及对甲酸的电催化氧化性能研究

以中孔硅SBA-15为硬模板、蔗糖为炭源,合成了有序中孔炭CMK-3,并以此CMK-3为载体,采用络合还原法制备了负载量为20%的催化剂Pd/CMK-3.X射线衍射(XRD)和透射电镜(TEM)的结果表明,CMK-3孔结构高度有序,呈现二维六方结构,Pd/CMK-3和Pd/AC(活性炭)催化剂中Pd纳米颗粒分散均匀,平均粒径分别为4.2 nm和4.5 nm;拉曼光谱测试表明,CMK-3比活性炭的石墨化程度更高,导电性更强;N2吸附/脱附实验表明,CMK-3具有典型的中孔结构,CMK-3的最可几孔径为4.5 nm,显著大于活性炭的0.54 nm,CMK-3的BET比表面积为1 114 m2.g-1,大于活性炭的871 m2.g-1.在对甲酸电催化氧化的循环伏安(CV)和计时电流(CA)测试中,Pd/CMK-3的初始催化活性显著高于Pd/AC,而两者在100 s后的计时电流稳定性则基本相当.