电流密度对AZ31B镁合金阳极氧化及膜层性能的影响

采用KOH-Na2SiO3-Na2B4O7-Na2CO3环保型电解液体系,研究了电流密度对AZ 31B铁合金阳极氧化过程、氧化膜微观形貌、膜层厚度、氧化膜耐蚀性等的影响.结果表明:在恒电流阳极氧化过程中,根据电压-时间曲线,阳极氧化过程可分为电压快速升高阶段、电压缓慢升高阶段、电压相对稳定阶段.随着电流密度的增大,电压-时间曲线的斜率增大,电压明显增大,点火时间缩短,但对击穿电压影响不大;随着电流密度的增加,膜层致密性、厚度、耐蚀性都呈先增大后减小的趋势.当电流密度为1.5 A/dm2时,阳极氧化膜的致密性和耐蚀性最好.     

双极膜电去离子过程制备四甲基氢氧化铵

采用酸室填充离子交换树脂的双极膜电去离子(BMEDI)装置,以四甲基氯化铵(TMAC)为原料制备四甲基氢氧化铵(TMAH).研究了树脂体积比、电流密度和原料浓度对TMAH制备过程的影响,并对2种不同的均相阴膜进行了对比考察.结果表明,在电流密度40 mA·cm-2,原料TMAC浓度0.1 mol·L-1的条件下,TMAH转化率可达91.2%.电流密度提高,TMAH转化率和过程能耗随之增大,在更高的原料浓度下可获得更高的电流效率,酸室填充100%阴树脂效果较好.此外,与JAM-10膜相比,UTX-UIF-A膜的面电阻较小,取得了更佳的试验效果.     

基于液体催化燃料电池的葡萄糖电解制氢性能分析

以葡萄糖为原料,利用液体催化燃料电池搭建生物质电解制氢系统,并对磷钼酸催化氧化葡萄糖电解制氢的性能进行分析。结果表明,当将浓度为0. 2 mol/L的磷钼酸与质量浓度为15 g/L的葡萄糖混合溶液在120℃下连续加热24 h后,葡萄糖的有机物降解率达到43%,混合溶液连续进行5次加热-电解循环后,葡萄糖中有机物降解率可达到71%。将首次加热后的混合溶液在恒电压1 V下测试电流-电压曲线,初始电流密度和产氢量分别可达到191 mA/cm~2和175 mL。     

均相和异相离子交换膜在NaCl浓缩中性能对比

通过考察均相与异相离子交换膜在不同操作条件下的能耗、电流效率、浓缩极限等参数,比较了2种离子交换膜的物理化学性能,并进行了操作参数优化实验。结果表明,均相离子交换膜的优化操作电压和最佳进料液NaCl的质量浓度分别为6 V和30 g/L,异相离子交换膜的优化操作电压和进料液NaCl的质量浓度分别为7.5 V和50g/L。在该优化条件下,采用均相离子交换膜和异相离子交换膜进行浓缩时,浓缩室的NaCl的最高质量浓度分别可达到191.2 g/L和149.3 g/L。异相离子交换膜比均相离子交换膜具有更好的结构稳定性。实验结果对电渗析工程应用中均相离子交换膜与异相离子交换膜的选择具有一定的借鉴与指导意义。     

电渗析用于多元醇溶液脱盐的实验研究

考察了操作电压、浓淡室流速比、浓淡室溶液体积比3种操作条件变化对普通离子交换膜、化工分离专用离子交换膜、均相离子交换膜脱盐性能的影响。研究表明,采用电渗析法能够有效脱除多元醇溶液中有机酸盐,化工分离专用离子交换膜的综合性能优于普通离子交换膜和均相离子交换膜,当采用化工分离专用离子交换膜浓淡室流速比为3∶1时,多元醇损失率为1%,浓淡室溶液体积比为1∶4时,对化工分离专用离子交换膜性能基本没有影响。     

新型膜电解反应器深度处理含盐农药废水

在传统三室膜电解槽的基础上进行改进,将各槽室之间通过阴阳离子交换膜(均相离子交换膜)隔开,分成中间淡化室和两侧的阴阳极室,各槽室中的溶液不断循环。以期改善传统反应器无法去除有机物和脱盐率低等缺点。结果表明,电压越高脱盐率越高,但当电压升高到18 V时反应器运行电流已接近极限电流值,同时三环唑的去除率随电压升高的幅度较小。Na_2SO_4含量升高脱盐率和三环唑去除率随之升高,但当Na_2SO_4的质量浓度为10 g/L时脱盐开始出现下降。新型反应器脱盐率、电流效率更高,尤其是在高盐分的情况下,同时对有机物具有直接的降解作用,出水毒性有机物含量极低。     

离子交换膜电解分离溶液中硫酸根离子的实验研究

离子交换膜电解技术,由于膜的离子选择透过性,在分离无机离子和浓缩酸碱方面具有良好的发展前景。本文利用阴离子交换膜电解,分离(NH4)2SO4和CuSO4溶液中的SO42-。通过实验得出了电流密度对阳极浓缩H2SO4浓度的影响、温度和电流密度对电流效率的影响以及不同电流密度下最佳能耗和电流效率。     

反电渗析应用于盐差能提取的研究

开发新能源是当今备受关注的研究领域,盐差能已经成为开发新能源的目标之一。使用不同的商业化常规离子交换膜,进行功率密度的筛选,筛选出在反电渗析(RED)中功率密度较高的膜材料,其中使用的商业化的离子交换膜分别是DF-120离子交换膜和CJ-3阴阳离子交换膜。DF-120在流速是0.72 cm/s时,电压为1.66 V,最大功率密度是0.693 W/m~2;CJ-3阴阳离子交换膜是在流速为1.2 cm/s时,电压为1.6 V,最高功率密度为0.83 W/m~2。     

纳米TiO_2膜电极上乙醛酸的电催化合成研究

运用电化学循环伏安法 (CV)对纳米TiO2 膜电极 (Ti/nano TiO2 )在硫酸和草酸溶液中的电化学行为进行了研究。在c(H2 SO4 ) =1mol/L溶液中的循环伏安图上Epac1=- 0 .5 6V(vs.SCE)和Epac2 =- 0 96V(vs.SCE)处 ,出现两对可逆氧化还原峰 ,而在相同扫描速度下草酸溶液中的循环伏安曲线上 ,这两对电极反应氧化峰基本消失 ,还原峰电流增大 ,表明Ti/nano TiO2 膜电极对电还原草酸成为乙醛酸的反应具有较高的电催化活性和选择性。常温常压下 ,控制电位Epc=- 1 0V左右电解合成乙醛酸 ,乙醛酸的产率和电流效率分别达到 96 5 %和 90 %。     

电去离子净水设备的最佳工作参数

通过对1t／h电去离子(EDI)净水设备的实验研究,得出确定其最佳工作参数的方法。介绍实验得出的EDI净水设备的电压-电流曲线和电流与产水电阻率曲线,依据这些曲线来确定EDI净水设备的极限电流密度和最佳工作参数,方便、可靠、形象、直观．且较简单。     

A study of ionic transfer in electrodialysis process with laminar flow

The concentration profile in a laminar flow of the diluent of a parallel-plate electrodialysis stack is derived by assuming operation at the limiting current density. The Nusselt mass transfer number is found to depend on the Reynolds number, the Schmidt number and the dimensionless hydraulic equivalent diameter according to (Nu)_theo. = 3.7 · (Re · Sc · de/L)^1/3. An empirical correlation of the Reynolds number, the Schmidt number, and the shape factor of the electrodialysis cell, with the ionic mass transfer rate in ion exchange membrane electrodialysis is obtained by measuring the limiting current densities at various conditions. The resulting empirical mass-transfer correlation, (Nu)_exp. = 3.91 · Re^0.333 · Sc^0.328 · (de/L)^0.352, holds for sodium acetate as dialysate at concentrations ranging from 0.0106 to 0.0508 kmol/m³, viscosities ranging from 0.608 to 0.926 mPa · s, temperatures ranging from 15 to 55°C, axial velocities ranging from 0.341 to 4.55 cm/s, and for cell thicknesses of 0.32 and 0.94 cm, and is found to be in agreement with the equation obtained from theory. The effects of concentration, flow rate and temperature on the limiting current density are also studied. The relationship between the thicknesses of the diffusion layer and the Reynolds number has been analyzed.     

Application of response surface methodology to optimize the operation process for regeneration of acid and base using bipolar membrane electrodialysis

BACKGROUND: Bipolar membrane electrodialysis (BMED) has been widely used for desalination, concentration, separation, and purification in many fields. The purpose of this study is to optimize the operation conditions using response surface methodology (RSM) for the regeneration of sulfuric acid and ammonia from ammonium sulfate solution by BMED coupled with ammonia in situ stripping. RESULTS: A three‐factor central composite design of RSM was used to analyze the effect of operation conditions (current density, flow rate, initial acid concentration) on average current efficiency (ACE) and establish the optimal operation conditions. The ACE was 76.7 ± 2.2% under optimal operation conditions (current density 23.8 mA cm^?2, flow rate 27.3 L h^?1, initial acid concentration 0.09 mol L^?1). CONCLUSION: A suitable regression model for predicting ACE within the ranges of variables used was developed based on experimental results. The operation conditions were optimized by RSM and the ACE obtained under the optimal operation conditions was in good agreement with the value predicted by the regression model (78%), which proved the validity of the model. Copyright © 2007 Society of Chemical Industry     

电解法回收废盐酸实验研究

采用滤压式隔膜电解槽对低质量分数废盐酸进行电解回收利用实验研究,实验分别讨论了电流密度、电解液流量、温度和HCl、NaCl混合电解液质量分数对槽电压和电流效率的影响,通过实验得出,电流效率影响最显著的因素是电解液流量,槽电压的最主要影响因素是电流密度。最佳工艺水平为:流量12 mL/min,电流密度0.2 A/cm2,电解温度50℃,电解液为质量分数7%HCl与NaCl混合液。验证实验得出电流效率为95.11%,槽电压为4.1 V。     

MASS TRANSFER IN AC ELECTROLYSIS: EXTENSION OF A FILM MODEL TO TURBULENT FLOW ON A ROTATING HEMISPHERE

Turbulent mass transfer to a rotating hemisphere during AC electrolysis was examined with a film model. The analytical results for the limiting AC current density were compared to the experimental data obtained with sinusoidal, square and triangular wave AC. The limiting AC current density in turbulent flow was found to depend on both the Reynolds number as a dimensionless AC frequency K = (ω/Ω)Sc^1/3. The prediction by the film model agreed with the experimental data to within ±15%. For a given root-mean-square of applied AC, the periodic concentration overpotential decreased in the order of quare, sinusoidal, and triangular AC. The phase shift between the applied AC and the concentration overpotential wave decreased with increasing Reynolds number in turbulent flow.     

MASS TRANSFER IN AC ELECTROLYSIS: EXTENSION OF A FILM MODEL TO TURBULENT FLOW ON A ROTATING HEMISPHERE

Turbulent mass transfer to a rotating hemisphere during AC electrolysis was examined with a film model. The analytical results for the limiting AC current density were compared to the experimental data obtained with sinusoidal, square and triangular wave AC. The limiting AC current density in turbulent flow was found to depend on both the Reynolds number as a dimensionless AC frequency K = (ω/Ω)Sc^1/3 The prediction by the film model agreed with the experimental data to within ±15%. For a given root-mean-square of applied AC, the periodic concentration overpotential decreased in the order of quare, sinusoidal, and triangular AC. The phase shift between the applied AC and the concentration overpotential wave decreased with increasing Reynolds number in turbulent flow.     

双极膜电渗析法由硫酸铵制备硫酸的工艺研究

利用两室双极膜电渗析法从硫酸铵溶液中制备硫酸。探讨了电渗析过程中的电流效率、能耗、产酸量等指标。实验结果表明,产酸量随时间的延长而增加,在恒定电流密度（0.09A.cm-2）的条件下,硫酸的电流效率达到90%,能耗为2.5～2.6kW.h.kg-1。     

亚硫酸铵催化氧化实验研究

经济高效的将亚硫酸铵转为硫酸铵,是氨法脱硫工艺的关键。采用氧气作为氧化剂,硫酸钴为催化剂,在搅拌反应器中对亚硫酸铵催化氧化过程进行了实验研究。考察了亚硫酸铵初始浓度、硫酸铵初始浓度、催化剂浓度、反应温度、空气流量、溶液pH对亚硫酸铵氧化率的影响。结果表明：控制亚硫酸铵初始浓度为0.3 mol.L-1,硫酸铵初始浓度为0.3 mol.L-1,硫酸钴为0.001 mol.L-1,空气流量为400 L.h-1,pH为6.0,反应温度50℃,反应4 h后,氧化率达到90%。     

MASS TRANSFER IN AC ELECTROLYSIS: EXTENSION OF A FILM MODEL TO TURBULENT FLOW ON A ROTATING HEMISPHERE

Turbulent mass transfer to a rotating hemisphere during AC electrolysis was examined with a film model. The analytical results for the limiting AC current density were compared to the experimental data obtained with sinusoidal, square and triangular wave AC. The limiting AC current density in turbulent flow was found to depend on both the Reynolds number as a dimensionless AC frequency K = (ω/Ω)Sc^1/3 The prediction by the film model agreed with the experimental data to within ±15%. For a given root-mean-square of applied AC, the periodic concentration overpotential decreased in the order of quare, sinusoidal, and triangular AC. The phase shift between the applied AC and the concentration overpotential wave decreased with increasing Reynolds number in turbulent flow.     

MASS TRANSFER IN AC ELECTROLYSIS: EXTENSION OF A FILM MODEL TO TURBULENT FLOW ON A ROTATING HEMISPHERE

Turbulent mass transfer to a rotating hemisphere during AC electrolysis was examined with a film model. The analytical results for the limiting AC current density were compared to the experimental data obtained with sinusoidal, square and triangular wave AC. The limiting AC current density in turbulent flow was found to depend on both the Reynolds number as a dimensionless AC frequency K = (ω/Ω)Sc^1/3. The prediction by the film model agreed with the experimental data to within ±15%. For a given root-mean-square of applied AC, the periodic concentration overpotential decreased in the order of quare, sinusoidal, and triangular AC. The phase shift between the applied AC and the concentration overpotential wave decreased with increasing Reynolds number in turbulent flow.     

含钒灰渣酸浸液结晶铵明矾的工艺条件

为获得含钒灰渣酸浸液结晶铵明矾的优化工艺条件,利用正交优选法研究了Al2(SO4)3浓度、铵/铝摩尔比、冷却速度和结晶温度对铵明矾结晶率的影响,分析了铵明矾晶体和滤液的成分,计算得到了铵明矾的结晶率. 结果表明,4种因素对铵明矾结晶率均有较大影响,Al2(SO4)3浓度、铵/铝摩尔比对铵明矾结晶率影响较为显著. 合理的铵明矾结晶工艺条件为：Al2(SO4)3浓度150~200g/L,铵/铝摩尔比1.2左右,冷却速度15℃/h左右,结晶温度5℃左右. 在此条件下,铵明矾结晶率为89.32%.