Chemically modified peat as an economical means of water treatment†

The data presented in this study indicate the feasibility of utilizing modified forms of peat as a cation exchanger, anion exchanger, and oil coalescer. The‐modification processes require relatively inexpensive chemicals in small amounts and only simple procedures are involved. This factor in conjunction with the availability of peat makes these modified systems well suited for large scale applications.     

Techno-economic analysis for the electrocoagulation of fluoride-contaminated drinking water

Electrocoagulation (EC) technique was adopted for the treatment of fluoride-containing drinking water in a 3?L capacity batch reactor. Experimental investigation was carried out to observe the effect of different operating parameters, such as initial fluoride concentration, current density, inter-electrode distance, on the removal of fluoride from the fluoride-rich drinking water. Aluminum flat sheet was used as the electrode material. It was observed that with an increase in current density, percentage removal of fluoride increased. It was seen that at electrode distance of 0.005?m, removal of fluoride attained its maximum compared to the other performances obtained at different inter-electrode distances. Life time of the aluminum electrodes was estimated from the electrode corrosion observed during the experiment. Total operating cost was estimated as a combination of energy cost and electrode cost. The total operating cost was evaluated as 0.38?US$?m^?3 to remove fluoride from the solution with an initial fluoride concentration 10?mg?L^?1. Characterizations of the electrochemically generated by-products were carried out by powder X-ray diffraction, Fourier transform infra-red Raman spectroscopy, scanning electron microscopy image and corresponding elemental analysis.     

Carbon paste electrode modified with chromium thiopental for the potentiometric flow injection analysis of chromium (III)

A chemically modified carbon paste electrode for chromium (III) based on the formation of ion-association complex of chromium with 5-ethyl-6-oxo-5-pentan-2-yl-sulfanyl-pyrimidin-4-olate (thiopental, THP) as electroactive ion-exchanger (Cr-THP) was prepared and investigated. The electrode has a linear dynamic range of 1.7?×?10^?6–1.3?×?10^?2?mol?L^?1, with a Nernstian slope of 19.6?±?0.5?mV per decade and a detection limit of 9.0?×?10^?7?mol?L^?1. It has a fast response time of <15?s and can be used for at least 7 weeks without any considerable divergence in potential. The proposed sensor revealed good selectivity for Cr(III) over a wide variety of mono-, di-, and trivalent cations and could be used in the pH range of 2.3–6.5. The proposed electrode was used in batch measurements and in flow injection analysis. The Cr-CMCPE was successfully applied for the determination of Cr(III) in real samples (wastewater of hot dip galvanizing unit and alloys). The present electrode was also used as an indicator electrode in potentiometric titration of Cr(III). The results were highly satisfactory.     

Toxiwasp∗

TOXIWASP combines most of the kinetic structure of EXAMS 2 with the transport capabilities of WASP (Water Analysis Simulation Program). TOXIWASP uses variable chemical degradation rates from chemical properties and the environmental conditions of the aquatic ecosystem. These rates are reduced from pseudo first‐order rates to first‐order rates including the processes hydrolysis, biotransfor‐mation, phototransformation, oxidation, and volatilisation. Assuming ultimate local equilibrium, and using a chemical dependent partition coefficient as well as spatially varying environmental carbon fractions, sorption onto sediments and biomass is calculated. Environmental alternations could be specified in any time scale by providing monitoring data.

TOXIWASP generates total sediment and chemical concentrations every time step in every segment, including surface water, subsurface water, surface bed and subsurface bed. Advection, dispersion, mass loading, sedimentation, and scour affect sediment concentration in the water column and in the bed sediment concentrations depend on burial and erosion. In addition chemical concentrations are influenced by degradation, sediment‐water dispersion, and percolation. Lateral transport of chemical within the bed is neglected and transport data are not calculated in the program. TOXIWASP is developed to model stratified lakes, reservoirs, large rivers, estuaries, and coastal waters. As for EXAMS 2 (Burns et al.²) the TOXIWASP user has to accept the model's inability to connect the water body to a chemically contaminated atmosphere.     

负载型粒子电极电催化氧化苯酚的研究

以颗粒活性炭(AC)为载体,分别采用氧化还原法和热分解法制备了炭载纳米MnO2、SnO2-Sb-Mn粒子电极,并通过X射线衍射(XRD)、扫描电镜(SEM)及电化学测试对其物相组成、微观形貌和电催化活性进行表征.结果表明,制备的MnO2晶粒主要以α-MnO2与δ-MnO2晶型聚团存在于AC孔隙边缘,SnO2-Sb-Mn活性组分则以固溶体形式分布于AC表面及孔隙内,两类晶体平均粒径分别为11.47,13.70nm,金属氧化物镀层可增加循环伏安曲线测试过程的伏安电荷量,提高粒子电极电催化活性.填充床苯酚模拟废水电催化降解实验表明,MnO2/AC与SnO2-Sb-Mn/AC填充床电极反应器出水苯酚及COD去除率均高于AC填充床,电流效率增大而能耗降低.在电流密度12.0mA/cm2和反应时间140min条件下,SnO2-Sb-Mn/AC粒子电极的苯酚及COD去除率分别为94.7%和90.4%,电流效率达62.7%,能耗为20.3kWh/kgCOD.     

纳米金修饰丝网印刷电极检测水中对苯二酚

采用丝网印刷技术及直接电化学沉积法,制备一次性使用的纳米金颗粒修饰电极,并将其用于水中对苯二酚的检测.扫描电子显微镜表征显示,纳米金粒子以聚集态沉积在电极表面;对苯二酚在纳米金修饰丝网印刷电极上的电化学行为研究表明,该电极对对苯二酚的氧化还原反应产生了明显的电催化作用;以示差脉冲伏安法测定对苯二酚,其峰电流与浓度在4.98×10-5mol.l-1—1.30×10-3mol.l-1范围内呈良好的线性关系,检出限达3.41×10-6mol.l-1;对水样进行测定,加标回收率在98%—101%之间.研究结果表明纳米金修饰的丝网印刷电极可应用于水中对苯二酚现场快速检测.     

气体扩散电极体系的电化学消毒

以自制活性炭/聚四氟乙烯(PTFE)气体扩散电极在无隔膜体系发生H2O2进行电化学消毒的系统研究,探讨了膜电极中PTFE质量分数WPTFE对氧气电还原特性的影响,研究了膜电极中载铂量WPt和造孔剂含量WNH4HCO3、外部操作条件pH值、氧气流速、溶液含盐量和电流密度对杀菌效率的影响.结果表明,WPTFE对H2O2的产率有明显的影响:产H2O2的峰电流先是随着WPTFE的增加而增大,然后减小.当WPTFE=50%时,峰电流最高.杀菌效果随着载铂量的提高而改善,WPt增加到4‰,杀菌效果和WPt=3‰时的杀菌效果基本相当.适量造孔剂的添加有效地改善了杀菌效果.杀菌效率随着pH值的下降迅速提高;该体系pH值适用范围较广:当原水细菌总数为106cfu.ml-1,pH=3—10,以载铂量WPt=3‰的气体扩散电极作为阴极进行电解,30 min后杀菌效率均能达到80%以上.在一定范围内增加氧气流速对H2O2的产生及杀菌效率的变化无太大影响.一方面,高的氧气流速增大了水的电阻,增加了杀菌能耗,提高了气体扩散电极体系杀菌的运行成本;另一方面,高的氧气流速在一定程度上缩短了处理时间,降低了设备投资.含盐量的增加使杀菌能耗减小,因此本电化学杀菌体系更加适合于高含盐量的水.杀菌效率随电流的升高而增加,但电流较大时,杀菌效率增加幅度较小.电流密度控制在6.6 mA.cm-2较为适宜.     

离子色谱-三重四级杆质谱法测定生活饮用水中痕量碘乙酸

水样经MAX固相萃取小柱富集后,用体积分数为1%的甲酸-甲醇溶液洗脱,洗脱液经0.22 μm滤膜过滤,在离子色谱柱上分离后采用三重四级杆质谱法测定水样中的碘乙酸。该方法在0 μg/L~1 000 μg/L范围内线性良好,方法检出限为0.3 μg/L。生活饮用水样品3个质量浓度水平的加标回收率为94.0%~106%,5次测定结果的RSD为2.1%~5.3%。将该方法用于测定江苏地区生活饮用水,结果未检出,高碘地区原水的加氯模拟消毒试验测得消毒后水样中碘乙酸为1.3 μg/L。     

氧化物修饰电极降解有机污染物的电催化特性

采用高温热解氧化沉积法将金属氧化物SnO₂, RuO₂, Cr₂O₃, PdO修饰到钛基体表面,制备得到4种金属氧化物修饰电极.比较4种电极氧化降解苯、苯甲酸、苯酚、苯胺、硝基苯以及甲基橙染料6种有机污染物的氧化电流效率,结果表明,电极在各种介质中的析氧电位和氧化反应传递系数(β值)是衡量电极能否有效处理有机污染物废水的两个重要指标,其中SnO₂电极的析氧电位最高,PbO电极的b值最大,SnO₂电极的β 值次之.这为研制和筛选高效催化电极提供了理论依据.     

电极喷嘴布置对NO电晕氧化过程影响的试验研究

使用湿空气作为自由基源物质 ,研究了电极喷嘴布置对电晕放电特性、NO电晕氧化过程的影响 .结果表明 ,随着电极喷嘴数的增加 ,总电晕区域变大 ,流光的脉动重复率增加 ,NO的氧化率提高 .试验条件下 ,对应B(14 )、B(8)、A(7)、A(4 )的放电电极 ,电晕反应器NO的氧化率最高可分别达到 65 3 %、5 0 5 %、5 1 3 %、2 7 5 % .采用喷嘴数较多的电极时 ,NO电晕氧化的能量效率较高 ,有效工作区内 ,对应B(14 )、B(8)、A(7)、A(4 )的放电电极 ,电晕反应器NO氧化的能量效率最高分别为 5 3 1g·kWh- 1 、5 0 2g·kWh- 1 、5 0 7g·kWh- 1 、3 8 0g·kWh- 1 ,它们对应的NO氧化率分别为 5 3 8%、42 5 %、48 8%、2 3 0 % .喷嘴数目相同时 ,A型电极所形成的电晕流光在电晕反应器内具有更好的充满度 ,更有利于烟气NOx 脱除 .