电化学氧化法处理高浓度垃圾渗滤液的研究

实验利用电化学氧化法去除垃圾渗滤波中部分难降解有机物以提高废水的可生化性,为后续生物处理创造条件。系统考察了温度、极板间距、氯离子浓度、pH值等因素对电化学处理垃圾渗滤波效果的影响,并通过GC-MS分析,探讨渗滤波中有机污染物的去除情况,包括渗滤液中典型有毒难降解有机化合物的电化学氧化结果。结果表明:温度升高,COD和NH_3-N的去除率均提高;极板间距太大或太小都会降低去除效果,极板间距10mm,处理效果较好,COD和NH_3-N去除率分别达到86％和100％;随着渗滤液中Cl-浓度的增加,COD去除率明显提高,同时高浓度Cl-和较高的电流密度对垃圾渗滤液中难降解有机污染物的处理有相当强的协同作用效应,可以明显提高处理效果;在强酸性和强碱性条件下的电化学反应都不利于对COD、NH_3-N的去除;在添加Cl-4000mg/L,极板间距为10mm,电流密度为15A/dm^2,pH为8,初始温度为50℃的条件下,经4h的电化学氧化,COD、氨氮和色度的去除率分别达到88％、100％和98％,苯酚的去除率为82％,电流效率可达84％以上。可见电化学氧化法不仅可有效的去除COD、氨氮、色度,而且对有毒的难降解有机污染物(苯酚等)有很好的去除作用,采用电化学氧化作为垃圾渗滤液废水处理的前处理,可大大改善后续生物处理的效果。

Electrochemical oxidation of aniline by a novel Ti/TiO_xH_y/Sb-SnO_2 electrode

Electrochemical oxidation of aniline in aqueous solution was investigated over a novel Ti/TiOxHy/Sb-SnO2 electrode prepared by the electrodeposition method.Scanning electron microscopy,X-ray diffraction,and electrochemical measurements were used to characterize its morphology,crystal structure,and electrochemical properties.Removal of aniline by the Ti/TiOxHy/Sb-SnO2electrode was investigated by ultraviolet-Visible spectroscopy and chemical oxygen demand（COD）analysis under different conditions,including current densities,initial concentrations of aniline,pH values,concentrations of chloride ions,and types of reactor.It was found that a higher current density,a lower initial concentration of aniline,an acidic solution,the presence of chloride ions（0.2wt%NaCl）,and a three-dimensional（3D） reactor promoted the removal efficiency of aniline.Electrochemical degradation of aniline followed pseudo-first-order kinetics.The aniline（200 mL of 100mg·L-（-1）） and COD removal efficiencies reached 100%and 73.5%,respectively,at a current density of 20 mA·cm-（-2）,pH of 7.0,and supporting electrolyte of 0.5 wt%Na2SO4 after 2 h electrolysis in a 3D reactor.These results show that aniline can be significantly removed on the Ti/TiOxHy/Sb-SnO2electrode,which provides an efficient way for elimination of aniline from aqueous solution.

Ag-Ni alloy nanoparticles for electrocatalytic reduction of benzyl chloride

Ag-based nanocatalysts exhibit good catalytic activity for the electrochemical reduction of organic halides. Ag-Ni alloy nanoparticles（NPs） were facilely prepared by chemical reduction, and the as-prepared nanocatalysts were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The electrocatalytic activity of Ag-Ni NPs for benzyl chloride reduction was studied in organic medium using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the addition of Ni element can obviously decrease the size of Ag-Ni NPs, shift the reduction peak potential（φp） of benzyl chloride positively, and increase the catalytic activity of Ag-Ni NPs. However, when the Ni content reaches a certain value, the catalytic activity of Ag-Ni NPs decreases. Meanwhile, the synergistic catalytic effect of Ag-Ni NPs was also discussed.

集成Ti/TiO_(2)敏感电极和液接式Ag/AgCl参比电极的pH微纳传感器

常见的pH传感器大多采用电位法进行检测,基于电位法进行检测的传感器由敏感电极和参比电极组成。在尺寸仅为5 mm×5 mm的传感器芯片上制备了钛电极、银电极和铂电阻丝。采用电化学氧化的方法对钛电极进行阳极氧化制成Ti/TiO_(2)敏感电极。采用电化学氯化的方法对银电极进行阳极氯化,再将饱和KCl溶液(3 mol/L)注入参比槽制成Ag/AgCl参比电极。铂电阻丝作为测温元件用于对pH值进行校准,电阻灵敏度约为14.21Ω/℃。在室温下、溶液温度为(13±1)℃时,测试芯片在不同pH值(4~10)溶液中的电压。通过线性分析得到传感器的分辨率约为17.92 mV/pH。控制溶液温度不变,对芯片在不同pH值(4.00、6.00、8.00和10.00)溶液中的电压进行测试,并得到该温度下的传感器分辨率。在不同溶液温度下对传感器的分辨率进行测试。测得不同溶液温度(25、20、15和10℃)下传感器的分辨率分别为28.31、23.45、19.33和13.62 mV/pH。通过温度补偿公式对pH值进行校准,计算得到的理论pH值与实际测量值的偏差≤0.25。传感器芯片具有体积小且易于集成的特点,可应用于各种水环境的检测。

Electrochemical treatment of wastewater containing chlorophenols using boron-doped diamond film electrodes

The electrochemical treatment of wastewater containing chlorophenols （2-monochlorophenol, 4-monochlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol） was carried out experimentally with synthetic boron-d0ped diamond （BDD） thin film electrodes. Current vs time curves under different cell voltages were measured. Removal rate of COD, instant current efficiency （ICE） and energy consumption were investigated under different current densities. The influence of supporting media is reported, which plays an important role in determining the global oxidation rate. The oxidative chloride is stronger than peroxodisulphate. The electrochemical characteristics of boron-doped diamond electrodes were investigated in comparison with active coating Ti substrate anode （ACT）. The experimental results show that BDD is markedly superior to ACT due to its different absorption properties.

Initial corrosion behavior of pure zinc in simulated tropical marine atmosphereInitial corrosion behavior of pure zinc in simulated tropical marine atmosphere

The initial corrosion behavior of pure zinc in a simulated tropical marine atmosphere was investigated using gravimetric method,scanning electron microscope combined with energy dispersive spectroscopy(SEM-EDS),X-ray diffractometry(XRD),Fourier transform infrared spectrometry(FTIR)and electrochemical impedance spectroscopy(EIS).The kinetics of corrosion process is a decelerating process following the empirical equation D=At^n(n<1).The protectiveness of the corrosion product layer could be attributed to the formation of simonkolleite,Zn5(OH)8Cl2·H2O,which could inhibit the rate determining step,namely charge transfer step,of the electrochemical corrosion process.A model of the evolution process of the product layers formed on zinc was proposed.In addition,the regularity of the corrosion rate of zinc as a function of the NaCl deposition rate can be described by a power function.

Electrochemical synthesis of Nb C-Sn composite powder in molten chloride

NbC-Sn composite powder was successfully prepared from SnO2,Nb2O5and carbon by electrochemical reduction andcarbonization in CaCl2-NaCl molten salt at900°C.The reaction pathway was investigated by terminating electrochemicalexperiments for various durations.The influence of carbon on the final products was considered.NbC particles were obtained byleaching the composite with acid.The results showed that the aggregated NbC-Sn composite powdev contained NbC particles about50-100nm and Sn particles about200nm.SnO2was reduced to Sn in the sintering process.Nb2O5was electrochemically reduced toNb in molten salt,experiencing some intermediate products of calcium niobates and niobium suboxides.Nb metal obtained wasconverted to NbC with assistance of carbon.The reduction of Nb oxides may be incomplete and Nb3Sn would be formed if carbon isinsufficient in the cathodic pellet.NbC with good dispersity is produced by leaching NbC-Sn with HCl.

Degradation of bond between steel bar and freeze-thaw concrete after electrochemical chloride extraction

The effect of electrochemical chloride extraction （ECE） on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 mm × 100 mm × 400 ram. During the experiment, 3% NaC1 （vs mass of cement, mass fraction） was mixed into concrete to simulate chloride contamination, and the specimens experienced 0, 25, 50, 75 freeze-thaw cycles before ECE. In the process of ECE, different current densities and durations were adopted. It is indicated that the bond strength between reinforcement and concrete decreases with the increase of freeze-thaw cycles; the more the current and the electric quantity of ECE are, the more the loss of bond strength is; and the largest loss is up to 58.7%. So, it is important to choose proper parameters of ECE for the reinforced concrete structures contaminated by chloride and subjected to freeze-thaw cycles.

Synthesis,characterization and application of BiVO_4 photoanode for photoelectrochemical oxidation of chlorate

A high‐quality polycrystalline bismuth vanadate(BiVO4)film was prepared on a fluorine‐doped tinoxide substrate via a facile two‐step strategy involving electrodeposition and annealing processes.The morphology and structural characterization of the resulting film were investigated by differentmethods including scanning electron microscopy,transmission electron microscopy,X‐ray diffraction(XRD),and Fourier transform infrared,ultraviolet‐visible(UV‐vis)absorption,and Ramanspectroscopies.XRD patterns as well as optical measurements revealed that BiVO4film crystallizedwith a pure monoclinic scheelite structure.The prepared BiVO4film was used for heterogeneousoxidation of chlorate ions in aqueous solution via electrochemical(EC),photochemical(PC),andphotoelectrochemical(PEC)processes.The decrease in concentration of chlorate was monitoredusing UV‐vis absorption spectroscopy.The results revealed that BiVO4could effectively performchlorate oxidation under light irradiation through a PEC method.The kinetics of chlorate oxidationwas consistent with a first‐order reaction,and the rate constant for the PEC process was found to bemuch higher than those of EC and PC.Furthermore,a possible photocatalytic oxidation mechanismfor chlorate mainly based on the formation of perchlorate ions is proposed.

Dechlorination by combined electrochemical reduction and oxidation

Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electro- chemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol.

The Role of the Dipole Interaction of Molecules with Charged Particles in the Polar Stratosphere

Our analysis of published results of experiments in the Polar Regions substantiates and further develops our new approach to the photochemical processes in the polar stratosphere involving the charged particles. The dipole interaction of molecules with charged particles, primarily with ions, leads to the adhesion and disintegration of a number of molecules including ozone. Molecules acquire additional energy on the surface of the charged particles, enabling reactions that are not possible in space. Galactic cosmic rays are the main source of ions in the polar stratosphere, their equilibrium concentration at altitudes of 15 to 25 km can reach up ~ （1-5） ~ 103 ions/cm3. Estimations show that if the ozone destruction in the regime of＂collision＂ with ions then the lifetime of ozone will vary from 10 days to 2 months. We suppose that alongside with the chlorine mechanism of ozone destruction there is a mechanism of ozone decay on a charged particle which can act also at those latitudes and altitudes where chlorine oxide CIO is absent, as well as in the night conditions. Here, we demonstrated the close connection of photochemical processes with the dynamic, electrical and condensational phenomena in the stratosphere, in particular, with the accumulation of unipolar charged particles on the upper and lower boundaries of the polar stratospheric clouds and aerosol layers as a result of the activity of the global electric circuit.

Direct electroreduction of solid cuprous chloride to copper powder in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.

Variable-temperature preparation and performance of NiCl_2 as a cathode material for thermal batteries

Nickel（II） chloride materials were synthesized via a novel two-step variable-temperature method for the use as a cathode material in Li-B/NiCI2 cells with the LiCI-LiBr- LiF electrolyte. The influence of temperature on its structure, surface morphology, and electrochemical performance was investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and electrochemical measurements of single cells. XRD results showed that after pre-dehydration for 2 h at 270℃ followed by sintering for 5 h at 600℃, the crystal water in nickel chloride hexahydrate could be removed effectively. The SEM results showed that particles recombined to form larger coarse particles and presented a layered structure. Discharge tests showed that the 600℃-treated materials demonstrated remarkable specific capacities of 210.42 and 242.84 mA h g^-1 at constant currents of 0.5 and 2.0 A, respectively. Therefore, the Li-B/NiCI2 thermal battery showed excellent discharge performance. The present work demonstrates that NiCl2 is a promising cathode material for thermal batteries and this two-step variable-temperature method is a simple and useful method for the fabrication of NiCl2 materials.

Electrochemical extraction of cerium and formation of Al–Ce alloy from CeO_2 assisted by AlCl_3 in LiCl–KCl melts

This work presents an electrochemical extraction of cerium and synthesization of Al–Ce alloy in LiCl–KCl melts on Mo and Al electrodes by chlorination of CeO2 using AlCl3 at 873 K. The cyclic voltammogram on Mo electrodes in LiCl–KCl–CeO2 melt showed no obvious reduction wave other than the reduction of Li(I). After the addition of AlCl3, the signals of the reaction of Ce(ⅡI)/Ce(0) and the synthesization of Al–Ce and Al–Li alloys were investigated by cyclic voltammetry, square-wave voltammetry, open-circuit chronopotentiometry and chronopotentiometry. These results indicated that AlCl3 can chloridize CeO2 and that it is possible to extract cerium and form Al–Ce and Al–Li–Ce alloys in LiCl–KCl–CeO2–AlCl3 melts. According to potentiostatic electrolysis, only the Al4 Ce layer coated the Al electrodes. According to galvanostatic electrolysis, Al–Ce(Al4Ce, Al3 Ce, and Al92Ce8), Al2Li3, and Al phases were formed on Mo electrodes, and the content of cerium in the Al–Li–Ce alloys was more than 17 wt%.