The use of carbon-based particle electrodes in three-dimensional electrode reactors for wastewater treatment

The use of three-dimensional(3D)electrodes in water treatment is competitive because of their high catalytic efficiency,low energy consumption and promising development.The use of particle electrodes is a key research focus in this technology.They are usually in the form of particles that fill the space between the cathode and anode,and the selection of materials used is important.Carbon-based materials are widely used because of their large specific surface area,good adsorption performance,high chemical stability and low cost.The principles of 3D electrode technology are introduced and recent research on its use for degrading organic pollutants using carbon-based particle electrodes is summarized.The classification of particle electrodes is introduced and the challenges for the future development of carbon-based particle electrodes in wastewater treatment are discussed.

Decomplexation of Cu-1-hydroxyethylidene-1,1-diphosphonic acid by a three-dimensional electrolysis system with activated biochar as particle electrodes

The feasibility of decomplexation removal of typical contaminants in electroplating wastewater,complexed Cu(Ⅱ)with 1-hydroxyethylidene-1,1-diphosphonic acid(Cu-HEDP),was first performed by a three-dimensional electrode reactor with activated biochar as particle electrodes.For the case of 50 mg/L Cu-HEDP,Cu(Ⅱ)removal(90.7%)and PO_(4)^(3−)conversion(34.9%)were achieved under the conditions of electric current 40 mA,initial pH 7,acid-treated almond shell biochar(AASB)addition 20 g/L,and reaction time 180 min,with second-order rate constants of 1.10×10^(−3) and 1.94×10^(−5) min^(−1) respectively.The growing chelating effect between Cu(II)and HEDP and the comprehensive actions of adsorptive accumulation,direct and indirect oxidation given by particle electrodes accounted for the enhanced removal of Cu-HEDP,even though the mineralization of HEDP was mainly dependent on anode oxidation.The performance attenuation of AASB particle electrodes was ascribed to the excessive consumption of oxygen-containing functionalities during the reaction,especially acidic carboxylic groups and quinones on particle electrodes,which decreased from 446.74 to 291.48μmol/g,and 377.55 to 247.71μmol/g,respectively.Based on the determination of adsorption behavior and indirect electrochemical oxidation mediated by in situ electrogenerated H_(2)O_(2) and reactive oxygen species(e.g.,•OH),a possible removal mechanism of Cu-HEDP by three-dimensional electrolysis was further proposed.

Numerical computation of central crack growth in an active particle of electrodes influenced by multiple factors

Mechanical degradation, especially fractures in active particles in an electrode, is a major reason why the capacity of lithiumion batteries fades. This paper proposes a model that couples Li-ion diffusion, stress evolution, and damage mechanics to simulate the growth of central cracks in cathode particles（Li Mn_2 O_4） by an extended finite element method by considering the influence of multiple factors. The simulation shows that particles are likely to crack at a high discharge rate, when the particle radius is large, or when the initial central crack is longer. It also shows that the maximum principal tensile stress decreases and cracking becomes more difficult when the influence of crack surface diffusion is considered. The fracturing process occurs according to the following stages： no crack growth, stable crack growth, and unstable crack growth. Changing the charge/discharge strategy before unstable crack growth sets in is beneficial to prevent further capacity fading during electrochemical cycling.

Continuous Separation of Multiple Size Microparticles using Alternating Current Dielectrophoresis in Microfluidic Device with Acupuncture Needle Electrodes

The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.

Sensitization of Microporous Nanocrystalline TiO_2 Electrode with Quantum Sized RuS2 Particles

The microporous nanocry'sta1line TiO2 electrode with large surface roughness factor hasbeen prepared on a conducting glass support. Modification of the TiO2 electrode by in situ preparingquantum sized RuS2 particles on the surface of TiO2 electrode extends the optical absorptionspectrum and photocurrent action specmim into visible region. In addition, compared with RuS2 bulknlaterials- a blue shifi in both absorption spectrum and photocurrent action speCtrum of RuS2rriO2elcctrode is obserived and explained in terms of quantum sized effect.

Study on Distribution of Electrocatalytic Reaction Efficiency in a Three-Dimensional Electrocatalytic Reactor

In order to explore the effect of particle position on the electrocatalytic reaction rate at different positions in three-dimensional electrocatalytic reactor,using methylene blue as the simulated organic wastewater,and spherical graphite particles as the particle electrode,the potential distribution in three-dimensional electrocatalytic reactor was simulated by using COMSOL Multiphysics software.A multivariate logarithmic regression model of reaction kinetic constant and position was established by mathematical statistics.The electrocatalytic reaction rates were predicted at different locations in the reactor.The results show that the degradation ability of particle electrode to pollutants is uneven in the electrocatalytic reactor.The increase of electric field intensity and particle size will improve the difference of reaction rate.The closer the particle electrode is to the anode,the stronger the pollutant degradation ability would be.The reaction rate of the same particle electrode at different locations varies greatly,which can be roughly divided into three regions according to the degree of difference,among which the central region of the particle has the highest electrocatalytic reaction efficiency.