Studies of Adsorption of Cadmium Ions by Biowaste Adsorbent from Aqueous Solutions with Ion-Selective Electrodes and ICP-OES

Using environment-friendly and low-cost biowaste adsorbents as toxic metal ion removal substrates from aqueous solutions has a great economic advantage. This work evaluated pumpkin and potato peel biowastes for the adsorption of cadmium ions. The biowastes were treated with acid or base. Batch experiments were carried out by introducing a known concentration of metal ion solution into the biowaste sorbent at various pH levels. The pH and metal ion concentration was monitored with pH and cadmium ion-selective electrode continuously for two hours, and the final concentration for the metal ion after 24 hours was measured with the cadmium electrode and then confirmed with ICP-OES. L-type isotherms were obtained that fit to Freundlich model. Adsorption isotherms showed chemical adsorption and the kinetics following the second order model. Equilibrium adsorption capacity is higher than 29 mg/g at pH 5.6 when the initial concentration is 220 ppm. Dynamic cadmium adsorption capacity is 17 mg/g from aqueous solution when the feed solution is 220 ppm with pumpkin peel biowaste sorbent. The biowaste materials can be regenerated with acid washing.

Probing the electric double layer structure at nitrogen-doped graphite electrodes by constant-potential molecular dynamics simulations

Electric double layer(EDL)is a critical topic in electrochemistry and largely determines the working performance of lithium batteries.However,atomic insights into the EDL structures on heteroatom-modified graphite anodes and EDL evolution with electrode potential are very lacking.Herein,a constant-potential molecular dynamics(CPMD)method is proposed to probe the EDL structure under working conditions,taking N-doped graphite electrodes and carbonate electrolytes as an example.An interface model was developed,incorporating the electrode potential and atom electronegativities.As a result,an insightful atomic scenario for the EDL structure under varied electrode potentials has been established,which unveils the important role of doping sites in regulating both the EDL structures and the following electrochemical reactions at the atomic level.Specifically,the negatively charged N atoms repel the anions and adsorb Li~+at high and low potentials,respectively.Such preferential adsorption suggests that Ndoped graphite can promote Li~+desolvation and regulate the location of Li~+deposition.This CPMD method not only unveils the mysterious function of N-doping from the viewpoint of EDL at the atomic level but also applies to probe the interfacial structure on other complicated electrodes.

Preparation of CeO_2 Nanoparticles and Its Application to Ion-selective Electrodes Based on Acetyl Cellulose

CeO2 nanoparticles with an average diameter of about 30 nm were prepared by sol-gel method at lower temperature. The gel, transformed from the aqueous solution of metal nitrate and citric acid, can be combusted completely at lower temperature. The redox behavior and the crystallization process of the dried gel were studied by thermogravimetric analysis and infrared spectroscopy. The synthesized powders were characterized by X-ray powder diffraction and transmission electron microscopy. In addition, rare earth elements ion-selective electrodes based on acetyl cellulose were prepared using ultra fine cerium oxide powders.

Direct Determination of Potassium-Sodium Activity Ratio in Soil Suspension with Two Ion-Selective Electrodes

A K+-selective electrode and a Na+-selective electrode were used to construct a measuring cell without liquid-junction for the determination of the ion activity ratio of K+ to Na+ in soil suspensions. The measured cell potential was not affected by the total electrolyte concentration when the total cation concentration was 10-1-10-3 mol L-1 and the concentration ratio CK+ / CNa+. was 10:1 to 1:50. When the concentration ratios were equal to 1and the total electrolyte concentrations were 10-2 and 10-3 mol L-1, the ion activity ratio measurement would not be affected by pH in the pH range of 3.5 to 11.5 and 4.4 to 11 respectively. Ions other than H+ have no remarkable influence on the measurement. The ion activity ratio of K+ to Na+ measured directly in soil suspension agree well with those in centrifuged supernant solution. The relative deviation was within 4%. From the measured ion activity ratio, the difference of the bonding energies of K+ and Na+ ions was calculated.

Construction and Application of a PVC Membrane Enoxacin Ion-selective Electrode Based on a Needle-shaped Inner Reference Electrode

A PVC membrane enoxacin ion-selective electrode based on a needle-shaped inner reference electrode was prepared. A Ag/AgCl wire was used as the substrate of this electrode. It was previously coated with a thin sheet of urea-formaldehyde resin containing Cl - ions to form a needle-shaped inner reference electrode, then the inner reference electrode was coated with a thin sheet of a PVC membrane containing an enoxacin tetraphenylborate ion-pair complex. The influences of various ion-pair complexes, concentrations of the active components in the membrane and the plasticizers on the performance of the electrode were studied by orthogonal design. The linear response range of the electrode was 7.9×10 -5 -1.0×10 -2 mol/L. The detection limit was 2.0×10 -5 mol/L. The slope was 30.4 mV/decade(25 ℃). The electrode can be used for the potentiometric determination of enoxacin tablets directly. The average recovery was 100.4%, and the RSD was 0.9%. The results agreed with those determined by the method in Chinese Pharmacopoeia.

Potentiometric Urea Biosensor Based on Ion-Selective Electrode by Different Immobilization Procedures

Enzyme was immobilized on an ammonium ion-selective electrode by different methods.An ion-selective electrode is not completely ion-specific,and interfering ions react with the ion-selective electrode membrane,altering the measured potential.Therefore,the characteristics of the effect of other ions on ammonium ion-selective electrode-based urea biosensors are considered.Based on the experimental results,the urea biosensor based on entrapment had a high response voltage of around 189 mV and fast response time of around 16 sec.Moreover,selectivity of the urea biosensor in different interfering ions was considered to elucidate the characteristics of ammonium ion-selective electrode-based biosensors.

STUDY OF CALCIUM ION-SELECTIVE ELECTRODE BASED ON A NEW NEUTRAL CARRIER

A calcium ion-setective eletrode based on a new neutral carrier was studied.The electrode gives a Nernstian response in the rang 5.9-1 Pa and the response is stable in a wide pH range.Logarithms of setectivity coefficents are -2.3 Li(+),-3.5 Na(+),-4.0 K(+),-3.7NH_4(+),-4.5 Mg(2+) and -4.4Zn(2+).

Advances in Mn‑Based Electrode Materials for Aqueous Sodium‑Ion Batteries

Aqueous sodium-ion batteries have attracted extensive attention for large-scale energy storage applications,due to abundant sodium resources,low cost,intrinsic safety of aqueous electrolytes and eco-friendliness.The electrochemical performance of aqueous sodium-ion batteries is affected by the properties of electrode materials and electrolytes.Among various electrode materials,Mn-based electrode materials have attracted tremendous attention because of the abundance of Mn,low cost,nontoxicity,eco-friendliness and interesting electrochemical performance.Aqueous electrolytes having narrow electrochemical window also affect the electrochemical performance of Mn-based electrode materials.In this review,we introduce systematically Mn-based electrode materials for aqueous sodium-ion batteries from cathode and anode materials and offer a comprehensive overview about their recent development.These Mn-based materials include oxides,Prussian blue analogues and polyanion compounds.We summarize and discuss the composition,crystal structure,morphology and electrochemical properties of Mn-based electrode materials.The improvement methods based on electrolyte optimization,element doping or substitution,optimization of morphology and carbon modification are highlighted.The perspectives of Mn-based electrode materials for future studies are also provided.We believe this review is important and helpful to explore and apply Mn-based electrode materials in aqueous sodium-ion batteries.

Efficient Preparation and Electrochemical Properties of BiOCl/Graphite by One-step Solvothermal Method

We used the surface-pretreated graphite paper(Gp)as a carrier and loaded BiOCl with high selectivity to Cl^(-)on its surface by solvothermal method to form BiOCl@Gp electrode.The morphology,structure,and composition of the materials were characterized by scanning electron microscopy and nitrogen adsorption/desorption,and the results showed that the spherical BiOCl particles were uniformly dispersed on the surface of the Gp,forming a mesoporous BiOCl@Gp composite with a specific surface area of 22.82 m^(2)/g and a pore volume of 0.043 cm3/g.Furthermore,cyclic voltammetry and electrochemical impedance spectroscopy were used to test the electrochemical properties of the composites,and the stability of BiOCl and the high conductivity of Gp were synergistic,the BiOCl@Gp exhibited a specific capacitance of 30.2 F·g^(-1) at a current density of 0.5 A·g^(-1),and the selectivity of the BiOCl@Gp materials for Cl^(-)was significantly higher than that of SO_(4)^(2-),NO_(2)^(-),and HCO_(3)^(-).Therefore,BiOCl@Gp composite electrode materials can be used for the selective adsorption of Cl^(-)in wastewater,in order to achieve efficient wastewater recycling.

A Novel Method of the Preparation ofChemically Modified Electrodes

ＡＮｏｖｅｌＭｅｔｈｏｄｏｆｔｈｅＰｒｅｐａｒａｔｉｏｎｏｆＣｈｅｍｉｃａｌｌｙＭｏｄｉｆｉｅｄＥｌｅｃｔｒｏｄｅｓＬＩＧｅｎ－ｘｉ，ＬＩＡＯＸｉａｎｇ－ｍｉｎ，ＦＡＮＧＨｕｉ－ｑｕｎａｎｄＣＨＥＮＨｏｎｇ－ｙｕａｎ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍ...

Simulation of Needle-Type Corona Electrodes by the Finite Element Method

This paper describes a software tool, called LEVSOFT, suitable for the electric field simulations of corona electrodes by the Finite Element Method （FEM）. Special attention was paid to the user friendly construction of geometries with corners and sharp points, and to the fast generation of highly refined triangular meshes and field maps. The execution of selfadaptive meshes was also implemented. These customized features make the code attractive for the simulation of needle-type corona electrodes. Some case examples involving needle type electrodes are presented.

Study on the Drift Calibration Method and Device for the Tin Oxide pH Electrode

Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabrication process to improve the properties of the front-ended device.Another is to compensate the drift phenomenon by adding extra drift compensation circuit or software in the back-ended readout circuit.In this study,a drift calibration method for the potentiometric sensor was presented and the drift calibration method was performed by using the circuit.According to experimental results,the drift phenomenon of the SnO_2 pH electrode was reduced by the drift calibration device.

Study on Detection of Negative Corona Discharge Generated in Rod-Plane Air Gap by Using External Electrode Method

A detective method of a negative corona discharge by means of an external electrode is presented. The relationship between an area of the external electrode and a detected voltage waveform is examined experimentally. This experimental study is carried out with the use of a rod-plane air gap. The results obtained will be applicable to problems associated with silos, ducts, and high-voltage equipment.

A Method of Using a Carbon Fiber Spiral-Contact Electrode to Achieve Atmospheric Pressure Glow Discharge in Air

During discharge, appropriately changing the development paths of electron avalanches and increasing the number of initial electrons can effectively inhibit the formation of filamentary discharge. Based on the aforementioned phenomenon, we propose a method of using microdischarge electrodes to produce a macroscopic discharge phenomenon. In the form of an asymmetric structure composed of a carbon fiber electrode, an electrode structure of carbon fiber spiral-contact type is designed to achieve an atmospheric pressure glow discharge in air, which is characterized by low discharge voltage, low energy consumption, good diffusion and less ozone generation.

术语“Homogeneous Membrane Electrodes”和“Heterogeneous Membrane Electrodes”的中文译文的商榷

IUPAC在确定"离子选择电极"术语时,指出不能使用"离子特效电极"说明准确命名和术语使用的重要性。作者曾于1983年对术语"homogeneous membrane electrodes"和"heterogeneous membrane electrodes"的中文译文提出商榷并受到"离子选择电极通讯"编辑部的关注。自那以后,仍有不少文献,特别是博士和硕士论文,采用了过去的不恰当的译法。为此再次就对此问题进行商榷。"homogeneous"一词可以指"同一种"或者"同一相",而"heterogeneous"一词可以指"不同种"或者"不同相";根据IUPAC对上述电极的定义,显然应该各取前一含义。

The Impact of Electrode Configuration on Characteristics of Vacuum Discharge Plasma

Generation characteristics of vacuum discharge plasma are very important for the applied research of metal plasma. The vacuum discharge electrode configuration and the cathode material affect the generation characteristics of the metal plasma which consists of metal ions coming from cathode and generated by vacuum discharge. In this research, the generation characteristics of the metal plasma generated by vacuum discharge are discussed for four patterns of electrode configurations, i.e. cone-mesh electrode setup, cone-cross line electrode setup, cone-line electrode setup and cone-ring electrode setup. Characteristics of the metal plasma, such as elec- tron density, electron temperature, space potential, ion energy, are measured by the probe method for discussing the impacts of different electrode configurations on the density of generated metal plasma. Moreover, the diffusion velocities of the metal plasma are measured for cathode materials of Pb, Al, and Cu, respectively. The experimental results indicate that the plasma generated by the discharge of cone-ring electrode configuration possesses the maximum density and the metal plasma generated by the Al cathode possesses the fastest diffusion velocity and the highest kinetic energy.

Functional porous carbon-based composite electrode materials for lithium secondary batteries

The synthetic routes of porous carbons and the applications of the functional porous carbon-based composite electrode materials for lithium secondary batteries are reviewed. The synthetic methods have made great breakthroughs to control the pore size and volume, wall thickness, surface area, and connectivity of porous carbons, which result in the development of functional porous carbon-based composite electrode materials. The effects of porous carbons on the electrochemical properties are further discussed. The porous carbons as ideal matrixes to incorporate active materials make a great improvement on the electrochemical properties because of high surface area and pore volume, excellent electronic conductivity, and strong adsorption capacity. Large numbers of the composite electrode materials have been used for the devices of electrochemical energy conversion and storage, such as lithium-ion batteries （LIBs）, Li-S batteries, and Li-O2 batteries. It is believed that functional porous carbon-based composite electrode materials will continuously contribute to the field of lithium secondary batteries.

A comparative study of four 20-membered N_2S_4-crown ethers as ionophores for polymeric membrane silver selective electrodes

Four 20-membered N_2S_4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag^+-selective electrodes.Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag^+ ions.The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione(C) with 2-nitrophenyl octyl ether(o-NPOE) as solvent in a poly(vinyl chloride)(PVC) membrane matrix sho...

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.

Analytical expression of non steady-state concentration profiles at planar electrode for the CE mechanism

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are presented. These simple new approximate expressions of concentrations are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. Moreover, in this work we employ the Homotopy perturbation method to solve the boundary value problem.