•Rate of phosphate removal by electrocoagulation is governed by precipitation of AlPO4(s) and/or adsorption on Al(OH)3.•Kinetics of phosphate removal is depending only on electrical charge whatever ...the time of treatment and the current density.•Electrical consumption is lower at low current density because of the limited ohmic voltage drop.•pH variation depends on production of OH- at the cathode and its reaction with Al3+.
Treatment of water containing phosphate by electrocoagulation has been studied in a laboratory batch reactor. The effect of operating parameters on both phosphate removal efficiency and pH evolution has been investigated. Influence of distance between electrodes, current density, initial pH, temperature and conductivity has been extensively studied in a wide range of values. The results show that the removal efficiency depends on the electrical charges; the same efficiency is obtained with low current density with long time of treatment, or higher current intensity with short treatment time. The time evolution of the pH during the treatment strongly depends on the operating conditions but the final pH is more or less the same due to the buffering effect of Al(OH)3/Al(OH)4- mixture. Effects of the temperature, often disregarded in the literature shows that treatment rate is strongly increased with temperature whereas conductivity near 1mS/cm is enough to ensure reasonable treatment rate. The electrical energy consumption (around 4Kw/m3) is acceptable to achieve 90% of conversion but lower current density is preferable because of the lower voltage drop.
This paper deals with occurrence of lithium plating on the negative electrode of lithium-ion batteries, a significant ageing phenomenon known to damage lithium-ion battery performances. Charge ...transfer process, one of the two different steps of the process of Li insertion in the negative active material being the cause of this ageing, was considered here to be the limiting process. This transfer occurs at short-time scales. The second process, the diffusion of lithium in the solid insertion compound, occurring at relatively long-time scales, has not been fully examined here. The aim of this paper was to develop a new method to evaluate the maximal rate of a charge pulse solicitation to prevent this ageing phenomenon. The approach relies on the use of a fundamental model of lithium ion battery with coupled mass and charge transfer. To validate the method, 2 s microcycles have been performed on a commercial VL41M SAFT cell. Theoretical and experimental works led to the maximum current density to be applied without undesired Li deposition, depending on the state of charge (SOC). The abacus established for the cell of interest can orient further specifications for suitable use of the battery.
•COD and Cr(III) species can be simultaneously removed by electrocoagulation.•Cu-containing Al alloy is more efficient than pure Al as electrodes.•Dilution of too concentrated tannery wastewater is ...required for efficient treatment.
This paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6h with a 400A/m2 current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency.
This work deals with investigation of electrochemical technique for the treatment of milk liquid fractions. The removal of COD, phosphate and turbidity was investigated by varying the operating ...conditions. The batch experimental results revealed that the removal efficiencies of the overall turbidity, COD and phosphate concentration, depend on the nature of the electrodes material. The results indicated that turbidity is eliminated only by coagulation process and depends principally on aluminum concentration, whereas, soluble COD and phosphate might be eliminated by indirect oxidation. The greatest removal efficiency was obtained with the use of both cathode and anode made of aluminum (Al–Al system). With this latest system, optimal values of current density, initial pH, NaCl concentration and electrolysis time were 0.5
mA/cm
2, 6.6, 1.5
g/L and 2
min respectively. For these optimal parameter values, the removal efficiency of COD, phosphate and turbidity attained respectively 80%, 59% and 96%. Corresponding energy consumption was very low and equal 0.03
kWh/kg and 0.04
kWh/kg, for COD and phosphate removal respectively. Scanning electron microscopy (SEM), energy dispersion spectra (EDS) and fourier transform infrared spectroscopy (FT-IR), were used to characterize the resulting sludge.
► Effect of the main operating parameters on the process efficiency was investigated. ► COD and phosphates were removed by both coagulation and electro-oxidation processes. ► Turbidity removal was controlled solely by coagulation process. ► Sludge formed during the process treatment was characterized by SEM, EDS and FT-IR.
In this study we report a detailed exploration of the use of two different co-adsorbents - namely bis-methoxyphenylphosphinic acid (BMPP) and chenodeoxycholic acid (CDCA) - known to increase ...photoconversion efficiency (PCE) of DSSCs sensitized with N719. We have explored the variation of their abilities with the co-ads/D ratio of the sensitization bath in order to lower the intermolecular deactivations (anti-π-stacking effect) and recombinations between photo-injected electrons and the oxidized mediator (shield effect). EIS-λ technique has been used for this purpose, allowing the two effects considered here to be accurately quantified. DSSC containing BMPP allowed to improve the cell PCE by 60% with a ratio co-ads/D = 1, exhibiting a strong shield effect, while the maximum PCE obtained with CDCA was slightly over 7% (corresponding to 30% improvement) with a ratio co-ads/D = 10 and exhibiting a strong anti-π-stacking effect.
The treatment of very concentrated oil–water emulsions by electrocoagulation (EC) was experimentally investigated as a pre-treatment step prior to a membrane process. The oil–water emulsion was ...prepared from a cutting mineral oil B22 currently used for drilling and machining operations. The electrocoagulation progress was followed by the measurement of COD, turbidity and pH in a batch process with recirculation of the liquid. This study is mainly focused on the effects of operating parameters such as initial pH, current density, oil concentration and recirculation rate, on the de-emulsification efficiency. Kinetic curves showed that the EC process exhibits two phases: a “reactive phase” during which the COD and the turbidity removals increase with electrolysis, and a stationary phase for which further aluminium dissolution is useless in the pollution abatement. The results showed that the treatment efficiency increases with increasing current density, but decreases with oil concentration. It appears that treatment of the considered cutting oil is completed through dissolution of around 10
mg
Al/g oil, with a slight positive effect of the liquid flow rate. Best results are also obtained with initial pH near 7.
•Current (cd) distributions in PEM fuel cells can reveal maldistribution of gases.•Troublesome gas transport and local flooding are evidenced by cd distributions.•Aged fuel cells exhibit far less ...uniform distributions of current density.
Distributions of current density (cd) in a 100 cm2 single polymer fuel cell have been measured, leading to a 12 × 12 data array. For a freshly matured MEA, the dimensionless distributions have been shown to be of moderate uniformity, whatever the cell current, with average deviations of the dimensionless cd in the range 0.16–0.25 (i.e. cd measured deviated from 16 to 25% from the expected value). More thorough examination of the data acquired showed that the non-uniformity is likely due to maldistribution of the gas in the 23 parallel channels of the multiple serpentine pattern of the commercial bipolar plates. For the sake of comparison, the MEA – including the two GDL was submitted to ageing with a standard cycling protocol (FC_DLC) emulating transportation conditions for 500 h. Characterisation of the cell state of health afterwards revealed visible degradation of the GDL, whereas the catalytic layer and the membrane were little affected. In the aged cell, distributions were shown to be far more non-uniform, with deviations ranging from 0.30 to 0.50: the current distributions were then depending on the cell current density. Presumably, due to the GDL ageing, liquid water produced at high cd, could not be removed efficiently, resulting in very low cd’s near the outlet.
This paper deals with treatment of industrial wastewaters by electrocoagulation technique, with emphasis on settling process. The influence of electrode material, current density, pH, treatment ...period on the sludge settling characteristics has been investigated. The wastewater issued from textile industry is characterized by its high suspended solids content (SS
0), its high turbidity (NTU) and a fair chemical oxygen demand (COD). The wastewater treatment process consisted in a preliminary electrocoagulation step, followed by a settling step conducted without addition of flocculating agents. Sludge settling velocity after electrocoagulation was measured depending on the operating conditions. The data were employed to investigate the influence of the process parameters on the settling process. The sludge settling data were utilized to compare the efficiency of various empirical models for estimation of sludge settling velocity. Finally, the sludge aptitude to settling was studied in terms of sludge volume index (SVI) to determine the best operating conditions.
A fundamental model of lithium-ion battery cell based on Newman's works is presented in this article, including migration and diffusion of species and charges in electrodes and electrolyte. The ...particularity of our work is that the double layer capacitance, which is commonly neglected, is integrated in the model. We especially emphasize how to include correctly, in a physical point of view, the double layer capacitance in the electrochemical lithium-ion cell model. It is first demonstrated that the widely used mathematical formulation of the model leads to a physical error when the double layer capacitance is included, and a new formulation free of this error is proposed. Then are given the conditions for which the physical error mentioned before may cause appreciable inaccuracy in the prediction. Simulations have been carried out to validate the present analysis, and the results obtained show that the difference in cell voltage can attain several tens of millivolts.
•We include double layer capacitance in a mathematical model of lithium-ion battery.•We demonstrate that the usual model formulation leads to a physical error.•We develop a new formulation suitable for double layer capacitance implementation.•We compare the two model formulations with double layer capacitance.•We determinate conditions for which significant differences are obtained.
The present paper deals with the treatment of an industrial wastewater containing Cr (VI) by electrocoagulation using Al or Fe electrodes, in a discontinuous system with forced recirculation of the ...solution. Treatment of the waste impurities is achieved by electrocoagulation whereas Cr (VI) removal requires its reduction to Cr (III) prior to precipitation in the form of neutral hydroxide. The speciation of the various trivalent species, namely Cr (III), Fe (III) and Al (III) was investigated to determine the optimal pH range for treatment of Cr-containing wastes by using Al or Fe electrodes. With aluminium electrodes, the presence of Cr (VI) does not affect the COD abatement. Moreover Cr (VI) species was observed to be faster removed from the wastewater with higher current densities. However it was shown that the occurrence of the direct electrochemical reduction of Cr (VI) at the Al cathode surface, does not suffice to predict the experimental reduction rates. With Fe electrodes, COD abatement by electrocoagulation is retarded by the presence of Cr (VI), whereas the rate of iron dissolution is unaffected by chromate in the wastewater. The observed difference in the COD abatement rates suggests that the removal of generated Cr (III) by precipitation might be assisted by the presence of coagulant Fe(OH)
3. Removal of Cr (VI) from the wastewater in the cell could be successfully modelled taking into account the chemical reaction with electrogenerated Fe (II), its side oxidation by air oxygen, and the electrochemical reduction of Cr (VI) at the iron cathode.
