Filter-press Electrochemical Reactor Research Articles

Additive manufactured metal lattice structures used as flow-through electrodes in a filter-press electrochemical reactor

This study deals with the electrochemical and hydraulic performances of additive manufactured metal periodic lattice structure electrodes. These electrodes are fabricated by Laser Powder Bed Fusion (LPBF) from the titanium alloy TA6V and two structures have been studied: diagonal and octet-truss. They are integrated, as flow-through electrodes, in an electrochemical filter-press reactor. Current–potential curves are experimentally obtained by linear sweep voltammetry when feeding the reactor with a ferricyanide solution. From the measurement of the limiting current of ferricyanide ions reduction, the volumetric mass transfer coefficient kAe is determined for several flow rates. Numerical simulations of fluid flow and mass transfer in these structures are also performed. Results show high values of kAe for these structures (competing with carbon felt electrodes) while maintaining a high permeability (low flow resistance). The surface roughness, inherent to the additive manufacturing process, is found to induce a low (≲10%) enhancement of mass transfer despite the roughness size (Ra in the range 10-20μm) is close to the average thickness of the diffusion layer (for the investigated fluid velocities). As a result, these electrode structures show promising potential to be used in intensified electrochemical reactors by being further optimized to find the optimal internal dimensions that maximize mass transfer while limiting flow resistance.

A hybrid process combining electrocoagulation and active chlorine-based photoelectro-Fenton-like methods during the removal of Acid Blue 29 dye

• Electrocoagulation (EC) and active chlorine-based photoelectro-Fenton-like (PEF-like). • Acid blue 29 (AB 29) dyestuff removal on iron flocs (76–58%) by EC. • Residual AB 29 after EC was mineralized (100%) by • OH generated in PEF-like. • AB 29 dyestuff solutions of 150–300 mg L −1 COD having 2000 mg L −1 chlorides. This paper deals with the development of an innovative process combining electrocoagulation (EC) and active chlorine-based photoelectro-Fenton-like (PEF-like) methods for eliminating the Acid Blue 29 (AB 29) dye from synthetic water (initially having 150–300 mg L −1 COD, in 2000 mg L −1 NaCl at pH 7.3). The EC process was performed in a continuous EC reactor equipped with 1018 steel plates as sacrificial electrodes. The PEF-like electrolysis was carried out in a filter-press electrochemical reactor equipped with Ti|Ir-Sn-Sb oxides and stainless-steel plates as the anode and cathode, respectively. The hydrodynamics influence in terms of the mean linear flow rate (0.69 ≤ u ≤ 3.47 cm s −1 ) and current density (12 ≤ j ≤ 36 mA cm −2 ) in the continuous EC reactor was systematically examined. The best EC trial was achieved at j = 36 mA cm −2 and u = 0.69 cm s −1 reaching 62 % bleaching and 84 % COD removal. Then, the remaining solution after EC passed through the PEF-like process (adjusting the pH = 3 and the catalyst at 0.4 mM Fe 2+ ), reaching complete discoloration and COD removal at 15 mA cm −2 , 24.2 cm s −1 . Hydroxyl radicals were responsible for the mineralization of the AB 29 dye in the PEF-like process. The obtained flocs after EC were analyzed by XRD, XRF, and FTIR to elucidate the removal pathway of the AB 29 dye on flocs. Finally, the carboxylic and inorganic byproducts produced during the incineration of AB 29 dye by PEF-like were followed by HPLC techniques.

Electro-Fenton mineralization of diazo dye Black NT2 using a pre-pilot flow plant

This project assessed the mineralization of Black NT2 (BNT2), a diazo dye frequently used in tanneries, using electrochemical technologies based on boron-doped diamond electrodes (BDD). The experimental trials included adding an Fe2+-catalyzed process known as the electro-Fenton (EF) reaction. The process was carried out in a recirculating pre-pilot plant that used a filter-press electrochemical reactor connected to a reservoir. The pre-pilot reactor was equipped with a BDD plate anode coupled with a BDD cathode to electrogenerate hydrogen peroxide (H2O2) in situ. The effects of experimental variables such as current density (j) and initial BNT2 concentration were tested. The best conditions to mineralize an initial BNT2 concentration equivalent to 250 mg L−1 of total organic carbon (TOC) in a 50 mM Na2SO4 solution using the EF process were 0.3 mM Fe2+, pH 3.0, j = 30 mA cm2, and Q = 12 L min−1. After 90 min of treatment, 100% TOC abatement was achieved. In all cases, TOC decreased following a pseudo-first-order kinetics. For the highest initial dye concentration, 100% TOC was achieved after 120 min, with 70% average current efficiency and 0.01088 KWh (g TOC)−1 energy consumption at the end of the process. For experiments without complete mineralization, the evolution of some nontoxic, short-chain carboxylic acids—such as oxalic, maleic, succinic, acetic, and formic—were quantified using high performance liquid chromatography (HPLC) analysis. These findings suggest that the EF reaction is an interesting, feasible alternative for enhanced dye degradation in tannery water treatment processes.

Degradation of cytarabine, creatinine, and urea in artificial urine by a photo-assisted sono-electrochemical process

The present work had as its objective, the evaluation of the combination of electrochemical, photochemical and sonrochemical techniques (sono-electrochemical photoassisted) applied to degradation of cytarabine (chemotherapeutic drug) in a simulated urine that continues with creatinine and laboratory research. The paper involved laboratory research with both a qualitative and quantitative approach. A continuous-flow filter-press electrochemical reactor was employed using Dimensionally Stable Anode (DSA® - Ti/Ru0.3Ti0.7O2) as the electrode material. A 23 factorial design was used to optimize the degradation of organic compounds contained in artificial urine (creatinine and urea) together with cytarabine, varying applied current, retention time and flow rate, the response variable was total organic carbon (TOC) removal. Additionally, UHPLC analyses demonstrated the removal of ancitabine (precursor of cytarabine), corroborating with the data obtained by the from the experimental design. The use of artificial urine as an electronic support interferes with the electrochemical process, taking TOC to high levels. However, it was observed that there was significant removal of the organic load present in the effluent solution, even when a more complex degradation matrix is used (artificial urine).

Mineralization of Methyl Orange azo dye by processes based on H2O2 electrogeneration at a 3D-like air-diffusion cathode

This work addresses the mineralization of the widely used Methyl Orange (MO) azo dye by technologies based on H2O2 electrogeneration at a 3D-like air-diffusion cathode. These include two Fe2+-catalyzed processes such as electro-Fenton (EF) and photoelectro-Fenton (PEF). Bulk electrolyses were performed in a recirculation flow plant, in which the Eco-Cell filter-press electrochemical reactor was connected in series with a UVA photoreactor. The former reactor was equipped with a Ti|Ir–Sn–Sb oxide plate anode alongside a 3D-like air-diffusion cathode made from graphite felt and hydrophobized carbon cloth, aimed at electrogenerating H2O2 on site. The influence of current density (j), volumetric flow rate (Q) and initial MO concentration was examined. The greatest oxidation power corresponded to PEF process. The best operation conditions to treat 30 mg L−1 of total organic carbon of MO in a 50 mM Na2SO4 solution by PEF were found at 0.50 mM Fe2+, pH 3.0, j = 20 mA cm−2 and Q = 2.0 L min−1, obtaining 100% and 94% of color and TOC removals at 30 and 240–300 min, respectively. This accounted for 35% of mineralization current efficiency and 0.12 kWh (g TOC)−1 of energy consumption at the end of the electrolysis. The oxidation power of EF and PEF was compared with that of anodic oxidation (AO), and the sequence obtained was: PEF > EF > AO. The dye was gradually degraded, yielding non-toxic short carboxylic acids, like maleic, fumaric, formic, oxalic and oxamic, whose Fe(III) complexes were rapidly photolyzed.

Electrochemical Engineering Assessment of a Novel 3D-Printed Filter-Press Electrochemical Reactor for Multipurpose Laboratory Applications

Flow devices fabricated by means of 3D-printing offer an economic and effective approach for testing different electrochemical systems at the laboratory scale. Here, the fabrication and optimizatio...

Degradation of paracetamol in a bubble column reactor with ozone generated in electrolyte-free water using a solid polymer electrolyte filter-press electrochemical reactor

A porous anode composed of β-PbO2 was electrochemically deposited onto a carbon cloth substrate (e.g., CC/β-PbO2) aiming for the electrochemical ozone production (EOP) in electrolyte-free water using a solid polymer electrolyte (SPE) filter-press reactor. Scanning electron microscopy (SEM) images revealed the presence of a three-dimensional oxide structure necessary to obtain a fluid-permeable anode. X-ray analysis showed the predominance of the β-PbO2 phase. The maximum current efficiency for the EOP was 9.5% with an ozone production rate of 1.40 g h−1. Using a constant ozone production rate of 0.5 g h−1, the oxidative degradation of paracetamol (PCT) dissolved in water was accomplished as a function of the PCT concentration (20, 30, and 50 mg L−1) and the pH (acid, natural (without adjustment), and alkaline). The UV-Vis spectrophotometric analysis showed that the degradation process is more pronounced in alkaline media with a strong reduction in the electrical energy per order (E EO). A reduction of the chemical oxygen demand (COD) of up to 80% was observed. A linear correlation between data referring to COD and HPLC measurements with the UV absorbance measured at 243 nm (UV243) was verified indicating that these different techniques can be complementary to each other. The nuclear magnetic resonance (NMR) study of the ozonation by-products revealed that the oxidation of PCT occurred through the rupture of the aromatic ring. The major part of phenol’s ring was oxidized to CO3 2− while no reaction occurs in the acetamide group of paracetamol during the ozonation reaction.

Electrogeneration of Active Chlorine in a Filter-Press-Type Reactor Using a New Sb2O5Doped Ti/RuO2-ZrO2Electrode: Indirect Indigoid Dye Oxidation

AbstractThis paper presents the study on active chlorine mediated electrochemical oxidation of model solutions that simulate textile effluents containing an indigoid dye (indigo carmine) and sodium chloride (0.05 M) using a new Sb2O5-doped Ti/RuO2-ZrO2electrode. The study was carried out in a filter-press electrochemical reactor specially designed to minimize flow deviations and provide homogeneous mass transfer flux over the electrode surface. Firstly, the mass-transfer-limited chloride oxidation reaction was studied in the absence of dye in order to understand the active chlorine formation process. Changes in pH, chloride concentration and UV-visible absorption spectra during electrolysis reveal the formation of active chlorine (mainly hypochlorite) with current efficiencies for chloride oxidation of 0.558 and 0.503 at 10 and 20 mA cm−2, respectively. Secondly, chloride oxidation was investigated in the presence of indigo carmine dye (0.5 mM) wherein-situgenerated active chlorine was responsible for -C=C- bond breaking and dye degradation. The solution discoloration followed a pseudo-first order kinetics where kinetic coefficient was inversely proportional to dye concentration. The oxidation with active chlorine had an average efficiency of 0.7 and a very competitive energy consumption between 49.2 and 128.5 kW h (kg COD removed)−1depending on current density and flow rate.

Electrochemical ozone production using electrolyte-free water for environmental applications

Oxide fine-mesh electrodes composed of lead dioxide doped with Fe3+ (OFM-Fe-PbO2) were prepared by electrodeposition onto a stainless-steel fine-mesh support in order to obtain fluid-permeable electrodes for an electrochemical filter-press reactor. These electrodes were used in electrochemical ozone production (EOP) carried out during the electrolysis of electrolyte-free water in order to obtain an environmentally friendly technology for the “in situ” water treatment. SEM images of electrodes prepared using different electrodeposition conditions showed the formation of well-defined crystalline grains, which uniformly covered the metallic wires of the support. X-ray analysis revealed that the formation of a β-PbO2 phase is more pronounced than the α-PbO2 phase. A maximum EOP current efficiency of 10%, obtained at j=1.5Acm−2, corresponding to a rate for the ozone generation of 1.58gh−1 and a specific electric energy consumption of 0.250kWhg−1, was attained for the OFM-Fe-PbO2 electrode formed using the electrodeposition bath containing 1.0mM Fe3+. The performance of the electrochemical reactor was evaluated during long-term galvanostatic electrolysis (t=60 days, j=1.0Acm−2 and 24°C), during which it was verified that the reactor voltage (U) and EOP current efficiency (ΦEOP) were both stable. The robustness of the SPE filter-press electrochemical reactor allied to a moderate EOP current efficiency indicated that the OFM-Fe-PbO2 electrode (1.0mM Fe3+) is promising for in situ ozone production from the electrolysis of electrolyte-free water.

Electrochemical degradation of sulfamethoxazole and trimethoprim at boron-doped diamond electrode: Performance, kinetics and reaction pathway

The results for the simultaneous electrochemical degradation of two antibiotics (sulfamethoxazole – SMX and trimethoprim – TMP) in a filter-press electrochemical reactor employing a boron-doped diamond (BDD) electrode are presented and discussed. The obtained hydrodynamic voltammograms, which are related to the oxidation of [Fe(CN)6]4- to [Fe(CN)6]3- carried out at different flow rates (1.0Lmin−1 up to 5.0Lmin−1), allowed the maximization of the mass transport conditions in the filter-press electrochemical reactor. The performance of the BDD electrode in the SMX/TMP oxidation obtained at optimized conditions (i=36mAcm−2, pH=5.0 and flow rate=5.0Lmin−1) showed that at the end of only 3h of electrolysis (corresponding to 7.8AhL−1) both antibiotics were virtually all degraded and ∼90% of both COD and TOC were reduced. Although p-benzoquinone was detected during the electrolyses it was completely consumed by the end of the electrolysis carried out at under optimized conditions. Under optimized conditions, the intermediate compounds were properly identified by GC–MS and an oxidation pathway of the simultaneous SMX and TMP electrochemical degradation was proposed. The results obtained for the BDD electrode show that it has an excellent performance for the degradation of both SMX and TMP.

Electrochemical treatment as a pre-oxidative step for algae removal using Chlorella vulgaris as a model organism and BDD anodes

An experimental work is presented in this paper on the inactivation of algae through electrochemical treatment. A green algae (Chlorella vulgaris) was adopted as a model. A commercial filter-press electrochemical reactor (Electro MP-Cell), equipped with a boron doped diamond (BDD) anode and a stainless steel cathode, was used to perform the electrolysis. The cell was inserted in a hydraulic circuit and used in either a closed loop, as a recirculating batch reactor, or in the continuous mode. The effects of current density and hydrodynamics were studied, as well as the formation of active chlorine and other chloride oxidation products. Active chlorine concentrations on the order of 0.3mmoldm−3 were obtained when algae were not present in the initial solution (batch experiments) or in the feed (continuous experiments). In the presence of algae, the value was 0.03mmoldm−3. The highest values were measured with i=75Acm−2 and flow conditions corresponding to a Reynolds number of 100 (batch experiments) or a hydraulic residence time of 4min (continuous experiments). The process led to the total inactivation of algae when 100mgdm−3 of chlorides was present in the solution, which is a typical value for natural waters. The results indicated that, under the adopted conditions, the prevailing mechanism was inactivation by means of long-life oxidants electrogenerated. A simple model of continuous stirred tank reactors (CSTRs) in-series was adopted to account for the non-ideal flow conditions in the continuous experiments, which was able to interpret the data under all the conditions tested.

Preliminary studies on the electrochemical recovery of Zn and Cd from effluent produced by a zinc refinery plant using a filterpress reactor

BACKGROUND Fundamental studies are reported investigating the electrochemical deposition of cadmium and zinc contained in solutions from a zinc electro-refining plant. This work also analyzes the performance of a filterpress electrochemical reactor used in the recovery of zinc and cadmium from this effluent. RESULTS The cathodic polarization curves showed electrochemical processes with mixed control for 304 SS and Al. The cyclic voltammetry studies on stainless steel revealed the presence of metal deposits at low current densities, whereas Zn and Cd were preferentially deposited at high overpotentials. The greatest recovery of cadmium (19%) and zinc (24%) at jap = 4 mA cm-2 was obtained with a 304 SS cathode and t = 180 min. The SEM micrographs of cathode plates confirmed the presence of cadmium and zinc deposits. In addition, EDS analyses revealed that the composition of such deposits depends on the deposition time and the cathode material. CONCLUSION A continuous filterpress electrochemical reactor with 304 SS and Al cathodes exhibited a promising performance level for cadmium and zinc recovery from industrial solutions.

Conversion of carbon dioxide into formate using a continuous electrochemical reduction process in a lead cathode

Among the different strategies for CO2 emissions reduction and climate change mitigation that are being considered, valorisation of CO2 appears as a more interesting option than carbon storage, since it allows the recycling of CO2 into added-value products. The purpose of this work is to study the influence of key variables on the performance of an experimental system for continuous electro-reduction of CO2 to formate in aqueous solutions under ambient conditions, using a filter-press electrochemical reactor with a lead plate as cathode. A 22 factorial design of experiments at different levels of current density (“j”) and electrolyte flow rate/electrode area ratio (“Q/A ratio”) was followed by additional tests at the mean level of each variable. The obtained results confirmed general suggested trends in previous works, but they also offered a detailed analysis of the influence of these variables. Regarding j, it should be emphasised that a significant increase of the rate of formate production was observed at the expense of lowering the Faradaic efficiency when increasing j up to a limit value of 10.5mAcm−2, where a Faradaic efficiency of 57% was maintained. The influence of Q/A turned out to be more limited than that of j, since the results revealed that increasing the catholyte flow to overcome mass transport limitations only had beneficial effects for the lowest Q/A ratios (i.e. ⩽0.76mLmin−1cm−2). This study is a reference for the evaluation of future improvements in the development of these continuous electro-reduction processes for CO2 valorisation, derived from further research to overcome current limitations.

Optimized design of an electrochemical filter-press reactor using CFD methods

A former laboratory filter-press electrochemical reactor previously used in electrodialysis, electrosynthesis and wastewater treatment was studied from a hydrodynamic point of view using computational fluid dynamics (CFD). A finite elements method (FEM) software environment was used in order to simulate both fluid velocity field and tracer diffusion in the reactor for different low Reynolds numbers, enabling the estimation of active and stagnant areas inside the reactor. These results provided interesting information in order to design a new electrochemical compartment focusing on the entrance-exit manifolds to minimize the formation of stagnant areas within the reactor. CFD methods were again employed to study and optimize the new reactor in order to predict its performance. In both cases, CFD calculations were compared with residence time distribution (RTD) studies in order to validate the simulations.

Analysis of the Use of Copper Electrode in a Filter-Press Electrochemical Reactor for the Electrochemical Reduction of Cr(VI)

In this work, the Cr(VI) electrochemical reduction by Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV), in acidic solutions and on a copper electrode, was studied. Cr(VI) reduction occurs in one step by a diffusive process at -230 mV / Ag/AgCl. The results obtained by LSV suggest a mass- transfer control for Cr(VI) reduction. The diffusion coefficient obtained for Cr(VI) was DHCrO4- = 1.1x10-5 cm2 s-1. The polarization curves obtained in a Filter-Press Electrochemical Reactor (FPER) corroborate the mechanism obtained with smaller electrodes and this allowed determining the best electrolysis voltage (2.0 V). The electrolysis showed conversions up to 70% in 60 min for solutions with 110 ppm of Cr (VI) in batch recycle mode.

The application of flow dispersion models to the FM01-LC laboratory filter-press reactor

The flow distribution in the rectangular channel of a laboratory filter-press electrochemical reactor was evaluated using three flow models namely: (a) axial dispersion, (b) sum of two phases and (c) fast and stagnant zones. In the case of the axial-dispersion model, several methods have been used to calculate the Peclet number; the moment method, the non-linear least-squares and the Laplace transform technique. Several boundary conditions, involving different physical and experimental assumptions of the flow were used to solve the partial differential equation that describes the flow behaviour. A total of nine expressions to examine flow dispersion has been used. The comparison of experimental and predicted response signals was made by evaluating the root mean squared error. A data fit in real time has been found to be a better choice as solutions based on the evaluation of moments are prone to error due the overweight of the signal at long times. Data fitting in the Laplace plane is very accurate but it does not guarantee a good fit in real time. Models based on the sum of a fast and a slow or stagnant phase resulted in solutions having very low values of the extension of the slow and stagnant phases, the assumption of a single phase with some degree of dispersion was considered more appropriate.

Analysis of the Use of Copper Electrode in a Filter-Press Electrochemical Reactor for the Electrochemical Reduction of Cr(VI).

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Design and Modelling of a Dialysis Membrane Electrochemical Reactor (D-MER) for Oxidoreductase-Catalysed Synthesis

The study is the first step in a design of an electrochemical reactor able to process enzyme catalysed electrochemical synthesis. To develop economically efficient synthesis, the enzymes must be confined very close to the electrode surface. Here, the confinement was achieved with a dialysis membrane integrated in a classic filter-press electrochemical reactor. A simple electrochemical reaction, without enzymatic catalysis, was used to model the behaviour of the ‘dialysis membrane electrochemical reactor’ (D-MER). The values of the physicochemical parameters were determined by independent experiments, and the thickness of the reaction layer in the reactor was the only parameter to be adjusted numerically. The conditions of this adjustment were discussed. The model gave a good fit to the experimental data and consequently proved that the current design of the reactor is ready to be used with more complex reactions as enzymatic synthesis. A first example was described, based on the glucose oxidase-catalysed synthesis of gluconic acid.

Electrochemical recovery of silver from cyanide leaching solutions

In the hydrometallurgy industry cyanide solutions are the most common leaching baths used during the extraction of metals such as silver and gold. After extraction, the solution containing various cyanide species, and usually copper cyanide, has a higher concentration than the gold and silver complexes. Higher concentration of copper species may interfere during the selective recovery of precious metals. This work presents a study of the selective recovery of silver from leaching solutions mimicking those used in industry. Chemical speciation and cyclic voltammetry studies showed that copper reduction occurs at more negative potentials than silver in the cyanide leaching solutions. The cyclic voltammetry of cyanide solutions on a vitreous carbon electrode showed that copper cyanide ions modify the interface properties, lowering the overpotential required for silver reduction. A macroelectrolysis study of a simulated leaching solution (10−4 M Ag(I), 0.1 M Cu(I) in 0.5 M CN− at pH 10), was carried out in a filter press electrochemical reactor (ElectroCell AB) with a reticulated vitreous carbon electrode (RVC), nominally having 45 pores per inch and a flow rate of 5 cm3 s−1 at 25 °C. The study showed that the high copper concentration does not interfere in the selective deposition of silver.

Hydrogen Peroxide Electrosynthesis Using Recycled Graphite Granules as 3D Cathode. Comparison with Other Commercial Materials and Optimization Studies

This study aims to evaluate the ability of the graphite granules (GG) recycled from spent Zn-C batteries to act as 3D cathode for hydrogen peroxide (HP) electrosynthesis (HPE) in eco-friendly conditions (unbuffered 0.05 M Na2SO4 solution, air as O2 source). The performances of GG were compared to those of other usual carbonaceous cathode materials for HPE such as graphite bloc, graphite felt and reticulate vitreous carbon (RVC), using a divided filter-press electrochemical reactor. The operational parameters such as the polarization mode, electrolyte and air flow rates, applied potentials or imposed currents, and aeration mode were optimized by 1 h tests of electrosynthesized HP accumulation (EHPA). Considering as optimization criteria the best compromise between the final HP concentration, global current efficiency and electrical energy specific consumption, we find that the most efficient material for EHPA was RVC of 500 ppi, exploited in galvanostatic mode and using an original aeration system. In optimized conditions, for the GG cathode, very promising efficiency indicators were evaluated, suggesting that better results can be obtained by electrode geometry optimization and GG pretreatment.