Sacrificial Electrodes Research Articles

Bifunctional Cu(II)-based 2D coordination polymer and its composite for high-performance photocatalysis and electrochemical energy storage.

Coordination polymers (CPs) have been widely proven as sacrificial electrode materials for energy storage applications because of their high porosity, specific surface area and tunable structural topology. In this work, a new 2D Cu(II)-based CP, formulated as [Cu2(btc)(μ-Cl)2(H2O)4]n (CP-1) (H3btc = benzene-1,3,5-tricarboxylic acid), fabrication of copper oxide nanoparticles (CuO NPs) and its composite (CuO@CP-1) were successfully synthesized using solvothermal, precipitation and mechanochemical grinding approaches. Single-crystal X-ray analysis authenticated a two-dimensional (2D) layered network of CP-1. Further, CP-1, CuO NPs and composite were characterized by diffraction (Powder-XRD), spectroscopic (FTIR), microscopic (SEM), and thermal (TGA) techniques. The porosity and surface behavior of CP-1 and the composite were demonstrated using BET analyzer. Topological simplification of CP-1 shows a 3-c connected hcb periodic net. The photocatalytic behavior of CP-1 was examined over methyl red (MR) dye in the presence of sunlight and showed a promising degradation efficiency of 96.80%. The electrochemical energy storage properties of CP-1, CuO NPs and composite were investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis under aqueous 1 M H2SO4 electrolyte. The electrochemical results show better charge storage performance of CP-1 with a specific capacitance of 602.25 F g-1 at 1 A g-1 current density by maintaining a retention of up to 84.51% after 5000 cycles at 10 A g-1 current density. Comparative electrochemical studies reveal that CP-1 is a promising electrode material for energy storage.

Recent Developments in the Electroreductive Functionalization of Carbon–Halogen Bonds

AbstractElectrochemical organic transformations have witnessed significant progress over the past decades owing to their idiosyncratic redox nature. Electrochemistry is globally acknowledged for its sustainability and environmental friendliness, whilst several well-known redox processes are available that do not generate chemical waste or toxic by-products. Apart from this, electrochemistry has adequate potential to steer numerous non-spontaneous reactions, such as cross-coupling, C–C bond cleavage, radical generation, directed C–H functionalization, etc., in a straightforward manner. Beyond electrochemical oxidation reactions, electrochemical reductive transformations have also been enriched in the last few years. Electrochemical reduction can be facilitated by using different strategies, for example, by using a sacrificial electrode or a sacrificial reagent, or can be accomplished in a divided cell. In this short review, different methods for the functionalization of C–halogen bonds, including detailed mechanistic approaches, are discussed.1 Introduction2 Different Strategies for Electrochemical Reduction3 Functionalization of Carbon–Halogen Bonds through Electrochemical Reduction3.1 E lectroreductive Hydrodehalogenation3.2 Electroreductive C–C Coupling of Organohalides3.2.1 Aryl–Aryl C–C Coupling3.2.2 Aryl–Alkenyl C–C Coupling3.2.3 Aryl–Alkyl C–C Coupling3.2.4 Alkyl–Alkenyl C–C Coupling3.2.5 Alkyl–Alkyl C–C Coupling3.3 Electroreductive Coupling of Organohalides with Carbonyls (C=O)3.4 Electroreductive Coupling of Organohalides with Organoboranes4 Conclusion

Hydrogen evolution mitigation in iron-chromium redox flow batteries via electrochemical purification of the electrolyte

The redox flow battery (RFB) is a promising electrochemical energy storage solution that has seen limited deployment due, in part, to the high capital costs of current offerings. While the search for lower-cost chemistries has led to exciting expansions in available material sets, recent advances in RFB science and engineering may revivify older chemistries with suitable property profiles. One such system is the iron-chromium (Fe–Cr) RFB, which utilizes a low-cost, high-abundance chemistry, but whose efficient and long-term operation is challenged by the poor Cr redox reaction kinetics and high hydrogen evolution reaction (HER) rates . Of late, renewed efforts have focused on HER mitigation through materials innovation including electrocatalysts and electrolyte additives. Here, we show electrochemical purification, where soluble contaminants are deposited onto a sacrificial electrode prior to cell operation, can lead to a ca. 5× reduction in capacity fade rates. Leveraging data harvested from prior literature, we identify an association between coulombic efficiency and discharge capacity decay rate, finding that electrochemical purification can enable cell performance equivalent to that with new and potentially-expensive materials. We anticipate this method of mitigating HER may reduce capacity maintenance needs and, in combination with other advances, further long-duration Fe–Cr RFBs.

Evaluation of scrap metallic waste electrode materials for the application in electrocoagulation treatment of wastewater

The constant need for sacrificial electrodes is one of the limitations of applying the EC in wastewater treatment. Accordingly, this study proposes a sustainable alternative in reusing scrap metallic wastes as electrode materials. Four different types of metallic wastes (beverage cans, used aluminum (Al) foil, scrap iron, and scrap mild steel) are proposed as sacrificial electrodes for grey water (GW) treatment using the EC technique. At electrical current densities (CD) ranging between 5 and 20 mA/cm2, the treatment performance was evaluated for a reaction time of 10 min in terms of the removal efficiency of some key parameters such as color, turbidity, chemical oxygen demand (COD), and electrical conductivity, energy and material consumption, and metal contamination of GW from electrodes. The results demonstrated that using metallic wastes as sacrificial electrodes can achieve a considerable reduction in color, turbidity, COD, and electric conductivity of about 97.2%, 99%, 88%, and 89%, respectively. However, their reuse as electrodes revealed some important concerns. Al foil undergoes quick and substantial perforation and loss of surface area during electrolysis. The scrap iron and scrap mild steel were found to cause metal contamination by increasing Fe ions in the treated GW. Generally, metal scrap wastes can serve effectively as alternative sustainable electrodes. However, further research is recommended regarding the operating costs, which are considered crucial aspects of the EC process in terms of energy consumption and the most efficient method of fabricating the metallic wastes into a form suitable for reuse in the EC technique.

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.

Sulphate Removal in Industrial Effluents Using Electrocoagulation Sludge as an Adsorbent

The high concentration of sulphates is detrimental to the infrastructure of wastewater treatment plants. Hence in this study, we present the application of electrocoagulation sludge as an adsorbent to remove sulphates from industrial effluents before they are released back to the environment. The sludge contains iron and aluminium cations and cationic complexes that precipitate sulphates in water. Corrugated iron sheet was used as a sacrificial electrode during electrocoagulation (EC) to generate sludge. FTIR, XRD, SEM, TEM, and Zeta Potential were used to characterize the sludge. The following parameters: contact time, pH, initial concentration, and adsorbent dosage were optimized to 120 min, 2, 100 mg/L and 150 mg, respectively. For the synthetic water, the sulphate removal was 99.1%, whereas for the real water it was found to be 98.7%. The adsorption capacity of the EC sludge was 66.76% for 2 h under acidic conditions. The Langmuir isotherm fitted better than the Freundlich isotherm. This confirmed the homogenous distribution of the active sites on the EC sludge. At different EC’s sludge, the pseudo-second order kinetic model produced the best fitting experimental results which confirmed the removal of sulphate ions by chemisorption. This approach (method) is useful for purifying industrial effluents before they are discharged into the environment.

Electrical Discharge Coating a Potential Surface Engineering Technique: A State of the Art

Electrical discharge coating (EDC) process is used to deposit material on workpiece surface from sacrificial or green compact tool electrode in an electrical discharge machine. The paper presents the mechanism of EDC using green compact electrode and powder mixed dielectric methods. The tool electrode material, electrode size, process parameters, and type of dielectrics can directly affect the surface integrity of workpiece. Here, a process map of EDC as a function of process parameters, its classification, advantages, and applications for a wide range of engineering materials offers a proper template for the evaluation of coating phenomena. This study shows that EDC is an economic process as compared to other costlier techniques. Additionally, the effect of various EDM and EDC parameters on surface integrity and tribological behavior of deposited coatings is studied with their pros and cons. Finally, the current research trends of EDC and its challenges are elaborated.

Improvement of electrochemically mediated atom transfer radical polymerization: Use of aluminum as a sacrificial anode in water

The simplest electrolytic devices are undivided electrochemical cells without any separator between anodic and cathodic compartments. These simple yet efficient electrochemical cells often require the use of sacrificial metal counter electrodes, which, however, are incompatible with many electrocatalytic systems. In this article, we investigate the effect of the presence of an Al anode on an electrocatalytic reaction in water, namely electrochemically-mediated atom transfer radical polymerization (eATRP) catalyzed by common Cu complexes with amine ligands. It was found that the sacrificial anode could undermine the reactivity of the aqueous Cu catalysts in two ways: i) protonation of the amine ligand promoted by the release of acidic Al3+ ions; ii) spontaneous deposition of Cu0 on the Al metal surface. Both pathways led to decomposition of the original copper catalyst. To avoid undesired side reactions arising from the Al anode, simple strategies involving the use of appropriate amine ligands and pH buffers are described.

High-Productivity Single-Pass Electrochemical Birch Reduction of Naphthalenes in a Continuous Flow Electrochemical Taylor Vortex Reactor.

We report the development of a single-pass electrochemical Birch reduction carried out in a small footprint electrochemical Taylor vortex reactor with projected productivities of >80 g day–1 (based on 32.2 mmol h–1), using a modified version of our previously reported reactor [Org. Process Res. Dev.2021, 25, 7, 1619–1627], consisting of a static outer electrode and a rapidly rotating cylindrical inner electrode. In this study, we used an aluminum tube as the sacrificial outer electrode and stainless steel as the rotating inner electrode. We have established the viability of using a sacrificial aluminum anode for the electrochemical reduction of naphthalene, and by varying the current, we can switch between high selectivity (>90%) for either the single ring reduction or double ring reduction with >80 g day–1 projected productivity for either product. The concentration of LiBr in solution changes the fluid dynamics of the reaction mixture investigated by computational fluid dynamics, and this affects equilibration time, monitored using Fourier transform infrared spectroscopy. We show that the concentrations of electrolyte (LiBr) and proton source (dimethylurea) can be reduced while maintaining high reaction efficiency. We also report the reduction of 1-aminonaphthalene, which has been used as a precursor to the API Ropinirole. We find that our methodology produces the corresponding dihydronaphthalene with excellent selectivity and 88% isolated yield in an uninterrupted run of >8 h with a projected productivity of >100 g day–1.

Simultaneous removal of arsenic, fluoride, and hydrated silica from deep well water by electrocoagulation using hybrid Al-Fe electrodes

This paper deals with the simultaneous removal of arsenic, fluoride, and hydrated silica (HSi) from natural deep well water (26 µg L−1 As, 1.65 mg L−1F−, 160 mg L−1 HSi, 0.3 mg L−1PO43−, pH 7.5, and conductivity 450 µS cm−1) by electrocoagulation (EC). An up-flow EC reactor made up of an eight-cell stack using aluminum and iron plates as sacrificial electrodes in horizontal mode was used. The influence of the mean linear flow velocity (1.2 <u < 4.8 cm s−1) and current density (3 < j < 5 mA cm−2) applied to the EC reactor on the removal efficiency of As, F−and HSi was systematically examined. The best electrocoagulation trial was obtained at j = 5 mA cm−2 and u = 1.2 cm s−1, producing an aluminum and iron coagulant dose of 33.73 and 68.4 mg L−1, respectively, attaining residual concentrations of arsenic (CAs = 0.02 μg L−1) and fluoride (CF− = 0.88 mg L−1) below the World Health Organization (WHO) guideline (As < 10 μg L−1 and F− < 1.5 mg L−1). The residual HSi concentration was CHSi = 33 mg L−1, with electrolytic energy consumption and total operating cost of EC of 2.07 KWh m−3 and 0.29 USD m−3, respectively. The SEM-EDS, FXRD, XRD, FTIR, and Raman analyses of the Al-Fe flocs evidence the formation of iron silicates and aluminosilicates formed by the reaction between iron and aluminum with silica, respectively, and the existence of iron oxides and iron oxyhydroxides. The arsenic was removed by adsorption on aluminum and iron aggregates, while fluoride substitutes a hydroxyl from aluminum flocs.

Electroorganic Synthesis of Copper and Zinc Complexes with Novel Ligand Oxalic Acid

A convenient electroorganic synthesis of divalent metal complexes of empirical formulation [ML2] (M (II) = Cu and Zn; L= oxalic acid) were synthesized at sacrificial metal electrode anode. The metal, as the anode in an undivided cell, is oxidized in the presence of the parent compound of the ligand (HL) in an organic solvent mixture. Gram quantities of complex can be produced in a few hours. Complexes were characterized by elemental analysis, Infrared spectral data, Atomic Absorption spectroscopy and thermal spectral data. The geometrical structure of the synthesized complexes has been identified.

Simulations of aluminum dosage and H2O-H2 flow in a pre-pilot twelve-cell electrocoagulation stack

This paper investigates the aluminum dosage generation and H2O-H2 flow simulations in a pre-pilot twelve-cell stack electrocoagulation (EC) reactor in continuous operation mode. Each cell contains two aluminum plate electrodes. The electrochemical reactor is open to the atmosphere at the top to facilitate the H2 release produced at the cathodes, while aluminum oxidation occurs at the anodes. The two-phase (H2O-H2) flow simulations were performed by solving the Navier-Stokes (NS) equations for the continuous (H2O) phase and the bubbly flow model for the dispersed (H2) phase. Since H2 formation is promoted at the cathode due to H2O reduction, the momentum and Laplace's equations were simultaneously solved. The aluminum dosage calculations were attained by solving the diffusion-convection equation. The influence of volumetric inflow rate (8.3 ≤ Q ≤ 33.3 cm3 s−1) and applied current density (4 ≤ j ≤ 8 mA cm−2) on the coagulant dosage, current distribution, and H2O-H2 flow dispersion was systematically examined. The H2 volume fraction showed a typical bubble curtain profile close to the cathode surface. Homogeneous current distribution along the electrodes was obtained due to the well-engineering cell design, guaranteeing even wear of the sacrificial electrodes. There was an excellent agreement between the experimental and theoretical data for residence time distribution (RTD) curves and aluminum dosage generation.

Photovoltaic-driven electrochemical remediation of drilling fluid wastewater with simultaneous hydrogen production.

In this work, we studied the application of photovoltaic solar energy for driving the electrochemical processes of electrocoagulation and electrooxidation to remediate drilling fluid wastewater, and simultaneously harvest energy in the form of electrolytic hydrogen gas produced at the cathode. The electrocoagulation was performed with sacrificial aluminium electrodes and electrooxidation with dimensionally stable boron-doped diamond electrodes in batch-wise and continuously operated mode, and their efficiency in both pollutants removal and hydrogen gas production was elucidated. The parameters affecting the efficiency of the applied electrochemical processes, such as applied current density, pH, electroprocessing time and flow rate, were investigated. The electrochemical processing was monitored by measuring the chemical oxygen demand (COD) of treated wastewater. The electrocoagulation treatment conducted with current densities of 30, 60 and 90 mA/cm2 reduced the wastewater COD by about 67%, whereas the electrooxidation treatment at the same conditions yielded a COD removal of over 95%. The amount of produced hydrogen was 171 L/g COD removed from treated wastewater.

Simple and Scalable Cathodic Synthesis of 1H-1-Hydroxyquninolin-4-ons and 4H-4-Hydroxy-1,2,4-benzothiadiazine-1,1-dioxides

Cathodic synthesis is a highly attractive technique for N,O bond reduction.[1] Especially, electro-reductions of nitro arenes enable the access to high-valuable products like nitrones and N-heterocycles.[2] These substances are in general unique structural motifs in natural products or in compounds with significant biological properties, such as antibiotic, antiplasmodial, antimycotic, antihypertensive, hyperglycemic and cytotoxic activities.[3] Commonly used synthesis methods require large amounts of metallic reducing agents, expensive transition metal catalysts, or hazardous oxidizers in case the corresponding heterocycles are accessible otherwise.[4] Several examples have been described with constant potential conditions using mercury or sacrificial lead electrodes.[5] Due to cathodic corrosion of heavy metals, this proves to be a critical aspect and mercury is banned in the most countries for technical applications.[6] Therefore, the urge for more sustainable processes is of high focus.We describe an access to 1H-1-hydroxyquninolin-4-ons by cathodic reaction of nitrobenzoyl acetones synthesized from broad available nitrobenzoic acids. Using metal-free BDD cathodes (boron-doped diamond), sulfuric acid as a simple supporting electrolyte, in addition to an aqueous electrolyte system with an environmentally benign co-solvent agree with sustainable and green aspects. The scalability under constant current conditions in an undivided cell has been shown in a twentyfold scale. The electrochemical synthesis protocol was applied to 18 examples including the antibiotic substance HQNO (1H-2-heptyl-1-hydroxy quinolin-4-ons) and various precursors for enzymatic aurachine synthesis.[7] Furthermore, we developed a method to a novel substance class of 4H-4-hydroxy-1,2,4-benzothiadiazine-1,1-dioxides. Reduction of the nitro precursors applying BDD cathodes result in hydroxylamines using divided cells with glass frits as separators. The applicability of this electro-reductive cyclisation is demonstrated by the synthesis of a broad product scope with activated, deactivated, labile and sterically demanding substitution patterns for potential further modification towards pharmaceutical applications.[8] Particularly, we described the synthesis of the N-Hydroxy analogues of diazoxide, a medication on the WHO list of essential medicines.[8,9] Studies on the biological activities of these new compounds are currently performed.

Individual Dye Removal Efficiencies in a Ternary Dye Mixture by Electrocoagulation

The electrocoagulation (EC) of synthetic ternary dye mixture was investigated using sacrificial iron electrodes. Erionyl Red (ER), Isolan Bordeaux (IB), and Remazol Red (RR) textile dyes were used for preparing the ternary solution. Different operational parameters, including initial dye concentrations, salt amount, current density, EC time, and pH, were analyzed to optimize removal efficiency and energy consumption conditions. After EC treatment, the individual remaining dye concentrations were calculated by applying classical least squares (CLS). The fastest removed dye was RR and the obtained efficiency was 100% in 20 minutes at pH 6. The removal rates of IB and ER were 94% and 90% in 20 minutes and raised 98% and 95% in 60 minutes. These removal rates were obtained with 100 mg/L of each dye concentration at 293.15 K. The energy consumption was also investigated. The calculated value increased from 1.67 kWh/m3 to 5.00 kWh/m3 by raising the time from 20 minutes to 60 minutes when the current density was 2.33 mA/cm2 and the electrolyte (NaCl) amount was 3.0 g/L.

Development of electrocoagulation process for wastewater treatment: optimization by response surface methodology

Electrocoagulation (EC) is a process used by supply of electric current with sacrificial electrodes for the removal of pollutant from wastewater. The study was experimentally investigated taking into account various factors such as pH (3–7.5), current (0.03–0.09 A), distance between the electrodes (1–2 cm), electrolytic concentration (1–3 g/L), and electrolysis time (20–60 min) which is impact on the % removal efficiency of color, chemical oxygen demand (COD), turbidity and determination of energy consumption used for aluminum (Al) electrode used. The surface response design process based on the central composite design (CCD) has been used to optimize different operational parameters for treatment of hospital wastewater using EC process. The % color, COD and turbidity removal, and energy consumption under different conditions were predicted with the aid of a quadratic model, as were the significance and their interaction with independent variables assessed by analysis of variance (ANOVA). The optimal conditions were obtained through mathematical and statistical methods to reach maximum % color, COD, and turbidity removal with minimum energy consumption. The results showed that the maximum removal of color (92.30%), COD (95.28%), and turbidity (83.33%) were achieved at pH–7.5, current–0.09A, electrolytic concentration–3g/L, distance between electrodes–2 cm and reaction time 60 min. This means that, the process of EC can remove pollutants from various types of wastewaters and industrial effluent under the various operating parameters.

Removal of brilliant green tannery dye by electrocoagulation

• Bright green dye (BG) removal from tannery wastewater by electrocoagulation (EC). • Continuous up-flow parallel plate EC reactor with 1018 steel plates as electrodes. • Decolorization and COD removal reached values up to 100% and 96%, respectively. • Best conditions were 6 mA cm −2 and 0.69 cm s −1 giving overall cost of 0.193 USD m −3 . • The removal of BG occurs by adsorption on iron oxyhydroxides flocs. This paper deals with the removal of brilliant green (BG) tannery dye from synthetically prepared water (chemical oxygen demand 660 ≤ COD ≤ 2065 mg L −1 , in 6000 mg L −1 C l - at pH 6.0) by electrocoagulation (EC) using a continuous up-flow parallel plate EC reactor. The reactor employed two 1018 steel plates as sacrificial electrodes. The influence of flocculation time (15 ≤ τ f ≤ 35 min) on the dye removal efficiency was examined, using a jar test coupled to the exit of the EC reactor. The effect of hydrodynamics, in terms of mean linear flow rate and Reynolds number (0.69 ≤ u ≤ 3.47 cm s −1 and 72 ≤ Re ≤ 362), and current density, applied to the EC reactor, and the initial BG dye concentration on the elimination of color and COD was systematically analyzed. The range of Reynolds numbers studied in the EC reactor obeys a laminar flow, Re <2100. Laminar flow pattern allows the initial floc growth to occur orderly within the EC reactor. The decolorization and COD removal reached values up to 100% and 86%, respectively, at j = 6 mA cm −2 and u = 0.69 cm s −1 ( Re = 72), giving electrolytic energy consumption and overall operating cost of 0.077 kWh m −3 (0.134 kWh (kg COD) −1 ) and of 0.193 USD m −3 (0.34 USD (kg COD) −1 ), respectively. XRD, XRF-EDS, SEM, FTIR, and OEA analysis of the dried flocs indicated the removal of BG by adsorption on iron oxyhydroxides flocs.

Electro-coagulation of Bio-treated Pharmaceutical Wastewater for RO Pretreatment

Background: The advanced wastewater and water treatment by Reverse Osmosis (RO) system have almost become a common treatment option in industries. However, achieving a consistent RO feed water quality and the rigor of RO pre-treatment pose a big challenge for water treatment specialists. Due to the RO critical limiting feed parameters (Silica, Turbidity, BOD, and Total hardness) and the inadequate consideration of the limiting feed parameters in the recycling plant design, the Reverse Plant likely fails due to scaling of membrane and poor productivity. This calls for judicious consideration of an appropriate pre-treatment technology in line with the feed water quality.&#x0D; Objective: The objective of the work was to study the electro-coagulation treatment of pharmaceutical wastewater with reference to critical RO feed parameters.&#x0D; Materials and Methods: In this paper, the Electro-coagulation (EC) treatment of Bio-treated pharmaceutical wastewater was explored as a Pre-treatment for the RO system. In the EC reactor of 1m3 working volume, bipolar sacrificial Iron electrodes were used, and RO Critical parameters were examined post electro-coagulation treatment.&#x0D; Results: Among the 14 RO critical parameters that was investigated, five parameters namely Aluminium as Al, Iron as Fe, Turbidity, Zinc as Zn, and Silica as SiO2 have registered a reduction range of 80 to 96 %, in the RO feed water after electro-coagulation. Four other parameters like Manganese as Mn, BOD, Phosphate as P, and Magnesium as Mg have shown a reduction range of 50 to 80%.&#x0D; This enables the plant to be operated at higher efficiency with increased RO recovery. The test parameters before and after the study were subjected to regression analysis and were found to have a statistical significance of one and P&lt;0.01.&#x0D; Conclusion: EC pre-treatment is applicable for all types of RO (Disc &amp; plate, conventional wound) membranes and enhances the life of the membrane by reducing membrane fouling, maintenance, chemical cleaning, and overall treatment cost.

Nannochloropsis oceanica biomass enriched by electrocoagulation harvesting with promising agricultural applications

Electrocoagulation is a promising technology to harvest and concentrate microalgae while saving costs on secondary dewatering steps. However, the sacrificial electrodes release salts that impact the media and the harvested biomass. This study evaluated the effects of Fe, Zn, and Mg electrodes on Nannochloropsis oceanica harvesting and elementary composition of biomass and supernatants. Moreover, plant bioavailability of electrocoagulation minerals attached to biomass was assessed in the tomato plant model Solanum lycopersicum (cv. ‘Cherry’). Fe electrodes had better performance at lower power consumption and operation costs, followed by Zn and Mg. Electrocoagulation changes biomass and supernatant nutrient composition. Electrodes precipitated Mg and Ca from the nutrient media, enriching N. oceanica biomass, but increased Pb 2–4 times and depleted P in supernatants. Finally, Fe and Mg electrode metals in the biomass were proven bioavailable to S. lycopersicum seedlings, making electrocoagulation harvested biomass a promising bioresource to agricultural applications.

Abatement of As and hydrated silica from natural groundwater by electrocoagulation in a continuous plant having an electrolyzer and a flocculator-settler

• As and hydrated silica elimination from deep well water by electrocoagulation (EC). • Aluminum sacrificial anodes in an EC reactor coupled to a flocculator-settler. • Aluminum and hydrated silica react, forming aluminosilicates, As adsorbs on flocs. • As concentration after EC treatment met the WHO guideline, hydrated silica is abated. • EC is a cheap (0.48 USD m −3 ) and accessible technology to treat natural groundwater. This paper shows the elimination of arsenic (As) and hydrated silica from natural groundwater (48.63 µg L −1 arsenic, 77.5 mg L −1 hydrated silica, 0.33 mg L −1 phosphate, 5 mg L −1 sulfate, 240 mg L −1 alkalinity, 89.5 mg L −1 hardness, pH 8.44 and 450 µS cm −1 conductivity) by electrocoagulation (EC). The flow plant employed a parallel plates EC reactor in series with a flocculator-settler. Aluminum was used as the sacrificial electrode. Before the electrolysis in the flow plant, a systematic study of the aluminum dose was carried using the EC reactor adapted to a jar test. The influence of the mean linear flow velocity (1.2–4.8 cm s −1 ) and current density (6–9 mA cm −2 ) on the removal of As and hydrated silica was addressed. The residual concentration of As and hydrated silica in the flow plant was C As = 4.2 µg L −1 and C hs = 4.5 mg L −1 , respectively, at 9 mA cm −2 and 1.2 cm s −1 , which agree well with that obtained in the jar test array. The residual As concentration fulfills the World Health Organization (WHO) recommendation (<10 μg L −1 ). The total operating cost of EC was 0.48 USD m −3 , considering electrolytic energy consumption, aluminum price, pumping costs, and sludge confinement. Flocs analyses performed by SEM-EDS, XRF-EDS, XRD, and FTIR showed the existence of aluminosilicates formed by the reaction of aluminum and hydrated silica. At the same time, As, phosphates and sulfates were separated by adsorption on flocs.