Electroflotation Cell Research Articles

Produced Water Treatment Using a New Designed Electroflotation Cell

A novel continuous electroflotation cell, about 0.6 liter volume capacity, using aluminum electrodes was designed for oil produced water treatment. The treating performance of a novel continuous electroflotation cell for oil produced water was investigated. The pH, current density, and feed water flow rate as affecting parameters of electroflotation process were studied. The results show that the removal efficiency decreased with increasing feed flow rate. However, it increased with increasing current density. The AC current was preferred because DC current causes passivation of the anode with time. The maximum removal for all types of pollutants is achieved at pH6. The designed electroflotation cell could remove different constituents of oil produced water with range 87.5 - 99.5 % at 25°C, 5V, pH7 and AC current density of 80A/m2 through a bipolar connection of the 8 electrodes with feed water flow rate of 60ml/min (3.6l/hr). The energy consumption was about 1.38Kwh/m3 and the operating cost (cost/m3) was about 0.3US$/m3 for the produced water treatment.

A novel continuous electroflotation cell design for industrial effluent treatment

The performance of a continuous flow electroflotation (EF) unit designed for industrial effluents treatment was investigated. The employment of synthetic wastewater composed of some heavy metal ions (Cr3+, Cu2+ and Pb2+), soluble dyes (Acid Red 1 and Basic Violet 3), and ultrafine particles (copper metal and copper oxide) was set for studying the cell parameters. The affecting parameters of the EF unit which are current density and type and ionic strength (conductivity) and feed flow rate were studied. The continuous flow EF unit was employed for the treatment of different industrial effluents which was supplied by Textile, Tannery and Wood factories. For synthetic wastewater, the removal efficiency of industrial effluents increased with increasing current density and ionic strength. DC current causes passivation of the anode, thus AC current was preferred. The lower feed flow rate increased the removal efficiency but consumed more power. The removal efficiency was achieved up to 95% at 25 °C, 5 V and an AC current intensity of 1 A with a feed flow rate of 50 ml/min (3 l/h). The energy consumption was 1.67 kWh/m3. For different industrial effluents, the removal efficiency approached up to 90%, at 25 °C, 5 V and an AC current intensity of about 1 A and a 30 ml/min feed flow rate. The energy consumption was about 3 kWh/m3. The removal efficiency could be increased up to about 99% by a further cleaning step with total energy consumption of about 6 kWh/m3.

Removal of bitumen from mature oil sands tailings slurries by electro-flotation

The separation of bitumen from mature oil sand tailings slurries was carried out in an electro-flotation (EF) cell equipped with titanium coated with iridium oxide (Ti-IrO2) mesh as anode and stainless steel (SS 316) mesh as cathode. The effects of operating parameters such as pH, current density, bitumen concentration, and sodium chloride (NaCl) dosage on the performance of batch cell flotation were examined. The representative kinetics of the electro-flotation of bitumen in mature oil sand tailings slurries is best described as a first order reaction. Analysis of variance (ANOVA) is carried out to find out the statistical significance of influencing factors with respect to the first order flotation rate. The P-values in ANOVA show the order of significant factors as current density>bitumen concentration>pH. Though NaCl dosage doesn’t have significant effect on flotation kinetics however it serves a significant role on reducing the power consumption of EF treatment. It is observed that at current density 150A/m2, it is possible to reduce the bitumen concentration from 106.8mg/L to less than 10mg/L within 90min of flotation to meet the Environmental Protection and Enhancement Act (EPEA) maximum discharge limit.

The influence of some parameters on bubble average diameter in an electroflotation cell by laser diffraction method

The distribution of micro-bubbles generated by the electroflotation process has great importance in the flotation process for fine and ultrafine particles. The objective of this study was to evaluate the influence of some parameters on the average bubble size, generated in an electroflotation cell, on 316 stainless steel cathodes with different geometries, surface finishing, and a Ti/RuO2 mesh as an anode, by the laser diffraction method and image analysis. The average bubble size determination was conducted at different pH values, different cathode surfaces, and different types of collector. Results show that an increase in pH and current density led to a decrease of the bubble size, and that mesh electrodes and electrodes polished with coarser grit sandpaper give smaller gas bubbles. Conversely, when Flotigam EDA, sodium N-lauroyl sarcosinate or sodium oleate were added, larger bubbles were observed. Under the conditions of generation of small bubbles, higher recoveries of fine phosphate particles were observed.

Improvements in permeate flux by aluminum electroflotation pretreatment during microfiltration of surface water

Cathodic production of fine hydrogen bubbles over relatively long durations during aluminum electrochemical treatment of natural waters was empirically observed to induce floc flotation. Such electrochemically assisted flotation, termed electroflotation, was employed for microfiltration (MF) pretreatment by skimming off the surficial floc layer and drawing water from near the bottom of the electroflotation cell. This approach significantly increased permeate fluxes during surface water dead-end MF by reducing both the cake mass and the cumulative hydraulic resistance. These results were compared with a closely related process – electrocoagulation – wherein the entire destabilized suspension was sent to MF. Electrocoagulation pretreatment also improved MF fluxes compared with raw water, but not as much as electroflotation. In both pretreatment scenarios, amorphous Al(OH)3 was dominant as revealed by X-ray photoelectron spectroscopy. The absence of an intermediate particle removal step in electrocoagulation contributed to a higher cake mass and greater total cake resistance even though it reduced the specific resistance by forming larger aggregates. In addition to improving MF flux during forward filtration, electroflotation pretreatment appears to form largely reversible fouling layers that may lead to more effective MF backwashing. In contrast, nitrogen and silicon detected on membranes, even after cake removal suggests a greater extent of irreversible MF fouling following electrocoagulation pretreatment. Significant improvements in flux and potential improvements in backwashing effectiveness following aluminum electroflotation of surface water in laboratory-scale experiments points to the need for larger-scale evaluations before a hybrid electroflotation-MF process can be implemented for drinking water treatment.

Hydrogen bubble flotation of silica

In this study the flotation recovery of silica using air, and molecular and electrolytically-generated hydrogen was investigated. For comparison of air and molecular hydrogen recoveries, a laboratory Denver, type D12, flotation machine was used. For both gases, pH of the suspension, gas flow rate, concentration of collector and frother, solids concentration, particle size and speed of impeller were kept constant. Almost identical recoveries were obtained for both gases, suggesting that gas composition played no significant role in silica flotation. Electroflotation experiments were carried out using 12.6 μm mean diameter silica particles. While fine particles had very poor recovery in the Denver cell, greater than 70% recoveries were achieved in the electroflotation cell. This was thought to be the result of the very small (less than 40 μm) bubbles generated by the electroflotation process. A population-balance model, incorporating the hydrogen generation process, supported the conclusion that increased recovery for electroflotation, for very fine silica particles at least, was attributed to the reduced bubble size and not by the composition of the gas.

Degradation of EDTA by in-situ electrogenerated active chlorine in an electroflotation cell

table water-soluble complexes with metals. Yet, it is among refractory and poorly degradable organics. Its degradation is indubitably becoming a major environmental concern. In this work, electrochlorination of EDTA on Ti/RuO2 anode proved to be effective for such an aim, and thus this electrochemical process may be a promising alternative to conventional EDTA treatments. The effects of NaCl concentration, EDTA concentration, current intensity, and the presence of metallic ions on the EDTA oxidative degradation were investigated. The results herein reported showed that a complete degradation of EDTA was achieved under the following conditions: EDTA concentration, 400 mg.L-1, NaCl concentration, 10 g.L-1; time, 2 h, current intensity 800 mA. In the absence of chloride ions, no degradation was observed, whereas significant extents of degradation were obtained in their presence. Thus, the oxidation of EDTA took place in the bulk solution by the electrolytically generated active chlorine. Increasing the curre...

Electroflotation of emulsified oil in industrial wastes evaluated with a full factorial design

The use of electroflotation in emulsified oil wastes was studied. A rectangular electroflotation cell was designed and constructed in acrylic with stainless steel cathode and DSA® anode with a nominal composition of Ti/Ru0.34Ti0.66O2. The variables studied in the present work were current density and oil, flocculant and electrolyte (NaCl) concentrations. The experiments were carried out in accordance with 2(4) full factorial experimental designs with two center points. The STATISTICA 5.5 software was used for calculations in order to relate experimental data to a statistical model. The best results, yielded 99.71% oil removal were obtained from 1050ppm of emulsified oil feed.

Oil field effluent water treatment for safe disposal by electroflotation

Abstract The separation of finely dispersed oil from oil–water emulsion was carried out in an electroflotation cell which has a set of perforated aluminium electrodes. The effect of operating parameters on the performance of batch cell were examined. The parameters investigated are pH, voltage, oil concentration, flotation time, and salinity. The batch experiments have been conducted to optimize electrical input in the effluent. It was observed that at 5.0 V and 0.4 A current is optimum and for this condition the energy consumption was 0.67 kWh/m 3 . The optimal treatment time was observed at 20 min. Also oil removal efficiency is 90% at 4.72 pH in 30 min treatment time for 50 mg/l concentration of oil and 94.44% of oil removed within 30 min at 4 mg/l of salinity. It has also been observed that decrease in salinity and increase in oil content of the effluent enhances the efficiency of the electroflotation process.

Influence of current density on oxygen transfer in an electroflotation cell

The objective of this work is to study the transfer of oxygen from gas to liquid phase in an electroflotation cell. The measurements were performed in a laboratory scale cell using insoluble electrodes, titanium coated with ruthenium oxide as anode and stainless steel as cathode. The volumetric mass transfer coefficient KLa, was characterized for clean tap water as liquid phase for different values of current density (J). The global coefficient of mass transfer based on the liquid film, KL, and the specific interfacial area, a, were characterized. A model which relates KLa to current density was established. Different evaluation criteria of oxygen transfer in electroflotation process were determined and compared with other aeration process.

The removal of zinc from liquid streams by electroflotation

The removal of heavy metals from dilute aqueous solutions (in the range of 10 −7–10 −4 mol dm −3) is often not acceptable using classical methods, which do not achieve levels in accordance with environmental quality standards. Electroflotation has certain desirable characteristics, compared to dissolved and dispersed air flotation, particularly in regard to the small bubble size distribution of the process. The aim of this work was to develop an electroflotation (EF)/electrocoagulation (EC) cell to study this combined process and the influence of some relevant parameters/variables, such as collector concentration, tension and current density variation, on the removal of zinc from synthetic solutions containing 20 mg l −1 of the metal. A platinum gore (5 mm) anode and stainless steel mesh cathode were used in the electroflotation cell. The work showed that it was possible to remove zinc by electroflotation, 96% removal being achieved using sodium dodecyl sulfate (SDS) as collector in the stoichiometric ratio 1:3, current density of around 8 mA/cm 2 and an inlet pH of about 7.0.

Reaction pathways in the electrochemical degradation of thiocarbamate herbicides in NaCl solution

We have identified the intermediates and end products which are formed during the electrolytic degradation of thiocarbamate pesticides in aqueous NaCl solutions and investigated how the intermediate and end product volumes and ratios depend on reaction conditions. Further, we have defined both the reaction pathways leading to intermediate and end product formation and the methods affecting this process. The degradation of the molecular part containing the N atom is accounted for, as are the listed reactions and reaction pathways that affect degradation. If pH is changed, the ratio of degradation products NO3 and N2 can be influenced in favour of N2 gas. This pH change can then be produced without additional material by changing the construction of an electroflotation cell. To implement degradation, ‘‘flotation electrolysis’’ has been found to be an effective method as it facilitates a regulated pH-shift, foam handling and gas bubble rising velocity. The efficiency of the method can be further enhanced by UV photolysis.

Separating oil from oil-water emulsions by electroflotation technique

The separation of finely dispersed oil from oil-water emulsions was carried out in an electroflotation cell which has a set of electrodes, a lead anode and stainless steel screen cathode. The effect of operating parameters on the performance of the batch cell was examined. The parameters investigated are electrical current, oil concentration, flotation time and flocculant agent concentrations. A well-fitted empirical correlation represents the change in percentage oil removal with wide range of operating conditions was obtained. The oil separation reached 65% at optimum conditions; 75% in the presence of NaCl (3.5% by wt. of solution); and 92% with the presence of NaCl and at optimum concentration of flocculant agent. Electrical energy consumption varied from 0.5 to 10.6 KWh/m 3 according to experimental conditions. An equation relates the K with I was obtained. The general form of the equation is K = constant ( I) n ; where the n values are 0.6 4 and 0.62 for solutions with and without NaCl, respectively. The previous relation is valid only for current values from 0.3 to 1.2 A. The effect of emulsion flow rate on the separation process was determined on continuous scale.

Separation of oil from oil/water emulsions using an electroflotation cell with insoluble electrodes

Finely dispersed oil was separated from oil-water emulsions in an electroflotation cell equipped with a lead anode and stainless steel screen cathode. The effect of operating parameters such as current, oil concentration, flotation time, and height, on the performance of the electroflotation cell was examined. Oil removal reached 60% at optimum conditions; 70% in the presence of NaCl (3.5% by wt); and 88% in the presence of both NACl and an optimum concentration of a flocculant. Electrical energy consumption varied from 0.46 to 10.63 kWh/m 3 according to experimental conditions. The performance of the oil removal process was also represented as a first order kinetic rate model. The constants obtained fit the experimental data well, with their values varying from 1.305 × 10 −5 to 9.94 × 10 −5 m/s. Good correlation was found for the change in percentage oil removal with a wide range of operating parameters.

Electrochemical treatment of effluents: A preliminary study of anodic oxidation of simple sugars using lead dioxide‐coated titanium anodes

AbstractThe electrolysis of simple sugar solutions, containing 0.5% NaCl or Na2SO4, using lead dioxide‐coated titanium mesh anodes in a simple electroflotation cell indicated that electrode corrosion and dissolution of polluting Pb2+ ions from the electrode material were negligible even after prolonged use; the sugars were concomitantly electrooxidised at such anodes. The rate of electrooxidation followed linear removal kinetics and the relative ease of electrochemical destruction was in the order sucrose>maltose∼glucose. Such oxidation processes represent added advantages in the use of these electrodes in electrochemical treatment of effluent containing the sugars. Cyclic voltammetric analysis of the glucose solution indicated that oxygen evolution on the lead dioxide‐titanium anode appeared to be promoted by the presence of the sugar. A much more detailed study is required to give further insight into the mechanism of the anodic oxidation of these compounds.

Improved electroflotation for the removal of suspended solids from algal pond effluents

Experiments with a patented modification of an electroflotation cell showed that the power requirements for the treatment of pond effluents were less than for other electroflotation methods. The relationship between current densities and removal efficiencies of algae in suspension was found in laboratory and pilot-scale experiments. It was found that simultaneous flocculation-electroflotation gives better results than consecutive operation. The results obtained with electroflotation even with low current densities were almost equal to dissolved air flotation. It is believed that better adherence of electrolytically produced gases to the floc is responsible for the superiority of electroflotation.