Performance Of Electrocoagulation Research Articles

OPTIMIZATION OF THE COMBINED UV/ELECTROCOAGULATION PROCESS FOR DYE REMOVAL FROM TEXTILE WASTEWATER USING RESPONSE SURFACE METHODOLOGY

In this study, response surface methodology (RSM) method was applied based on a five-level and four-variable central composite design. The optimization of the C.I. Direct Red 81 (DR81) removal by the combination of electrocoagulation (EC) and UV processes was also performed. The effect of initial pH, reaction time, current density and initial dye concentration on the dye removal was investigated to obtain the optimal experimental conditions. The optimal conditions with the dye removal of 95% were found to be at initial pH of 3.78, reaction time of 6.44 min, current density of 62 A/m2 and initial dye concentration of 111.5 mg/L. The experimental value for dye removal (94.36%) was in a satisfactory agreement with the predicted value. The kinetic of dye removal was investigated at various initial pH and high correlation coefficients (R2 > 0.95) indicated that the DR81 removal has followed second order kinetic model. The results showed that UV irradiation has enhanced the EC performance and COD removal efficiency. The results also indicate that the proposed combined method has a high efficiency and RSM experimental design is a proper method for modeling the removal processing of DR81.

COMPARISON OF ELECTROCOAGULATION AND CHEMICAL COAGULATION IN THE TREATMENT OF ARTISANAL TANNERY EFFLUENTS

In this study, the treatment of the effluents of an artisanal tannery by electrocoagulation with iron electrodes was carried out. During electrolytic treatment, a current intensity of 0.4 A was used, and the electrolysis time was varied from 0 to 40 minutes. The performance of electrocoagulation was compared with that of chemical coagulation with ferric sulfate . The results obtained showed that highest removals after electrocoagulation were 71.15, 98.26, and 86.59% for the COD, colour and turbidity respectively. Chemical coagulation reduced the COD up to 83.17%, while colour and turbidity removals were 99.81 and 98.62% respectively. Although chemical coagulation leads to highest percentage removals after treatment, electrocoagulation results in near neutral pH values and also decrease conductivity weakly . By contrast, chemical coagulation increases the acidity of the effluent and its conductivity. Hence with close to neutral pH and weak conductivity values obtained for effluents treated by electrocoagulation, it is inferred that such treated effluents can be recycled. http://dx.doi.org/10.4314/njt.v35i1.29

Optimal Synthesis of Refinery Property-Based Water Networks with Electrocoagulation Treatment Systems

This paper presents an optimization approach to the incorporation of electrocoagulation in the design of integrated water networks for oil refineries. A disjunctive programming formulation is developed to minimize the cost of the water-management system while including the characteristics of process water streams, recycle, reuse, and treatment of wastewater streams, performance of candidate technologies, and composition and property constraints for the process units and the environmental discharges. The performance of electrocoagulation was related to temperature pH and the concentration of phenols and sodium chloride. Ancillary units including pH adjustment, reverse osmosis, and heat exchangers were used to support the electrocoagulation unit. Two case studies are presented to show the applicability of the proposed model and the feasibility of using electrocoagulation as part of an integrated water management scheme for oil refineries.

Effect of presence of chemical species on removal of phenol in electrocoagulation process

Effect of the presence of chemical species, namely, NaHCO3, CaSO4, MgSO4, and MgCl2, on the performance of electrocoagulation (EC) process when treating synthetic phenolic wastewater was investigated. The investigation was performed using individual and combinations of two, three, and four species. Chemical species, under investigation, were added to phenol solution that was prepared using distilled water. Additionally, effects of operational parameters, namely, initial phenol concentration, current density, and supporting electrolyte (NaCl) concentration on the process performance was also studied using phenol solution that was prepared using tap water. The results showed that presence of chemical species such as bicarbonates and sulfates have negative effects on the performance of EC process. Removal efficiency of phenol was found to decrease with respect to time when CaSO4, MgSO4, and NaHCO3 were added to phenol solution. As an example, when only CaSO4 was added to the solution, more than 30% of phenol remained in solution after 10 min of investigation, while complete removal of phenol was achieved after 2 min when chemical species under investigation were not added. The results also showed that addition of more species resulted in more reduction of phenol removal efficiency. When CaSO4 and MgSO4 were added to the solution, 35% of phenol remained in solution after 10 min of treatment period.

Treatment of raw tannery wastewater by electrocoagulation technique: optimization of effective parameters using Taguchi method

In this study, the electrocoagulation (EC) technique for tannery wastewater treatment was examined using iron and aluminum electrodes. The effects of operating parameters that include current density, initial pH, and electrolysis time on EC performance were accomplished. In addition, Taguchi method was carried out in order to design the experiments and to optimize the experimental results. L25 orthogonal array (OA, three factors in five levels), signal-to-noise (S/N) ratio (the larger-the-better), and analysis of variance were applied to find the optimum levels and relative magnitude of the effects of parameters. The removal efficiency of chemical oxygen demand (COD), total chrome, and color are considered as the response parameters. In the case of iron electrodes, the optimum conditions of COD were found to be at the fifth level of current density (50 mA/cm2), the fourth level of initial pH (7), and fifth level of electrolysis time (25 min). According to total chrome, they were found at the third level of current density (30 mA/cm2), the fifth level of initial pH (8), and the fifth level of electrolysis time (25 min). In addition, with regard to color removal efficiency, they were determined to be at the fifth level of current density (50 mA/cm2), the fourth level of initial pH (7), and the fifth level of electrolysis time (25 min). At the optimum conditions of COD, total chrome and color removal efficiencies were achieved as 63.3, 99.7, and 82%, respectively. Also, operating costs for both COD and color removals were evaluated as 0.88 $/m3; but for chrome removal, they were 0.70 $/m3. In the case of aluminum electrode, the optimum conditions of COD, total chrome, and color removal were found to be at the fifth level for each operating parameter corresponding to current density (50 mA/cm2), initial pH (7), and electrolysis time (25 min). As a result, the observed removal efficiencies of COD, total chrome, and color under these optimum conditions were 64.4, 99, and 88%, respectively. In addition, operating costs for COD, chrome, and color removals were 0.94 $/m3.

Effect of Electrode Shape and Current Source on Performance of Electrocoagulation

AbstractElectrocoagulation is a versatile technique used for treating various types of industrial effluent. The material of the construction and shape of the electrodes are crucial in the electrocoagulation process. The effect of the electrode shape on the performance of the electrocoagulation has been studied by performing experiments for the removal of the dye from the synthetic dye solution using punched electrodes and the results have been evaluated in terms of color removal efficiency. The effect of the number of holes, the diameter of the hole, and the configuration of the holes (square, triangular, and random pitch of the holes) on the color removal efficiency was investigated. An increase in the color removal efficiency was obtained using the punched electrode compared with the plane electrode. The effect of the current source (direct and alternating current) on the performance of the electrocoagulation was studied and no significant effect of the current source on the performance of the electroco...

Removal of Cr(VI) ions from waste water by electrocoagulation using iron electrode

The performance of electrocoagulation using iron electrodes for the treatment of aqueous solutions containing chromium hexavalent ions using fixed bed electrochemical batch reactor was studied. A new anode design consisting of hex nuts was connected together with a thin rode of iron. The helical shape in the nuts increases the anode surface area allowing high chromium removal rate within very short coagulation time. The effect of different parameters affecting the electrocoagulation process, such as initial hexavalent chromium concentration, applied current, electrolyte type [sodium chloride and sodium sulfate] concentration and initial pH of the solution was investigated. The optimum conditions for the EC process by using the present cell based on minimum initial hexavalent chromium concentration, energy consumption and operating cost were 100mg of Cr(VI)/l, 0.55A, 1.5g of sodium chloride/land pH of 1.

Taguchi experimental design for electrocoagulation process using alternating and direct current on fluoride removal from water

AbstractTaguchi experimental design with the alternating and direct current (AC and DC) electrocoagulation (EC) using initial fluoride concentration of contaminant, retention time, pH, electrode type, and voltage was used on fluoride removal. DC current is significantly more efficient than AC, and Al has a higher performance than Fe electrode (p < 0.05). Neutral pH is more effective than acidic and alkaline condition in which significant differences are observed in reaction time of 60 min (p = 0.02). Elevation of cell potential from 15 to 25 V led to enhancing efficiency, but beyond these range fluoride removal declined. Fluoride concentration increase from 3 to 8 mg/l declined the EC performance with a significant impact in reaction times of 20 and 40 min (p = 0.004). In similar cell potential, increasing in reaction time from 20 to 60 min led to decreasing in residual fluoride from 1.75 to 1.06 mg/l, and 1.64 to 0.76 mg/l in 25 and 40 V, respectively.

Removal of Sulfonated Humic Acid through a Hybrid Electrocoagulation–Ultrafiltration Process

This study investigated the removal of sulfonated humic acid (SHA) from water through a hybrid electrocoagulation–ultrafiltration treatment process. The effects of major operating parameters including electrocoagulation time, current density, and initial pH on the electrocoagulation performance were evaluated. The increase in current density and operating time as well as decrease of pH improved the SHA removal efficiency. The operating conditions of electrocoagulation process were optimized through Box–Behnken design to maximize SHA removal. The optimum conditions for electrocoagulation included time of 7 min, current density of 10 mA/cm2, and pH of 5. Effective SHA removal was further achieved in the hybrid electrocoagulation–ultrafiltration treatment process. The performances of three molecular weight cutoff membranes were examined. The results showed that the SHA removal efficiency increased with the increasing initial concentration of SHA and decreased with the increasing transmembrane pressure. The SHA removal efficiency was more than 95% by 5 kDa membrane. The SHA removal efficiency by different membranes from high to low in turn was: 5 kDa > 8 kDa > 10 kDa. The results will have significant implications for the treatment of complex drilling and hydraulic fracturing wastewater through electrocoagulation–ultrafiltration process.

Electrochemically assisted coagulation for the adsorptive removal of dimethyl phthalate from aqueous solutions using iron hydroxides

In this study, the adsorptive removal of dimethyl phthalate (DMP) from aqueous solutions by electrochemically generated iron hydroxides was investigated in batch mode. Four electrode pairs were used to characterize the performance of electro-coagulation (EC) for the DMP removal efficiency. Experimental results indicated that a Fe/Al electrode pair was the optimum choice out of four different electrode pair combinations. In addition, the effects of varying current density and solution temperature on DMP adsorption characteristics were evaluated. The findings indicated that complete DMP removal could be achieved within reasonable removal efficiency and with relatively low electrical energy consumption. The optimum current density and temperature were found to be 20 mA/cm2 and 298 K, respectively. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the DMP adsorption of aqueous solutions on metal hydroxides was feasible, spontaneous and endothermic in the temperature range of 288–318 K. The experimental data were fitted with several adsorption isotherm models to describe the EC process. The adsorption of DMP preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules.

REMOVAL OF CARBAMAZEPINE BY ELECTROCOAGULATION: INVESTIGATION OF SOME KEY OPERATIONAL PARAMETERS

The performance of electrocoagulation (EC) process, a non-specific electrochemical technology, was investigated for the removal of carbamazepine (CBZ), an antiepileptic drug, from water. Experiments were carried out in synthetic wastewater in a batch cell. The respective influences of some key process parameters were studied, such as mixing conditions, initial pH, and current on aluminium electrodes. Experimental results showed that a CBZ removal efficiency of 62% was observed under slightly acidic initial conditions (pH 4) with a current density as high as 44 mA cm -2 (I=4.5 A) using Al electrode. This clearly indicates that CBZ removal proceeds through an electrochemical mechanism, while the adsorption of CBZ onto the aluminum hydroxide flocs was shown to be negligible. Furthermore, the increase of initial pH to alkaline values was shown to decrease the drug elimination efficiency. Conversely, as expected, an increase of current intensity improved the removal of CBZ. As a result, low initial pH 4 coupled with high current elevates the electrochemical elimination of CBZ: in this case, one metabolite could also be detected.

Removal of zinc ions from synthetic and industrial Tunisian wastewater by electrocoagulation using aluminum electrodes

AbstractElectrocoagulation (EC) is an efficient technique for cleaning waste water containing heavy metals before discharge in the environment. The performance of electro coagulation for zinc ions removal using aluminum electrodes was investigated in this paper. Several electrochemical parameters such as pH, current density, electrolyte doses, energy consumption, initial concentration, EC time, the state of the aluminum plates, and heavy metal ions concentration were studied in an attempt to achieve high zinc removal efficiency. Optimum conditions for zinc removal were found at a pH value of 7, a current density of 7.35 mA cm−2, an inter-electrode potential of 5 V, a conductivity of 5.3 mS cm−1, and an EC time of 30 min. These operating conditions can simultaneously achieve a good mix, good flotation, high flocs stability, and thus efficient removal in a relatively short reaction time and low cost with a removal percentage up to 98.96. The testing of zinc removal from industrial waste water showed that th...

Heavy Metal Removal by Electrocoagulation Integrated Membrane Bioreactor

This study investigates the performance of electrocoagulation integrated membrane bioreactor (EMBR) in treating synthetic wastewater enriched with heavy metals (Cu, Cr, and Zn). This hybrid system was compared with a conventional membrane bioreactor (MBR). The results suggest that it is superior to conventional MBR in terms to chemical oxygen demand removal, flux improvement, fouling reduction, and metal removal. The metal removal efficiencies in both MBR and EMBR followed the sequence Cr &gt; Cu &gt; Zn. The average removal efficiencies in MBR were 60.90, 53.24, and 48.22% for Cr, Cu, and Zn, respectively, while for the EMBR 98.60, 97.53, and 93.52% could be achieved, respectively. The mixed liquor suspended solids (MLSS) concentration was also found to affect the metal removal potential of the MBR. In MBR, metal removal and MLSS concentration showed significant relationship, while in EMBR, this correlation was found to be less. The specific energy consumption for removing each metal by EMBR was calculated and found to be 6.62, 6.94, and 6.69 kWh/kg removed for Cr, Zn, and Cu, respectively.

Effect of operational parameters on heavy metal removal by electrocoagulation.

In the present paper, the performance of electrocoagulation (EC) for the treatability of mixed metals (chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn)) from metal plating industrial wastewater (EPW) has been investigated. The study mainly focused on the affecting parameters of EC process, such as electrode material, initial pH, distance between electrodes, electrode size, and applied voltage. The pH 8 is observed to be the best for metal removal. Fe-Fe electrode pair with 1-cm inter-electrode distance and electrode surface area of 40 cm(2) at an applied voltage of 8 V is observed to more efficient in the metal removal. Experiments have shown that the maximum removal percentage of the metals like Cr, Ni, Zn, Cu, and Pb are reported to be 96.2, 96.4, 99.9, 98, and 99.5 %, respectively, at a reaction time of 30 min. Under optimum conditions, the energy consumption is observed to be 51.40 kWh/m(3). The method is observed to be very effective in the removal of metals from electroplating effluent.

Electrocoagulation treatment of metal finishing wastewater.

Electrocoagulation has been found to be a consistent and reliable industrial wastewater treatment process capable of removing heavy metals to levels well below pretreatment discharge standards. Results from the testing of a 113 L/min pilot scale electrocoagulation unit indicated that electrocoagulation was capable of decreasing the cadmium, chromium, and nickel concentrations from 0.14, 18.1, and 0.06 parts per million (ppm) to 0.029, 0.039, and 0.020 ppm respectively, at a 1-min hydraulic retention time. In the presence of a strong chelating substance, electrocoagulation performance was found to be effective in reducing both chromium and nickel concentrations to levels well below discharge limits. At a pH of 8.0, chromium and nickel influent concentrations of 0.328 and 0.062 ppm, respectively, were reduced to 0.005 and 0.04 ppm. The electrocoagulation removal efficiency for chromium remained high at over 98% and appeared to be unaffected by the presence of chelating substances. Utilizing aluminum as the sacrificial anode improved the removal efficiency of targeted heavy metals when the industrial wastewater was treated under acidic conditions. At a pH of 5.6, the influent concentrations of the regulated heavy metals cadmium, chromium, and nickel were reduced from 0.55, 49.7, and 13.7 ppm, respectively, to 0.013, 2.7, and 0.8 ppm at a 1-min hydraulic retention time. The results of these tests suggest that the formation of ferric hydroxide and aluminum hydroxide through the electrocoagulation process may be an effective approach for treating metal finishing wastewaters.

Removal of Diazinon from aqueous solution by electrocoagulation process using aluminum electrodes

Electrocoagulation (EC) is an electrochemical method to treat polluted wastewaters and aqueous solutions. In this paper, the removal of Diazinon was studied by EC on aluminum electrode. The effect of several parameters such as initial concentration of Diazinon, current density, solution conductivity, effect of pH, and electrolysis time were investigated on EC performance. The obtained results showed that the removal efficiency of EC depends on the current density, initial concentration of Diazinon and electrolysis time. The optimum pH is 3 and also the solution conductivity has no significant effect on removal efficiency.

Treatment of geothermal water with high fluoride content by electrocoagulation

The performance of electrocoagulation (EC) process in the treatment of geothermal water with high fluoride content was studied. The effect of applied current density, electrode plate number, electrode plate distance, and the temperature of geothermal water was investigated. The results show that EC can effectively reduce fluoride content to a low level, which can supply sanitary standard for drinking water in China (GB 5749-2006, 2006). With the increase in current density and electrode plate area, the removal efficiency of fluoride in geothermal water was also increased. However, with electrode plate distance increased from 0.5 to 2.0 cm, the fluoride removal efficiency decreased accordingly. The fluoride removal efficiency was improved when geothermal water temperature was increased from 18 to 38°C, while the fluoride removal efficiency changed little with geothermal water temperature from 38 to 62°C.

Abatements of reduced sulphur compounds, colour, and organic matter from indigo dyeing effluents by electrocoagulation

In the present study, the treatability of indigo dyeing effluents by the electrocoagulation (EC) process using stainless steel electrodes was experimentally investigated. The samples used were concentrated with main pollutant parameters of chemical oxygen demand (COD) (1000–1100 mg/L), reduced sulphur species (over 2000 mg , and colour (0.12–0.13 1/cm). The study focused on the effect of main operation parameters on the EC process performance in terms of abatement of reduced sulphur compounds as well as decolourization and organic matter reduction. Results indicated that the performance of EC proved to be high providing total oxidation of the reduced sulphur compounds, almost complete decolourization, and COD removal up to 90%. Increasing applied current density from 22.5 to 45 mA/cm2 appreciably improved abatement of the reduced sulphur compounds for Sample I, but a further increase in the applied current density to 67.5 mA/cm2 did not accelerate the conversion rate to sulphate. The process performance was adversely affected by increasing initial concentration of the reduced sulphur compounds. Decolourization and organic matter removal efficiency enhanced with increasing applied current density. The main removal mechanism of the reduced sulphur compounds by EC was explained as conversion to sulphate via oxidation. Conversion rate to sulphate fitted pseudo-first-order kinetics very well.

Removal of heavy metals by hybrid electrocoagulation and microfiltration processes

This study is based on the investigation of the performance of electrocoagulation (EC), followed by the microfiltration process for heavy metal removal in synthetic model waste water containing Zn2+, Ni2+ and Cd2+ ions. Effects of initial concentration, current density and pH on metal removal were analysed to optimize the EC process. The optimized EC process was then integrated with dead-end microfiltration (MF) and was found that the hybrid process was capable of 99% removal of heavy metals. The cake layer formed over the membrane by the hybrid process was analysed through scanning electron microscope-energy-dispersive X-ray spectroscopy. The particle size analysis of the sludge formed during EC was done to investigate the fouling caused during the process.

The importance of current distribution and cell hydrodynamic analysis for the design of electrocoagulation reactors

AbstractBACKGROUNDThe effects of current distribution and cell hydrodynamics on the performance of an electrocoagulation (EC) reactor were studied. This analysis only considered the distributions of primary potential and current density. The hydrodynamic behavior was analyzed by means of computational fluid dynamics (CFD) using a turbulent model (k–ϵ). For this study, only the fluid movement between electrodes was taken into account.RESULTSThe analysis of current distribution showed the effects of cell geometry and electrode configuration on both the potential and current distributions on the anodes. Insulators placed at the edges of the electrodes produced border effects on the potential values that favored a secondary reaction and diminished the formation of aluminum clots. The CFD analysis indicated that the cell geometry arrangement generates low velocity profiles between the electrodes. From the experimental evaluation, it was observed that EC performance was improved when uniform potential and current densities were achieved with low flow velocity profiles.CONCLUSIONSAnalysis of the hydrodynamic behavior showed the impact of different hydrodynamic phenomena on both the formation of clots and the removal of the sludge formed. Likewise, it was confirmed that in optimizing energy consumption, an analysis of current distribution is a very useful tool for evaluating the arrangement of electrodes and the cell geometry.