Direct Current Electrocoagulation Research Articles

Development of an electrocoagulation method using alternating pulse current to treat wastewater generated by tanneries

ABSTRACT Direct current electrocoagulation has various drawbacks, including electrode passivation, heat creation from energy consumption, and high sludge formation. The restrictions limit its usage in tannery wastewater treatment. Therefore, alternating pulse current EC (APC-EC) was developed to solve these obstacles. The study was empirically examined, considering high-frequency (3,000–11,000 Hz), stirring speed (400–1,200 rpm), and reaction time (15–30 min). This research examined how factors affect chemical oxygen demand (COD) removal efficiency, turbidity from trivalent chromium (Cr+3), and energy consumption for perforated aluminum electrodes. The central composite design in the surface response design approach has improved various operational parameters in the APC-EC process for tannery wastewater treatment. The employment of mathematical and statistical methods resulted in optimal removal of COD, Cr+3, and turbidity while reducing energy usage. Using mathematical and statistical methods, we achieved maximum COD, Cr+3 ion, and turbidity reduction while reducing energy use. The investigation found that COD (70.3%), Cr+3 (89.56%), and turbidity (96%) were the most rapidly removed components at 11,000 Hz, 576 rpm, and 30 min. Surface response data explain high-frequency APC-EC dynamics.

Investigation on pulsed-electrocoagulation process for the treatment of wet coffee processing wastewater using an aluminum electrode

The use of conventional direct current-electrocoagulation in wastewater treatment is limited by its drawbacks, which include electrode passivation, high energy consumption, and significant sludge generation. Therefore, to address these issues, pulsed-electrocoagulation (PECP) has been developed. The PECP is an advanced wastewater treatment technique that uses intermittent electrical pulses to target and break down organic compounds in wastewater. It offers several benefits, including enhanced removal of organic compounds, reduced chemical consumption, energy efficiency, treatment of complex wastewater composition, pathogen inactivation, environmental compliance, and potential for water reuse. In this research, removal efficiency of % Chemical Oxygen Demand (COD), % Color, % Turbidity, % phosphate, and %nitrate was investigated for the wet coffee processing wastewater by using PECP and the obtained results as the COD-98.75%, color-99.92%, turbidity-99.00%, phosphate-99.02%, and nitrate-98.83%, respectively. Independent variables were the major significant factors and the optimum value was investigated and obtained at pH of 7, electrolyte dosage of 0.75 g L−1, electrolysis time of 45 min, and current of 0.45 Amp. As a result, PECP with NaCl and CaCl2 as an electrolyte is an effective treatment technique for pollutant removal from wastewater. As a consequence, the specific benefits may vary depending on the system design, operational parameters, and wastewater characteristics. The pilot-scale studies and optimization are essential for assessing PECP feasibility and performance.

Performance analysis of pulsed direct current electrocoagulation for chemical oxygen demand removal from wastewater: energy savings and cost minimization

Performance analysis of pulsed direct current electrocoagulation for chemical oxygen demand removal from wastewater: energy savings and cost minimization

(Digital Presentation) Application of Polarity Reversal and Performance Analysis of Continuous Electrocoagulation

An important challenge for continuous treatment by electrocoagulation (EC) is the passivation and fouling of electrodes which increases during the longer operation (Ingelsson et al., 2020). The application of polarity reversal (PR) and treatment performance of EC was investigated using continuous flow reactor for simultaneous removal of silica and hardness (calcium and magnesium) from produced water. Polarity reversal times (PRT) from 30 s to 10 min were studied at a fixed charge loading of 2000 C L- 1 (i.e., the amount of charge passed per unit volume of produced water treated) using Fe and Al electrodes. Periodic PR was found to reduce the fouling and de-passivate the electrodes by changing the surface chemistry at the electrode-electrolyte interface (Ingelsson et al., 2020; Yasri et al., 2022). During 90 minutes of continuous treatment the chronopotentiometric data indicated that a PRT of 10 min was more effective in reducing the cell voltage for both Fe and Al electrodes [Fig. 1 (a & b)]. With a longer PRT of 10 min, there is more time for the acid boundary layer to form on the anode, which mitigates metal precipitation at the anode. In contrast the higher cell voltage that persists in direct current EC (DC-EC) could be due to the precipitation of Ca and Mg minerals in the alkaline solution on the cathode surface, leading to cathode passivation (Chow et al., 2021). After the first polarity reversal, both electrodes have been anodic, removing passivation layers from the surface and reducing the cell voltage. On reversing the polarity, the cathode becomes the anode, and the acidic pH on the formed at the electrode interface will facilitate the dissolution of Ca and Mg precipitates on the electrode surface, reducing the cell voltage significantly. For Fe-EC, the contaminant removal performance increased with PRT, and the highest removal was observed with DC-EC (Fig. 1c). The increasing removal performance with PRT for Fe-EC is consistent with the increase in faradaic efficiency observed of 55%, 68%, 85%, and 99.8% with 30 sec, 2 min and 10 min PRT, and DC respectively. The lower faradaic efficiencies for Fe-EC with short PRTs are likely due to redox reactions of iron species at the electrode surface (Chow et al. 2021).The contaminant removal at a charge loading of 2000 C L–1 using DC-EC with Al electrodes was similar to that for PR-EC with PRTs of 2 to 10 min (Fig. 1d). Slightly lower Si and hardness removal was observed for Al-EC at the shortest PRT of 30 s. For Al-EC, the faradaic efficiency was also observed to increase with PRT, with values of 150%, 220% and 287% obtained at 30 sec, 2 min and 10 min PRT respectively. The super-faradaic (>100%) efficiencies can be explained by dissolution of the Al from the cathode under the local alkaline conditions that develop on the electrode surface. With a short PRT, there is less time for the alkaline pH to develop at the surface and hence the faradaic efficiency was reduced.

Comparison of sono-direct and sono-alternate current electro-coagulation processes for removal of color and turbidity from domestic wastewater

Background: Nowadays there is a problem related to wastewater handling which is released from different activities. Electrocoagulation has been a dominant treatment method for wastewater treatment. There are different forms of electrocoagulation methods for wastewater treatment. Nevertheless, there was no comparison made for the removal efficiency of the sono-alternate current (SAC), alternate current (AC), sono-direct current (SDC), and direct current (DC) electrocoagulation process. Methods: The efficiency of electrocoagulation method was compared for removal of color and turbidity from Jimma University domestic wastewater. Batch reactor DC/AC electrocoagulation cell was used to determine the removal efficiency. During the comparison, the response surface methodology (RSM) was used to analyze and optimize the data taken from the laboratory. In addition, ANOVA was used to analyze the interaction effects of different parameters. Results: The removal of color and turbidity from domestic wastewater was about 97.53% and 95.28% respectively, using direct current electrocoagulation (DCE). For alternate current electrocoagulation (ACE), the removal of color and turbidity was 98.35% and 96.12%, respectively. The removal of color and turbidity for sono-DCE (SDCE) was obtained to be 98.55% and 98.27%, respectively and for sono-ACE (SACE), the removal of color and turbidity was 99.95% and 99.76%, respectively at the optimum experimental conditions of chemical oxygen demand (COD) 960 g/L, initial wastewater pH of 6.8, the current density of 0.4 A/dm2 , inter-terminal spacing of 1 cm, and the association of electrode of Al-Al. Conclusion: According to the findings of this study, it can be concluded that, the SAC electrocoagulation method is the best and promising technique compared with all other electrocoagulation methods.

Effect of iron ion configurations on Ni2+ removal in electrocoagulation

Electrocoagulation (EC) has been widely used to treat the heavy metal wastewater in industry. A novel process of sinusoidal alternating current electrocoagulation (SACC) is adopted to remove Ni2+ in wastewater in this study. The morphology of precipitates and the distribution of the main functional iron configurations were investigated. Ferron timed complex spectroscopy can identify the monomeric iron configurations [Fe(a)], oligomeric iron configurations [Fe(b)] and polymeric iron configurations [Fe(c)]. The optimal operating conditions of SACC process were determined through single-factor experiments. The maximum Ni2+ removal efficiency [Re(Ni2+)] was achieved under the conditions of pH0=7, current density (j) = 7 A/m2, electrolysis time (t) = 25 min, c0(Ni2+) = 100 mg/L. At pH=7, the proportion of Fe(b) and Fe(c) in the system was 50.4 at.% and 23.1 at.%, respectively. In the SACC process, Fe(b) and Fe(c) are the main iron configurations in solution, while Fe(c) are the vast majority of the iron configurations in the direct current electrocoagulation (DCC) process. Re(Ni2+) is 99.56% for SACC and 98.75% for DCC under the same optimum conditions, respectively. The precipitates produced by SACC have a high proportion of Fe(b) configurations with spherical α-FeOOH and γ-FeOOH structures which contain abundant hydroxyl groups. Moreover, it is demonstrated that Fe(b) has better adsorption capacity than Fe(c) through adsorption experiments of methyl orange (MO) dye. Fe(a) configurations in the homogeneous solution had no effect on the removal of nickel.

Investigation of electrode passivation during electrocoagulation treatment with aluminum electrodes for high silica content produced water.

One of the main challenges for the implementation of electrocoagulation (EC) in water treatment are fouling and passivation of the electrodes, especially for applications with high contaminant concentrations. For the first time, we investigated in this study the process of fouling mitigation by polarity reversal during the EC treatment of boiler blowdown water from oil-sands produced water, characterized by high silica concentrations (0.5-4 g L-1). This effluent is typically obtained from an evaporative desalination process in oil production industries. Potentiodynamic characterisation was used to study the impact of passivation on the anode dissolution. Although a charge loading of 4,800 C L-1 was found to remove about 98% of silica from a 1 L batch of 4 g L-1 Si solution, fouling reduced the performance significantly to about 40% in consecutive cycles of direct current EC (DC-EC) treatment. Periodic polarity reversal (PR) was found to reduce the amount of electrode fouling. Decreasing the polarity period from 60 to 10 s led to the formation of a soft powdery fouling layer that was easily removed from the electrodes. In contrast, with DC operation, a hard scale deposit was observed. The presence of organics in the field samples did not significantly affect the Si removal, and organics with high levels of oxygen and sulfate groups were preferentially removed. Detailed electrochemical and economic investigations suggest that the process operating at 85 °C achieves 95% silica removal (from an initial concentration of 481 mg L-1) with an electrical energy requirement of 0.52 kWh m-3, based on a charge loading of 1,200 C L-1, an inter-electrode gap of 1.8 cm and a current density of 16 mA cm-2.

High-efficiency and energy-saving alternating pulse current electrocoagulation to remove polyvinyl alcohol in wastewater.

Conventional direct current electrocoagulation (DC-EC) has disadvantages such as easy passivation of electrodes, high energy consumption, and large sludge production, which limit its use in polyvinyl alcohol (PVA) wastewater. Therefore, alternating pulse current electrocoagulation (APC-EC) has been developed to overcome these problems. In this study, the influencing factors and energy consumption of PVA treatment by APC-EC and DC-EC were explored, and the best operating conditions of APC-EC were obtained via the response surface method (RSM). The best process conditions for APC-EC were determined to be the electrode type of Fe/Fe, current density of 1.0 mA cm−2, initial pH of 7, electrode distance of 2.0 cm, supporting electrolyte of 0.08 mol L−1 NaCl, initial PVA concentration of 150 mg L−1, duty cycle of 30%, and frequency of 500 Hz. In addition, the floc properties of APC-EC and DC-EC were compared to explore the basic mechanism for the removal of PVA. Adsorption and co-precipitation with hydroxide iron complexes are the main methods for removing PVA from wastewater in the APC-EC process. Compared with DC-EC, the application of APC-EC can reduce electrode passivation and production of sludge and operating costs, and improve electrode stability and PVA removal efficiency. This study provides a new strategy and method for the PVA removal from wastewater by APC-EC with low cost and high efficiency, showing broad prospect for the applications of the APC-EC in removing PVA.

Investigation of direct and alternating current–electrocoagulation process for the treatment of distillery industrial effluent: Studies on operating parameters

The main objective of this study is to analyze the influence of direct and alternating – current on electrocoagulation process in terms of % color and % COD removal along with electrical energy consumption from distillery industrial effluent. The percentage of color and COD removal and electrical energy consumption were about 90.57%, 86.54% and 3.50 kWhr/m3 with Direct – Current Electrocoagulation (DCE). For Alternating – Current Electrocoagulation (ACE), it was 100%, 95% and 3.20 kWhr/m3, respectively at the optimal experimental condition of COD – 3000 mg/L, initial wastewater pH – 7, current density – 0.4 A/dm2, inter–electrode spacing – 1 cm, combination of electrode – Fe/Fe, pulse duty cycle – 0.45, frequency – 50 Hz and treatment time – 3.5 h. The ACE was more successful in eliminating % color and % COD with less electrical energy consumption than DCE process. In DCE, the formation of an impermeable oxide layer on the cathode and the occurrence of corrosion on the anode due to oxidation have decreased the efficiency of this process compared to the ACE process. As a result, experimental findings have shown that with less electrical energy usage and process efficiency, the ACE could be a more promising solution to removing pollutants from wastewater and industrial effluent than the DCE method.

Cd removal by direct and positive single pulse current electrocoagulation: Operating conditions and energy consumption

Abstract Due to its toxicity, cadmium (Cd) is a well-known pollutant in aquatic environments. Although direct current electrocoagulation (DC-EC) has shown great potential in industrial applications, the presence of a passive film on the electrode impedes the Cd removal efficiency and increases energy consumption during long-term operation. This issue can be resolved using positive single pulse current EC (PSPC-EC). In this study, two kinds of EC, i.e., DC-EC and PSPC-EC, were applied to remove Cd from aqueous solutions, where the optimal operating conditions, energy consumption, and Cd removal mechanisms were explored using the two EC kinds. The optimum operating conditions of the DC-EC were a pH of 8, an initial Cd concentration of 28 mg/L, a current density of 40 A/m2, and a plate spacing of 15 mm. Based on the optimum operating conditions of the DC-EC, the optimum average current density, frequency, and duty ratio were 16 A/m2, 2000 Hz, and 40% in the PSPC-EC process, respectively. Also, the removal rates of the DC-EC and PSPC-EC reached 99.74% and 99.92% with energy consumption values of 0.714 and 0.400 kWh/m3, respectively. In addition, it was indicated that the energy consumption of the PSPC-EC was 44% less than that of the DC-EC. Through the study of the flocs, it was found that the flocs produced by the PSPC-EC exhibited a larger surface for the Cd adsorption and formed larger particles in comparison with the DC-EC. In addition, the green rust-Cl (GRCl) produced by the PSPC-EC had a better Cd removal property, which removed the Cd by adsorption, coagulation, and Cd hydroxide precipitation. The results described herein provide a basis for the treatment of heavy metal-containing wastewater using the PSPC-EC method, and they can be used in future industrial applications.

Comparison of Cr(VI) removal by direct and pulse current electrocoagulation: Implications for energy consumption optimization, sludge reduction and floc magnetism

Conventional direct current electrocoagulation (DC-EC) suffers from issues of plate passivation, large energy consumption and sludge weight, which greatly restrict its application to wastewater treatment with Cr(VI). In this study, positive single pulse current electrocoagulation (PSPC-EC) and alternating pulse current electrocoagulation (APC-EC) were used to solve the above problems. The optimum removal efficiencies of Cr(VI) obtained by DC-EC, PSPC-EC and APC-EC were all over 99 %. The energy consumptions of DC-EC, PSPC-EC and APC-EC were 3.8 × 10−3, 4.0 × 10−4 and 7.6 × 10−4 kWh/mgCr(VI) and the amounts of dry sludge produced were 1.8612, 1.3024 and 1.1246 g/L, respectively. Among the three types of EC, PSPC-EC consumed the least electrical energy and APC-EC produced the least amount of sludge, indicating their advantages over DC-EC. The flocs produced by PSPC-EC had a better spread performance than those of DC-EC and APC-EC, which contributed to a larger surface area for adsorbing Cr(VI). It should be noted that EC may generate magnetic flocs with easily available iron electrode. Our findings indicate it is possible to adjust the magnetic strength of the flocs simply by adjusting the pulse current on electrode, which has not been reported in previous studies. This exhibits the potential to avoid adding complicated synthetic magnetic coagulants in the water treatment construction and cut down chemical operation cost. Also, it enlightens those dedicated to electrochemistry to develop magnetic-floc-generating electrodes for enhancing contaminant separation and water purification.

Comparison between Nanosecond Pulse and Direct Current Electrocoagulation for Textile Wastewater Treatment

Comparison between Nanosecond Pulse and Direct Current Electrocoagulation for Textile Wastewater Treatment

A solar powered direct current electrocoagulation system with hydrogen recovery for wastewater treatment

ABSTRACT The operation of a tube-in-tube electrocoagulator powered directly by photovoltaic solar panel with simultaneous hydrogen production for dye decolorization was illustrated. It has been shown that a method of adjusting the dye wastewater feed flow rate to the fluctuating PV output current is effective for retaining high decolorization of Reactive Blue 21 (>97% color removal) even though the PV output current varied between 2 and 8.5 A with instantaneous changes in solar radiation. The hydrogen product from the oxidation-reduction reactions can be harvested and was found to be 70% of the theoretical amount.

Application of Pulse Electrocoagulation to Dye Wastewater Treatment

Electrocoagulation (EC) has been proven by a substantial number of studies to be an efficient technology to remove organic pollutants from wastewater. Nevertheless, the high energy consumption of this technology inhibits its extensive application. The objective of this work is to investigate the feasibility of electrical energy conservation and high efficiency by using Pulse Electrocoagulation (PE). PE, a combination of a pulsing technique and EC, was proposed in an attempt to treat the dye wastewater. The results demonstrated that PE, as compared with DCE (direct current electrocoagulation), resulted in up to 51.66% energy conservation by using two iron electrodes as anode and cathode. Moreover, this high energy conservation was obtained during a high level of treatment efficiency: 99.62% of color removal and 91.15% of COD removal for 1000 mg L-1 4BS solution in a short electrolyzing time of 15 mins.

Simultaneous decolorization of binary mixture of Reactive Yellow and Acid Violet from wastewaters by electrocoagulation

Dyes are common pollutants in a large variety of industrial wastewaters, and the treatment of these wastes has been extensively studied by coagulation. For the removal of pollutants from the wastewaters, different techniques have been used and electrocougulation is one of the widely used methods. This process is very effective in removing organic pollutants including dyestuff wastewater. The purposes of this study were to investigate the effects of the operating parameters, such as current density, electrolyte concentration, dyestuff concentration, and pH of solution on decolorization and chemical oxygen demand (COD) removal of wastewater containing two different dyes in same solution by direct current electrocoagulation. The amount of dye removed was found by application of first derivative spectrophotometric method to the synthetic dye mixtures. In this work synthetic dye mixture which include C.I. Reactive Yellow 145 (RY145) and C.I. Acid Violet 90 (AV 90) were used for electrocougulation (EC) process with iron electrodes. In the presence of both dye molecules, the optimum pH was found to be 4, optimum NaCI concentration was 3000 mg/L and optimum current density was 5.56 mA/cm2. Under these conditions in the case of 100 mg/L-1 each dye concentration at 20 degrees C and 3 cm interelectro distance the color removal efficiency was reached 97.7% for AV 90 and 97.1% for RY145 in 10 minutes time duration. Dye concentration dependent highest COD removal efficiency was measured as 82% around at 100 mg/L dye concentration.

Treatment of lixiviate from Jebel Chakir-Tunis by electrocoagulation

The removal of organic pollutants fromlixiviate was experimentally studied using direct current electrocoagulation (EC) with aluminum electrodes. The effects of operating parameters such as current density, initial pH and electrolysis time were further studied in order to optimize conditions for the treatment of lixiviate. Two different electrode connections (monopolar and bipolar) were examined for choosing the best alternative in order to intensify the performance of the process. It was observed that high removal capacity was better for monopolar connection than for bipolar connection. The subsequence of EC tests performed with Al electrodes showed that optimal operating conditions are an initial pH of 6; a current density 15 A cm−2 and EC time of 90 min. Treatment reduces chemical oxygen demand (COD) to 94%. The color removal efficiency reached 96%. Cost estimation was adopted and presented as well. Total operating costs for monopolar connection was evaluated at about 43.315 US$ m−3 for the optimal ope...

The decolorization of C.I. Reactive Black 5 in aqueous solution by electrocoagulation using sacrificial iron electrodes

The removal of color from synthetic wastewater containing Reactive Black 5 was experimentally investigated using direct current electrocoagulation at iron electrodes. The effects of operational parameters such as current density, initial pH, electrolysis time, initial dye concentration and solution conductivity on color removal efficiency were investigated in this study. The optimum operating range for each of these operating variables was experimentally determined. The experimental results show that the color of Reactive Black 5 in the aqueous phase was removed effectively. Under the conditions of an initial dye concentration of 100 mg L −1, initial pH of 5, current density of 4.575 mA cm −2, salt concentration of 3000 mg L −1, temperature of 20 °C, and interelectrode distance of 2.5 cm, the color removal efficiency reached 98.8%. Electrical energy consumption in the above conditions for the decolorization of the dye solution containing Reactive Black 5 was 4.96 kWh/kg dye. Results show that the first-order rate equation provides the best correlation for the decolorization rate of Reactive Black 5.

Prospective randomized comparative study of bipolar versus direct current electrocoagulation for treatment of bleeding internal hemorrhoids

Internal hemorrhoids are the most common cause of lower gastrointestinal bleeding. Although new anoscopic therapies are available, few comparative randomized studies have evaluated them in regard to long-term efficacy, recurrence rates, and safety. Our purpose was to compare the treatment of internal hemorrhoids with direct current (Ultroid, Cabot Medical, Langhorn, Pa.) and bipolar (BICAP, Circon ACMI, Stamford, Conn.) hemorrhoid probes. One hundred patients with symptomatic internal hemorrhoids were randomized: 50 to direct current electrocoagulation and 50 to bipolar electrocoagulation. Follow-up and treatment were at 3- to 4-weekly intervals; two to three hemorrhoid segments were treated at each session until relief of symptoms (bleeding, prolapse, and discharge) and a reduction in hemorrhoid size to grade 1 or 0 were noted. The hemorrhoids of 98% of all patients studied were grade 2 or 3; 2% of patients had grade 1 hemorrhoids and none had grade 4 hemorrhoids. At 1 year after treatment, most patients had no (69%) or only mild (23%) recurrence, and a few had severe, symptomatic (8%) hemorrhoid recurrence. A greater recurrence rate was noted after direct current treatment (34%) than bipolar treatment (29%). In contrast, rebleeding at 1 year occurred less frequently after direct current treatment (5%) than after bipolar treatment (20%). Our conclusions were as follows: (1) Both direct current and bipolar probes were effective for control of chronic bleeding from grade 1 to 3 internal hemorrhoids. (2) Bipolar probe was significantly faster than direct current probe. (3) Direct current treatment produced fewer complications than bipolar treatment (12% versus 14%). (4) Recurrence rates were low after 1 year with either device (8%). (5) More recurrences were noted after direct current electrocoagulation (34%) than after bipolar electrocoagulation (29%). (Gastrointest Endosc 1994;40:403-10.)

Randomized, prospective trial of direct current versus bipolar electrocoagulation for bleeding internal hemorrhoids

Fifty patients with bleeding internal hemorrhoids unresponsive to 6 weeks of standard medical therapy were randomly assigned to receive treatment with direct current or bipolar electrocoagulation. Treatment groups were similar in bleeding severity and internal hemorrhoid grade. Treatment sessions were significantly longer for direct current electrocoagulation (8.8 +/- 0.2 minutes) than for bipolar electrocoagulation (0.1 +/- 0.03 minutes) (p < 0.001). When compared to the bipolar electrocoagulation group, direct current electrocoagulation patients had more procedural pain that terminated therapy (5 of 25 patients [20%] versus 0 of 25 [0%], for a difference of 20% [95% confidence interval, 4% to 36%]; p = 0.05) and prolonged pain after the procedure (4 of 25 patients [16%] versus 1 of 25 [4%], for a difference of 12% [95% confidence interval, -4% to 28%]; p = 0.35). However, more post-treatment rectal ulcerations were seen in the bipolar electrocoagulation-treated group (6 of 25 patients [24%] versus 1 of 25 [4%], for a difference of 20% [95% confidence interval, 2% to 38%]; p = 0.10). Treatment groups did not differ in number of treatment sessions or months of follow-up. The rates of success, defined as obliteration of the hemorrhoids or cessation of bleeding with reduction of the hemorrhoids to grade 1 or less, for the direct current electrocoagulation and the bipolar electrocoagulation groups were 88% and 92%, respectively. Failures in the direct current electrocoagulation group were uncontrollable bleeding (n = 1) and refusal to continue therapy because of pain (n = 2).(ABSTRACT TRUNCATED AT 250 WORDS)