Current Electrocoagulation Research Articles

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 effects of alternating current electrocoagulation on dye removal from aqueous solutions

The main goal of this study is to investigate the effects of alternating current (AC) on dye removal from aqueous solutions by electrocoagulation (EC). An EC system with parallel-connected aluminium electrodes was operated in batch mode. Two different aqueous dye solutions were used: one was obtained from Dianix Yellow CC (DY) and the other was obtained using Procion Yellow (PY). The experiments employing direct current (DC) were carried out using a DC power supply. The AC experiments were conducted using rectangular wave, which is produced with an adjustable time relay connected to the output of DC power supply. This current is called alternating pulse current (APC) in order to refer AC system in this study. Total organic carbon (TOC) and dye removal efficiencies were measured to assess treatment efficiency. Operating cost was calculated for both power supply systems and alternating pulse current was found superior to direct current for the treatment of reactive and disperse dyes used in this study.

Treatment of tannery liming drum wastewater by electrocoagulation

The removal of COD, suphide and oil–grease from tannery liming drum wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of the wastewater, the effects of initial pH, electrolysis time and current density were examined. The COD, sulphide and oil–grease in the aqueous phase were effectively removed when mild steel electrodes were used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The experimental results show that COD, sulphide and oil–grease was removed effectively. The overall COD, sulphide and oil–grease removal efficiencies reached 82%, 90% and 96%, respectively. The optimum current density for removal of COD, sulphide and oil–grease in the tannery liming drum wastewater were 35 mA/cm 2, 35 mA/cm 2 and 3.5 mA/cm 2 at 10 min electrolysis time and pH 3, respectively. Mean energy consumptions were 5.768 kWh/m 3 of COD, 0.524 kWh/m 3 of sulphide and 0.00015 kWh/m 3 of oil–grease. Results show that the pseudo-second-order rate equation provides the best correlation for the removal rate of the parameters.

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.

Alternating pulse current in electrocoagulation for wastewater treatment to prevent the passivation of al electrode

A novel current feed style, alternating pulse current, was proposed in electrocoagulation aiming at preventing the passivation of electrode materials. The open circuit potential (OCP) measurements after anodic and cathodic potentiodynamic polarization showed that cathodic polarization could activate Al electrode. The surface of Al electrode after alternating pulse current electrocoagulation was investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), and the results indicate that passivation of Al is not observed. Furthermore, the simulated wastewater treatment tests show that alternating pulse current electrocoagulation has a visible energy saving effect and is worthy of generalization.

Treatment of dairy wastewaters by electrocoagulation using mild steel electrodes

The removal of COD and oil–grease from dairy wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of dairy wastewater, the effects of initial pH, electrolysis time, initial concentration of COD, conductivity and current density were examined. The COD and oil–grease in the aqueous phase were effectively removed when iron was used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The batch experimental results revealed that COD and oil–grease in aqueous phase was effectively removed. The overall COD and oil–grease removal efficiencies reached 98 and 99%, respectively. The optimum current density, pH and electrolysis time for 18,300 mg COD/L and 4570 mg oil–grease/L were 0.6 mA/cm 2, 7 and 1 min, respectively. Mean energy consumption was 0.003 kWh/kg of COD.

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.)

Hazardous waste storage, disposal, remediation, and closure

Hazardous waste storage, disposal, remediation, and closure

Alternating Current Electrocoagulation for Superfund Site Remediation

Abstract The Superfund Innovative Technology Evaluation (SITE) Emerging Technology (ET) Program, authorized under the Superfund Amendments and Reauthorization Act (SARA) of 1986, implements the goal of the SITE Program to promote, accelerate the development of, and make commercially available alternative innovative treatment technologies for use at Superfund sites. Under this program, the technical and economical feasibility of alternating current electrocoagulation (ACE) developed by Electro-Pure Systems, Inc., was evaluated for a two-year period. ACE is an electrochemical technology where highly-charged aluminum polyhydroxide species are introduced into aqueous media for the removal of suspended solids, oil droplets and soluble ionic pollutants. ACE can break stable aqueous colloidal suspensions of up to 10 percent total solids and stable emulsions containing up to 5 percent oil. Major operating parameters have been defined for different classes of effluents based on experimental results using complex s...

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)