Iron Electrocoagulation Research Articles

Influence of the anodic material on electrocoagulation performance

The removal of organic pollutants from a highly complex industrial wastewater by aluminum, iron and aluminum + iron electrocoagulation systems was evaluated. Under optimal conditions of pH 8 and 45.45 A m −2 current density, the electrochemical method yields a very effective reduction of all organic pollutants. The optimal treatment (aluminum + iron) reduced chemical oxygen demand (COD) by 69%, biochemical oxygen demand (BOD 5 ) by 71%, color by 83%, turbidity by 80% and total coliforms by 99%. The raw and treated wastewater was characterized by UV–vis spectroscopy and cyclic voltammetry to confirm the increase in water quality. Finally, the sludge produced during electrocoagulation was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS).

A Comparison of Iron and Aluminium Electrodes in Hydrogen Peroxide-Assisted Electrocoagulation of Organic Pollutants

Removal of organic pollutants from a highly complex industrial wastewater by aluminium and iron electrocoagulation assisted with hydrogen peroxide was evaluated. Under optimal conditions the electrochemical method yields a very effective reduction of all organic pollutants, which was enhanced when the hydrogen peroxide was applied during electrocoagulation. Treatment reduced chemical oxygen demand (COD) by 92%, biochemical oxygen demand (BOD5) by 89%, color by 92%, turbidity by 95%, and total coliforms by 99%. The chemical species ditribution of aluminium and iron formed in aqueous solution are presented. Initial and final pollutant levels in the wastewater were monitored using UV-Vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the sludge produced was characterized with scanning electron microscopy (SEM) and energy dispersion X-ray spectra (EDS).

Evaluation of iron chemical coagulation and electrocoagulation pretreatment for surface water microfiltration

A bench-scale study was undertaken to evaluate iron chemical coagulation and electrocoagulation pretreatment for dead-end, constant pressure microfiltration of surface water. Fouling of a commercially available PVDF membrane with conventional chemical coagulation pretreatment was found to (1) be insensitive to pH in the range 6.4–8.3, (2) decrease only when ≥10 mg/L Fe 3+ were dosed and (3) exacerbate with increasing transmembrane pressure. These results were consistent with creation of larger flocs at high iron dosages that decreased cake specific resistance and formation of compressible cakes that increased hydraulic resistance at higher pressures. A substantial intermediate blocking stage was observed prior to cake formation during raw water microfiltration whereas for coagulated waters, cake filtration was the predominant flux decline mechanism for almost the entire duration of microfiltration. Fouling was not alleviated significantly by iron electrocoagulation in the entire range of experimental conditions investigated since soluble ferrous iron was unexpectedly generated at the anode. Hence, conventional iron chemical coagulation is recommended over iron electrocoagulation for pretreatment of surface waters prior to low-pressure membrane filtration. Chemical- and electrocoagulation pretreatment decreased ultraviolet absorbance to a greater extent than dissolved organic carbon. Hence, disinfection by-product control by coagulation–microfiltration is achieved by decreasing the concentration of natural organic matter precursors as well as their reactivity towards chlorine.

Comparison of electrocoagulation and chemical coagulation pretreatment for enhanced virus removal using microfiltration membranes

This research studied virus removal by iron electrocoagulation (EC) followed by microfiltration (MF) in water treatment using the MS2 bacteriophage as a tracer virus. In the absence of EC, MF alone achieved less than a 0.5-log removal of MS2 virus, but, as the iron-coagulant dosage increased, the log virus removal increased dramatically. More than 4-log virus removal, as required by the Surface Water Treatment Rule, was achieved with 6–9 mg/L Fe 3+. The experimental data indicated that at lower iron dosages and pH (<∼8 mg Fe/L and pH 6.3 and 7.3) negatively charged MS2 viruses first adsorbed onto the positively charged iron hydroxide floc particles before being removed by MF. At higher iron dosages and pH (>∼9 mg Fe/L and pH 8.3), virus removal was attributed predominantly to enmeshment and subsequent removal by MF. Additionally, the experimental data showed no obvious influence of ionic strength in the natural water range of 10 −7–10 −2 M on MS2 virus removal by EC-MF. Finally, EC pretreatment significantly outperformed chemical coagulation pretreatment for virus removal. The proposed mechanism for this improved performance by EC is that locally higher iron and virus concentrations and locally lower pH near the anode improved MS2 enmeshment by iron flocs as well as adsorption of MS2 viruses onto the iron floc particles.