Electrochemical arsenic remediation for rural Bangladesh

Abstract

Professor Ashok Gadgil, Co-Chair Professor Robert Jacobsen, Co-Chair Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation (ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis.In this work, ECAR was shown to effectively reduce 550 -580 µg/L arsenic (including both As [III] and As[V] in a 1:1 ratio) to below the WHO recommended maximum limit of 10 µg/L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic 2 removal capacity, the pattern was: 0.02 mA/cm 2 > 0.07 mA/cm 2 > 0.30 -1.1 mA/cm 2 > 5.0 -100 mA/cm 2 . Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA/cm 2 ) and ruled out oxygen evolution as the cause of decreasing removal capacity with current density. Simple settling and decantation required approximately 3 days to achieve arsenic removal comparable to filtration with a 0.1 µm membrane.X-ray Absorption Spectroscopy (XAS) showed that (1) there is no significant difference in the arsenic removal mechanism of ECAR during operation at different current densities and (2) the arsenic removal mechanism in ECAR is consistent with arsenate adsorption onto a homogenous Fe(III)oxyhydroxide similar in structure to 2-line ferrihydrite.ECAR effectively reduced high arsenic concentrations (100 -500 µg/L) in real Bangladesh tube well water collected from three regions to below the WHO limit of 10 µg/L. Prototype fabrication and field testing are currently underway.

Modeling As(III) Oxidation and Removal with Iron Electrocoagulation in Groundwater

“…6,7 EC systems are easy to operate and maintain, produce less waste than other coagulation methods, 8 and, perhaps most important to sustainable operation in rural areas, can be implemented and operated with only relatively low levels of technical skill and small inputs of locally available materials. 9,10 EC is based on the production of Fe(II) 7 through the electrolytic dissolution of an Fe(0) anode (eq 1). The reaction occurring at the cathode is frequently cited as H + reduction to H 2 gas 7,11,12 (eq 2), though we note that detailed electrochemical studies were beyond the scope of this work (refer to eq 1 and 2 for electrochemical equations).…”

“…Among the typical iron-based techniques used to remediate arsenic-contaminated water, electrocoagulation (EC) using Fe(0) electrodes has the potential to be one of the most efficient and cost-effective. , EC systems are easy to operate and maintain, produce less waste than other coagulation methods, and, perhaps most important to sustainable operation in rural areas, can be implemented and operated with only relatively low levels of technical skill and small inputs of locally available materials. , EC is based on the production of Fe(II) through the electrolytic dissolution of an Fe(0) anode (eq ). The reaction occurring at the cathode is frequently cited as H + reduction to H 2 gas ,, (eq ), though we note that detailed electrochemical studies were beyond the scope of this work (refer to eq and for electrochemical equations). Fe ( 0 ) → Fe ( II ) + 2 e − 2 normalH + + 2 e − → normalH 2 ( g ) The generated Fe(II) is rapidly oxidized by dissolved oxygen (DO) in aerated solutions leading to the formation of reactive hydrous ferric oxide (HFO) precipitates with a high arsenic sorption affinity .…”

Arsenic removal from groundwater using iron electrocoagulation: Effect of charge dosage rate

“…[10][11][12][13][14] In EC using iron electrodes, electrolytic oxidation of a sacrificial iron anode produces hydrous ferric oxide (HFO; also …”

Removing Arsenic from Synthetic Groundwater with Iron Electrocoagulation: An Fe and As K-Edge EXAFS Study

“…Despite much research during the past decade, the need for a sustainable solution to the arsenic crisis still exists. Electrocoagulation (EC) using Fe(0) electrodes is a promising arsenic removal strategy for Bangladesh because it is effective and low cost, produces minimal waste, and is easy to maintain and operate with locally available materials. − …”