Removal of Cr(VI) from Cr-contaminated groundwater through electrochemical addition of Fe(II).
The conventional chemical reduction-precipitation technique in the removal of Cr(VI) from contaminated groundwater involves a two-step process whereby Cr(VI) is first reduced to Cr(III) at an acidic pH by a reducing agent and in a subsequent step, Cr(III) is precipitated as insoluble hydroxide at an alkaline pH. In a variation of this method, Fe(II) is added electrochemically to the Cr(VI) containing water. From a pure iron electrode, Fe(2+) ions are released into the solution and bring forth the reduction of Cr(VI). At the cathode, H(2)O is reduced whereby the OH(-) ions entering the solution keep the pH of the solution in the alkaline range. This latter fact greatly facilitates simultaneous reduction of Cr(VI) to Cr(III) and co-precipitation of hydroxides of trivalent Cr and Fe. On the basis of a set of experimental data, it is shown that this process is both thermodynamically and kinetically efficient, meaning, with the electrochemical method, rapid and nearly complete removal of Cr(VI) from a groundwater source with both high and low levels of Cr-contamination can be achieved. These factors make the electrochemical process superior to the conventional chemical process in remediation of Cr-contaminated groundwater.
Mukhopadhyay
Biswajit
B
Ecology and Environment, Inc. 1412 Main Street, Dallas, TX 75202, USA. bmukhopadhyay@walterpmoore.com
Sundquist
Jon
J
Schmitz
Rodney J
RJ
D002413:Cations, Divalent; D002857:Chromium / Q000302:isolation & purification*; D004563:Electrochemistry; D004566:Electrodes; D005843:Geography; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014881:Water Supply
D002413:Cations, Divalent; D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D007501:Iron