PbO2(s, plattnerite) reductive dissolution by aqueous manganous and ferrous ions.
Pb(IV)O2(s, plattnerite) nanoparticle aggregrates in aqueous suspension are readily reduced by Mn2+(aq) and Fe2+(aq) between pH 3.0 and 8.5, yielding pb2+(aq) and adsorbed Pb". Fe2+(aq) oxidation generates Fe(III) (hydr)oxides that impede Pb(IV) reduction, especially at pH > or =5. Under acidic conditions, production of dissolved Fe(III) may also be significant. Mn2+(aq) oxidation generates mixed Mn(III)/Mn(IV) (hydr)oxides that are less of an impediment to Pb(IV) reduction. Adding both Fe2+(aq) and Mn2+(aq) can set in motion a Mn redox cycle that catalyzes PbO2(s) reduction by Fe2+(aq). Reaction with Fe2+(aq) and Mn2+(aq) can affect subsequent reactions with natural organic matter. Hydroquinone was employed as a representative organic reductant. Both hydroquinone and its two-electron oxidation product p-benzoquinone are readily quantified by HPLC. Adding Fe2+(aq) before hydroquinone greatly diminishes p-benzoquinone production. Adding Mn2+(aq) before hydroquinone has little effect on p-benzoquinone production. Free chlorine residual variations in premise plumbing can setthe stage for the reactions documented here.
Shi
Zhi
Z
Department of Geography and Environmental Engineering, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA. zshi4@jhu.edu
Stone
Alan T
AT
D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006873:Hydroquinones / Q000737:chemistry; D007477:Ions; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D012995:Solubility
D002712:Chlorides; D005290:Ferric Compounds; D006873:Hydroquinones; D007477:Ions; D017895:Manganese Compounds; D010087:Oxides; D007854:Lead; C047365:lead oxide; C025340:manganese chloride; C024555:ferric chloride; C031927:hydroquinone