Ferrate(VI) pretreatment of water containing natural organic matter, bromide, and iodide: A potential strategy to control soluble lead release from PbO2(s).

Lead dioxide (PbO2(s)) is a corrosion product of lead-containing plumbing materials in water distribution pipelines. The presence of reductants in water could cause the release of soluble lead (mainly Pb(II)) from PbO2(s). Lead in drinking water is detrimental to public health. This paper presents the first application of ferrate (FeVIO42-, Fe(VI)) to decreasing the generation of soluble lead in water containing PbO2(s) and common reducing constituents (e.g., natural organic matter (NOM), iodide (I-), and bromide (Br-)) at different pH conditions (i.e., 6.0, 7.0, and 8.0). The released soluble lead from PbO2(s) was found to be dominantly controlled by NOM in water, via the redox dissolution of PbO2(s) and the reduction of PbO2(s) by reducing moieties of NOM. The feasibility of both processes increased when pH decreased. The I- and Br- in water played minor roles in generating soluble lead. Fe(VI) reacted with reducing functional groups of NOM, as determined by 13C nuclear magnetic resonance spectroscopy. Water pretreatment with Fe(VI) inhibited the reaction of NOM with PbO2(s) and therefore, caused lower soluble lead concentrations compared to water samples without Fe(VI) treatment. This study indicates that Fe(VI) pretreatment is a potential approach to controlling soluble lead in drinking water.