Adsorption of free chlorine on tetravalent lead corrosion product (PbO 2)
Journal
Environmental Engineering Science
Journal Volume
29
Journal Issue
1
Pages
52-58
Date Issued
2012
Author(s)
Abstract
Abstract Lead dioxide (PbO 2 ) is a new form of lead corrosion product discovered in the drinking water distribution systems. It is formed via the chlorination of lead-containing plumbing materials. In this study, we investigated the adsorption of free chlorine (HOCl/OCl − ) on PbO 2 to explore the loss of free chlorine in the bulk solution and the reactivity of adsorbed free chlorine in the presence of PbO 2 . Our results indicated that adsorption reached equilibrium in approximately 6 h and ionic strength did not significantly affect adsorption. Langmuir adsorption isotherm provided good fittings of the experimental data. Maximum adsorption capacity of PbO 2 was dependent on the solution pH value, with the maximum occurring at pH 8, which can be explained by electrostatic interactions between free chlorine and PbO 2 surfaces. Both carbonate and phosphate buffers inhibited free chlorine adsorption, and phosphate was a stronger inhibitor. Adsorbed free chlorine was found to maintain its oxidation ability. Our results indicated that the presence of PbO 2 may induce a loss of free chlorine in the bulk solution because of adsorption. Nevertheless, adsorbed free chlorine remains active and may exhibit disinfection capability. This is the first study to show that free chlorine can act as an “adsorbate” in the distribution system and this reaction should be considered in the redox transformation of corrosion products.
SDGs
Type
journal article