Authors: Sinha, Alok; Bose, Purnendu

Source: Water, Air, and Soil Pollution, Volume 172, Numbers 1-4, May 2006 , pp. 375-390(16)

Publisher: Springer

Abstract:

Aqueous 2-chloronapthalene was contacted with cast iron in batch systems, resulting in an initial rapid increase in the sorbed 2-chloronapthalene concentration (C _s ) followed by a slow decline, and an initial rapid decline in the aqueous 2-chloronapthalene concentration (C _a ) followed by a slower decline. The initial rapid partitioning of 2-chloronapthalene to the solid phase was due to its adsorption on elemental carbon present on the cast iron surface, while the residual aqueous phase 2-chloronapthalene underwent reductive dehalogenation at a slower rate through interaction with the metallic iron surface. The overall rate of change of total 2-chloronapthalene concentration (C _T = C _s +C _a ) with time, i.e., (d/C _T }{{d}T}) could be described by the expression,−k ₁ ⋅M⋅ (C _a ) ⁿ , where M is the concentration of cast iron. The values of k ₁ and n were determined to be 1.576 × 10⁻⁵ hr⁻¹ g⁻¹ iron L and 1.945 respectively. Equilibrium partitioning of 2-chloronapthalene between solid and aqueous phases could be described by a Freundlich isotherm, C _s = k⋅ [C _a ] ^M , where M and K were determined to be 0.55 and 4.92 × 10⁻³ L g⁻¹. Considering K to be the ratio of the adsorption (k ₂) and desorption (k ₃) rate constants, expressions were developed for describing the evolution of C _s and C _a with time. Putting k ₃ = 1 hr⁻¹ in these expressions resulted in adequate model fit to the experimental data. Napthalene was identified as the major dehalogenation by-product, with greater than 99 percent of the naphthalene produced partitioning to carbon present on the cast iron surface. No competition between 2-chloronapthalene and naphthalene for adsorption on the carbon surface was observed, suggesting non-specific adsorption of these compounds restricted only by the physical size of the molecules and the available carbon surface area.

Keywords: 2-chloronapthalene; cast iron; napthalene; dehalogenation

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11270-006-9102-5

Affiliations: 1: Email: pbose@iitk.ac.in

Publication date: 2006-05-01

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