Journal of Colloid and Interface Science, Vol.314, No.2, 552-561, 2007
Interaction of 2-chloronaphthalene with high carbon iron filings (HCIF): Adsorption, dehalogenation and mass transfer limitations
Interaction of 2-chloronaphthalene (2-CN) with high-carbon iron filings (HCIF) was studied in anaerobic batch systems, both under well mixed and poorly-mixed conditions. In well-mixed conditions, partitioning of 2-CN between solid and aqueous phases was fast, resulting in rapid attainment of equilibrium. Equilibrium partitioning could be described by a Freundlich isotherm, C-s = K.[Ca](m), where C-s (mu moles g(-1) iron) and Ca (mu moles L-1) were the solid and aqueous phase 2-CN concentrations, respectively. Isotherm parameters, m and K were determined to be 0.76 and 5.6 x 10(-2) (mu mole g(-1) iron)/(mu mole L-1), respectively. Sorption (k(2)) and desorption (k(3)) rate constants were determined to be 5.60 x 10(-1) h(-1) g(-1) iron L and 10 h(-1), respectively. Reductive dehalogenation of aqueous phase 2-CN occurred concurrently but at a slower rate, and could be described by the expression (dC(T)/dt) = -k(1.) M. (C-a)(N), where C-T (mu moles L-1) was the total 2-CN concentration and M (g iron L-1) the concentration of HCIF. The values of k(1) and N were determined to be 1.09 x 10(-2) h(-1) g(-1) iron L and 1.647, respectively. In poorly mixed conditions, adsorption (k(2)) and desorption (k(3)) rate constants were 3.92 x 10(-5) h(-1) g(-1) iron L and 7 x 10(-4) h(-1), respectively, i.e., several orders of magnitude less than in well-mixed systems. The dehalogenation rate parameters, k(1) and N were determined to be 2.22 x 10(-4) h(-1) g(-1) iron L and 0.986, respectively, suggesting slower dehalogenation. These results highlight how mass-transfer limitations during the interaction between HCIF and 2-CN in poorly mixed systems, such as permeable reactive barriers (PRBs), can potentially impact the dehalogenation process. (c) 2007 Elsevier Inc. All rights reserved.