title: Experimental determination of nonequilibrium transport parameters reflecting the competitive sorption between Cu and Pb in slag-sand column.
abstract: Competitive sorption and resulting nonequilibrium transport of Cu and Pb were investigated using slag as a primary sorbent. A series of estimation models were applied based on the equilibrium, and nonequilibrium sorption respectively, and finally calibrated by incorporating the experimentally determined batch kinetic data. When applied individually, the behavior of metals in slag-sand column were well predicted by both equilibrium and nonequilibrium models in CXTFIT code. However, coexisting Cu and Pb exhibited competition for sorption sites, generating an irregular breakthrough curves such as overshoot (higher concentration in effluent than the feed concentration) of Cu and corresponding earlier peak of Pb followed by gradual re-rising. Although two-site nonequilibrium model further considers coupled hydrochemical process, desorption of the Cu from competition made the model prediction inaccurate. However, the parameter estimation could be improved by incorporating the experimentally determined mass transfer rate, ωexp from batch kinetics. Based on the calibrated model, the fraction of instantaneous retardation, βexp of Pb decreased from 0.41 in the single system to 0.30 in the binary system, indicating the shift from equilibrium to nonequilibrium state, where which of Cu increased from 0.39 to 0.94, representing the shift towards equilibrium. The modified results were also compared with five-step sequential extraction data, confirming that the shift of particular metal fractions from the competition triggered the nonequilibrium transport.
authors.affiliation: Center for Water Resource Cycle, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea; Department of Environmental Engineering Sciences, University of Florida, P.O. Box 116450, Gainesville, FL 32611-6450, USA.
authors.forename: Jaeshik
authors.initials: J
authors.lastname: Chung
authors.affiliation: Samsung C&T, Seoul 137-857, Republic of Korea.
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Civil and Environmental Engineering, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Gwanghun
authors.initials: G
authors.lastname: Lee
authors.affiliation: Department of Civil and Environmental Engineering, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: kpnam@snu.ac.kr.
authors.forename: Kyoungphile
authors.initials: K
authors.lastname: Nam
mesh_terms: D000327:Adsorption; D003300:Copper / Q000737:chemistry*; D007220:Industrial Waste / Q000032:analysis*; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D000072499:Manufacturing and Industrial Facilities; D008962:Models, Theoretical; D012822:Silicon Dioxide / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D012987:Soil; D007854:Lead; D012822:Silicon Dioxide; D003300:Copper
keywords: CXTFIT; Competitive sorption; Damköhler number; Nonequilibrium transport; Overshoot; Sequential extraction