title: A transport model with coupled ternary exchange and chemisorption retention for hydrazinium cations.
abstract: A numerical model was developed to describe the fate and transport of hydrazinium (N2H5+) and competing Ca2+ and H+ cations applied in acidic solutions to columns of Ca2+/H+-saturated sandy soil during steady saturated flow conditions. Instantaneous ternary H+-Ca2+-N2H5+ cation exchange using the Gaines-Thomas approach was combined with second-order, irreversible, kinetic chemisorption of exchange-phase N2H5+ ions as major retention mechanisms for N2H5+. Exchange-mediated chemisorption is assumed to occur as chemical binding of N2H5+ ions located on carboxyl-group exchange sites to nearby carbonyl groups, consequently decreasing the effective soil cation exchange capacity (CEC). Comparison of simulated and observed breakthrough curves (BTCs) for concentrations of N2H5+ and Ca2+ ions in column effluent was used in model evaluation. The cation transport model with cation exchange coupled with exchange-mediated chemisorption provided a valid first approximation for N2H5+ transport.
authors.affiliation: Soil & Water Science, Univ. of Florida, Gainesville 32611-0290, USA. rsm@gnv.ifas.ufl.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Mansell
authors.forename: S A
authors.initials: SA
authors.lastname: Bloom
authors.forename: W C
authors.initials: WC
authors.lastname: Downs
mesh_terms: D000042:Absorption; D002118:Calcium / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007474:Ion Exchange; D007700:Kinetics; D008962:Models, Theoretical; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements
chemical_list: D006834:Hydrazines; D012989:Soil Pollutants; C007969:hydrazinium; D006859:Hydrogen; D002118:Calcium