title: Slow desorption behavior of one highly resistant aromatic amine in Lake Macatawa, Michigan, USA, sediment.
abstract: The desorption behavior of benzidine from Lake Macatawa (Holland, MI, USA) sediment was investigated in this study using batch solvent extraction method. Seven solvents were tested as the extracting reagents: Deionized water (DI), calcium chloride in DI (CaCl2), sodium hydroxide in DI (NaOH), acetonitrile (ACN), a mixture of acetonitrile and ammonium acetate in DI (ACN-NH4OAc), methanol (MeOH), and hydrochloric acid in DI (HCl). These solvents are proposed to react with sediment-associated benzidine by different mechanisms (e.g., cation exchange, hydrophobic partitioning, and covalent binding). Three sets of sorption isotherm experiments were conducted separately in these seven solvents with a 7-d, three-week, and two-month contact time. The results demonstrated nonlinear isotherms with Freundlich 1/n values varying from 0.25 to 0.52. The desorption behavior of benzidine in the solvents was evaluated after the sorption of benzidine onto the sediment with same contact times of 7 d, three weeks, and two months. A two-stage model subsequently was applied to simulate the experimental data. The rapidly desorbing rate constants were on the order of one to two per day for ACN, ACN-NH4OAc, and NaOH solvents, and the slowly desorbing rate constants were on the order of 10(-5) to 10(-4)/d. Sequential desorption experiment demonstrated low total extraction efficiency of less than 40%. Both the observed sorption and desorption phenomena suggested that hysteresis and/or mass-transfer limited diffusion may result in the slow desorption behavior observed in this study.
authors.affiliation: Department of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Shihua
authors.initials: S
authors.lastname: Chen
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Nyman
mesh_terms: D000085:Acetates / Q000737:chemistry; D000097:Acetonitriles / Q000737:chemistry; D000327:Adsorption; D000588:Amines / Q000032:analysis* / Q000737:chemistry; D002122:Calcium Chloride / Q000737:chemistry; D004058:Diffusion; D005618:Fresh Water; D019015:Geologic Sediments / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D000085:Acetates; D000097:Acetonitriles; D000588:Amines; D011084:Polycyclic Aromatic Hydrocarbons; D012997:Solvents; D014874:Water Pollutants, Chemical; D012972:Sodium Hydroxide; D002122:Calcium Chloride; C018824:ammonium acetate; C032159:acetonitrile