title: Kinetics and isotherm analysis of 2,4-dichlorophenoxyl acetic acid adsorption onto soil components under oxic and anoxic conditions.
abstract: 2,4-dichlorophenoxyl acetic acid (2,4-D, pKa = 2.8) is used extensively as a herbicide in agricultural practices. Its sorption behavior on both untreated and soils treated to significantly remove specific components (organic and iron and manganese [Fe-Mn] oxides and hydroxides phases) was investigated under oxic and anoxic conditions. The chemical and structural heterogeneity of the soil components were characterized by elemental analysis and X-ray diffraction (XRD). The coexistence of the various components seems to either mask sorption sites on the untreated soil surfaces or inhibit interlayer diffusion of 2,4-D. All sorption data conform to the Freundlich description and a pseudo-second-order kinetic model. There was a strong positive correlation between sorption capacity K(d), and surface area (r(2) ≤ 0.704), but a negative correlation was uncovered with both pH and organic carbon (r(2) ≤ -0.860). The results indicate that 2,4-D is preferably sorbed under oxic rather than anoxic conditions and it is greater on soils containing a high Fe content. There was incomplete 2,4-D sorption reversibility, with desorption occurring more rapidly under anoxic conditions. The study suggests that stimulation of Fe III reduction could be used for the bioremediation of a 2,4-D-contaminated site.
authors.affiliation: a Department of Chemical Sciences , Adekunle Ajasin University , Akungba-Akoko , Ondo-State , Nigeria.
authors.forename: Isaac A
authors.initials: IA
authors.lastname: Ololade
authors.forename: Folasade
authors.initials: F
authors.lastname: Alomaja
authors.forename: Nurudeen A
authors.initials: NA
authors.lastname: Oladoja
authors.forename: Oluwaranti O
authors.initials: OO
authors.lastname: Ololade
authors.forename: Femi F
authors.initials: FF
authors.lastname: Oloye
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D006540:Herbicides; D017895:Manganese Compounds; D010087:Oxides; D012987:Soil; D012989:Soil Pollutants; C000499:ferric oxide; D015084:2,4-Dichlorophenoxyacetic Acid; C027424:manganese oxide
keywords: 2; 4-dichlorophenoxyl acetic acid; desorption; herbicide; organic matter; soil components; sorption