title: Binding of Pb(II) in the system humic acid/goethite at acidic pH.
abstract: The study of Pb(II) binding to the system humic acid/goethite in acidic medium is reported in the present paper. From a macroscopic point of view, we have constructed the experimental sorption isotherms (using atomic absorption spectroscopy) and compared them with the prediction of the additivity rule. It is found that this system presents positive deviations, that is, the amount sorbed is about an order of magnitude higher than predicted. Apart from this, microscopic and structural aspects have also been studied using in situ and ex situ infrared spectroscopy. These results suggest that the presence of Pb(II) increases the amount of humic acid bound to the oxide. It is proposed that proton displacement due to the interaction between humic substances and the oxide, along with the formation of ternary complexes with the Pb(II) cation bridging the oxide and the humic substances (Type A complexes), cause the deviation from additivity.
authors.affiliation: INQUIMAE, DQIAQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria Pabellón II, 1428 Buenos Aires, Argentina.
authors.forename: Silvia
authors.initials: S
authors.lastname: Orsetti
authors.forename: María de las Mercedes
authors.initials: Mde L
authors.lastname: Quiroga
authors.forename: Estela María
authors.initials: EM
authors.lastname: Andrade
mesh_terms: D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008903:Minerals; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D006812:Humic Substances; D058085:Iron Compounds; D008903:Minerals; C094886:goethite; D007854:Lead