title: Influence of mineral characteristics on the retention of low molecular weight organic compounds: a batch sorption-desorption and ATR-FTIR study.
abstract: Batch experiments were conducted to evaluate the sorption-desorption behaviour of (14)C-labelled carboxylic acids (citric and oxalic) and amino acids (glutamic, alanine, phenylalanine and lysine) on pure minerals (kaolinite, illite, montmorillonite, ferrihydrite and goethite). The sorption experiments were complemented by ATR-FTIR spectroscopy to gain possible mechanistic insight into the organic acids-mineral interactions. In terms of charge, the organic solutes ranged from strongly negative (i.e., citric) to positively charged solutes (i.e., lysine); similarly the mineral phases also ranged from positively to negatively charged surfaces. In general, sorption of anionic carboxylic and glutamic acids was higher compared to the other compounds (except lysine). Cationic lysine showed a stronger affinity to permanently charged phyllosilicates than Fe oxides. The sorption of alanine and phenylalanine was consistently low for all minerals, with relatively higher sorption and lower desorption of phenylalanine than alanine. Overall, the role of carboxylic functional groups for the sorption and retention of these carboxylic and amino acids on Fe oxides (and kaolinite) and of amino group on 2:1 phyllosilicates was noticeable. Mineral properties (surface chemistry, specific surface area), chemistry of the organic compounds (pKa value, functional groups) and the equilibrium pH of the system together controlled the differences in sorption-desorption patterns. The results of this study aid to understand the effects of mineralogical and chemical factors that affect naturally occurring low molecular weight organic compounds sorption under field conditions.
authors.affiliation: Department of Environmental Sciences, Faculty of Agriculture and Environment, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: sabina.yeasmin@sydney.edu.au.
authors.forename: Sabina
authors.initials: S
authors.lastname: Yeasmin
authors.affiliation: Department of Environmental Sciences, Faculty of Agriculture and Environment, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Balwant
authors.initials: B
authors.lastname: Singh
authors.affiliation: CSIRO Land and Water/Sustainable Agriculture Flagship, PMB 2, Glen Osmond, SA 5064, Australia.
authors.forename: Rai S
authors.initials: RS
authors.lastname: Kookana
authors.affiliation: CSIRO Land and Water/Sustainable Agriculture Flagship, PMB 2, Glen Osmond, SA 5064, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Farrell
authors.affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Sparks
authors.affiliation: Crop, Soil and Environmental Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Cliff T
authors.initials: CT
authors.lastname: Johnston
mesh_terms: D000327:Adsorption; D000596:Amino Acids / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D019815:Oxalic Acid / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000596:Amino Acids; D008903:Minerals; D019343:Citric Acid; D019815:Oxalic Acid
keywords: Amino acids; Carboxylic acids; Organic carbon stabilisation; Organo-mineral interaction; Sorption mechanism; Spectroscopy