title: Equilibrium adsorption of caffeic, chlorogenic and rosmarinic acids on cationic cross-linked starch with quaternary ammonium groups.
abstract: In the present study, the equilibrium adsorption of caffeic acid (CA) and its derivatives, namely, chlorogenic (CGA) and rosmarinic (RA) acids on cationic cross-linked starch (CCS) with degree of substitution of quaternary ammonium groups of 0.42 have been investigated in relation to the structure and acidity of phenolic acids. The Langmuir, Freundlich and Dubinin-Radushkevich adsorption models have been used to describe the equilibrium adsorption of CA, CGA and RA from their initial solutions and solutions having the equimolar amount of NaOH at different temperatures. In the case of adsorption from the initial solutions of acids the values of adsorption parameters were closely related to the dissociation constants of investigated acids. According to the increasing effectiveness of adsorption, phenolic acids could be arranged in the following order: CA<CGA<RA, i.e. in the range contrary to increasing value of pKa. At temperature of 30°C the maximum Langmuir sorption capacity was 0.76, 1.11 and 2.68mmol/g for CA, CGA and RA, respectively. The addition of equimolar amounts of NaOH to the acids solutions changed their sorption properties which became mostly related to the acids structure.
authors.affiliation: Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu rd. 19, LT-50254 Kaunas, Lithuania. Electronic address: deimante.simanaviciute@ktu.edu.
authors.forename: Deimante
authors.initials: D
authors.lastname: Simanaviciute
authors.affiliation: Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu rd. 19, LT-50254 Kaunas, Lithuania.
authors.forename: Rima
authors.initials: R
authors.lastname: Klimaviciute
authors.affiliation: Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu rd. 19, LT-50254 Kaunas, Lithuania.
authors.forename: Ramune
authors.initials: R
authors.lastname: Rutkaite
mesh_terms: D000327:Adsorption; D002109:Caffeic Acids / Q000737:chemistry*; D002726:Chlorogenic Acid / Q000737:chemistry*; D002934:Cinnamates / Q000737:chemistry*; D053630:Depsides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry; D011198:Solanum tuberosum / Q000737:chemistry; D013213:Starch / Q000737:chemistry*; D013696:Temperature; D000097123:Rosmarinic Acid
chemical_list: D002109:Caffeic Acids; D002726:Chlorogenic Acid; D002934:Cinnamates; D053630:Depsides; D000644:Quaternary Ammonium Compounds; D012972:Sodium Hydroxide; D013213:Starch; D000097123:Rosmarinic Acid; C040048:caffeic acid
keywords: Caffeic acid; Cationic cross-linked starch; Chlorogenic acid; Equilibrium adsorption; Rosmarinic acid