title: The interaction of an azo compound with a surfactant and ion pair adsorption to solid phases.
abstract: The adsorption of SPADNS (trisodium salt of 2-(p-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid) onto resins XAD 2, XAD 7 and silica gel was studied in the presence and in the absence of the cationic surfactant CTAB (cetyl trimethylammonium bromide). At a ratio of 2.5 CTAB to 1 SPADNS, the surfactant caused a marked increase in SPADNS adsorption. The experimental results for adsorption versus time were applied on the basis of three kinetic models (pseudo-first-order Lagergren, pseudo-second-order, and intraparticle diffusion). The interaction between CTAB and SPADNS was investigated using spectrophotometric, conductometric, and computational techniques. Theoretical results point to the formation of an ion pair between CTAB and SPADNS that influences the solution spectra, in agreement with conductometric and spectrophotometric data.
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adélia, 166, 09210-170 Santo André, Brazil. carolina_arg@bol.com.br
authors.forename: Ana Carolina Ribeiro
authors.initials: AC
authors.lastname: Gomes
authors.forename: Luciene Dias Fernandes
authors.initials: LD
authors.lastname: Cafer
authors.forename: Paula
authors.initials: P
authors.lastname: Homem-de-Mello
authors.forename: Maurício Domingues
authors.initials: MD
authors.lastname: Coutinho-Neto
authors.forename: Ivanise
authors.initials: I
authors.lastname: Gaubeur
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000327:Adsorption; D001391:Azo Compounds / Q000737:chemistry / Q000302:isolation & purification*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D009282:Naphthalenesulfonates / Q000737:chemistry / Q000302:isolation & purification*; D011137:Polystyrenes / Q000737:chemistry*; D058428:Silica Gel / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D001391:Azo Compounds; D002593:Cetrimonium Compounds; D009282:Naphthalenesulfonates; D011137:Polystyrenes; D013501:Surface-Active Agents; C015661:amberlite XAD 7; D058428:Silica Gel; C546208:2-(4-sulphophenyloazo)-1,8-dihydroxy-3,6-napthalenedisulphonic acid; C003771:Amberlite XAD-2 resin; D000077286:Cetrimonium