title: Comparative analysis of tropaeolin adsorption onto raw and acid-treated kaolinite: optimization by Response Surface Methodology.
abstract: The comparative adsorption of Tropaeolin (TP) onto raw kaolinite (RK) and kaolinite submitted to acid treatment (AK) was studied. RK and AK were characterized by zeta potential and energy dispersive X-ray spectroscopy (EDS). The adsorption was investigated using Composite Central Design (CCD) and the parameters evaluated were initial TP solution concentration, quantity of adsorbent and the pH of the solution. The optimized parameters were: initial TP solution concentration of 75 mg L(-1), pH 4 and 0.12 g adsorbent. Kinetic data were evaluated by pseudo-first order, pseudo-second order and Avrami models. The equilibrium adsorption was analyzed by Langmuir, Freundlich and Sips isotherms. The kinetic data were best fitted to the pseudo-second order model. The Sips isotherm model gives the better correlation to predict the adsorption equilibrium. The maximum adsorption capacities were 18.3 mg g(-1) and 23.2 mg g(-1) for RK and AK, respectively. The calculated thermodynamic parameters showed that the process was spontaneous, endothermic and involving the disorganization of the adsorption system for both adsorbents. The desorption step showed that the AK sample was more suitable as an adsorbent.
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: priscila.ferreirasa@yahoo.com.br.
authors.forename: Priscila F
authors.initials: PF
authors.lastname: de Sales
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: zuy@dqi.ufla.br.
authors.forename: Zuy M
authors.initials: ZM
authors.lastname: Magriotis
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: marcoalsrossi@yahoo.com.
authors.forename: Marco A L S
authors.initials: MA
authors.lastname: Rossi
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: ricardoflar@hotmail.com.
authors.forename: Ricardo F
authors.initials: RF
authors.lastname: Resende
authors.affiliation: Departamento de Ciência dos Alimentos, Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: cleitonnunes@dca.ufla.br.
authors.forename: Cleiton A
authors.initials: CA
authors.lastname: Nunes
mesh_terms: D000143:Acids / Q000737:chemistry; D000327:Adsorption; D001391:Azo Compounds / Q000737:chemistry*; D001557:Benzenesulfonates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000143:Acids; D001391:Azo Compounds; D001557:Benzenesulfonates; D014874:Water Pollutants, Chemical; D007616:Kaolin; C014722:2-naphthol orange
keywords: Acid treatment; Adsorption; Kaolinite; Response Surface Methodology; Tropaeolin