title: Kinetics and equilibrium parameters of Hg(II) adsorption on silica-dithizone.
abstract: Sílica-dithizone (Sil-dtz) was synthesized and used to adsorb Hg(II) in solution at pH 6.0. Increasing the temperature accelerates the mass transfer of Hg(II) to the silica surface. The kinetic data were evaluated using the traditional pseudo-first-order Lagergren equation and an alternative Avrami kinetic equation. From the latter equation, two regions presenting distinct kinetic parameters were found, at 25 and 35 degrees C, and the use of the parameter n was also related to the determination of distinct kinetic orders. Variations of the adsorption kinetic rate in relation to the time and the temperature were also calculated and are discussed. The adsorption isotherms data were well fitted to the Freundlich model. Interestingly, good adsorption data correlation of the Langmuir model and experimental values was observed only at 45 and 50 degrees C, suggesting, for this temperature range, the formation of complexes with the proportion Hg:dithizone 1:1 on the silica surface.
authors.affiliation: Laboratory of Materials and Calorimetry, Departamento de Química/CCET, Universidade Federal de Sergipe, 49000-000 São Cristovão, Sergipe, Brazil. cestari@ufs.br
authors.forename: Antonio R
authors.initials: AR
authors.lastname: Cestari
authors.forename: Eunice F S
authors.initials: EF
authors.lastname: Vieira
authors.forename: Elaine C N
authors.initials: EC
authors.lastname: Lopes
authors.forename: Roberto G
authors.initials: RG
authors.lastname: da Silva
mesh_terms: D000327:Adsorption; D004230:Dithizone / Q000138:chemical synthesis / Q000737:chemistry*; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D015394:Molecular Structure; D012822:Silicon Dioxide / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D004230:Dithizone; D012822:Silicon Dioxide; D008628:Mercury