engleski

Removal of copper and cobalt ions by fly ash-based geopolymer from solutions-equilibrium study

Fly ash-based geopolymer was used for removal of copper and cobalt ions from aqueous solutions by a batch technique. The experimental data were obtained at constant geopolymer particles size (0.071 – 0.090 mm) for the different initial concentrations (in the range from 3.881 – 39.390 mmol L-1) of copper and cobalt solutions, respectively, and at various temperatures (T = 298, 308 and 318 K). For characterization of synthesized geopolimer, before and after sorption of heavy metals, FTIR, XRD and SEM/EDS analysis were used to confirm the dissolution of geopolymer structure. SEM/EDS analysis also confirmed that sorption process occurred, as well as the fact that Na ions are outgoing ions. Various types of isotherm models, two-parameter isotherms: Langmuir, Freundlich, Jovanovic, and Dubinin-Radushkevich and three-parameter isotherms: Hill, Redlich-Peterson and Sips were fitted to the experimental data obtained. In order to calculate parameters of the isotherms a non-linear regression method was used. According to the results obtained the most appropriate models for describing equilibrium data were Langmuir, Jovanovic, Hill and Redlich-Peterson isotherm models. Thermodynamic parameters indicated endothermic (positive values of ΔH0) and spontaneous nature (negative values of ΔG0) of sorption process.

geopolymer; copper; cobalt; thermodynamics; isotherm models

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