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Adsorption kinetics, isotherms and desorption studies of Hg(II) from aqueous solution at different temperatures on magnetic sodium alginate-thiourea microbeads

Patiño-Ruiz, D., Bonfante, H., De Ávila, G., Herrera, Adriana
Environmental nanotechnology, monitoring & management 2019 pp. 100243
Fourier transform infrared spectroscopy, adsorption, aqueous solutions, chemical bonding, coprecipitation, desorption, electrostatic interactions, energy-dispersive X-ray analysis, ions, iron, magnetic materials, magnetism, magnetite, mercury, microbeads, models, moieties, nanoparticles, scanning electron microscopy, sodium, sodium alginate, sorption isotherms, temperature, thiols, thiourea
Thiourea and magnetite (Fe3O4) nanoparticles were employed to modify sodium alginate (MAT) microbeads for adsorption of Hg(II) ions from aqueous solution. The Fe3O4 nanoparticles were initially synthesized by a co-precipitation method. Fourier infrared spectroscopy (FTIR) provided representative patterns to determine the presence of hydroxyl, carboxyl, thiol and amine functional groups in the microbead molecular structure. Scanning electron microscopy (SEM) equipped with an EDX systems allowed to obtain morphological information of the MAT microbeads in which was possible to observe the presence of the main elements introduced by the modification with thiol groups and iron ions, and this is in agreement with the FTIR patterns. The saturation magnetization (Ms) of microbeads determined by a vibrating sample magnetometer (VSM) is the typical value for superparamagnetic materials which compared to that of magnetite nanoparticles, was slightly decreased by the low amount of magnetic materials within the sodium alginate structure. Adsorption kinetics showed the highest Hg(II) recovery of about 98% in the first 20 min and the equilibrium in the next 100 min, which decrease with the increasing of temperature. Pseudo-first order was the model that better fitted to the adsorption experimental data with a value about 2.6 mg/g, meanwhile, adsorption isotherm were better described through the Langmuir model, suggesting that the Hg(II) ions adsorption was mainly given by the electrostatic interaction and chemical bonding with the functional groups, as well as the formation of a saturated layer onto the microbead surface occupying all the available sites.