Remoção de Cr(VI) de soluções aquosas por adsorção em hidróxidos duplos lamelares e em quitosana quimicamente modificada e suas aplicações em efluentes de galvanoplastia

• Autor(a) principal: Toledo, Thiago Vinícius
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/229
• topic: Adsorção; Troca iônica; Biomoléculas - Purificação; Cromo (VI); Hidróxidos duplos lamelares; Adsorption; Ion exchange; Biomolecules - Purification; Chromium (VI); Layered double hydroxides; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

In this work, hydrotalcite, a layered double hydroxide, had its ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe 500. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. Removal of chromium(VI) from aqueous solutions using HT-Fe 500 was achieved using batch adsorption experiments. The adsorption capacity, calculated with the Langmuir-Freundlich model showed to be dependent on temperature, reaching values of 25.93 and 48.31 mg g-1, respectively, for temperature values of 25 and 30 ° Results C. were satisfactory when employing the adsorbent for removal of Cr(VI) from an effluent generated by electroplating processes. Adsorption of Cr(VI) by layered double hydroxides (LDHs) containing the metal cations Mg(II)/Al(III), Mg(II)/Fe(III), Co(II)/Al(III), Co(II)/Fe(III), Ni(II)/Al(III), Ni(II)/Fe(III), Zn(II)/Al(III) and Zn(II)/Fe(III) also was invested in this study. For these LDHs the interlayer anion was varied (CO32- and Cl-). Materials containing CO32- were submitted to calcination for evaluating the increase in adsorption efficiency by the memory effect. After preliminary study of adsorption of Cr (VI) by the synthesized materials, the group of HDLs containing chloride as the interlayer anion showed the highest adsorption efficiency. Thus, the Ni-Al LDH-Cl, Mg-Al-Cl and Co-Al- Cl were selected for further studies. For these HDLs, the experimental data of the adsorption of Cr (VI) were adjusted to the kinetic model of pseudo-second order, indicating chemisorption. At equilibrium, the experimental data fitted the Langmuir model, proving that the adsorption occurs in monolayer. The adsorption capacities provided by this model (25 to 45 ° C) for three HDLs were between 39.49 and 67.39 mg g-1. The thermodynamic parameters were determined and indicated spontaneous and exothermic chemical nature of adsorption. In this study, the adsorption of Cr(VI) by magnetic chitosan particles modified with ethylenediamine and Fe3+ (MCP-EDA-Fe(III)) also was studied by the batch and fixed bed column methods. According to the Langmuir model, the maximum adsorption capacity was between 78.43 and 59.07 mg g -1. The thermodynamic parameters were determined (-14.22 < &#916;G° < -12.50 kJ mol-1, &#916;H° = - 39.85 kJ mol-1 and &#916;S° = - 0.086 kJ mol-1K-1) indicated the spontaneous, exothermic and chemical nature of adsorption. In study of the fixed bed column, the maximum adsorption capacities of the columns were greater than 52.27 mg g-1. The results were satisfactory when it was used adsorbents for the removal of Cr (VI) effluent electroplating process.