Desenvolvimento de metodologia analítica ambientalmente segura para determinação de cromo em amostras de interesse ambiental por extração em sistemas bifásicos baseados em água

• Ano de defesa: 2016
• Autor(a) principal: Betânia Aparecida de Araujo Faria
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Extração; Cromo; Sistemas Aquosos Bifásicos; Curtume; Determinação; Química analítica; Curtumes; Química ambiental; Espectroscopia de chama; Extração (Quimica)
• Link de acesso: http://hdl.handle.net/1843/SFSA-ADQTUC

A new simple and environmentally safe method has been developed for the extraction and determination of chromium using the hydrophobic extractor 1.5-diphenylcarbazide (DFC) in Aqueous Two-phase Systems (ATPS) formed by triblock copolymer (L35 or L64), electrolyte (Na2SO4, C6H5Na3O7, C4H4Na2O6 or MgSO4), and H2O. The influence of the following parameters on the extraction behavior of chromium were evaluated: concentration of the extracting agent, pH of the medium, type of ATPS-forming copolymer; type of ATPS-forming electrolyte and ratio between top (TP) and bottom (BP) phases of the system (mTP/mBP). Cr(VI) was quantitatively extracted to the top phase (E% = 99.3%) using the ATPS consisting of L35 + Na2SO4 at pH = 1.00, molar ratio DFC/Cr(VI) = 130 and mass ratio (mTP/mBP) = 1. Under these conditions, the ions Cr(III) concentrate preferentially in the electrolyte enriched phase (% E 0%), which allows chromium speciation using ATPS. The optimized method presented the following analytical features: linear range of 0.38 to 20 mg kg-1 (R2 = 0.9950); precision ranges from 3,40 to 5,98%; recovery rates range from 88,7 to 125%; limit of detection (LD) and limit of quantification (LQ) equal to 0.10 mg kg-1 and 0.38 mg kg-1, respectively, which are according to Brazilian legislation for the released of industrial effluents. Besides, excellent agreement between the proposed method and the Flame Atomic Absorption Spectrometry (FAAS) technique was observed for the analysis of chromium in a real sample of tannery effluent.