Desenvolvimento de um método de extração ambientalmente seguro para a remoção de corantes têxteis empregando sistemas aquosos bifásicos

Abstract

This work presents a simple, efficient and environmentally safe extraction method to removal the textile dyes Malachite Green (VM), Methylene Blue (AM) and Reactive Red 195 (VR), exploiting Aqueous Two Phase Systems (ATPS). News ATPS phase diagrams were determined, which are formed by PEO 4000 + sodium tartrate + water and PEO 6000 + sodium tartrate + water, at 25 ºC. The polymer PEO6000 showed a higher capacity than PEO 4000 to induce the phase separation process, due its higher molar mass, providing a larger biphasic region in the diagram. In the optimization step of the methodology, the influence of the following experimental parameters on the partition coefficient (K) and residual percentage (%R) of the dyes was evaluated: tie line length (TLL) of the system; pH of the medium; type of ATPS-forming electrolyte and type ATPS-forming polymer. For VM, the best removal conditions (K = 4.10 x 104 and %R = 0.0069 %) were obtained at ATPS PEO 1500 + Na2C4H4O6, TLL = 50.21 % (w/w), pH = 6.00. For AM, the maximum extraction (K = 559.9 and %R = 0.258 %) were achieved at ATPS PEO 400 + Na2SO4, TLL = 50.31 % (w/w), pH = 1.00. Finally for VR, the method presented the best results (K = 3.75 x 104 and %R = 0.237 %) at ATPS PEO 400 + Na2SO4, TLL = 50.31 % (w/w), pH = 6.00. The method was applied to the recovery of the dyes from a textile effluent sample and quantitative removals were obtained for all analytes. The values of K were 1.17 x 104, 724.1 and 3.98 x 104, and the %R were 0.0038 %, 0.154 % e 0.023 %, for VM, AM and VR, respectively. Moreover, the ATPS methodology presented high rate of color removal (%D) of the textile effluent, which ranged from 96.5 to 97.95 %, showing an excellent potential of the ATPS technique to be applied to treatment of this type of waste.