A method for dye extraction using an aqueous two-phase system : effect of co-occurrence of contaminants in textile industry wastewater.

Abstract

This paper reports a green and efficient procedure for extraction of the dyes Malachite Green (MG), Methylene Blue (MB), and Reactive Red 195 (RR) using an aqueous two-phase system (ATPS). An ATPS consists mainly of water, together with polymer and salt, and does not employ any organic solvent. The extraction efficiency was evaluated by means of the partition coefficients (K) and residual percentages (% R) of the dyes, under different experimental conditions, varying the tie-line length (TLL) of the system, the pH, the type of ATPS-forming electrolyte, and the type of ATPS-forming polymer. For MG, the best removal (K ¼ 4.10 104, %R ¼ 0.0069%) was obtained with the ATPS: PEO 1500 þ Na2C4H4O6 (TLL ¼ 50.21% (w/w), pH ¼ 6.00). For MB, the maximum extraction (K ¼ 559.9, %R ¼ 0.258%) was achieved with the ATPS: PEO 400 þ Na2SO4 (TLL ¼ 50.31% (w/w), pH ¼ 1.00). Finally for RR, the method that presented the best results (K ¼ 3.75 104, %R ¼ 0.237%) was the ATPS: PEO 400 þ Na2SO4 (TLL ¼ 50.31% (w/w), pH ¼ 6.00). The method was applied to the recovery of these dyes from a textile effluent sample, resulting in values of K of 1.17 104, 724.1, and 3.98 104 for MG, MB, and RR, respectively, while the corresponding %R values were 0.0038, 0.154, and 0.023%, respectively. In addition, the ATPS methodology provided a high degree of color removal (96.5e97.95%) from the textile effluent.