Capillary membranes for separation of dye particles

Abstract

The study aimed at investigating the suitability of capillary modules to the decolorization of both synthetic and actual dye solutions by ultrafiltration. The process involved capillary membranes made of polysulfone and modified polysulfone. Membrane modules (UFTA PS10; UFTA PS30, and UFTA PSA50) of various molecular cut-off were applied. Comparable studies including the effect of hydraulic conditions existing in the system on membrane performance were reported. Transport and separation properties of the membranes in the presence of model dye solutions were investigated at three pressure values (0.05; 0.1, and 0.15 MPa), the linear velocity in the modules being varied for each of them (0.5; 1.0, and 1.5 m/s). Three organic dyes (Direct Black Meta, Helion Grey and Methyl Orange) were used in the experiments. The study on actual textile effluents (exhausted dye and rinsing baths) were carried out for 50 h at a pressure of 0.1 MPa and a linear velocity of 1.0 m/s. The results showed that increasing the linear velocity generally improves the permeability and selectivity of the membranes. This relationship becomes particularly pronounced at increasing molecular weight and for the UFTA PS10 module. It has been found that at an optimum velocity of feed flow (1.0 m/s) the retention coefficient for organic dyes of molecular weight higher than 780 exceeds 92–99% for all tested modules. In the presence of actual textile effluents the removal efficiency of TOC and colour amounted to 42–65% and 70–98%, respectively, and the permeability remained on a constant level (0.5–0.65 m 3/m 2/d for the UFTA PS10 module).