Removal of textile dye from aqueous solutions by nanofiltration process

The feasibility of employing nanofiltration (NF) in the decolorization of ionic (direct blue 86) and nonionic (disperse blue 56) dye aqueous solutions was investigated. The effects of feed concentration (60- 180 mg/l), pressure (0.5- 1.1 MPa) and pH (6- 10) were studied. Experiments were performed in a laboratory- scale set up by using a TFC commercial spiral wound polyamide nanofilter. The response surface method (RSM) was adopted in the experimental design to obtain the impact of the mentioned factors. It was found that increasing the dye concentration and pH enhances the removal efficiency up to 96 and 92% for direct and disperse dye, respectively. With an increase in pressure from 0.5 to 0.8 MPa the removal percentage increases and then, from 0.8 to 1.1 MPa decreases. The maximum dye removal efficiencies which were predicted at the optimum conditions by Design Expert software were 98 and 94% for direct blue 86 and disperse blue 56, respectively.