11 - Resource recovery from dye wastewaters using nanofiltration systems

Abstract

Textile wet processing industry involves the use of synthetic dyes, salts, and other chemical auxiliaries with an enormous amount of water and energy to manufacture a colored cloth. During the coloration process of a textile, all the colors are not absorbed by the cloth, and some percentage of colored wastewater is ejected out as effluent into the environment. These wastewaters affect the photosynthesis of plants and aquatic life and are also lethal to human beings. Conventional wastewater treatment methods are effective in the treatment of the dye wastewater, but cannot recover the resources such as dyes and salts from dye wastewater. Membrane technology can offer a solution to resource recovery. Nanofiltration (NF) is one of the pressure-driven membrane processes employed for recovering the resources from the dye wastewater. NF membranes have a pore size in the nanorange which falls in between microfiltration and ultrafiltration membranes. Due to the nanopore size with a negative charge surface, NF membranes can easily recover dyes and salts effectively. NF membranes are highly advantageous because of high selectivity and operate under less pressure as compared to expensive reverse osmosis membranes used for desalination. This chapter provides an overview about textile wet processing and membrane technology with emphasis on NF systems, mechanisms, fabrication methods, configuration, recent studies, challenges and possible solutions, and economical aspects of NF membranes for recovering the resources from the dye wastewater.