Development of a treatment method for the removal of basic dyes in reed & coir dyeing industry

Abstract

Handcraft manufacturing using natural fibers is one of the important domestic industries in developing countries including Sri Lanka. Synthetic dyes are currently being used as coloring agents and basic dyes play a vital role in the dyeing process. The effluent with coloring agent is a major pollutant in small scale industries. Even though effective and efficient effluent treatment methods are applied by large-scale factories, small-scale domestic manufacturers are not concerned with effluent treatment in the coloring process, and they discharge industrial effluent of the dyeing process directly to the environment making a threat to the aquatic ecosystems. Therefore, introducing a low-cost small-scale effluent treatment system for the removal of industrial dyes is an essential need to safeguard the fauna in aquatic ecosystems. Much research has been carried out for effective dye removal using physical, chemical and biological treatment techniques, and dye removal by adsorption is one of the most effective techniques among others. A wide range of locally available and effective adsorbents are tested and elimination studies described the equilibrium adsorption capacity based on isotherm studies. In this study, a prototype, low-cost, effluent treatment system that uses rice husk charcoal as a sorbent was built up for the removal of Methylene Blue (MB), one of the major basic dyes that is applied in dying natural fibers. According to the laboratory studies, the removal capacity of MB by the sorbent is in the range of 19 – 22 g kg -1 at neutral pH conditions. After adjustment of the pH of the influent to neutral, this system can be applied for the treatment of effluent containing MB in the range of 1-50 mg L-1 and the system can be operated at the rate of 15 L h-1 for 38 h maintaining level of MB of the treated effluent within 0.1 mg L-1 which is 10% of the maximum permissible of MB stipulated by EU Directives.