Development of dyes removal method from textile waste water

Abstract

Discharge of colored effluents without discoloration originated from textile industries may cause serious problems in the receiving environments. In this study, natural materials that are saw dust, coconut coir and jute stick powder were used as adsorbents to remove various dyestuffs used in the textile industry. These materials are cheap and available in large quantities in Bangladesh. The objective of the present study is to investigate the adsorption of reactive, direct and disperse dyes on these adsorbents. But my main concern is the reactive dyes, which I have studied details. During preliminary experiments it was seen that adsorption equilibrium was reached in about 24 hours. In adsorption experiments, in order to obtain adsorption isotherms, a fixed amount of adsorbent and 50 mL dye solutions of different concentrations were placed in glass bottles which were shaken at 120 rpm at 25±2oC for 24 hours. Then, samples were filtered and the equilibrium concentrations of dyestuffs in the solutions were determined by using spectrophotometer at appropriate wavelength corresponding to the maximum absorbence. After equilibrium concentrations of the solutions were obtained, Langmuir and Freundlich adsorption isotherm constants, kinetic constants were calculated for the adsorbents used in this study. The removal efficiencies for anionic dyes (reactive, direct) are higher than those for disperse dyes with the natural materials. Removal efficiencies of natural materials were very poor (40-50%). Therefore, modification of surface properties of natural materials with H2SO4 and ZnCl2 or NaCl was considered to increase the removal efficiencies of anionic dyes. After modification of the surface properties, adsorption capacities of adsorbents were higher than those of natural materials (85-96%). Finally, the adsorption capacity of treated adsorbents for the different dyes was determined to compare removal efficiency of dyes towards modified materials. The results showed that the adsorption of dyes on adsorbents used in this study fitted nicely the Langmuir Isotherm and Freundlich Isotherm Equations. Pseudo-second order equation was found to be in good agreement with those of experimental values.