Dynamics of the process of colour adsorption from waste waters after dyeing textile fibres on natural zeolites

摘要

This study analyses the process of purifying waste waters from textile fibre dyeing by adsorption of colour on natural zeolites from “Nemetali” mine, Vranjska Banja, Serbia. The process has been analyzed in an adsorption column filled with natural zeolite as the adsorbent. Adsorbents are organic substances, i.e. colour residues from waste waters, left after textile fibres dyeing. The concentration change in waste waters is represented with the parameter of chemical oxygen demand (COD). Two models of diffusion have been considered: diffusion in pores and diffusion in adsorbent phase on solid adsorbent, for different input loads and two zeolite granulations (13 and 35 mm). It was found that the diffusion in zeolite pores that were in adsorbed phase is dominant in this case, which can be explained by large dimensions of used colours’ molecules. This is the reason why its adsorption in zeolite micro pores is minimal, and yet it diffuse well in already adsorbed phase on solid adsorbents. Since this process is slower, it will determine the overall rate of colour adsorption from waste waters. Specific equilibrium capacity, specific dynamic capacity, as well as the level of adsorbent utilization were determined by the use of mass transfer zone concept. It has been shown that the adsorption of organic substances from waste waters is satisfactory, and is around 80%. The highest degree of adsorbent utilization is obtained at the lowest flow of 0.167 cm3 s-1, while the lowest degree of utilization of 30%, is obtained at the highest flow of 3.27 cm3 s-1. Input load has significant influence on the degree of column utilization, while higher values of COD0 result in lower degrees of column utilization. Key words: waste waters, natural zeolite, adsorption, colour adsorption, textile dyes