Single and multicomponent acid dye adsorption equilibrium studies on tyre demineralised activated carbon

Abstract

This study investigated the adsorption properties of demineralised activated carbon adsorbents produced from waste tyre char. The produced carbon was tested for its dye adsorption capacities in the textile industry effluent treatment. Two acid dyes with different molecular sizes were used, namely Acid Blue 25 (AB25) and Acid Yellow 117 (AY117) to simulate the textile effluent. In a single component system, it was found that the larger size dye, AY117, showed little adsorption and for both dyes the maximum capacity is higher than the commercial activated carbon F400 for both dyes. Furthermore, the results of the single component system were fitted to equilibrium isotherm models using Langmuir, Freundlich, Redlich–Peterson and Langmuir–Freundlich or Sips for the single component system. The adsorption of AB25 followed the Langmuir isotherm, while the adsorption of AY117 can be better described with Langmuir–Freundlich model. A binary AB25–AY117 mixture was used to test the possibility of the molecular sieve effect. For the binary component system, it is found that none of the predictive models work well, hence the system is non-ideal. Overall, the correlative extended Freundlich isotherm models were the best to fit the experimental data.