Equilibrium and a two-stage batch adsorber design for reactive or disperse dye removal to minimize adsorbent amount

The adsorption of a reactive dye (Reactive Yellow K-4G) and a disperse dye (Disperse yellow brown S-2RFL) onto polyepicholorohydrin-dimethylamine (EPIDMA) cationic polymer modified bentonite (EPIDMA–bentonite) in batch adsorber was studied, respectively. Two equilibrium models, the Langmuir and Freundlich models were selected to follow the adsorption process. It was shown that the equilibrium experimental data for reactive dye adsorption could be well described by the Freundlich model, but for disperse dye the Langmuir model could be better. Based on the well correlated adsorption isotherm, an adsorption process design model was developed for the design of a two-stage batch adsorber to predict the minimum amount of adsorbent to achieve a specified percentage of dye removal at a given volume of wastewater effluents. The adsorption process design analysis indicated that compared with the single-stage batch adsorption, the two-stage process could significantly save adsorbent to meet the higher demands of dye removal efficiency.

Research highlights
► Both adsorption process and mechanism are different for reactive and disperse dye.
► Different adsorption process design models depend on different equilibrium models.
► Two-stage batch adsorption process can save more adsorbent than single-stage batch.
► Two-stage batch adsorption process is suitable for optimizing the use of adsorbent.