Modeling of zinc adsorption onto clinoptilolite in a slurry bubble column

This paper presents experimental results and a successful model for zinc removal from Acid Rock Drainage by adsorption on clinoptilolite. The experiments were conducted in a slurry bubble column of 0.09 m inner diameter and 1.4 m height, loaded with 100 g of clinoptilolite particles of diameter 0.3–1.4 mm/kg liquid. Aqueous zinc ion concentrations were determined before and during the adsorption tests. Zeolite was then regenerated by a sodium chloride solution, whose zinc concentration was determined against time. The Langmuir isotherm model was fitted to the experimental results under batch conditions to characterize the adsorption capacity of the solid surfaces. A global kinetic model with mass transfer to the particles and uptake on adsorption sites facilitates interpretation of the ARD slurry bubble column adsorption–desorption results. Due to air injection, perfect mixing could be assumed. The effect of particle size on the forward rate constant kf of the adsorption process is important. The model is also applied to the sorbent regeneration by zinc desorption to provide a complete description. Consistent with the model, external mass transfer is not rate-limiting in this adsorption–desorption process.

► Zinc is removed from Acid Rock Drainage by adsorption on clinoptilolite.
► Experiments were conducted in a slurry bubble column.
► Global kinetic model fits data well with mass transfer and uptake on adsorption sites.
► External mass transfer is not the rate-limiting step in this process.