Adsorption mechanism of Zn, Ni, Cd, and Cu ions by carbon-based adsorbents: interpretation of the adsorption isotherms via physical modelling.

A theoretical physicochemical and thermodynamic investigation of the adsorption of heavy metals Zn, Cd, Ni, and Cuon carbon-based adsorbents was performed with statistical physics fundaments. Particularly, the experimental adsorption isotherms of heavy metal removal, at 30°C and pH 5, using adsorbents obtained from the pyrolysis of three biomasses (cauliflower cores, broccoli stalks, and coconut shell) were modelled and interpreted with a homogeneous statistical physics adsorption model. Calculations indicated that the heavy metal adsorption with these carbon-based materials was a multi-ionic process where several ions interact simultaneously with the same carboxylic functional group on the adsorbent surface.