Polypyrrole-decorated Mg-Al layered double oxides for dye adsorption: Isotherm, kinetics, and thermodynamic investigations

Polypyrrole-decorated Mg-Al layered double oxides (PPy/Mg-Al) were prepared via the in-situ polymerization for enhancing the adsorption capacity of Rhodamine B (RhB). For comparison to Mg-Al layered double oxides, PPy/Mg-Al composites presented the better adsorption capacity, which climbed and then declined with an in-crease PPy content. The optimal 2-PPy/Mg-Al had the best Langmuir adsorption capacity of 200.10 mg g-1, and its tested adsorption capacity decreased from 137.13 to 118.13 mg g-1 after seven cycles due to the change in the valance sates of surface compositions and surface discharge nature. 2-PPy/Mg-Al exhibited a spontaneous and endothermic adsorption process for RhB removal, and its adsorption isotherms and kinetics were respectively described by Langmuir and second-order models. Hence, the in-situ polymerization of pyrrole was a promising route to enhance the adsorption activity of Mg-Al LDO for dyes removal from wastewater.