Adsorption study of reactive dyes onto porous clay heterostructures

The present research evaluates the adsorption of reactive dyes, Remazol Violet 5R (RV5R) and Acid Blue 25 (AB25), using Porous Clay Heterostructures (PCHs) prepared from natural bentonite. Natural bentonite, PCH with silica pillars (Si-PCH) and PCH with silica-zirconia (SiZr-PCH) were characterized by elemental analysis, XRD, N2 adsorption-desorption at − 196 °C, FT-IR, TG and XPS. The adsorption experiments were carried out in a stirred tank in order to evaluate the effect of pH, contact time and initial concentration. The adsorption isotherms were well fitted by Langmuir (L), Langmuir-Freundlich (LF) and Redlich Peterson (RP) models. The equilibrium data were described using the Langmuir-Freundlich model for both dyes and both materials, obtaining a maximum adsorption capacity of 209.9 mg g− 1 and 265.9 mg g− 1 for AB25 using Si-PCH and SiZr-PCH, respectively. In the case of RV5R, the maximum adsorption capacity was 127.07 mg g− 1 and 185.7 mg g− 1 for Si-PCH and SiZr-PCH, respectively. The adsorption process takes place by electrostatic interactions between the silanol groups of the PCHs with functional groups of the dyes, such as amine or hydroxyl. From the obtained results, it can be concluded that PCHs showed to be a promising material for the adsorption of dye.