Design of Dye Adsorption by Amine Terminated Dendritic Functionalized Halloysite Nanotubes Using Response Surface Methodology (RSM)

In this study, the adsorption performance of a modified halloysite for the removal of anionic dye (C.I. Acid Blue 92) was demonstrated. Halloysite was modified in a multistep process by the synthesis of amine terminated dendritic structures on its surface. The transmission electron microscopy images were used to characterize the nanotubes forms of pristine halloysite. The adsorption processes were performed using classical and statistical response surface methodology (RSM) techniques. The effect of important parameters such as pH, adsorbent concentration, and dye dosage was investigated. The results showed that all the independent factors except time were significant to the dye removal efficiency. The dye removal at equilibrium time was well fitted to the Langmuir isotherm model and followed the monolayer adsorption style. The adsorption rate was also described by the pseudo-second-order kinetic model. The adsorption process revealed an exothermic behavior according to the thermodynamic investigations. The removal efficiency of AB92 improved significantly from 8% to 97% after modification.