Hydrogen phosphate anions modified hydrogen titanate nanotubes for methylene blue adsorption from aqueous solution: Validating novel method of predicting adsorption capacity

A new method for predicting the adsorption capacity of pure hydrogen titanate (H2Ti3O7) nanotubes (HTN) via one-step dye-removal method of chemically-activated catalytic process conducted in the dark has been recently demonstrated. In this work, hydrogen phosphate anions (HPO42-) modified H2Ti3O7 nanotubes (HP-HTN) have been synthesized via the hydrothermal treatment of sol-gel derived titanyl phosphate (TiP2O7)/phosphate (PO43-) ions modified nanocrystalline anatase-titania (TiO2). The methylene blue (MB) adsorption capacity of HP-HTN has been determined to be 139 mg g(-1) which is higher than that (105-121 mg g(-1)) of pure HTN. It has been demonstrated that HP-HTN can decompose the MB dye in an aqueous solution via the hydrogen peroxide (H2O2) activation. It is observed that the HP-HTN exhibit higher dye-decomposition rate-capacity compared with that of pure-HTN. The maximum MB dye-removal rate-capacity of 194 and 393 mg g(-1) h(-1) has been determined at the initial H2O2 concentration of 3 and 15 wt%. The HP-HTN exhibit a perfect liner relationship (slope and regression correlation coefficient, , values of 17 mg g(-1) h(-1) wt% (-1) and 0.999) between the maximum MB dye-removal rate-capacity as a function of initial H2O2 concentration which strongly supports the new method for the prediction of adsorption capacity via the one-step dye-removal method of chemically-activated catalytic process conducted in the dark. (C) 2016 Elsevier Ltd. All rights reserved.