Adsorption mechanism of phosphate by polyaniline/TiO2 composite from wastewater

The adsorption behavior of polyaniline/TiO2 (PANI/TiO2) for phosphate from wastewater Was investigated, and the mechanism was interpreted in details in this study. PANI/TiO2 exhibited enhanced adsorption efficiency and high stability for phosphate removal in wide pH range (1-6) compared with PANI and TiO2. The equilibrium time was much shorter than other similar sorbents reported, like HFG-201 and La 201, and 60 min was enough for the adsorption of 98% phosphate (10 mg P/L). After 5 times reuse of the NaOH (0.5 mol L-1) for desorption, phosphate solution was concentrated from 10 mg P/L to 180 mg P/L without obvious loss of adsorption and desorption efficiency. The mechanism of the phosphate adsorption onto PANI/TiO2 was revealed with the aid of SEM, XRD, EDS, FTIR and XPS. Two adsorption sites of protonated imino groups in PANI chains and the Ti(OH)(n)((4-n)+) from TiO2 part were verified, and the binding force of Ti-P was the main pathway for the removal of phosphate. Generally, electrostatic interaction, ion-exchange and hydrogen bond were demonstrated to be involved during the adsorption. The synergistic effect of the PANI and TiO2 make the organic/inorganic composite a promising sorbent for phosphate removal from wastewater. (C) 2017 Elsevier B.V. All rights reserved.