Adsorption of Benzene-Polycarboxylic Acids on the Electrosynthesized Polyaniline Films: Experimental and DFT Calculation

摘要

The polyaniline (PANi) film was synthesized by electrochemical polymerization and is used as adsorbent for removal of trimellitic and pyromellitic acids from aqueous solution. The effects of experimental parameters such as: pH, contact time, initial concentration, and temperature were investigated. The optimum adsorption is achieved at pH = 6.5 after 120 min of contact time. The experimental adsorption data were best described by the pseudo-second order model and Langmuir isotherm model. The maximum adsorption capacities of PANi film are of 190.17 and 204.18 mg/g for trimellitic and pyromellitic acids, respectively. The values of thermodynamic parameters indicate that the adsorption is endothermic and spontaneous in nature. The regeneration of the PANi film showed a low reduction (< 9 %) in the adsorption efficiency after four cycles of adsorption-desorption. In addition, the quantum calculations using density functional theory at B3LYP/6-31G(d) level confirmed that the adsorption mechanism was a physisorption process with small values of interaction energy between adsorbate and adsorbent. The trimellitic and pyromellitic acids were adsorbed via carbonyl oxygen atoms of their carboxylic groups on the amino group of PANi. The PANi film can be used as a potential, reusable and easily separable adsorbent for removal of aromatic acids from water.