Experimental and theoretical studies on the removal of polycarboxy-benzoic acids by adsorption onto polyaniline from aqueous solution

The adsorption of trimellitic and pyromellitic acids has been performed onto synthesized polyaniline (PANi) by chemical oxidative polymerization. Different parameters that influence the adsorption processes (pH, temperature, ratio solid/liquid, initial concentration, and contact time) had been examined. Adsorption kinetic study indicates a great adjustment with pseudo-second-order kinetic model. The equilibrium data were best fitted by Langmuir isotherm model. The maximum monolayer adsorption capacities are 67.4 and 94.5 mg/g for trimellitic and pyromellitic acids, respectively. Comparison of the adsorption capacities indicates that increasing the number of carboxylic functional groups promotes adsorption on the PANi. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) indicate that the adsorption is spontaneous and endothermic in nature. The calculations of chemical quantum parameters were performed for optimized molecular structures using the AM1 and MINDO semi-empirical methods. The theoretical data were well correlated with the experimental results.