Application of Density Functional Theory computation (DFT) and Process Capability Study for performance evaluation of Orthophosphate removal process using Polyaniline@Hematite-titaniferous sand composite (PANI@HTS) as a substrate

A new approach is adopted in this study to eliminate orthophosphates in the aqueous medium. It is about synthesizing a composite from a conductive polymer (Polyaniline) and a sandy material (Hematite-titaniferous sand). The synthesized composite (PANI@HTS) and its components were characterized with (XRD) X-ray diffraction, (XRF) X-ray fluorescence, (SEM) scanning electron microscopy coupled with (EDS) energy dispersive X-ray spectroscopy, (FTIR) Fourier-transform infrared spectroscopy and laser diffraction particle size analysis. The phenomenon of adsorption of orthophosphates on PANI@HTS has found to be dependent on several factors, such as adsorbent dose, pH, contact time and pollutant concentration. From the study of adsorption kinetics and the effect of pollutant concentration, the Langmuir model and the pseudo second order model were the most suited for explaining adsorption phenomena with a highest correlation (R-2 > 0.98). The adsorbed amount that was found in this study reaches 16.15 mg/g. The adsorption mechanism of orthophosphate ions onto PANI@HTS composite was computationally investigated using Density Functional Theory (DFT). The adsorbate-adsorbent interfacial interactions are assumed to be physisorption in nature due to the low values of binding energy and electronic charge transfer. This DFT simulation result is in good adequacy with the experiment. The capability study of the present process has shown that our method is capable, satisfactory and can be applied on a large scale.