Low-cost polyaniline/weathered basalt composites for methylene blue uptake from aqueous solutions

Abstract

The removal of chemical pollutants from water using low-cost natural materials has been a recent trend in water treatment technologies. Therefore, the low-cost natural weathered basalt (WB) and its calcinated derivative at 900 °C/3h (calcinated weathered basalt, CWB) were used for the first time to synthesise innovative composites (C-RWB and C-CWB, respectively) via an oxidation polymerization process with polyaniline (PANI) using ammonium per sulphate (APS) as initiator. Characterizations of these adsorbents were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR analysis, and Brunauer-Emmett-Teller (BET) surface area. As well, the potential use of these natural (WB), modified (CWB), and as-synthesised materials (C-RWB and C-CWB) in the purification of methylene blue (MB) from standard solutions at different experimental parameters was evaluated, and their efficiencies were compared. The pseudo-second-order equation with its very high determination coefficients (R2 > 0.996 for all adsorbents) fitted the MB uptake data better than the first-order one. In the meantime, intra-particle diffusion (IPD) was not the only driving rate in MB adsorption by the addressed adsorbents. Similarly, the MB adsorption data was well described using the Langmuir equation with maximum removal capacity (qmax) of 18.86, 10.18, 38.17, and 43.7 mg/g for RWB, CWB, C-CWB and C-RWB, respectively, at ambient temperature, better than the other applied models. The MB removal by the examined adsorbents was driven by electrostatic interaction and hydrogen bonding in mutable degree according to the dominating pH condition.