Protonated polyaniline and its derivatives as potential adsorbents for simultaneous reclamation of textile dyes and oil/water separation

Abstract

Potential adsorbents hold vital importance for the removal of conventional and hazardous micropollutants from waste water. The present study reports the synthesis and characterization of polyaniline (PANI) and its two derivatives by selecting pre-substituted monomers at ring (poly 4-amino phenol; PpAP) and nitrogen atom (poly N-methyl aniline; PNMA) prior to polymerization. The synthesized polymers were characterized by FTIR, XRD, TGA, SEM, TEM, BET and UV–Vis techniques. These polymers were exploited simultaneously for the removal of textile dyes and o il/water (O/W) separation. Initially, the adsorption potential of adsorbents towards removal of methylene blue (MB) dye was investigated in batch mode study by diversifying the effective factors like contact time, initial concentration of MB dye, amount of adsorbent and pH. The maximum dye adsorption capacity was found to be 320, 311, 299 mg/g for PNMA, PpAP and PANI respectively. These results were further verified by the computational studies. Thermodynamics of adsorption studies revealed that Langmiur adsorption isotherm is best fitted whereas kinetic studies were best described by pseudo second order model. The polymers were regenerated without any significant reduction in adsorption capacity by washing simply with water and ethanol. On the other hand, FTIR analysis before and after adsorption of MB explains that a variety of interactions are involved in the adsorption of MB. Moreover, the synthesized polymers were also applied for the separation of non-polar solvents from water (oil/water separation). Interestingly, PNMA, PpAP and PANI have shown promising results towards O/W separation studies obtaining separation efficiency values of 98%, 97% and 96% respectively. Good separation efficiency of prepared polymers is attainable due to hydrophilic nature of polyanilines. Overall, this study explores the potentiality of conducting polymer adsorbents for textile waste water treatment as well as for O/W separation.