Core–shell polypyrrole/Fe3O4 nanocomposite as sorbent for magnetic dispersive solid-phase extraction of Al+3 ions from solutions: investigation of the operational parameters

Abstract

In the current study, polypyrrole (ppy)/Fe3O4 nanoparticles were synthesized and applied for the removal of Al+3 metal ions from the aqueous medium. The nanocomposite was characterized using several analytical techniques such as SEM, TEM, FTIR, XRD, EDAX, and BET. The results showed that the synthesized composite has an average diameter of 81 nm. BET surface area of 49.55 and 19.44 m2/g before and after adsorption, respectively, verified that Al+3 was adsorbed by ppy/Fe3O4. The effect of main operating parameters, including pH value, contact time, target pollutant concentration, adsorbent dosage, temperature, and competing ions were examined. Al+3 adsorption was strongly dependent on solution pH, the maximum adsorption of 82% was observed at pH 3. The uptake of Al+3 onto ppy/Fe3O4 was rapid and equilibrium established within 20 min. Adsorbate concentration and adsorbent dosage of 5 μg/ml and 100 μg/ml resulted in the highest Al+3 adsorption. Furthermore, adsorbent reusability was tested and it was shown that after five times recycling, the removal efficiency was still above 50%. The maximum adsorption efficiency of 100.7 mg/g was achieved in the current study. The presence of Fe+2, Na+, NH4+, and SO4−2 did not reduce adsorption efficiency, which is indicative of the high selectivity of the prepared adsorbent. Equilibrium data were in good accordance with the Freundlich model. The obtained results revealed that pseudo second model is the best one because of the greatest R2 value (0.9905) and it suggested that the adsorption mechanism follow chemisorption mechanism. Thermodynamic parameters such as ΔG°, ΔS° and ΔH° were estimated for the adsorption study and suggested that the adsorption was exothermic and maximum Al+3 adsorption occurred at 20 °C. Consequently, ppy/Fe3O4 nanocomposite could be utilized as an efficient and recyclable adsorbent for the removal of Al+3 ions from aqueous solutions.