Green synthesis of Pseudomonas aeruginosa immobilized Fe3O4-multiwalled carbon nanotubes bio-adsorbent for the removal of 2,4,6-trinitrophenol from aqueous solution

Abstract In this study, Pseudomonas aeruginosa immobilized Fe3O4-multiwalled carbon nanotubes (P.a@Fe3O4-MCNT) were synthesized as a green item and applied as a bio-adsorbent to remove 2,4,6-trinitrophenol (TNP) from aqueous solution. The morphology, structure, and property of the prepared magnetic bio-adsorbent were characterized by Fourier-transform infrared spectroscopy (FT-IR), Field emission-scanning electron microscopy (FE-SEM), X-ray Diffraction (XRD) Brunauer-Emmett-Teller (BET), and vibrating-sample magnetometer (VSM) techniques. Batch adsorption experiments, such as range of pH, temperature, contact time, TNP concentration, and bio-adsorbent dose were investigated in detail. The adsorption kinetic studies were well followed by the pseudo-second-order kinetic model for the prepared bio-adsorbent. The linear adsorption isotherm models, Langmuir, Freundlich, and Redlich–Peterson (R–P) were examined, as well. The data well fitted the Langmuir isotherm model, which displays monolayer sorption. In this regard, the maximum adsorption capacity of TNP was obtained equal to 100 mg/g by P.a@Fe3O4-MCNT bio-adsorbent. The findings of thermodynamic studies demonstrated that the adsorption process was exothermic and spontaneous. Moreover, desorption studies showed that TNP can be easily removed from the surface of P.a@Fe3O4-MCNT bio-adsorbent by methanol and can be reutilized up to 10 cycles of regeneration. The results supported the claim that the prepared bio-adsorbent is an eco-friendly adsorbent and can be used as a highly efficient, reusable, and a cost-effective martial with fast regeneration for the removal of TNP from aqueous solution.