Fabrication of Magnetic Fe3O4/Polypyrrole/Carbon Black Nanocomposite for Effective Uptake of Congo Red and Methylene Blue Dye: Adsorption Investigation and Mechanism

Abstract In most wastewater systems, the existence of more than one dye is a reality. Herein, mesoporous iron oxide/polypyrrole/carbon black (Fe 3 O 4 /PPy/C) nanocomposite with high saturation magnetization (45.2 emu/g) has been prepared by encapsulating very fine Fe 3 O 4 nanoparticles (4–7 nm) in PPy/C for the first time. The superior adsorption performance of the developed Fe 3 O 4 /PPy/C nanocomposite for the removal of basic dye (methylene blue, MB) and acidic dye (Congo red, CR) has been studied in single and binary systems. XRD, FESEM, EDX, HRTEM, FT-IR, VSM, BET, and zeta potential analyses were used for adsorbent characterization. XRD, EDX, and FT-IR findings confirmed the successful inclusion of Fe 3 O 4 into the polymer matrix. The XDR and HRTEM results revealed a significant reduction in the size of the grown Fe 3 O 4 with the addition of PPy/C, which acts as a particle growth inhibitor, and thus the nanocomposite has a greater surface area reached 341.01 m 2 /g relative to 210.66 m 2 /g and 277.59 m 2 /g for pure Fe 3 O 4 and PPy/C, respectively. The Langmuir isotherm matched the experimental data quite well, with R 2 and adsorption capacity of 0.994 and 500 mg/g for CR and 0.995 and 90.9 mg/g for MB, respectively. The effectiveness of Fe 3 O 4 /PPy/C nanocomposite to remove both CR and MB from binary solution reached 96.9% for CR and 95.9% for MB. In kinetic investigations, the sorption of both dyes obeyed the pseudo-second order model, where R 2 equals 0.999 and 0.998 for CR and MB, respectively. Desorption tests revealed the easy separation and good efficiency of the nanocomposite after four cycles. Finally, the sorption mechanism was discussed in detail based on FTIR analysis. Therefore, the developed nanocomposite is a bi-functional, recyclable, and efficient adsorbent for environmental applications.