Ultrasound-Assisted Catalytic Degradation of Methyl Orange with Fe₃O₄/Polyaniline in Near Neutral Solution

An ultrasound-assisted advanced oxidation process (AOP) has been demonstrated for sonocatalytic degradation of methyl orange (MO) with Fe 3 O 4 /polyaniline (Fe 3 O 4 /PANI) microspheres in near neutral solution (pH ∼6). The Fe 3 O 4 /PANI microspheres were characterized with XRD, SEM, TEM, FT-IR, XPS, and ζ-potential measurements, and were further tested in the role of adsorption and sonocatalytic decolorization of MO in solution. The isotherms and kinetics of MO adsorption with Fe 3 O 4 /PANI follow the Langmuir model and the pseudo-second-order model, respectively. The kinetics of sonocatalytic decolorization of MO with Fe 3 O 4 /PANI conforms to a combinational model involving the pseudo-second-order adsorption model and the pseudo-first-order degradation model, since Fe 3 O 4 /PANI has a high capacity to adsorb MO in solution. The percentage of room-temperature sonocatalytic degradation of MO with Fe 3 O 4 /PANI is about 4.8, 8.8, and 5.7 times that with Fe 3 O 4, dedoped Fe 3 O 4 /PANI, and ultrasonication alone, respectively. The eco-friendly Fe 3 O 4 /PANI featured with superparamagnetism and excellent reusability offers a promising sonocatalyst for rapid decolorization and enhanced degradation of azo dyes in effluents.