Evaluation of adsorptive and photocatalytic degradation properties of FeWO4/polypyrrole nanocomposite for rose bengal and alizarin red S from liquid phase: Modeling of adsorption isotherms and kinetics data

Abstract The FeWO 4 /polypyrrole nanocomposite (FeWO 4 /PPy NC), prepared by oxidative polymerization of pyrrole monomer with FeWO 4 NPs, is used for adsorption and photocatalytic degradation of rose bengal and alizarin red S. The characterization of the nanocomposite (NC) is performed by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, and transmission electron microscopy. The performance of FeWO 4 /PPy NC is appraised under varying conditions of agitation time/solar irradiation time, initial dyes concentration, adsorbent/photocatalyst dose, and initial solution pH. The Langmuir isotherm and pseudo‐second‐order kinetic models best express the equilibrium data. The FeWO 4 /PPy NC exhibits a maximum saturation capacity of 202.63 mg/g for rose bengal (RB) and 142.80 mg/g for alizarin red S (ARS). The adsorption of both dyes follows liquid film and intraparticle diffusion. Thermodynamic studies demonstrate feasibility, spontaneity, and exothermic essence of the removal process. The NC shows remarkable visible‐light photocatalytic activity at 100–120 min irradiation time, 40 mg/L dyes solution concentration, 0.5 g/L of photocatalyst, and pH 6. Photodegradation reaction obeys first‐order kinetics. The mechanism of adsorption of RB and ARS is governed by electrostatic attraction, hydrogen bonding, van der Waals, and π–π interactions. A good regeneration capacity up to four sorption–desorption cycles, high saturation capacity, and remarkable photodegradation efficiency depicts that FeWO 4 /PPy NC can be used efficiently for decolorization of RB and ARS in aqueous medium.