CoFe₂O₄/SWPS doped with silver bromide nanoparticles prepared from waste polystyrene for efficient congo red adsorption

Abstract

In this study, an adsorption method was used to recover Congo red from an aqueous solution employing a new type of nano adsorbent, the CoFe₂O₄/SWPS/AgBr nanocomposite. FT-IR, XRD, SEM, and EDS were used to characterize the nanocomposite, which was synthesized using waste sulfonated polystyrene via a co-precipitation technique. The effects of pH, concentration, amount of adsorbent, contact time, pH_PZC, and adsorbent recovery on the removal of Congo red were investigated. The optimal parameters for the adsorption studies were investigated. The maximum adsorption capacity (q_max) was 588 mg/g, and the adsorption data were analyzed using the Freundlich and Langmuir isotherms. The results demonstrated that the adsorption process followed the Langmuir isotherm, indicating monolayer and homogeneous adsorption. Kinetic studies revealed that the chemical adsorption of Congo red is best described by the pseudo-second-order model. The efficacy of the nanocomposite with varying concentrations of silver bromide (5, 12.5, and 20 wt%) in removing Congo red was also examined. The CoFe₂O₄/SWPS nanocomposite with 12.5 wt% AgBr showed the highest removal efficiency, achieving a 95% removal rate. The efficiency of the nanocomposite was further enhanced by reusing it up to six times, maintaining a removal of over 90%.