Studies on the adsorption of dyes, Methylene blue, Safranin T, and Malachite green onto Polystyrene foam

One-pot synthesis of functional material from waste expanded polystyrene foam, which displays good adsorption performance and reusability for dyes. [Display omitted] •Waste expanded polystyrene foam is transformed into adsorbent.•Adsorbent shows rapid adsorption, high adsorption capacity and good reusability.•Adsorbent shows excellent adaptability to pH and salt solutions.•Adsorbent can easily realize continuous column adsorption process.•Easy adsorption and desorption to achieve the separation of dyes. Many researchers focus on the conversion of waste into reusable materials in recent years. In this study, waste expanded polystyrene foam (WEPS) and 1,2,4-benzenetricarboxylic anhydride (BTA) were used as raw materials to prepare recyclable acylating waste expanded polystyrene adsorbent (WEPS-BTA) by Friedel-Crafts reaction and to recover dyes effectively. The WEPS-BTA was characterized by FT-IR, TGA, BET and SEM. WEPS-BTA showed good performance in a wide range of pH (2–12) and high concentration brine (0.2 M). The maximum adsorption capacity to methylene blue, safranine T, and malachite green were 859.9, 1036.7, and 1197.3 mg/g, respectively. It was found that Freundlich model and pseudo-second-order kinetics could describe the adsorption behavior. This is a heterogeneous, endothermic, and spontaneous multiple adsorption process. The plausible adsorption mechanism was explained by kinetic model, thermodynamic discussion, SEM-EDS, XPS and FT-IR. In addition, WEPS-BTA showed satisfactory reusability without significant loss of the removal efficiency of the three dyes after 5 cycles. Therefore, WEPS-BTA has the advantages of simple synthesis, efficient adsorption, easy recycling and reuse, and stable performance in a harsh environment. Converting waste polystyrene foam to an adsorbent is an economic way of handling waste and providing material for wastewater remediation simultaneously.