Conversion of Waste Thermocol into Effective Adsorbent by Chemical Modification: Removal of Malachite Green from Aqueous Media.

Expanded polystyrene (EPS) foam (thermocol waste) is produced at a rate of several million tons annually and poses serious environmental challenges due to its widespread use and lack of biodegradability. The present research is to design an effective Malachite Green (MG) dye adsorbent, RBT (Recycled polystyrene (RPS)—Benzophenone-3,3′,4′,4′-Tetracarboxylic dianhydride (BPTCDA)) by the chemical modification of RPS with BPTCDA via two-step reactions (namely the Friedel–Crafts followed by amidation reactions). The adsorbent's characteristics were studied using the Scanning Electron Microscope (SEM), X-Ray diffraction analysis (XRD), and Fourier-transform infrared spectroscopy (FTIR) techniques. Solution pH, contact duration, initial dye concentration, adsorbent dose, and temperature of the adsorption process were individually optimized. The adsorption is well matched (R² > 0.955) with pseudo second-order kinetics, and Freundlich isotherm was identified as most fitting with research findings. Thermodynamic analysis suggests that the adsorption is spontaneous and endothermic. The probable mechanism behind adsorption was predicted between adsorbent and adsorbate through FT-IR analysis. Finally, MG adsorbed RBT, was converted into 3D printing filaments by the extrusion process. When MG leaching of 3D filaments was evaluated, there was no evidence of MG leaching, which could imply that this approach is an environmentally benign way to remove toxic pollutants as well as reduce landfill polymer waste. Based on the adsorption experiment results, RBT is suitable for the adsorption of MG dye from a water-based medium; also the final product was converted into value-added products. [ABSTRACT FROM AUTHOR]