Functional upcycling of thermocol waste for Congo red dye removal: statistical analysis and adsorptive mechanism

ABSTRACT

The graphical abstract depicts a circular approach for converting thermocol waste into an active adsorbent for Congo red removal, followed by its valorization into 3D-printing filaments, enabling dye remediation while minimizing secondary waste generation.

The environment is severely harmed by nonbiodegradable plastics like polystyrene and the discharge of hazardous dyes into water systems. To address these issues, waste polystyrene (thermocol) was functionally upcycled to an effective dye adsorbent capable of removing harmful Congo red dye from aqueous media. A removal effectiveness of 98.9% was attained by optimizing the adsorption parameters, such as adsorbent dosage (0.02 g), pH (4), and contact period (120 min), using the Box–Behnken design–response surface methodology. The adsorption was best explained by the Langmuir isotherm and the pseudo-second-order model. Thermodynamic studies showed that the adsorption process is endothermic, and the potential adsorption mechanism was predicted from the Fourier transform infrared results. The solid waste from spent adsorbent was mitigated by extruding the spent adsorbent with commercial acrylonitrile butadiene styrene plastic to make 3D-printing filaments. These filaments were resistant to dye leaching in aqueous medium and retained their tensile strength. In addition to being an effective technique for managing thermocol waste, the synthesized adsorbent is efficient in eliminating harmful dyes from water. This study offers a promising method for environmental pollution and supports sustainable practices by recovering waste materials.