Superparamagnetic nanocomposites derived from waste polyurethane foam for the removal of Rhodamine B: batch and continuous column studies

The present study is aimed at the utilization of waste polyurethane (PU) foam derived magnetized carbon material for the treatment of simulated dye effluent. Activated carbon (AC) was prepared from waste PU foam by chemical activation method using K₂CO₃. The surface of the prepared AC was incorporated with nano-sized iron oxide particles to aid the recovery of the spent adsorbent. The polyurethane derived AC-iron oxide (PUAC-Fe₃O₄) nanocomposites were characterized with FE-SEM, XRD, Vibrating Sample Magnetometer (VSM), FT-IR, TGA, surface area and point of zero charge. The morphology of the prepared AC had an extremely porous texture which was incorporated with iron oxide nanoparticles of size less than 100 nm with a surface area of 250 m²/g. The nanocomposites had superparamagnetic properties as evident from the VSM plot. The prepared PUAC-Fe₃O₄ nanocomposites was used for the removal of Rhodamine B (RB) dye. Batch adsorption studies were performed and the equilibrium parameters were calculated by fitting the data with Langmuir and Freundlich isotherm models. The thermodynamic parameters were also evaluated. The adsorption of RB dye onto PUAC-Fe₃O₄ composites was spontaneous and endothermic. Kinetic studies were also carried out and the data were tested with different kinetic models. Intraparticle diffusion model and Boyd plots suggested that the boundary layer diffusion step controlled the rate of adsorption. Continuous column studies were also performed and it proved that 1 g of prepared material was able to treat 1.075 L of 10 mg/L RB dye with an efficiency of 64.87%. The interferential effect of the electrolytes on the RB dye removal was also studied. Reusability studies proved that the prepared PUAC-Fe₃O₄ nanocomposites was efficient even after three cycles of operation.