Thermally crosslinked electrospun nanofibrous mat from chrome-tanned solid wastes for cationic dye adsorption in wastewater treatment

Highlights

• Electrospun nanomat adsorbent was developed from chrome-tanned waste and PVA.

• The nanomat was thermally crosslinked to improve its stability in aqueous solution.

• The nanomat showed selective adsorption for cationic methylene blue.

• The adsorption phenomena followed pseudo-second-order kinetics.

• Equilibrium data best suited the Langmuir model.

Abstract

Chrome-tanned solid wastes from the tannery were used to extract collagen hydrolysate (CH) for the fabrication of electrospinning nanofibrous mat with polyvinyl alcohol (PVA) to remove cationic dye from wastewater. The nanofibrous mat was thermally crosslinked by heat curing to make it stable in neutral, acidic, and basic environments. The prepared nanofibrous mat was characterized by attenuated total reflectance infrared spectroscopy (ATR-IR), thermogravimetry (TGA), X-ray diffraction (XRD), and water dissolution properties. The detailed experimental results revealed that the nanomat prepared from CH: PVA (2:3) yielded better stability in an aqueous solution after thermal crosslinking. The nanofibrous mat was used as adsorbent and its adsorption properties were evaluated from the adsorption behaviour of methylene blue (MB), a common cationic dye. The adsorption results demonstrated that the nanomat showed maximum adsorption capacity of 99.9 mg g⁻¹ with 88.8% removal efficiency at pH 12. The adsorption parameters were optimized and revealed to be highly pH sensitive, with 12.0 being the optimum pH for the highest dye removal. The experimental results revealed that the adsorption capacity of the nanofibrous mat grew with increasing initial dye concentration and decreased with increasing adsorbent doses. The thermodynamic study indicated that the adsorption kinetics (R² > 0.99) followed pseudo-second-order equation, and the equilibrium data was the best suited by the Langmuir model (R² > 0.99). On the other hand, the electrospun nanofibrous mat showed significantly better adsorption than the prepared CH-PVA composite film. The results for cationic dye adsorption suggest that the potential broader applications of collagen hydrolysate-based nanofibrous mat for pollution control may include its use as potential adsorbent for wastewater treatment.