Functionalization of PET and WPET Nanofibres Grafted with oPrPy for the Recovery of Cu²⁺ Ions from Aqueous Solution ^†

The plastic and metal pollution accumulating in the marine environment has given many researchers motivation to investigate and provide solutions to this problem. The most abundant plastic waste found in the marine environment is polyethylene terephthalate (PET)-based plastic waste. Because PET based plastics are the most used polymers and globally pollute the marine environment, recycling these polymers is required so as to reduce the accumulated PET-based waste in the marine environment. Plastic waste which is PET-based can be recycled using electrospinning techniques. Nanofibres made of PET or waste PET (WPET) are rarely active adsorbents, however, chemical reactions can be carried out with the nanofibres to make them active for any desired purpose. The PET and WPET nanofibres were functionalized through grafting reactions, respectively. Grafting is one of the immobilization methods under amination, which is defined as introducing primary amines onto the surface of the PET or WPET nanofibres. The grafting method involves the reaction of the pendant amine compounds with the chelating ligand 2-(3-octyl-1H-pyrazol-5-yl)pyridine (oPrPy) as applied in this study. The ATR-FTIR patterns of PET-oPrPy and WPET-oPrPy nanofibres showed NH₂ and N-H peaks at 3258 cm⁻¹ and methyl C-H and methylene in the range of 2952 to 2853 cm⁻¹ that was assigned to oPrPy verifying the attachment of the oPrPy on the PET and WPET nanofibres surface. The degree of surface modification on PET or WPET nanofibres was examined through the adsorption of Cu²⁺ ions from an aqueous solution. Batch adsorption experiments were carried out using the functionalized materials and showed that the PET-oPrPy and WPET-oPrPy nanofibres were active adsorbents for the recovery of Cu²⁺ ions. PET-oPrPy and WPET-oPrPy nanofibres achieved adsorption equilibrium within the initial 90 min and 60 min of contact time with 9.70 mg/g and 16.43 mg/g Cu²⁺ adsorption capacity, respectively. The WPET-oPrPy nanofibres were best fitted in isotherms with this order: Langmuir > Freundlich > Redlich-Peterson with correlation coefficient R² = 0.9959 and ERRSQ approaching zero. Meanwhile, WPET-oPrPy nanofibres were best fitted in isotherms with this order: Langmuir > Freundlich > Redlich-Peterson with correlation coefficient R² > 0.99 and ERRSQ approaching zero.