Biocompatible membrane from the natural rubber-grafted-(2-hydroxyethyl methacrylate) and its metal removal application

This study describes the preparation and characterization of a green and safe membrane based on a natural polymer for metal adsorption. Natural rubber-grafted-(2-hydroxyethyl methacrylate) with a special nanostructure was synthesized by graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of natural rubber (NR) particles using tert-butylhydroperoxide/tetraethylenepentamine as initiators. Optimal conditions for achieving high conversion and grafting efficiency were identified. Characterization of the as-synthesized samples was performed using Fourier-transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, tensile measurement, swelling degree determination, and cytotoxicity testing. The results revealed that HEMA formed a nanoscale matrix surrounding NR particles, which improved the tensile strength, thermal resistance, and swelling degree of the as-prepared samples. Cytotoxicity testing demonstrated that the membrane was safe for human use, as it did not exhibit toxicity to Vero cells at concentrations up to 1024 µg/mL. Furthermore, the membrane displayed a high adsorption capacity toward Fe³⁺ and was well described by Koble-Corrigan isotherm model and the first–second-order kinetic equation. Moreover, the membrane demonstrated excellent recyclability maintaining its adsorption ability towards Fe³⁺ ions over five consecutive cycles. Overall, these findings may recommend the NR-HEMA membrane as a promising candidate for metal removal applications.

Graphical abstract

The adsorption of metal ions on the natural rubber with PHEMA matrix