Reinventing waste: Transforming discarded optical discs into polycarbonate-organosilane adsorbent for effective removal of mercury(II) in water

Abstract

Polycarbonate, renowned for its versatile properties, has become indispensable in numerous domestic applications. However, the escalating rates of consumption and disposal raise significant concerns for sustainable development. Of particular concern is the inadequate management of obsolete optical discs, which pose a serious environmental threat due to the non-biodegradable polycarbonate component. To address this challenge, this study aimed to repurpose polycarbonate derived from optical disc waste into adsorbent materials using 3-aminopropyl triethoxysilane (APTES) coupling. The waste-derived products underwent comprehensive characterization employing Fourier transform infrared spectroscopy, field emission-scanning electron microscopy, energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller, and Barrett-Joyner-Halenda techniques. Additionally, batch experiments were conducted to evaluate the mercury(II) adsorption behaviours. The successful immobilisation of APTES on polycarbonate surfaces was confirmed by the detection of nitrogen, silicon, and urethane groups. Notably, the product modified with 3 mL of APTES exhibited the highest surface area (61.992 m2 g−1), suggesting its potential for the adsorptive removal of mercury(II). Analysis based on the Langmuir (R2 =0.9824) and Redlich-Peterson (R2 =0.9834) isotherm models suggested a predominantly monolayer adsorption mechanism with an estimated maximum capacity of 1.284 mg g–1, while the adsorption process followed pseudo second-order kinetics (R2 =0.9998). The results highlight the efficacy of waste-derived polycarbonate-organosilane adsorbents in removing mercury(II) from diverse water matrices, rendering them attractive from both economic and environmental sustainability perspectives.