Environmentally-friendly recycling of polystyrene and disposal of metal-containing plant biomass from phytoremediation sites are major challenges. Strategies beyond waste-to-energy that can harness the circular chemical potential of such feed-stocks are needed. We present a “triple-green” approach using microwave irradiation (250 °C, 200 W, <10 min) for the accelerated de-polymerization of polystyrene and valorization of nickel-contaminated biomass to yield valuable chemical building blocks. Biomass from soil-grownStackhousia tryoniiplants that naturally hyperaccumulate nickel (1.5 wt%), alongside non-hyperaccumulator, hydroponically-grown willow (Salix viminalis, 0.1 wt% Ni) was tested. The presence of naturally-bound nickel in carbonized biomass (Ni-phytocat) fromS. tryoniiandS. viminaliswas shown to significantly accelerate de-polymerization (74% and 69% styrene selectivity; 18 kJ g−1and 24 kJ g−1microwave energy consumed, respectively) when compared to controlS. viminalis(<0.01 wt% Ni; 56%; 42 kJ g−1) and activated carbon (57%; 36 kJ g−1). The Ni-phytocat offered significant advantage in enabling rapid de-polymerization of polystyrene with up to 91% conversion efficiency as compared to control phytocat (up to 82%) and activated carbon (up to 79%) within 5 min. Use of this synergistic effect of bio-derived Ni and microwaves to maximize the de-polymerization efficiency is proposed.
Bibliographical noteFunding Information:
The authors acknowledge the financial support from the University of York (Wild Fund Scholarship) and Association of Commonwealth Universities (ACU Blue Charter fellowship). We also acknowledge the assistance of Dr Antony Van der Ent of the University of Queensland, Australia and Dr Chris Anderson of Massey University, New Zealand in the field collection of hyper-accumulator species. We are grateful to receive the technical support and assistance from Mr Karl Heaton, Dr Florent Bouxin and Dr Jon Barnard.
© The Royal Society of Chemistry 2021.
Copyright 2021 Elsevier B.V., All rights reserved.