Sustainable HMF synthesis from waste cooked rice water using fly-ash based Al2SiO5 supported nano-photocatalyst under halogen-ultrasound synergistic-energy: LCA and DFT based simulation

Innovative Fe 3+ /Fe 2+ /Al 2 SiO 5 /Ti 4+ nano-photocatalyst (FA_NPC*) was successfully prepared employing fly ash (FA)-based unique nano-Al 2 SiO 5 and nano-Fe 3+ /Fe 2+ in an innovative assimilated energy-system comprising tungsten-halogen radiation and ultrasound (THUS). The energy-efficient THUS activated optimal FA_NPC* (FA_NPC*°) possessed favourably higher specific surface area (142.11 m 2 / g), finer nanoparticles (47.50 nm) and lower band gap energy (2.78 eV) compared (89.72 m 2 / g, 62.43 nm, 2.97 eV respectively) to its conventionally prepared analog (FA_NPC CO ). The FA_NPC*° rendered a significantly higher HMF yield (38.37 mol%) from a kitchen waste viz., cooked rice water (CRW) under THUS at 70 °C in only 60 min compared to 21.67 mol% HMF yield provided by FA_NPC CO . The DFT based study revealed that the CRW conversion process to HMF occurred through water adsorption on FA_NPC* surface for H 3 O + formation, followed by H 3 O + induced CRW hydrolysis, subsequent glucose isomerization on -Ti active sites and finally fructose dehydration by H 3 O + . The LCA of the overall process confirmed that the FA_NPC*° catalysed CRW conversion process could appreciably alleviate harmful environmental parameters, viz. global warming, fossil depletion, human toxicity and metal depletion by 7.65%, 4.15%, 8.56% and 13.57% respectively in comparison with FA_NPC CO . Thus, the THUS stimulated system could favourably demonstrate the efficient and eco-friendly utilisations of two abundant waste resources, viz. fly ash and cooked rice water for a sustainable production of HMF. • Sustainable waste cooked rice water conversion by fly-ash based nanophoto-catalyst. • High HMF yield (38.37%) achieved by fly-ash based Fe 3+ /Fe 2+ /Al 2 SiO 5 /Ti 4+ at 70 °C. • Tungsten-halogen & ultrasound promoted catalyst owns finer nanoparticles (47.5 nm). • Catalytic reaction mechanism by DFTB along with water solvation model. • Appreciable reduction of GWP by 7.65% for overall process revealed through LCA.