Innovative Long-Lasting Catalytic Hydrothermal Reaction for High Efficient Energy Harvest and Carbon Capture from Recalcitrant Wastewater

Thiswork reveals, for the first time, a long-lasting catalytichydrothermal dehydrogenation for energy and carbon recovery from recalcitrantwastewater. Simultaneous recovery of energy andcarbon from recalcitrantwastewaterhas attracted ever-growing interest for water management. However,the existing technologies to break down recalcitrant pollutants aremainly energy and chemical intensive. Here, a novel hydrothermal reactionamended with activated carbon (AC) was demonstrated to enable an unprecedented99.5% removal of an exemplar difficult-to-degrade contaminant, polyvinylalcohol (PVA), from wastewater. Meanwhile, an easy-separated hydrochar(C6H7.08O0.99) with an abundanceof unsaturated aromatic rings was produced, exhibiting 118.46% ofenergy yield with a high heating value of 32.9 MJ/kg, outperformingthe hydrochar(s) reported to date. The retrieved energy from the hydrocharwas able to entirely offset the energy needs for this hydrothermalprocess. Interestingly, the AC catalyst can sustain in situ reuseover 125 cycles with no evidence of irreversible deactivation. Theadjacent carbonyl groups on AC were revealed to provide active sitesfor dehydrogenation from either the C-H (1.24 & ANGS;) or O-H(1.40 & ANGS;) bond in PVA, forming hydroxyl groups on AC and highlyreactive intermediates (& UDelta;G (0) = -11.5kcal/mol). It was further proved that the free oxygen in the headspaceextracted H atoms from the newly formed hydroxyl groups on AC (& UDelta;G (0) = -4.7 kcal/mol), thus regeneratingthe carbonyl sites on AC for the next catalytic hydrothermal dehydrogenationcycles. The long-lasting catalyst reusability and energy self-sufficientapproach offer a sustainable route to carbon neutrality in recalcitrantwastewater treatment.