Upcycling bentonite into nickel sorbent and its subsequent use as a heterogeneous catalyst in CO2-assisted pyrolysis of high-density polyethylene

초록

This study presented a strategy for utilizing sodium aluminosilicate hydrate (NASH), synthesized via alkali activation of bentonite, as a dual-function material for aqueous Ni2+ removal and subsequent catalytic application in CO2-assisted pyrolysis of high-density polyethylene (HDPE). The NASH samples exhibited high Ni sorption capabilities, achieving Ni loadings of 1.0-9.0 wt% through concentration-dependent sorption mechanisms. Subsequent calcination and H2 reduction successfully converted sorbed NiII species into metallic Ni0, as confirmed by XRD and XPS analyses. Pyrolysis experiments with HDPE revealed that 9.0% Ni-Cat. exhibited the highest catalytic activity, promoting syngas (H2 and CO) production while effectively suppressing coke formation under a CO2 atmosphere. Increasing the CO2 concentration from 20 to 80 vol% progressively enhanced cumulative CO yield from 18.2 to 58.9 mmol, with both H2 and CO yields reaching their maximum at 80 vol% CO2. Overall, this approach offered an integrated strategy for simultaneous spent sorbent upcycling, Ni-contaminated wastewater remediation, and thermochemical plastic waste valorization.

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