(2026) Applied Clay Science_Upcycling bentonite into nickel sorbent and its subsequent use as a heterogeneous catalyst in CO₂-assisted pyrolysis of high-density polyethylene

Yoon K.; Cha H.; Lee H.; Kwon E.E.; Lee T.; Song H.

(Elsevier Ltd) Applied Clay Science ISSN: 1691317 Vol.293 Issue. Article No.108401 DOI: 10.1016/j.clay.2026.108401

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 Ni^II 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. © 2026 Elsevier B.V.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) ( RS-2024-00347233 ). This research was supported by the ANCHOR program through the Jeju ANCHOR center , funded by the Ministry of Education (MOE) and the Jeju Special Self-Governing Province, Republic of Korea ( 2026-ANCHOR-17-001 ).