Engineered biochar-iron nanocomposite for efficient peroxymonosulfate activation: Degradation of naphthenic acids, toxicity evaluation, and economic assessment

This paper explores the use of engineered biochar coupled with zero-valent iron (Fe 0 ) and peroxymonosulfate (PMS) for the degradation of naphthenic acids (NAs) and fluorophore organic compounds (FOCs) in real oil sands process water (OSPW). Immobilizing Fe 0 on biochar, a stable, porous carbon-based material, enhanced catalyst stability and degradation efficiency. Experimental results demonstrated significant removal of FOCs, classical, and oxidized NAs. Notably, 1 g/L of catalyst achieved ∼80 % removal of O 2 -NAs within 120 min, primarily through the generation of sulfate and hydroxyl radicals. To assess the toxicity of treated OSPW, cell-based immunotoxicity assays were conducted by measuring pro-inflammatory cytokine secretion in human and mouse macrophage cells. Treated OSPW exhibited a significant reduction in cytokine secretion, indicating lower immunotoxicity. Additionally, bacterial toxicity tests using Staphylococcus warneri revealed a reduced inhibitory effect on bacterial growth post-treatment. A comprehensive economic assessment benchmarked this method against various advanced oxidation processes (AOPs), demonstrating its cost-effectiveness, particularly when compared to light-based AOPs. These findings highlight Fe 0 -biochar-PMS treatment as a sustainable and efficient approach for mitigating OSPW toxicity, offering a viable solution for improved wastewater management in oil sands operations. • PMS activation via a biochar-coupled Fe 0 demonstrated high efficiency in degrading naphthenic acids (NAs). • Approximately 80 % of classical NAs were degraded in 120 min using 1 g/L of catalyst. • Treatment resulted in a significant reduction in immunotoxicity and cytotoxicity of OSPW. • A comprehensive economic assessment was conducted and compared with the literature. • The use of a biochar-coupled catalyst effectively illustrates the waste-to-value concept.