Eco-friendly and stable triclosan removal from groundwater using peroxyacetic acid activated with biochar produced from saccharification residues

Abstract

Biochar is a cost-effective activator in advanced oxidation processes, its progressive release of soluble substances during application can potentially reduce the stability of its activation efficiency and induce secondary environmental pollution. Addressing these drawbacks of biochar, this study focused on enhancing its stability and the efficacy of peracetic acid (PAA) in removing triclosan from groundwater, employing a saccharification residue-based biochar (BC-SR). The research findings indicated that the efficacy of triclosan removal by BC-SR/PAA surpassed that of ordinary biochar (BC-O) by 1.33 times. Furthermore, utilizing the response surface methodology design, the synergistic efficiency of BC-SR/PAA was enhanced, achieving a removal rate of up to 90%. The high removal efficiency of BC-SR could be attributed to its microporous structure, surface area, loss of stability, and thermal stability, which were all significantly better than BC-O. Even after 10 cycles of reuse, the removal efficiency of BC-SR still maintained 77% of its initial efficiency. Notably, the activation mechanism of BC-SR/PAA was different from typical carbonaceous materials, as the degradation system's main active substances were ·O2− and 1O2, and BC-SR's active sites may be its surface's persistent free radicals. Moreover, column tests using natural groundwater and soil emulated BC-SR's role as a permeable reactive barrier. Results underscored the BC-SR/PAA system's formidable removal and anti-interference abilities. Analysis showed triclosan degradation products have lower toxicity, highlighting their practical value. This research addresses the challenge of inadequate removal efficiency and secondary pollution in in-situ groundwater remediation, particularly associated with complex substrates. This approach, unlike biochar ‘burdening’, offers a novel concept for ‘de-burdening’ biochar activation.