Cation–π-induced mixed-matrix nanocomposite for the detection and removal of Hg2+ and azinphos-methyl towards environment remediation†

Abstract

The unregulated use of pesticides, which constitutes organophosphates, demands their continuous monitoring from a human health perspective. The development of efficient, reliable and affordable methods for the effective quantification, removal and detoxification of pesticides is indeed a significant challenge in the fields of agriculture, environmental science and public health. Herein, we designed a simple approach for the construction of a functionalised electrochemical material that includes the following steps: (i) the cation–π induced non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs) with an organic cation IL, and (ii) the complexation of IL@MWCNTs with Hg²⁺ to accelerate electron transfer, apparently enhancing the response of Hg/IL@MWCNTs towards azinphos-methyl, as revealed by cyclic voltammetry. Hg/IL@MWCNTs/GCE exhibits electrocatalytic behaviour towards azinphos-methyl (AZM) with a low detection limit of 1.10 μM and a wide linear range (0.20–180 μM). The degradation of the AZM pesticide was supported by ³¹P NMR titration and mass spectrometry, which confirmed the conversion of AZM into its non-toxic products. Taking into account the aforementioned findings, the functionalised IL@MWCNT composite was fabricated into an ultrathin polyamide layer on a PES support membrane via interfacial polymerisation for practical application. The developed nanocomposite membrane removes the Hg²⁺ metal ion and azinphos-methyl pesticide from contaminated water with a removal efficiency of 95% and 90%, respectively.