Early warning sensors for monitoring mercury in water

[Display omitted] •3D nanostructuration of nanoporous membrane-electrodes allows a pre-concentration of mercury by passive adsorption.•Hg(II) sensors showed a good mercury recovery in mineral and ground waters.•Results in superficial waters pointed to Hg(II) instabilities when dissolved organic carbon content was superior to 3.5 mg/L.•streaming potential experiment was found efficient to fully characterize grafted charged polymer chains inside nanochannels. Poly-4-vinylpyridine grafted poly(vinylidene difluoride) (P4VP-g-PVDF) nanoporous polymer electrodes were found to be sensitive for Hg(II) analysis. The fabrication and characterization of functionalized nanoporous membrane-electrodes by FESEM and FTIR are presented. Functionalized nanopore charge state versus a large range of pH (1–10) was investigated by registering the streaming potential. This isoelectric point is achieved at the pKa of P4VP (pH = 5). Mercury adsorption at solid-liquid interface obeys a Langmuir law. A protocol for accurate Hg(II) analysis at ppb level was established. Calibration curves were performed and different real water samples (mineral water, ground water, surface water) were spiked and analyzed. The resulting sensor is intended to be integrated into existing systems or used standalone as portable devices. A first generation prototype exhibiting its own integrated potentiostat, its software and set of membrane-electrode pads is presented.