Fluorescent dendritic fibrous nanosilica/polyurethane composite membranes for selective and sensitive recognition and removal of Hg2+/Hg+ ions

Dendritic fiber nanosilica (DFNS) possesses a unique porous structure, and its potential application for adsorption and separation, particularly of heavy metals, should be explored. This study, to our knowledge, is the first time to introduce fluorescence recognition ability to DFNS and to combine it with polymer materials. Firstly, the fluorescent DFNS (FL-DFNS) was prepared by a Schiff base formation reaction between the naphthalamide fluorophore and the modified DFNS. Then, a two-step approach was employed to fabricate FL-DFNS/polyurethane (FL-DFNS/CSPU-02) nanocomposite materials. FL-DFNS functions as a "turn off" sensor for Hg2+/Hg+ ions, exhibiting fluorescence quenching of up to 81.1 %/75.9 %. It also has an excellent adsorption capacity to mercury. Specifically, FL-DFNS/CSPU-02 membrane enabled portable detection of Hg2+/Hg+ ions. Importantly, it exhibited superior performance in the adsorption and separation of Hg2+/Hg+ ions, achieving a removal efficiency of 97.7 % and 98.0 %, with an absorption capacity of 382.4/373.5 µg/cm2. And it can be recycled for at least nine times. Overall, this study confirms the practical application value of FL-DFNS and FL-DFNS/CSPU-02 membrane in the recognition and removal of Hg2+/Hg+ ions, it will achieve the real application in environmental science and engineering.