N, S-CDs encapsulated polyamide fluorescent membranes: An efficient strategy for the retention and detection of mercury (II) ions in aqueous environments

Abstract

Nanofiltration membranes are extensively implemented in water treatment, particularly for the efficient interception of toxic heavy metal ions. This work introduces a novel functional membrane fabricated via interfacial polymerization, incorporating nitrogen and sulfur co-doped carbon dots (N, S-CDs) as additives to enhance mercury removal from aqueous solutions. The integration of carbon dots has been demonstrated to significantly augment the membrane’s hydrophilicity, thereby improving the pure water flux. Moreover, it modulates the crosslinking degree of the polyamide layer, enhancing mercury retention. The N, S-CDs, due to their high selectivity for Hg (II), confer the modified membrane with fluorescence detection capabilities, allowing for the precise quantification of mercury rejection. The membrane achieved a remarkable Hg (II) retention rate of 94.85 %, with a pure water flux of 10.68 L m⁻² h⁻¹ bar⁻¹, and attained a detection limit of 5.49 × 10⁻⁷ M for Hg (II). The durability and reusability of the membrane are substantiated by soaking and recycling trials, underscoring the stable encapsulation of N, S-CDs within the nanofiltration matrix.