Reactive polythiosemicarbazide membranes featuring thiosemicarbazide ligands for selective chelation and dynamic mercury adsorption

Abstract

We report the development of a novel polymeric membrane based on polythiosemicarbazide (PTSC), engineered for highly selective and efficient mercury ion removal from contaminated water. Unlike conventional sorbents that require post-functionalization, PTSC incorporates a chelating thiosemicarbazide group in every repeating unit, offering a dense array of active sites for direct metal coordination. This intrinsic functionality eliminates the need for external modification and significantly enhances both adsorption capacity and operational simplicity. The membranes were fabricated via the phase inversion method, yielding an asymmetric porous structure with interconnected pathways that support high flow rates and pressure-driven filtration. This architecture overcomes the diffusional limitations typical of packed-bed adsorbents. Batch adsorption studies conducted under acidic conditions revealed an exceptionally high mercury uptake capacity of 1418 mg/g from 1000 ppm solutions. Dynamic filtration experiments further confirmed rapid and selective mercury removal (93–99 %) from low-concentration (10 ppm) samples. The membranes also demonstrate excellent reusability, with over 99 % regeneration efficiency using 0.1 M thiourea, retaining performance across multiple cycles. Selectivity tests confirmed strong selectivity for Hg²⁺ over competing heavy metals (Cu²⁺, Cr³⁺, Co²⁺, Pb²⁺, Cd²⁺), guided by hard-soft acid-base (HSAB) coordination principles. This work introduces a scalable, functional polymer platform with built-in chelation capability, offering a powerful alternative to conventional mercury adsorbents in water purification applications.