Thiol-Functionalized Membranes for Mercury Capture from Water

Pore functionalized membranes with appropriate ion exchange/chelate groups allow toxic metal sorption under convective flow conditions. This study explores the sorption capacity of ionic mercury in a polyvinylidene fluoride–poly­(acrylic acid) (PVDF–PAA) functionalized membrane immobilized with cysteamine (MEA). Two methods of MEA immobilization to the PVDF–PAA membrane have been assessed: (i) ion exchange (IE) and (ii) carbodiimide cross-linker chemistry using 1-(3-dimethylamino­propyl)-3-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), known as EDC/NHS coupling. The ion exchange method demonstrates that cysteamine (MEA) can be immobilized effectively on PVDF–PAA membranes without covalent attachment. The effectiveness of the MEA immobilized membranes to remove ionic mercury from the water was evaluated by passing a dissolved mercury­(II) nitrate solution through the membranes. The sorption capacity of mercury for MEA immobilized membrane prepared by the IE method is 1015 mg/g PAA. On the other hand, the sorption capacity of mercury for MEA immobilized membrane prepared by EDC/NHS chemistry is 2446 mg/g PAA, indicating that membrane functionalization by EDC/NHS coupling enhanced mercury sorption 2.4 times compared to the IE method. The efficiencies of Hg removal are 94.1 ± 1.1 and 99.1 ± 0.1% for the MEA immobilized membranes prepared by IE and EDC/NHS coupling methods, respectively. These results show potential applications of MEA immobilized PVDF–PAA membranes for industrial wastewater treatment specifically from energy and mining industries to remove mercury and other toxic metals.