Mercury Removal from Wastewater Using Cysteamine Functionalized Membranes

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Mercury contamination in wastewater poses significant environmental and health risks.
• Existing methods for mercury removal often face limitations in efficiency and scalability.

Purpose of the Study:

• To develop and evaluate a novel three-step filtration and adsorption process for effective mercury removal from wastewater.
• To synthesize and characterize thiol-functionalized microfiltration membranes for mercury capture.

Main Methods:

• A three-step process involving pre-filtration, ultrafiltration (UF), and adsorption using thiol-functionalized membranes.
• Synthesis of thiol membranes by functionalizing polyvinylidene fluoride membranes with cysteine or cysteamine precursors.
• Testing membrane performance using synthetic and industrial wastewater spiked with mercury sulfide nanoparticles (HgS NPs) and dissolved mercury (Hg²⁺).

Main Results:

• Ultrafiltration effectively removed HgS NPs to below detection levels (<2 ppb) with reversible flux reduction.
• Cysteamine-functionalized thiol membranes achieved ~97% removal of dissolved Hg²⁺ over 20 hours.
• Calcium ions reduced adsorption efficiency, with cysteamine membranes outperforming cysteine membranes.

Conclusions:

• The developed three-step process shows high potential for industrial wastewater treatment.
• Thiol-functionalized membranes, particularly those with cysteamine, offer efficient and robust mercury removal.
• Adsorption occurs throughout the membrane's pore length, not just the surface, and can be modeled.