(399l) Water Stable Metal-Organic Framework Based Adsorbent and Membrane for Precious Metal (Silver) Separation from Wastewater | AIChE

(399l) Water Stable Metal-Organic Framework Based Adsorbent and Membrane for Precious Metal (Silver) Separation from Wastewater

Authors 

WANG, C. - Presenter, National University of Singapore
Wastewater treatment techniques have gained significant importance nowadays because the water scarcity is threating all people around world. Adsorption based membrane purification techniques have an exciting potential owing to their economic and environmental advantages. In this study, water and acid stable UiO-66 was mixed with ‘green polymer’ cellulose to produce mixed matrix membranes for silver adsorption applications. Highly stable membranes were obtained because the desirable properties of cellulose (biodegradable, cheap, and natural polymer with highly stable structure due to –OH bonding in its structure) and consistency UiO-66 (water and acid stable porous filler with very high surface area) were combined successfully.

Firstly, zirconium metal-organic framework (UiO-66) is synthesized. Then, silver adsorption capacity of UiO-66 is investigated in detail at several varying parameters such as pH conditions, contact time and adsorption isotherms. Afterwards, pure cellulose and cellulose/UiO-66 mixed matrix membranes are synthesized, and their silver adsorption capacities are investigated in batch and continuous conditions. UiO-66 MOFs and cellulose/UIO-66 mixed matrix membranes are also characterized using XRD, FTIR, and SEM analysis techniques.

To the best of our knowledge, this is the first application of UiO-66 in silver pollutant removal from water supplies. Pure UiO-66 powders exhibited very promising performance for silver adsorption across a broad pH range from very acidic (1) to neutral (7) conditions, with the best adsorption capacity at pH 2. It achieved a remarkable silver uptake capacity of 77 mg/g, and it reached the equilibrium just after 1 hour of contact time. This remarkable performance of rapid silver adsorption and high stability of UiO-66 in water provides promising insights to the water treatment applications.

Cellulose/UiO-66 membranes showed better silver and arsenic adsorption capacity than pure cellulose membranes. Incorporation of MOF particles in cellulose resulted in highly porous green membranes with promising adsorption performances for silver. Cross-flow filtration geometry improved their efficiency further due to penetration of pollutants through the membrane due to applied positive pressure across the membrane. Finally, 4 grams/m2 silver adsorption rate was achieved with the cellulose/UiO-66 membrane in a 1-hour experiment.