(5aw) Application of Nano-Basis Technique Onto FEW (Food, Energy, Water) Research Via Membrane Technology

Developments of polymeric membranes, primarily over the last two decades, have advanced the use of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) in water treatment, industrial separation processes, and pollution prevention applications. Most challengeable problems in membrane processes are membrane fouling and scaling. These problems not only result in a decreased membrane permeate flux but also protein adhesion and mineral salt scale formation that may permanently alter the physical features of the surface and lead to irreparable membrane damage. In order to develop robust and efficient large-scale membrane separation processes membranes, it is crucial to understand and quantify membrane surface impact on fouling, permeate flux and selectivity.

Although numerous methods of scale and fouling detection have been proposed, it is only recently that real-time early detection of the onset of scale formation has become possible. Direct visual observations and detection of mineral scale on RO/NF membranes under high pressure have been made possible with an ex-situ scale observation detector (EXSOD) along with digital image analysis. Efficient on-line image analysis software was developed assisted with neural networks algorithms to enhance image analysis by providing image family groups to increase the accuracy of single crystal analysis, surface area covered by scale and shape and thus crystal type identification. Direct information on surface nucleation by mineral salt crystals and the rate of single crystal growth was determined over a range of operating conditions and different antiscalants, generating, for the first time, direct fundamental data on the kinetics of surface mineral salt crystallization on RO/NF membranes. These measurements, along with a comprehensive numerical concentration polarization model, enabled evaluation of the direct relationship between the observed flux decline and the surface area covered by mineral scale.

A promising approach to increasing membrane performance, while mitigating fouling, is the structuring of membrane surfaces at the nano-size levels. A novel atmospheric pressure plasma-induced graft polymerization method was developed to enable the generation of a high surface density of active surface sites for subsequent graft polymerization using a suitable monomer. Surface graft polymerization was then carried out to form a dense layer of grafted polymer chains that are covalently and terminally bound to the surface. The chemical and physical features of the resulting grafted polymer film may be tuned by altering the monomer chemistry as well as the reaction conditions to achieve unique architectures for effective advanced materials in membrane separations. Filtration tests of fouling-resistant RO/NF membrane are discussed with protein and polysaccharide solution. Finally, the technical feasibility of nanostructured polymeric membrane for sustainable energy will be discussed.

Discharge of engineered nanomaterials (ENMs) into freshwater and marine ecosystems is expected to increase with accelerating use of nanoparticles in manufacturing. Both biogenic and anthropogenic nanoparticles that are in the atmosphere may find their way to the aquatic environment via dry and wet deposition as well as via runoff. Studies of the potential environmental and human health impacts of ENMs are in their infancy despite and information on their removal from water systems is scarce. The literature is divided on the effectiveness of conventional methods for the removal of nanoparticles from wastewater as well as water sources intended for potable use. Given current knowledge of polyelectrolyte's coagulation of nanoparticles into aggregates or flocs, it is postulated that coagulation can be an effective method that can be coupled with membrane filtration for the removal of nanoparticles from aqueous systems with membrane clogging. With a series of laboratory studies, the potential for polyelectrolyte-enhanced ultrafiltration removal of nanoparticles was investigated. This study will evaluate the environmental impact of nanoparticles to address the application of theory and research in pollution remediation, as well as treatment of wastewater streams that may contain nanoparticles.