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With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to

With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to incorporate with RO to change the membrane performances. Silver is biocidal, which has been used in a variety of consumer products. Recent studies showed that fabricating silver nanoparticles (AgNPs) on membrane surfaces can mitigate the biofouling problem on the membrane. Studies have shown that Ag released from the membrane in the form of either Ag ions or AgNP will accelerate the antimicrobial activity of the membrane. However, the silver release from the membrane will lower the silver loading on the membrane, which will eventually shorten the antimicrobial activity lifetime of the membrane. Therefore, the silver leaching amount is a crucial parameter that needs to be determined for every type of Ag composite membrane.

This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.

The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
ContributorsHan, Bingru (Author) / Westerhoff, Paul (Thesis advisor) / Perreault, Francois (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2017
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Description
In order to produce efficient reverse osmosis membranes, it is necessary to minimize the effects of outside factors on the membrane surface that can reduce the flux of water through the membrane. One such problem is fouling. Fouling happens when particles are deposited on the membrane surface, blocking water flow

In order to produce efficient reverse osmosis membranes, it is necessary to minimize the effects of outside factors on the membrane surface that can reduce the flux of water through the membrane. One such problem is fouling. Fouling happens when particles are deposited on the membrane surface, blocking water flow through the membrane. Over time, the collection of foulants will prevent water through the membrane, increasing the amount of energy required in the system. Microgel, a heat-responsive colloidal gel, shows promise as an anti-foulant coating as it possesses functional groups similar to the membrane and compatible with common foulants and changes volume due to temperature differences. By coating the membrane with the microgel, foulants will attach to the functional groups of the microgel instead of those of the membrane Our hypothesis is that the change in volume of the microgel with different temperatures will help reduce and remove foulants. By functionalizing the surface of the membrane and the microgel, the microgel can covalently bond to the membrane surface and avoid detachment under reverse osmosis conditions. Microgel-coated reverse osmosis membranes have been fluorescently fouled to measure the decrease in foulants with heated crossflow under fluorescent microscopy. This process has shown a 50% decrease in fluorescence on the surface of the membrane indicating a decrease in foulants due to the presence of microgel. Under cross-flow conditions with a low flow rate, the microgel remains on the functionalized membrane for 8 hours with similar anti-fouling performance as the dip-coating process.
ContributorsKraetz, Andrea Nicole (Author) / Thomas, Marylaura (Thesis director) / Perreault, Francois (Committee member) / Chemical Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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Description
Bacteriophage provide high specificity to bacteria; receiving interest in various applications and have been used as target recognition tools in designing bioactive surfaces. Several current immobilization strategies to detect and capture bacteriophage require non-deliverable bioactive substrates or modifying the chemistry of the phage, procedures that are labor intensive and can

Bacteriophage provide high specificity to bacteria; receiving interest in various applications and have been used as target recognition tools in designing bioactive surfaces. Several current immobilization strategies to detect and capture bacteriophage require non-deliverable bioactive substrates or modifying the chemistry of the phage, procedures that are labor intensive and can damage the integrity of the virus. The aim of this research was to develop the framework to physisorb and chemisorb T4 coliphage on varied sized functionalized silica particles while retaining its infectivity. First, silica surface modification, silanization, altered pristine silica colloids to positively, amine coated silica. The phages remain infective to their host bacteria while adsorbed on the surface of the silica particles. It is reported that the number of infective phage bound to the silica is enhanced by the immobilization method. It was determined that covalent attachment yielded 106 PFU/ml while electrostatic attachment resulted in 105 PFU/ml.
ContributorsBone, Stephanie (Author) / Perreault, Francois (Thesis advisor) / Alum, Absar (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2017