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- All Subjects: Membranes (Technology)
- All Subjects: Leaching
- Creators: Chandra, Aman
- Creators: Han, Bingru
Description
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.
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
Description
CubeSats offer a compelling pathway towards lowering the cost of interplanetary exploration missions thanks to their low mass and volume. This has been possible due to miniaturization of electronics and sensors and increased efficiency of photovoltaics. Interplanetary communication using radio signals requires large parabolic antennas on the spacecraft and this often exceeds the total volume of CubeSat spacecraft. Mechanical deployable antennas have been proposed that would unfurl to form a large parabolic dish. These antennas much like an umbrella has many mechanical moving parts, are complex and are prone to jamming. An alternative are inflatables, due to their tenfold savings in mass, large surface area and very high packing efficiency of 20:1. The present work describes the process of designing and building inflatable parabolic reflectors for small satellite radio communications in the X band.
Tests show these inflatable reflectors to provide significantly higher gain characteristics as compared to conventional antennas. This would lead to much higher data rates from low earth orbits and would provide enabling communication capabilities for small satellites in deeper space. This technology is critical to lowering costs of small satellites while enhancing their capabilities.
Principle design challenges with inflatable membranes are maintaining accurate desired shape, reliable deployment mechanism and outer space environment protection. The present work tackles each of the mentioned challenges and provides an
understanding towards future work. In the course of our experimentation we have been able to address these challenges using building techniques that evolved out of a matured understanding of the inflation process.
Our design is based on low cost chemical sublimates as inflation substances that use a simple mechanism for inflation. To improve the reliability of the inflated shape, we use UV radiation hardened polymer support structures. The novelty of the design lies in its simplicity, low cost and high reliability. The design and development work provides an understanding towards extending these concepts to much larger deployable structures such as solar sails, inflatable truss structures for orbit servicing and large surface area inflatables for deceleration from hypersonic speeds when re-entering the atmosphere.
Tests show these inflatable reflectors to provide significantly higher gain characteristics as compared to conventional antennas. This would lead to much higher data rates from low earth orbits and would provide enabling communication capabilities for small satellites in deeper space. This technology is critical to lowering costs of small satellites while enhancing their capabilities.
Principle design challenges with inflatable membranes are maintaining accurate desired shape, reliable deployment mechanism and outer space environment protection. The present work tackles each of the mentioned challenges and provides an
understanding towards future work. In the course of our experimentation we have been able to address these challenges using building techniques that evolved out of a matured understanding of the inflation process.
Our design is based on low cost chemical sublimates as inflation substances that use a simple mechanism for inflation. To improve the reliability of the inflated shape, we use UV radiation hardened polymer support structures. The novelty of the design lies in its simplicity, low cost and high reliability. The design and development work provides an understanding towards extending these concepts to much larger deployable structures such as solar sails, inflatable truss structures for orbit servicing and large surface area inflatables for deceleration from hypersonic speeds when re-entering the atmosphere.
ContributorsChandra, Aman (Author) / Thangavelautham, Jekanthan (Thesis advisor) / Huang, Huei Ping (Thesis advisor) / Oswald, Jay (Committee member) / Arizona State University (Publisher)
Created2015