Browsing by Author "He, Ze"
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Item Impact of carbon nanomaterials on electrospun membranes for membrane distillation(2020-12-04) He, Ze; Li, QilinThis research is to elucidate the impact of carbon nanomaterials in electrospun membranes that are applied in membrane distillation. Different carbon nanomaterials including carbon black, carbon nanotubes and graphene oxide were incorporated into the polymer-based electrospun membranes. The membrane distillation performance was investigated by employing the fabricated membranes in a self-made setup. The physical properties of membranes were characterized and related to the membrane distillation performance by a self-developed theoretical model to understand the effect in various aspects. The experimental results revealed the impacts of membrane morphology, hydrophobicity and pore formation. And the simulation results indicated that the current proposed mechanisms are not sufficient to explain the performance of nanocomposite membranes. More promising endeavor was presented to further understand the mechanism.Item Embargo Material and Process Design for High-Performance Membrane Distillation(2024-04-19) He, Ze; Li, QilinMembrane distillation (MD) is a promising desalination technology, especially for hypersaline water desalination and brine management. However, the practical application of MD is hindered by several critical issues: membrane wetting, intensive energy consumption, and limited scalability and water recovery. This dissertation explores promising strategies in membrane material design and system process innovation to resolve the challenges, thereby advancing the implementation of membrane distillation. Carbon nanomaterial composite membranes were found capable of improving the membrane distillation flux but the underlying mechanism was not yet understood. Carbon nanotube (CNT) as a typical carbon nanomaterial was incorporated into electrospun polymeric membrane for MD. The membrane properties relevant to flux performance were characterized. Electrical impedance spectrum analysis was performed to evaluate the partial wetting degree quantitively. The mitigated partial wetting attributed to the nanostructure and smaller surface pore size was found to be the main mechanism of the improved flux performance. Polydopamine (PDA) coating is a widely used method of membrane surface modification for functional materials grafting. Cracking was found to occur on PDA thin film because of the internal stress in dehydration process and the mismatch of elastic stress between PDA and substrate. The cracking led to fragmentation of membrane substrates and impaired the membrane mechanical strength, especially for microporous membranes. PDA film cracking and its unfavorable impact on the mechanical stability of the membranes could be avoided by prewetting the membranes, using a composite membrane with a support layer or a dense membrane. Photothermal membrane distillation (PMD) enjoys high energy efficiency and scalability by reversing temperature polarization in conventional MD. A few previous works achieved gained output ratio (GOR) values of >1 with multi-effect design (ME-PMD). For the first time, this work examined the effects of operating and configuration parameters on the ME-PMD performance, providing a deeper insight into the design of ME-PMD. Low velocity of intermediate effect feed promoted high permeate flux through current effect, while presenting minor impact on flux of previous effect across a wide range (0.13~9.6 mm/s). Heat and mass transfer simulation with COMSOL Multiphysics revealed this was attributed to the less heat loss in intermediate effect. The total flux and GOR increased with the number of effects, but the marginal benefits decreased when adding more effects. With a low 2nd effect feed velocity, triple-effect PMD presented a GOR almost twice single-effect. The impacts of 1st effect feed and coolant velocities were also examined. A novel spiral wound ME-PMD reactor was designed and demonstrated with remarkable membrane distillation performance due to internal heat recovery between multiple effects of feed water in parallel. A 3.5-effect spiral wound ME-PMD presented a GOR around 2.5 treating feed water of 5 g/L. The impact of various operating parameters on system performance was investigated. The total flux increased with solar irradiance and decreased with feed salinity. Lower velocity in outer effect led to higher flux in all effects. On the other hand, inner effect velocity presented less significant impact on overall flux. A second-degree response surface model was developed to establish the relationships between system performance and operating parameters. The work demonstrated that this novel cross-flow spiral wound ME-PMD reactor could provide a feasible strategy of high-performance desalination and brine management using concentrated sunlight.Item Modeling and experimental validation of nanophotonics-enhanced solar membrane distillation technology for treating reverse osmosis brine(Springer Nature, 2024) Elrakhawi, Mayar; Tayel, Ahmed F.; Abdelrazek, Amr; He, Ze; Li, Qilin; Said, Ibrahim A.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT)A novel, cost-efficient Nanophotonic Enhanced Solar Membrane Distillation (NESMD) system, a solar-driven water desalination technology, was studied. The system features a photothermal membrane acting as a solar collector for water distillation, thus eliminating the need for an external condenser. To address the system’s vulnerability to thermal losses, a comprehensive mathematical model was developed and validated against real-world experimental data. This model represents intricately coupled heat and mass transfer within a sweeping-air NESMD system, incorporating heat loss considerations. The modeling strategy involved dividing the NESMD module into sub-cells and implementing a finite difference method for detailed analysis. This led to a series of nonlinear simultaneous equations, which were resolved via computational code using MATLAB software. The developed NESMD model exhibited commendable conformity to experimental data, exhibiting a relative percentage error of less than 10% for average permeate flux and identifying thermal losses as high as 63%. Depending on the operating conditions, heat transferred to the surroundings takes the lead among the heat loss contributors at higher feed rates (up to 25%), whereas heat conduction across the membrane dominates (up to 42%) thermal losses at low feed rates. The study established an exponential correlation between permeate production and solar energy, with a heat transfer coefficient ranging from 9.5 to 30 W m−2 K−1 and a coefficient of determination of 0.96. An integral part of this work includes calculating solar energy utilization and clarifying the system’s performance. Furthermore, this study examines the influence of diverse operational and geometric parameters, providing insights into enhancing production rates. Hence, an increase in feed layer thickness enhances freshwater production by 7%. Due to the intensification of solar irradiance, freshwater production increased ninefold, and specific energy consumption decreased by 134 kW hr m−3. This research underscores the potential of NESMD for sustainable desalination, providing a validated model that lays the groundwork for future advancements in membrane distillation technology.Item Polydopamine-assisted one-step immobilization of lipase on α-alumina membrane for fouling control in the treatment of oily wastewater(Elsevier, 2023) Mulinari, Jéssica; Ambrosi, Alan; Feng, Yuren; He, Ze; Huang, Xiaochuan; Li, Qilin; Di Luccio, Marco; Hotza, Dachamir; Oliveira, J. Vladimir; Nanotechnology-Enabled Water Treatment Center (NEWT)Covalent enzyme immobilization is generally a time-consuming and multistep procedure that uses toxic solvents and requires more than one chemical, making industrial upscaling unattractive. Using an aqueous polydopamine (PDA) solution for enzyme immobilization is a greener alternative. Usually, enzyme immobilization using PDA is performed in two steps: dopamine polymerization on the material surface followed by enzyme immobilization. A few recent studies applied a one-step strategy by mixing dopamine and enzyme in the coating solution, reducing the immobilization time, chemical consumption, and wastewater generation. This study compares the two-step and one-step approaches to immobilizing the lipase Eversa Transform 2.0 (ET2) on an α-alumina membrane. The one-step immobilization method achieved similar enzyme loading, membrane hydrolytic activity, and enzyme-specific activity to those of the two-step method. The ET2 immobilized using both strategies showed excellent fouling resistance and self-cleaning performance in oily wastewater filtration. The membrane modified by the one-step approach exhibited a lower reduction in pure water permeance after oil fouling (35%) and a higher permeance recovery (90%) than the one modified by the two-step method (40% and 74%, respectively). This better performance can be due to the higher hydrophilicity of the modified membrane and higher stability over reaction time shown by the enzyme immobilized by the one-step strategy. The higher stability can be attributed to more attachment points between the enzyme and PDA, increasing the enzyme rigidity and preventing conformational changes.Item Selective membranes in water and wastewater treatment: Role of advanced materials(Elsevier, 2021) Zuo, Kuichang; Wang, Kunpeng; DuChanois, Ryan M.; Fang, Qiyi; Deemer, Eva M.; Huang, Xiaochuan; Xin, Ruikun; Said, Ibrahim A.; He, Ze; Feng, Yuren; Walker, W. Shane; Lou, Jun; Elimelech, Menachem; Huang, Xia; Li, Qilin; NSF Nanosystems Engineering Research Center for Nanotechnology-Enabled Water TreatmentMembrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.