Baoxia Mi

Research Activities of the Membrane Innovation (MI) Lab: Our research centers on physicochemical processes emphasizing nanomaterials and membrane science/technology for drinking water purification and wastewater reuse. Ongoing research topics are described as follows.

Graphene-Enabled, High-Performance Membranes for Enhanced Energy Efficiency
Dwindling water resources and increasing water demands have forced us to consider treating water from non-traditional sources that may contain contaminants typically overlooked in conventional water treatment. Besides, new water contaminants (e.g., pharmaceuticals and endocrine disrupting compounds) are constantly emerging and many of these contaminants have potential adverse health effects and thereby have raised severe public concerns over water safety.  Membrane processes are among the most effective strategies to remove contaminants from water.  However, today’s membrane-based water separation in general suffers from high energy consumption. Therefore, it is very desirable to discover new materials to make high-performance membranes that will require much lower energy consumption.  Our research program in this area focuses on using novel nanomaterials and innovative methods to synthesize the next-generation, high-performance membranes. For instance, we have been innovatively exploiting the promising properties (e.g., fast water transport thus lower energy consumption, highly stackable 2D nanostructure, amenable functional groups, and antibacterial properties) of the emerging graphene oxide (GO) nanomaterials to synthesize a fundamentally new class of water filtration membranes.  Membranes made of stacked GO nanosheets demonstrate high water flux due to a nearly frictionless flow of mono-layered water molecules through the 2D capillaries formed by closely spaced GO nanosheets and unique separation capabilities.  Our research on GO-enabled membranes will very likely pave the way to the development of a new class of environmental friendly, high-performance, energy-efficient, low-cost membranes. 

Understanding Fundamental Fouling and Transport Mechanisms in Membrane Processes
The advancement of membrane technology is severely hampered by the long-standing problem of fouling, which is caused by the accumulation of foreign substances on membrane surfaces or inside pores.  Fouling can seriously deteriorate membrane performance by lowering water permeability, worsening product water quality, increasing energy consumption, shortening membrane life, increasing operating costs, and, in an unsustainable manner, releasing chemical wastes from mandated cleaning process into the environment. Therefore, membrane fouling is a major obstacle against the efficient use of membranes. To address this critical issue, we integrate multi-scale experiments and molecular simulation to systematically unveil the molecular-level membrane-foulant interactions, which cannot be fully understood by either experimental or simulation approaches alone.  This research provides keen insight into many membrane-foulant interactions, and thus facilitates the development of efficient fouling-mitigation strategies and fouling-resistant membranes. We also explore the use of layer-by-layer assembly of polyelectrolytes and nanoparticles to fabricate biofouling-resistant nanocomposite membranes. This research creates exciting opportunities for the development of the next-generation membrane filtration systems for water purification. 

Integrated Membrane System to Promote Water, Energy, and Environmental Sustainability
We also strive to transform our membrane research and knowledge into real-world technologies that can promote water, energy, and environmental sustainability. Our research efforts in this area center on developing sustainable membrane processes for emergency water supply, water reuse, desalination, and sustainable energy harvesting.  In the past years, we have been heavily working on newly emerging membrane processes, such as forward osmosis (FO), pressure retarded osmosis (PRO), and membrane distillation (MD).  FO uses natural osmotic pressure as the driving force for water flux, holding great promise for drastically cutting energy consumption in water treatment.  FO also leads to low fouling potential and superior cleaning efficiency.  PRO can be used to convert approximately 40 percent of the potential energy from the mixture of freshwater and seawater into mechanical energy, thereby exhibiting a significant possibility for renewable power production.  So far, the bottleneck problems for the PRO process include the unavailability of suitable membranes and serious membrane fouling.  My research in this area focuses on the development of novel, anti-fouling, high-performance PRO membranes and optimization of the PRO process.  We are also studying an integrated FO and MD system for water purification using sustainable energy source (e.g., waste heat, solar energy, geothermal).

Sponsors of our research include the National Science Foundation (NSF), U.S. Department of Energy (DOE), Environmental Protection Agency (EPA), U.S. Agency for International Development (USAID), National Water Research Institute (NWRI), and American Membrane Technology Association (AMTA).