Our research covers a wide spectrum of topics related to the transport, characterization, and removal of environmental colloids. We collaborate synergistically with microbiologists, chemical engineers, mathematicians, medical doctors, geologists, ecologists, and other environmental engineers and scientists. In particular, we investigate two seemingly disparate topics; water purification (treatment of drinking water, industrial and municipal wastewater including hydraulic fracturing water, etc.) and tropospheric aerosols:
(1) Membrane technologies for water purification. We investigate bacteria and virus removal by microfiltration or ultrafiltration. MF/UF are also being used as pretreatment to reduce fouling of higher-pressure membranes (i.e. nanofiltration and reverse osmosis) in integrated membrane systems. MF/UF fouling control and increasing contaminant removal by these low-pressure membranes following pretreatment by chemical- or electrocoagulation or by periodic backwashing is being studied. We are actively researching desalination of brackish surface water by nanofiltration and reverse osmosis. Our group published some of the early work quantifying the temperature effects and activation energies for water and solute transport across nanofilters. We are also interested in controlling and characterizing fouling in NF and RO membranes with applications to water reuse.
(2) (Electro)coagulation. We have pioneered the use of aluminum and iron electrocoagulation as pretreatment for micro- and ultrafiltration. Its ability to enhance virus removal/inactivation and NOM/DBP control during surface water treatment is also of interest. Electro- and conventional chemical coagulation are being investigated for treating produced water along with dissolved air flotation.
(3) Aerosols. Our research focuses on the elemental/isotopic characterization and source apportionment (positive matrix factorization and chemical mass balancing) of primary inhalable particulate matter. We develop novel microwave digestion and inductively coupled plasma – mass spectrometry techniques for rare earths and platinum group elements in PM2.5 and PM10. We were amongst the first to link rare earth metals to establish the contributions of petroleum refining catalytic cracking catalysts. We use lanthanoids as crustal markers to apportion long-range transported North African dust from the Sahara-Sahel region to the Houston area and in the Middle-East region in Qatar. We link rhodium, palladium, and platinum to light-duty gasoline-driven vehicles by making measurements in tunnels and surface roads. More recently, we are using Nd, Sr, and Pb isotopes for dust characterization.