These are some recent initiatives in the Ladner research group.

Coupling small-particle adsorbents with membranes for trace-contaminant removal in water treatment
National Science Foundation. CBET 1236070. $325,285. August 2012 through July 2015. David Ladner (PI), Tanju Karanfil (Co-PI), and Olin T. Mefford (Co-PI). Intellectual Merit: Superfine powdered activated carbon (200 to 500 nm particle size) and graphene are being evaluated as advanced materials that—coupled with membranes—remove synthetic organics better than conventional adsorbents. In particular, competitive adsorption of natural organic matter is being evaluated to understand the novel adsorbants’ advantages in real-world engineered treatments systems. Broader Impacts: This work may lead to low-footprint and low-energy processes for sustainably removing emerging contaminants. See the project abstract on the NSF website.

Dendritic polymers as biocompatible oil spill dispersants
US Environmental Protection Agency. STAR R835182. $500,000. May 2012 through May 2015. David Ladner (PI), Pu-Chun Ke, (Co-PI), Andrew Whelton (Co-PI), Sean Powers (Co-PI). Our objective is to gain a fundamental understanding of the interactions of dendritic polymers with crude oil, taking toxicity and biodegradability into consideration. Our community outreach program objectives are to use community input in developing the research and to educate a broad audience about current and novel dispersants and their environmental impacts. See the project abstract on the EPA website.

QR Code as a Sustainability Research Tool
University Research Grant Committee (URGC). $9,163. February to June, 2012. David Ladner (PI), Catherine Mobley (Co-PI). This is a collaborative project between the Department of Environmental Engineering and Earth Sciences and the Department of Sociology and Anthropology at Clemson. QR codes are attached to public water fixtures like drinking water fountains and toilet stalls to allow users with smartphones to learn about the water and energy required to operate the fixture they are using. Water and energy data were directly measured (e.g. fixture flow rates) or were obtained from Clemson’s records held in the University Facilities division. Users can also take a survey or play a quiz game to learn more about the water-energy nexus and about the source and flow path of Clemson’s drinking water. Visit the website.

Regenerable membranes
Fouling (a buildup of organic matter or other material that decreases productivity) is one of the most significant drawbacks to using membranes for water treatment. Membranes can be cleaned to remove the foulants, but rarely can they be cleaned completely. This project seeks to develop a new kind of membrane with a “regenerable skin.” The skin can be shed after fouling and a new skin can be applied to give a perfectly fresh membrane. The big question is what do we use for the skin and how do we attach it and release it. As part of this effort we are trying to find coatings that can adsorb low-concentration pollutants like endocrine disrupting compounds, pharmaceuticals, and personal care products.

Helical-flow reverse osmosis modules
In an effort to reduce fouling and energy consumption in reverse osmosis, we have envisioned a new kind of module. It is similar to current state-of-the-art spiral wound modules, but the spacer between the membranes causes water to flow in a helical path, the geometry of which can be adjusted to give maximum water productivity per energy input. Also, fouling is far less likely in the new flow channels than it is in the standard module. We are beginning bench-scale work as well as computational fluid dynamics (CFD) modeling to determine the usefulness of our concept.

Wind-powered desalination
We are working with a small business, Windation Energy Systems, in California, to couple a wind turbine directly to a reverse osmosis desalination unit. This involves the redesign of the RO system to accommodate low-intensity and intermittent wind. Bench-scale lab experiments as well as modeling of the system are both planned.

Algal biofuel separations
Much of the algal biofuel research currently ongoing is geared toward selecting and modifying strains to increase their lipid content. However, harvesting the algae (removing them from the water they grow in) is a key bottleneck in making algal biofuels sustainable and this is receiving much less attention. We are interested in determining the fundamental properties of the algal cells that affect the energy input required for harvesting. Our focus is on microfiltration and ultrafiltration membrane processes which show great promise for providing the needed separations, especially for the smallest microalgae that have the highest growth rates and lipid contents. The expected end result is to redesign the filtration system to enable low-energy harvesting which will help make algal biofuels viable and sustainable.

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