Collaborators
- Juanita Purdy, Science Teacher, J.M. Alexander Middle School
- Maya Foxworth, Krystal Wilson, Chyna Bly and Carrie Lowe, JCSU Student Researchers
- Todd Coolbaugh, Ph.D, Assistant Professor, Chemistry, Johnson C. Smith University
- Tracy Brown, Ph. D, Assistant Professor, Chemistry, Johnson C. Smith University
Project Focus
Stormwater runoff is a serious pollution concern at construction sites and is an emerging concern in urban areas with large coverages of hard surfaces such as roads and parking lots. In both cases one of the most detrimental, and difficult to control, environmental problems associated with stormwater runoff are colloidal suspensions, which consist of micro- to nanometer sized organic and inorganic particles — think dust and tiny oil drops. These particles usually bear surface charges which prevent them from sticking together and sinking in catchment basins. If these small particles are swept into waterways they result in increased turbidity, that is, cloudiness, a key water quality indicator. Nearly all of Charlotte’s waterways are characterized by high turbidity. One solution to this problem, widely adopted by the construction industry, including NCDOT, is to add flocculants to storm water catchments. “Flocculation is the process where multiple particles are bridged together to form flocs or flakes.” Flocculants are typically polymers (polyanions) that neutralize surface charge and cross-link the particles leading to coagulation and settling. The most commonly used polymers, currently, are polyacrylamide derivative. The use of polymers is not without some controversy. The monomeric precursors of both of these polymers are considered to be known carcinogens but there is no evidence the polymers are themselves carcinogenic. However concerns about small amounts of unreacted monomers and possible degradation products raises some concerns. A range of laboratory techniques, including Raman spectroscopy, as well as batch studies (jar studies) will be carried out with both artificial and grab samples of stormwater to investigate the use of cellulose nanofibrils as environmentally safe flocculating agents. Participants will also be introduced to pH, conductivity and turbidity measurements and will become more familiar with environmental science, nanotechnology and polymer science.
Research Abstract
Water Pollution is a major problem that is affecting urban areas environments and human health. One area of water pollution that is of a concern to Charlotte and other major development areas of North Carolina is storm water runoff. Storm water runoff can occur in areas that have large surface areas such as construction sites, farm land or industry sites. One problem associated with this runoff is colloidal suspensions such as dust particles and tiny oil drops which contain surfaces charges and prevents them from bonding together (flocculation). These particles remain in the water and increase turbidity, (water cloudiness) a key indicator of water quality.
This research examined TEMPO oxidized CNF (Cellulose Nanofibrils) that were provided by Forest Product Laboratory of the US Department of Agriculture. This product offers a sustainable solution for wastewater treatment due to being renewable and biodegradable. It is hypothesized these ionic nanoparticles have enough flexibility to allow sediments of wastewater to be settled out of the water without adding harsh or carcinogenic chemicals.
The soil samples that were collected from various locations were added to deionized water and subjected to magnetic stirring to simulate storm water runoff. The effects of CNF concentration, pH and setting time were investigated. From the samples, substantial sedimentation was observed and colloidal suspensions were formed. In addition, initial observations indicate that CNF addition causes some flocculation. The efficiency of flocculation increased with an increase of pH. At longer settling times, a substantial increase in turbidity was noted as well as the formation of stable colloids. CNF has not at this time affected turbidity in stable colloids which may suggest a possible negative charge of the colloidal particles. Additional research is needed for this determination.
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