Photochemical and Fungal Transformations of Carbon Nanotubes in the EnvironmentEPA Grant Number: R834858
Title: Photochemical and Fungal Transformations of Carbon Nanotubes in the Environment
Investigators: Jafvert, Chad T. , Fairbrother, D. Howard , Filley, Timothy
Institution: The Johns Hopkins University , Purdue University
Current Institution: Purdue University , The Johns Hopkins University
EPA Project Officer: Hahn, Intaek
Project Period: August 15, 2010 through August 14, 2013
Project Amount: $600,000
RFA: Increasing Scientific Data on the Fate, Transport and Behavior of Engineered Nanomaterials in Selected Environmental and Biological Matrices (2010) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability
The transformations of carbon nanotubes (CNTs) in the environment are likely to be dominated by abiotic oxidative and extracellular microbial processes. Consequently, we propose to study photochemical and fungal mediated transformations that occur to colloidal and solid phase CNTs, including CNTs immobilized in polymer composites. We plan to identify transformation products, reaction kinetics, and reaction mechanisms, including the effects of coupled photochemical-fungal exposures. For CNT-polymer composites, we will study transformations of the composites, and determine if and under what conditions CNTs are released from composites as a result of exposure to light and/or fungi. The capacity of fungi to use CNTs as a carbon source for metabolism and growth will also be investigated. Our objectives are based on two overarching hypotheses: (i) Photochemical and fungal transformations of CNTs will occur and proceed via oxidative processes with important consequences for their overall persistence in the environment, and (ii) that the rate of these reactions will depend on CNT physicochemical properties (e.g. surface properties), environmental conditions (e.g. pH, fungi type), and CNT form (e.g. colloids or immobilized in polymers).
Our experimental design involves three sequential steps: (i) Initial preparation and characterization of solid phase and colloidal CNT materials; (ii) Exposure of CNTs to solar irradiation and/or common fungi known to be capable of fullerol and PAH decay; and (iii) Characterization of solid phase and colloidal CNTs and their degradation products following exposure to light and fungi. Detailed physicochemical information will be obtained following exposures, using characterization techniques that include NIR and functional group specific XPS. In addition, reactions induced by solar radiation will be followed by monitoring reactive oxygen species and 13CO2 (via 13CO-labeled CNTs). The effects of fungi on CNTs and photochemically-modified CNTs will be monitored by spectral reflectance radiometry, and by using 13CO-labeled CNTs to track 13CO in inoculation growth media, in fungal lipids, and in CO2. Through international collaborations this project will: (i) Study bacterial interactions with CNT composites; (ii) Investigate photochemical reaction mechanisms; and (iii) Incorporate our results into assessment models.
This project will provide crucial information on the persistence, fate and transformations of CNTs in aquatic and terrestrial environments, including identification of transformation pathways that alter the bioavailability and toxicity of CNTs. Such life cycle analysis is urgently needed to assess the environmental risks posed by CNTs and to facilitate the manufacture of “safe-by-design” CNTs and the commercial products that contain CNTs.