Carbon nanomaterials have shown great promises in the removal of toxic pollutants in water and wastewater treatments, either as highly effective adsorbents or as the support of catalysts and oxidants. Herein, we report two important mechanisms via which carbon nanomaterials enhance the abiotic transformation of organic contaminants. First, we found that functionalized multi-walled carbon nanotubes, graphene oxide, and reduced graphene oxides can effectively catalyze dehydrochlorination of chlorinated solvents (using 1,1,2,2-tetrachloroethane as a model compound) at neutral to slightly basic pH, in that the surface basic groups (e.g., –NH2 group and deprotonated –COOH and –OH groups) serve as bases to catalyze the hydrolysis reaction. Modeling results indicate that the transformation kinetic constants of carbon nanomaterial-adsorbed 1,1,2,2-tetrachloroethane were up to 2 orders of magnitude greater than the respective kinetic constant of dissolved 1,1,2,2-tetrachloroethane. The overall catalytic effects of the carbon nanomaterials depended both on the basicity of the surface functionalities of the nanomaterials and on the adsorption affinities of the nanomaterials for the chlorinated solvents. Second, we report a new mechanism via which carbon supports of carbon–metal oxides nanocomposites enhance the oxidative transformation of organic contaminants by metal oxides. Specially, Mn3O4−rGO nanocomposites (Mn3O4 nanocubes anchored to reduced graphene oxide (rGO) nanosheets) resulted in much greater oxidative transformation of 1-naphthylamine than did bare Mn3O4, in that rGO could re-oxidize Mn(II) formed from the reaction between Mn3O4 and 1-naphthylamine, thereby regenerating the surface-associated oxidant Mn(III). Metal oxides are often anchored to carbon nanomaterials to achieve greater contaminant removal efficiency, and previously, the enhanced performance has mainly been attributed to the role of graphene materials as a sorbent and/or a conductor for electron transfer. Overall, these newly identified mechanisms may guide the development of novel carbon-based nanomaterials and nanocomposites for contaminant removal.

Catalytic effects of carbon nanomaterials in abiotic transformation of organic contaminants: Implications for water and wastewater treatments

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.