Carbon nanotube (CNT) enhanced membrane distillation is presented for water desalination. It is demonstrated that the immobilization of the CNTs in the pores of a hydrophobic membrane favorably alters the water-membrane interactions to promote vapor permeability while preventing liquid penetration into the membrane pores. For a salt concentration of 34 000 mg L(-1) and at 80 °C, the nanotube incorporation led to 1.85 and 15 times increase in flux and salt reduction, respectively.
The colloidal behavior of aqueous dispersions of functionalized multiwall carbon nanotubes (F-CNTS) formed via carboxylation and polymer wrapping with polyvinyl pyrrolidone (PVP) is presented. The presence of polymer on the nanotube surface provided steric stabilization, and the aggregation behavior of the colloidal system was quite different from its covalently functionalized analog. Based on hydrophobicity index, particle size distribution, zeta potential as well as the aggregation kinetics studied using time-resolved dynamic light scattering, the PVP wrapped CNT was somewhat less prone to agglomeration. However, its long term stability was lower, and this was attributed to the partial unwrapping of the polyvinyl pyrrolidone layer on the CNT surface.
This paper reports the development of novel carbon nanotube immobilized composite membranes (CNIM) for pervaporative removal of organics from an aqueous matrix. The nanotubes were immobilized into the pores of a composite, where they served as sorption sites that provided additional pathways for enhanced solute transport, affecting both the partitioning and diffusion through the membrane. Depending upon the process conditions, the enhancement in organic removal and mass transfer rates were higher by 108 and 95%, respectively. The CNIM demonstrated several advantages including enhanced recovery at low concentrations, lower temperatures, and higher flow rates. Overall, these lead to more energy efficient processes.
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