Carbon Nanotubes Functionalized with Calcium Carbonate for Flow-Through Sequential Electrochemical Phosphate Recovery

A new dendritic dispersant of carbon nanotubes (CNTs) was synthesized and applied for the noncovalent functionalization of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The 1,10-bis(decyloxy)decane core of the poly(amidoamine) dendrimer strongly adhered to the sidewalls of CNTs to form CNT/dendrimer supramolecular nanocomposites having many carboxyl groups (–COOH) on the surface. Then, crystallization of calcium carbonate (CaCO3) by the CO2 diffusion technique in aqueous environments using the CNT/dendrimer supramolecular nanocomposites as scaffolds afforded monodisperse spherical CNT/CaCO3 nanohybrids consisting of CNTs and calcite nanocrystals. The morphologies of the SWCNT/CaCO3 hybrids and MWCNT/CaCO3 hybrids were almost the same.

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Identifying the Mechanisms of Enhanced Water Flow Through Carbon Nanotubes

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C ◽

10.1115/imece2008-66489 ◽

2008 ◽

Author(s):

J. A. Thomas ◽

A. J. H. McGaughey

Keyword(s):

Carbon Nanotubes ◽

Water Flow ◽

Flow Rate ◽

Driving Force ◽

Slip Length ◽

Dynamics Simulation ◽

Flow Area ◽

Water Viscosity ◽

Flow Through ◽

External Driving

Pressure-driven water flow through carbon nanotubes (CNTs) with diameters ranging from 1.66 nm to 4.99 nm is examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Hagen-Poiseuille relation, is calculated for each CNT. The enhancement decreases with increasing CNT diameter and ranges from 433 to 47. By calculating the variation of water viscosity and slip length as a function of CNT diameter, it is found that the results can be fully explained in the context of continuum fluid mechanics. The enhancements are lower than previously reported experimental results, which range from 560 to 100000, suggesting a miscalculation of the available flow area and/or the presence of an uncontrolled external driving force (such as an electric field) in the experiments.

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Shear Induced Removal of Calcium Carbonate Scale From Polypropylene and Copper Tubes

ASME 2009 3rd International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2009-90006 ◽

2009 ◽

Author(s):

Matt Royer ◽

Jane H. Davidson ◽

Lorraine F. Francis ◽

Susan C. Mantell

Keyword(s):

Shear Stress ◽

Calcium Carbonate ◽

Wall Shear Stress ◽

Polymeric Materials ◽

Reynolds Numbers ◽

Shear Stresses ◽

Solar Absorbers ◽

Flow Through ◽

Wall Shear ◽

Calcium Carbonate Scale

This paper presents an analytical model and experimental study of adhesion and fluid shear removal of calcium carbonate scale on polypropylene and copper tubes in laminar and turbulent water flows, with a view toward understanding how scale can be controlled in solar absorbers and heat exchangers. The tubes are first coated with scale and then inserted in a flow through apparatus. Removal is measured gravimetrically for Reynolds numbers from 525 to 5550, corresponding to wall shear stresses from 0.16 to 6.0 Pa. The evolutionary structure of the scale is visualized with scanning electron microscopy. Consistent with the predictive model, calcium carbonate is more easily removed from polypropylene than copper. In a laminar flow with a wall shear stress of 0.16 Pa, 65% of the scale is removed from polypropylene while only 10% is removed from copper. Appreciable removal of scale from copper requires higher shear stresses. At Reynolds number of 5500, corresponding to a wall shear stress of 6.0 Pa, 30% of the scale is removed from the copper tubes. The results indicate scale will be more easily removed from polypropylene, and by inference other polymeric materials, than copper by flushing with water.

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