Combinations of different aromatic polymers and organic solvents have been studied as dispersing agents for preparing single-walled carbon nanotubes solutions, using optical absorbance, photoluminescence-excitation mapping, computer modeling, and electron microscopic imaging to characterize the solutions. Both the polymer structure and solvent used strongly influence the dispersion of the nanotubes, leading in some cases to very high selectivity in terms of diameter and chiral angle. The highest selectivities are observed using toluene with the rigid polymers PFO-BT and PFO to suspend isolated nanotubes. The specific nanotube species selected are also dependent on the solvent used and can be adjusted by the use of THF or xylene. Where the structure has more flexible conformations, the polymers are shown to be less selective but show an enhanced overall solubilization of nanotube material. When chloroform is used as the solvent, there is a large increase in the overall solubilization, but the nanotubes are suspended as bundles rather than as isolated tubes which leads to a quenching of their photoluminescence.

The pseudo-second-order (PSO) kinetic model has become among the most popular ways to fit rate data for adsorption of metal ions, dyes, and other compounds from aqueous solution onto cellulose-based materials. This review first considers published evidence regarding the validity of the mechanistic assumptions underlying application of the PSO model to adsorption kinetics. A literal interpretation of the model requires an assumption that different adsorption sites on a solid substrate randomly collide with each other during a rate-limiting mechanistic step. Because of problems revealed by the literature regarding the usual assumptions associated with the PSO model, this review also considers how else to account for good fits of adsorption data to the PSO model. Studies have shown that adsorption behavior that fits the PSO model well often can be explained by diffusion-based mechanisms. Hypothetical data generated using the assumption of pseudo-first-order rate behavior has been shown to fit the PSO model very well. In light of published evidence, adsorption kinetics of cellulosic materials is expected to mainly depend on diffusionlimited processes, as affected by heterogeneous distributions of pore sizes and continual partitioning of solute species between a dissolved state and a fixed state of adsorption.

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