The Effect of Phosphoric Acid Additive on the Porosity and the Distribution Coefficients of Solutes in Cellulose Acetate Particles.

Abstract

A series of cellulose acetate (CA) particles have been prepared by spraying method from the solutions containing different concentrations of phosphoric acid and CA. The pore sizes of particles obtained have been tested by means of gel chromatography using polyethylene glycol (PEG) with different molecular weights as molecular size probes. It is found that phosphoric acid additive acts as a pore adjusting solvent to from a suitable porosity in CA particles. At low CA concentration (5 wt%) the pore sizes decrease with phosphoric acid in a certain concentration, and at high CA concentration (17 wt%) the pore sizes increase by adding phosphoric acid additive. The water contents of particles and the stationary water contents in chromatographic columns have also been analysized. The results show that both the water contents and stationary water contents for prepared particles are larger than those for original CA powder and increase to a maximum in a certain pore sizes of particles. The equilibrium distribution coefficients (Kd) for aliphatic alcohols, acids and amines have been measured. The Kd values of original CA powder for all these organics are larger than those of prepared CA particles, especially for longer carbon chains of organics. We also found that the structure of prepared particles have some effects on the Kd values for the organics with longer carbon chains, but almost no effects for the organics with short carbon chains.