No abstract

Partitioning of ethylene oxide oligomers and polymers (PEO) in biphasic systems of water and chloroform or dichloromethane favors transfer to the organic phase as the molecular weight increases. For systems containing chlorobenzene, partitioning into the aqueous phase is always predominant. Calorimetric determination of the enthalpies of transfer for PEO from aqueous to organic phases reveals an endothermic process for all of the systems investigated, which was ascribed to the replacement of a more energetically favored PEO solvation in water for that in the organic phase. These results indicate that spontaneous PEO transfer from water to an organic phase is driven by an entropy increase. The number of water molecules transferred to the organic phase with PEO was determined to be ca. 0.08 water molecules per EO unit, smaller than hydration numbers reported in aqueous solutions. All of these findings lead to a picture where PEO may be extracted from water to an organic phase as long as the solvation by the organic solvent is relatively strong as compared to water. The displacement of water causes an entropy increase, which drives the transfer process. Chloroform and dichloromethane are suitable solvents for PEO extraction probably because of their hydrogen bonddonating capability.

A partição de PEO de água para CH 2 Cl 2 e CHCl 3 aumenta com a sua massa molar, até se tornar constante em torno de 3 000 g mol -1 . Estes resultados revelam que a partição de PEO é bastante sensível à contribuição dos grupos hidroxila, sugerindo a transição de caráter poliglicol para poliéter em torno de 3000 g mol -1 .PEO partitioning from water to CH 2 Cl 2 and CHCl 3 increases with its molar mass, leveling off at ca. 3 000 g mol -1 . Such a behaviour is related to PEO end-group contributions, suggesting a polyglycol to polyether transition at ca. 3 000 g mol -1 .

No abstract

This paper reports experiments involving the electrochemical combustion of humic acid (HA) and removal of algae from pond water. An electrochemical flow reactor with a boron-doped diamond film anode was used and constant current experiments were conducted in batch recirculation mode. The mass transfer characteristics of the electrochemical device were determined by voltammetric experiments in the potential region of water stability, followed by a controlled current experiment in the potential region of oxygen evolution. The average mass transfer coefficient was 5.2 9 10 -5 m s -1 . The pond water was then processed to remove HA and algae in the conditions in which the reaction combustion occurred under mass transfer control. To this end, the mass transfer coefficient was used to estimate the initial limiting current density applied in the electrolytic experiments. As expected, all the parameters analyzed here-solution absorbance at 270 nm, total phenol concentration and total organic carbon concentration-decayed according to first-order kinetics. Since the diamond film anode successfully incinerated organic matter, the electrochemical system proved to be predictable and programmable.