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The photocatalytic decolorization of municipal wastewater contaminated with textile dyes was studied using a batch reactor. Degussa P25 titanium dioxide was used as the photocatalyst and proved to be effective for dye degradation when irradiated with UV light in the presence of air. In addition to removing the color from the wastewater, the photocatalytic reaction simultaneously reduced the COD which suggests that the dissolved organics had been oxidized. The activation energy for the photocatalytic decolorization reaction was only about 3 to 6 kJ/ mole indicating a weak temperature dependence of the rate. These results suggest that the photocatalytic degradation of textile dyes may be a viable method for decolorizing and oxidizing organics in wastewater.zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res.,zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 66, 50 (1994).

Reducing the influence of an undesired product in an enzymatic reaction could have a significant impact on the productivity of such systems. Here, we focus on the removal of water formed during an enzymatic esterification in a batch reactor. A commercial immobilized lipase preparation, known as Lipozyme, is used as the biocatalyst and propionic acid and isoamyl alcohol dissolved in hexane are the substrates. In this system, the water formed will partition between the catalyst and the medium. As the more polar reactants are converted into the less polar ester product, the water is partitioned more towards the biocatalyst and the accumulation of water eventually causes lower reaction rates. Addition of a strong‐acid cation exchange resin in sodium form is found to control the water accumulation on the biocatalyst without stripping the essential water needed for the enzyme to function and substantial improvements in conversion are achieved. A mathematical model is developed to describe the batch reaction behavior with and without added absorbent, which successfully predicts the behavior of water and its effects. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 434–444, 1998.

A new expression to predict the diffusivity of a gas in a liquid is compared to previously developed equations. The new expression appears to work as well or better than the other equations in most cases.Uiffusion in liquids has been studied for many years (14, 16).Available expressions for calculating diffusion coefficients in liquids, however, only partially have been successful. There is no one equation which predicts diffusivities for all systems involving a liquid solvent.

Several amino acids and peptides were partitioned in poly(ethylene glycol) (PEG)/magnesium sulfate (MgSO4) aqueous two-phase systems. The partition coefficients measured for amino acids and peptides were proportional to the difference in PEG concentration between the phases. The partitioning data were used to calculate the relative hydrophobicities of individual amino acids, which were then used to estimate the hydrophobicities of peptides. The partition coefficients of several dipeptides were predicted from these estimated hydrophobicities. A series of peptide fragments that compose the pentapeptide leucine enkephalin was also partitioned in the PEG/MgSO4 system. Again, the partitioning depended upon the hydrophobicities of the individual exposed amino acids.