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Phenol degradation with TiO 2 photocatalyst under UV light is known to be an effective method. Under solar radiation, however, this approach does not receive adequate photons for catalyst activation, as the solar spectrum comprises mostly visible light (46%). In this study, we applied the dye-sensitization technique to prepare visible-light-active catalyst and used it under visible solar light generated from a solar simulator with a UV cutoff filter (λ > 420 nm) for phenol degradation. Eosin Y dye was used as a sensitizer for the TiO 2 catalyst with a very low level of platinum as a cocatalyst. Triethanolamine was used as a sacrificial electron donor. Parametric studies were performed for the catalyst loading, initial triethnolamine concentration, initial phenol concentration, platinum content on TiO 2 , solution pH, and visible light intensity. About 93% degradation of 40 ppm phenol solution was achieved within 90 min using Eosin Y−TiO 2 /Pt photocatalyst under optimum conditions (pH 7.0, catalyst loading of 0.8 g/L, triethnolamine concentration of 0.2 M, 0.5% Pt loading on TiO 2 , visible solar light intensity of 100 mW/cm 2 ). The kinetic rate constant and adsorption equilibrium constant were determined, and a Langmuir−Hinshelwood-type equation was proposed to describe phenol degradation on TiO 2 at different visible light intensities. The model equation was found to predict the experimental results quite well.

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RS)-2-Chloromandelic acid is a new example of chiral compounds that can exist as a racemic compound or a conglomerate depending on the crystallization conditions. Two polymorphic racemic compounds and one conglomerate were disclosed and characterized in this work. Commercially available racemic compound Form R can be prepared by crystallization from nonpolar solvents such as toluene. Freeze-drying leads to a conglomerate formation, Form γ. Crystallization from polar solvents always results in a mixture of Form R and Form γ under our experimental conditions. Thermodynamic calculation of the Gibbs free energy of racemic compound formation demonstrates that the conglomerate Form γ is slightly less stable than the racemic compound Form R. The conglomerate has a tendency to transform into racemic compound by a solid-solid transition. Another metastable racemic compound, Form β, was observed as a single crystal grown from methanol. But bulk crystals of Form β were not obtained.

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