Introduction.

Colored wastewater is a complex mixture containing recalcitrant substances that are difficult to oxidize by conventional methods. Photocatalysis with suspended TiO2 has been shown to be efficient in the oxidation of substances by photoactivation of catalyst with artificial light.The use of sunlight in the process reduces operation costs in a full scale application of this wastewater.

Objective.

Evaluate the treatment of a mixture of azoic dyes by photocatalysis with TiO2 suspensions using solar and artificial light.

Materials and methods.

An annular reactor with artificial light was tested, and an experimental design was applied to evaluate the effect of dyes, TiO2 and H2O2 concentrations. Under such favorable conditions, the dyes mixture was degraded using natural solar light and a batch reactor.

Results.

The artificial light system showed that dyes and TiO2 concentrations were the factors that significantly influenced on color and chemical oxygen demand (COD) removals. Favorable operational conditions and model equations for color and COD diminutions were established from the experimental design. The system with sunlight removed 100% of color and 80% of COD after 3h of treatment. UV-vis spectrum of dyes mixture was studied during the process and this showed possible formation of carboxylic acids and subsequent mineralization.

Conclusion.

Photocatalysis with TiO2 and sunlight showed the degradative capacity of the photocatalytic process for remediation of waters charged with mixtures of azoic dyes.