Photo-oxidation system hexavalent chromium-4-chlorophenol

Abstract

As a proposal to eliminate highly toxic chemical components derived from industrial waste, the researchers study the behavior of the compound hexavalent chromium / 4-chlorophenol system when subjected to photodegradation in a photo-reactor Compound Parabolic Cylinder (CPC) to scale pilot. The effect is analyzed in order to determine the operation conditions to reach the highest degradation levels possible. The analyzed variables were pH, concentration of catalyst (TiO2), time of recirculation and the relation of initial concentrations among polluting agents. The factor that most influences the levels of removal reached is the pH, which has a different effect for each of the pollutants. This implies that, theoretically, you cannot adopt a unique group of operation parameters to favor the degradation of both. However, in the practice, high levels of degradation of both pollutants are obtained in the optimal point of operation of the chrome.

It is also observed that the catalyst concentration does not influence the degradation of the polluting agents significantly, at least for the initial concentrations studied. The recirculation time is closely related to the kinetics of degradation of each polluting agent. Elevated degradation levels are reached in a short time for 4-chlorophenol, while more prolonged recirculation times are required for hexavalent chromium. The relation of initial concentrations of the polluting agents also exerts an opposite effect on the degradation levels reached for each polluting agent. The hexavalent chromium reduction is favored with high initial concentrations of 4-clorofenol, whereas the oxidation of 4-chlorofenol is favored with high initial hexavalent chromium concentrations, which suggests some synergy between the oxidation-reduction reactions of 4-chlorophenol and hexavalent chromium. Finally, a 97% hexavalent chromium reduction and a 94.9% oxidation of 4-chlorophenol were obtained.