Abstract
An Advanced Oxidation Process (AOPs) was carried out in this study with the use of immobilized ZnO and solar/UV as an energy source to degrade dairy wastewater. The semibatch reactor system consisted of metal plate of 800 × 250 mm and a glass tank. The reaction time was of 3 h for 3 L of dairy wastewater. Experiments were performed based on a surface response methodology in order to optimize the photocatalytic process. Degradation was measured in percentage terms by total organic carbon (TOC). The entry variables were ZnO coating thickness and pH, using three levels of each variable. The optimized results showed a TOC degradation of 31.7%. Optimal parameters were metal-plate coating of 100 μm of ZnO and pH of 8.0. Since solar/UV is a constant and free energy source in most tropical countries, this process tends to suggest an interesting contribution in dairy wastewater treatment, especially as a pretreatment and the optimal conditions to guarantee a better efficiency of the process.
Highlights
The use of ZnO as a semiconductor was studied for possible application in a photo-excitation-initiated degradation of the catalyst followed by the formation of a surface bandgap (see (1))
The Hydroxyl radical is a powerful nonselective oxidation agent leading to organic pollutants degradation [1,2,3]
Results from this study show that the photocatalytic degradation contributes to the organic load removal of effluents, and studies related to economic viability may expand the process
Summary
The use of ZnO as a semiconductor was studied for possible application in a photo-excitation-initiated degradation of the catalyst followed by the formation of a surface bandgap (see (1)). The oxidation potential (hVB+) permits the formation of active intermediates by the direct oxidation of an organic matter (see (2)). Many reactive hydroxyl radicals can be formed either by decomposition of water or by a bandgap reaction with OH− (see (3) and (4)). The Hydroxyl radical is a powerful nonselective oxidation agent leading to organic pollutants degradation [1,2,3]. → oxidation products (intermediates) hVB+ + H2O → H+ + ∙OH (3). The methodologies used in the design of experiments allow a similar result as the one obtained from conventional experiments with the advantage of the use of fewer experiments. In order to obtain the optimized variables for the study of International Journal of Chemical Engineering
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