Kinetic study of the phodegradation reaction of organic matter in domestic sewage using TiO2, Nb2O5 e WO3.
Domestic Sewage; Removal of Organic Matter; Heterogeneous Photocatalysis; Kinetics.
The current demand for drinking water faces the ever-decreasing availability of water resources that can be used daily. Therefore, proceeding with the treatment of domestic sewage is an indispensable task, since it enables the reuse of water for various purposes. The high oxidizing power of the •OH radicals generated by the Advanced Oxidative Processes means that these methods have the potential to degrade the organic matter present in effluents. In this sense, this paper proposes the use of heterogeneous solar photocatalysis as an alternative to the conventional secondary treatment given to sewage, thus reducing the generation of sludge and electricity costs. For this purpose, a synthetic sewage solution was fed to a batch photocatalytic reactor, under constant agitation and exposure to sunlight. The tests were performed with TiO2, Nb2O5 and WO3 at concentrations of 0.25; 0.50; 0.75; and 1.0 mg L-1and pH set at 3.0, in a total reaction time of four hours. Aliquots were collected every 40 min and the samples were filtered and analyzed for chemical oxygen demand. The best scenario observed was when in the presence of 1.0 mg L-1 of TiO2, which provided a removal of organic matter of 40.93%. However, removal of the order of 35.56% for Nb2O5at 0.75 mg L-1 shows that this oxide can reach an efficiency like TiO2 even in the lowest concentration in the medium; for higher Nb2O5 values in the solution, the process efficiency declined. With WO3, in turn, the removal of organic matter remained constant from the concentration of 0.50 mg L-1, reaching a peak of 30.87% when at 1.0 mg L-1. Regarding the reaction kinetic study, the predominance of second order kinetics was observed when working with Nb2O5 and TiO2, whereas first order kinetics prevailed when using WO3.