Author(s): Zhiyong Dong; Zhen Zhang
Linked Author(s): Zhiyong Dong
Keywords: Hydrodynamic cavitation; Triangular multi-orifice plates; Venturi tube; Hydrophilic and hydrophobic mixing pollutants
Abstract: Hydrodynamic cavitation is a novel technique that has been found to be substantially application in wastewater treatment, especially in degradation of refractory pollutants. Cavitation means phenomena of formation, growth and collapse of cavitatin bubbles. Microjets and shock waves due to collapse of cavitation bubbles can release high intensity energy, which generate strong oxidation conditions of chemical process such as hydroxyl radical (OH*) and hydrogen peroxide (H2O2) .This paper experimentally studied effects of the hydrodynamic cavitation due to triangular multi-orifice plates with Venturi tube on degradation of hydrophilic and hydrophobic mixing pollutants. The different combinations of triangular multi-orifice plates with Venturi tube to generate hydrodynamic cavitation were carried out. A mixture of p-nitrophenol (PNP) and nitrobenzene was prepared for hydrophilic and hydrophobic mixing wastewater in the hydrodynamic cavitation reactor, and the degradation rates due to the hydrodynamic cavitation were analyzed by an ult raviolet spectrophotometer. Effects of different flow velocities, cavitation numbers, orifice numbers, orifice sizes, initial wastewater concentrations a nd wastewater circulation cycles (treatment time) through the cavitation reactor on degradation of the hydrophilic and hydrophobic mixture were experimentally investigated. The experimental results showed that the higher initial flow velocity is, the greater the rate of degradation reaches, and as the reaction progresses, effect of the initial velocity on the degradation rate is more apparent; with the increase in the circulation cycle, cavitation number of the mixture increases, reaching a certain cycle, the degradation rate tends to be stable; degradation rate is affected by the initial concentration, exhibiting a variation in increase first and then decrease, and an optimal initial concentration corresponding to the maximum degradation rate exists; under the condition of the same orifice size, the more orifice number is, the greater the degradation rate reaches; and at the same orifice number, the larger orifice size results in higher turbulence intensity and shear stress, thus causing more intense cavitation and greater degradation rate.