Degradations of refractory pollutants by hydrodynamic cavitation were experimentally carried out in a self-developed hydrodynamic cavitation reactor with Venturi tubes, multi-orifice plates and their combinations. Effects of hydraulic elements of cavitation due to the Venturi tube on degradation of refractory hydrophobic pollutant were studied, and an optimal throat length corresponding to the maximum degradation rate was obtained. Effects of cavitation due to number, size and distribution of orifice for the multi-orifice plates on degradation of refractory hydrophilic pollutant were investigated, and comparisons and analyses were made. Effects of cavitation due to different combinations of the Venturi tubes with the triangular multi-orifice plates on degradation of hydrophilic and hydrophobic mixtures were studied, and an appropriate combination was determined. Also, effects of cavitation duration, pH value and initial concentration on the refractory pollutants were explored.
The pressure characteristics in the throats of Venturi tube and behind triangular multi-orifice plates were experimentally investigated by a pressure data acquisition system of SINOCERA-YE6263, and the effect of throat length of Venturi tube, different geometric parameters of multi-orifice plate and their combinations on the time-averaged pressure, cavitation number, and pressure frequency spectrum, correlation function calculated by FFT were analyzed. The experimental results showed that the throat length of L/R= 40 made for improving the fluctuation energy and promoting the uniform energy distribution, appropriately decreasing the size and increasing the number of orifice could accelerate the uniform distribution of the fluctuation energy in frequency domain. In the combination reactors, the cavitation number behind multi-orifice plates was lower and the fluctuation of correlation function was more intense.
