Degradation Of Caffeine In Aqueous Solution By Synergy Of Cavitation Effect

Caffeine (CAF) is one of the most widely used drugs in the world. As a kind of alkaloid, it is widely found in natural plant, and the moderately use of CAF have the effects of dispel fatigue and excitatory the nerve, but long-time use of CAF can cause damage to the human body, also there is a certain addictive. For its widespread occurrence in ocean, lake and river, caffeine can act as a tracer of water pollution.This paper studies the influence of two different systems on CAF removal, including ultrasonic cavitation synergistic cobalt ions activated sodium persulfate (US/Co2+/PS) system and ultrasonic cavitation synergistic cobalt ions activated oxone (US/Co2+/PMS) system. The optimal reaction conditions were found by the combination processes on caffeine removal efficiency. We also investigated the effects of single factor on caffeine degradation efficiency and explored the caffeine mineralization. Furthermore, the effect of presence of common inorganic ions and organic compound on the removal of CAF was also investigated. In this paper, venturi tube, Venturi tube with a multiple hole orifice plate and a multiple hole orifice plate hydrodynamic cavitator were simulation through FLUENT, the effects of structural parameters and the type of cavitator were studied. The results showed that:(1) CAF can be effectively degraded by US/Co2+/PS system, in the condition of initial concentration of caffeine 20 mg/L, ultrasonic power 200W, the dose of persulfate 10 mM, the concentration of cobalt ions 0.5 mM, the initial pH value 2.2,57.4% of the caffeine degradation rate can be reached, and ultrasonic cavitation and cobalt ion activated persulfate has good synergy effect, it can accelerate the reaction and increase the caffeine removal efficiency.(2) CAF can be effectively degraded by US/Co2+/PMS system, in the condition of initial concentration of caffeine 50 mg/L, ultrasonic power 200 W, the dose of persulfate 0.5 mM, the concentration of cobalt ions 0.02 mM, the initial pH value 7.0,90.0% degradation of CAF can be achieved within 40 min. The degradation rate of CAF increased significantly with increasing the concentration of cobalt ion and Oxone, based on our experiments,100% degradation of 50 mg/L CAF can be achieved within 4 min under the conditions of 1.00 mM oxone and 0.10 mM Co2+ ion at pH 5.0 to 7.0. The additions of chloride, bicarbonate, and sodium humate have negative effects on the removal of CAF.(3) For Venturi tube cavitator, the opening rate 0.025 and exit taper angle 6° are favorable for the cavitation efficiency; The cavitation efficiency of venturi tube is better than venturi tube with multiple hole orifice plate; The fewer the number of holes, the better of the cavitation efficiency for multiple hole orifice plate hydrodynamic cavitator at the same opening rate; The cavitation efficiency of venturi tube with multiple hole orifice plate is better than multiple hole orifice plate hydrodynamic cavitator.