Kinetic analysis of removal of methylene blue using fly ash assisted by ultrasound from aqueous solution

To develop more use of fly ash, fly ash is used to remove dye contaminants from water to achieve waste treatment. Methylene blue, a kind of dyes, was selected as a model pollutant to investigate the feasibility of the ultrasonic assisted fly ash process (US-FA system). The removal efficiency and the kinetics analysis of this combined system were studied. The experimental results show that the introduction of ultrasonic can improve the removal rate of methylene blue. The synergy effect between fly ash and ultrasound is significant. When fly ash dosage is 0.3, 0.5, 1.0 and 2.0 g, the synergistic factors are 1.05, 1.32, 1.55 and 2.27 respectively. In this experimental scheme, the thermal effect of ultrasonic can be ignored after constant temperature controlling. The pollutant is mainly removed by the adsorption role of fly ash and the degradation role of hydroxyl radicals. The enhancement effect of ultrasound on fly ash is mainly illustrated in aspects as follows: (1) ultrasound cavitation produces hydroxyl radical, and the interaction between ultrasonic wave and fly ash produces more hydroxyl radical, which has strong oxidation ability and non selectivity; therefore the dyes pollutant can be degraded by oxidation of hydroxyl radical. (2) Ultrasonic wave can promote to produce more active sites on the surface of fly ash, therefore ultrasound can greatly promote the adsorption performance of fly ash due to the chemical reaction is the controlling steps of adsorption process of fly ash. (3) Ultrasonic wave aggravates the solid-liquid mixing, promotes the movement of pollutants toward the solid surface, promotes more pollutants to enter into the pores of adsorbent particles, and hence increases the mass transfer of pollutant from liquid phase to solid phase. © All Right Reserved.