Abstract:

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.

Key words: fly ash, ultrasound, dye, adsorption, kinetics, methylene blue

摘要：

为了开发更多的粉煤灰用途，采用粉煤灰去除水中的染料污染物，达到以废治废的目的。采用超声波辅助粉煤灰的方法，以亚甲基蓝染料作为模拟污染物，考察此工艺的可行性，讨论亚甲基蓝的去除效果，分析其动力学。研究结果证明，超声波-粉煤灰联合体系（US-FA体系）具有良好的去除染料污染物的能力，超声波的引入能提高粉煤灰对染料污染物的去除率，协同效应非常明显，粉煤灰投加量0.3、0.5、1.0和2.0 g的情况下，协同因子分别达到1.05、1.32、1.55和2.27。在本实验体系内，经过恒温控制后，超声波的热效应可以忽略，主要通过粉煤灰吸附和羟基自由基降解两大主要途径去除污染物，超声波对去除性能的促进作用主要体现在以下几个方面：一是超声波空化作用产生羟基自由基，超声波和粉煤灰表面相互作用产生更多的羟基自由基；二是超声波能促进粉煤灰表面产生更多的活性位，促进了吸附过程的化学反应步骤，由于粉煤灰对亚甲基蓝的吸附过程以化学反应为控制步骤，所以超声波能大为促进粉煤灰的吸附性能；三是超声波的引入加剧了固液混合，促进污染物向固相表面移动，促进更多的污染物进入到吸附剂颗粒内部，改善了传质。

关键词: 粉煤灰, 超声波, 染料, 吸附, 动力学, 亚甲基蓝