Comparative study on activating fly ash by quick lime and slaked lime: effects and kinetics

Lime, which is a frequently used activating agent of fly ash (FA), has two main states: slaked lime and quick lime. We studied the effects of slaked lime and quick lime on activating FA, and discussed their kinetics. The results show that slaked lime is more beneficial for activating FA than quick lime given the condition of equivalent CaO amount. The use of slaked lime has superiority in technology and economy on activating FA. Theoretical analysis revealed that the kinetic constant of the activation reaction using slaked lime is higher than using quick lime, credited to the better volume stability and fineness, and smaller water demand of slaked lime.

Effects of Spraying Plant Nutrient, Slaked Lime and Pokeberry Root Powder on Cadmium Reduction in Rice

The pot experiment was carried out in this study to further explore the impact of plant nutrient, slaked lime, pokeberry root powder on cadmium （Cd） absorption by rice, and to screen practical agronomic measures which could reduce the accumulation of cadmium. In the control treatment nothing but water was sprayed into rice, while in other treatments, plant nutrient, slaked lime and pokeberry root powder were sprayed on rice at the tillering stage, the heading stage and the dough stage, respectively. The plant samples and soil samples were collected after the harvest and then analyzed on aimed indexes. The results showed that Cd contents in rice plants were significantly decreased, total Cd contents in brown rice were significantly （P〈0.05） decreased after rice was sprayed with plant nutrient, slaked lime and pokeberry root powder at different growing stages. However, while rice was sprayed with the three materials all at the tillering stage, the heading stage and the dough stage, the total Cd contents in brown rice were decreased by a maximum reduction that was 53.4% to 57.5% below that of the control, which was signifcantly （P〈0.05） lower than other treatments. Meanwhile, the biggest reduction of Cd inrice sprayed with the three materials at the tillering stage was 19.6% to 35.1% below that of the control, which was signifcantly （P〈0.05） lower than other treatments. In conclusion, spraying plant nutrient, slaked lime and pokeberry root powder on rice at different growing stages could not only reduce the absorption accumulation of Cd by root system, but also change the activities of rice and physical and chemical properties of soil, and then inhibit the absorption of Cd by the root system and the transfer of Cd in the rice plant. Therefore, the multiple factors may be the main causes of reducing Cd contents in the brown rice when the three materials are sprayed on rice at different growing stages.