Hydrated lime [Ca(OH) 2 ] is frequently used as a sorbent in the spray-drying flue gas desulfurization (FGD) and injection/humidification FGD processes to remove SO 2 from the flue gas. In the present study, the kinetics of the reaction of Ca(OH) 2 with SO 2 has been studied by using a differential reactor and a gas mixture of N 2 , SO 2 , and H 2 O under the conditions of 0-80% relative humidity, 60-90 °C, and 1000-5000 ppm SO 2 . The reaction ceased before 1 h, and Ca(OH) 2 was incompletely converted. The relative humidity of the gas significantly affected the initial reaction rate and the maximum conversion of Ca(OH) 2 . The temperature and SO 2 concentration had mild effects on the reaction. The sulfation of Ca(OH) 2 was well described by the asymptotic equation, which is obtained by assuming that the rate was controlled by the chemical reaction occurring on the water-adsorbed sorbent surface and by considering the surface coverage by the product. The results of this study are useful to the design and efficient operation of the processes using hydrated lime to remove SO 2 from the flue gas.

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Now, water pollution is one of the leading concerns in the world especially heavy metal polltion. In recent years, researches on the use of agricultural waste as biochar and modified biochar to treat heavy metals in water are receiving the attention of scientists because of the economy as well as the high processing efficiency that it brings. In this study, biochar from rice husk was synthesized and modified by iron, then the obtained materials were characterized by SEM, FTIR methods. The results show that the Fe-biochar shows a high potential to remove arsenic at pH = 4 and the adsorption capacity was 18,96 – 28,49 mg/g.