Reduction Of Fe(Ⅲ)EDTA Under The Catalysis Of Activated Carbon

The simultaneous control of SO2/NOx can be realized with the Fe(Ⅱ)EDTA aqueous solution. However, the Fe(Ⅱ)EDTA is easily oxidized to Fe(Ⅲ)EDTA by oxygen, which has no ability to bind NO. The reduction of Fe(Ⅲ)EDTA to Fe(Ⅱ)EDTA is a key to the maintenance of the NO removal efficiency with the Fe(Ⅱ)EDTA aqueous solution. The reduction of Fe(Ⅲ)EDTA can be accomplished by sulfite produced by SO2 dissolving in the aqueous solution under the catalysis of activated carbon.In this study, the adsorption of Fe(Ⅲ)EDTA on activated carbon from the aqueous solutions has been investigated in a batch stirred cell. Experimental results manifest that Fe(Ⅲ)EDTA adsorption rate increases with its concentration in the aqueous solutions, Fe(III)EDTA adsorption also increases with temperature. The Fe(Ⅲ)EDTA removal from the solution increases as activated carbon mass increases. The kinetic study shows that Fe(Ⅲ)EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The Langmuir and_Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R2= 0.9749 and 0.9965, respectively. The apparent activation energy calculated from the slope of the plot is found to be 14.21kJ mol-1, the relatively low positive activation energy indicates that that pHysical adsorption dominate the process of Fe(Ⅲ)EDTA adsorption on to activated carbon. A positive value of△H indicates that the adsorption process is endothermic in nature and negative value of AG show the spontaneous adsorption of Fe(Ⅲ)EDTA on the activated carbon, Positive△S shows the randomness of solid/solution interface during the adsorption of Fe(Ⅲ)EDTA on the activated carbon.In the paper, the kinetics of the reduction of Fe(Ⅲ)EDTA catalyzed by activated carbon coconut shell has been investigated in a stirred-cell reactor. The experimental results indicate that the activated carbon can obviously accelerate Fe(Ⅲ)EDTA reduction rate. The reaction rate stays relatively high at the activated carbon dosage of 16g/L and decreases as the activated carbon above 16g/L. pH is an important parameter for the conversion of Fe(Ⅲ)EDTA. An optimal PH range for the reduction of Fe(Ⅲ)EDTA is obtained between 5.6-7.0. An increase in the temperature can benefit to the Fe(Ⅲ)EDTA reduction in this catalytic system. The experiments indicate that the reaction rate is 0.6 order with respect to Fe(Ⅲ)EDTA, with intrinsic activation energy of 55.63±1.12 kJ mol-1 for. the Fe(Ⅲ)EDTA reduction catalyzed by coconut activated carbon has been obtained. The kinetic model of this reaction can be expressedThe experiments were performed in a fixed-bed reactor to investigate the regeneration of Fe(Ⅱ)EDTA catalyzed by activated carbon. The experimental results indicate that the Fe(Ⅲ)EDTA reduction increases with the Fe(Ⅲ)EDTA and sulfite concentrations. Rising the temperature can increase the Fe(Ⅲ)EDTA conversion. The optimal pH range for the reduction of Fe(Ⅲ)EDTA is 5.7-7.5. In the fixed-bed reactor, superficial liquid flow velocity affects the reaction. The apparent activation energy determined from the experimental results is 35.23±0.52 kJ mol"1. The kinetic equation of Fe(Ⅲ)EDTA reduction by sulfite catalyzed with activated carbon can be describedContinuous experiments were also carried out for the simultaneous absorption of NO and SO2 into the Fe(Ⅱ)EDTA and Na2SO3 solution. The nitric oxide removal efficiency can be maintained at a high level for a long time by Fe(Ⅱ)EDTA solution coupled with the regeneration of Fe(Ⅱ)EDTA catalyzed by activated carbon of coconut shell. During the whole operation, no SO2 is detected in the outlet gas stream by FTIR.