Removal Of Ammonia Derived From Livestock Farm By Modified Activated Carbon

In recent years, the scale of intensive farms have expanded larger and larger, and have brought the people great convenience. But the environmental problems about the malodorous gas from the intensive farms have become a public nuisance, it not only has a bad influence on the health of the livestock and poultry, but also seriously threatens people’s living environment, so it is urgent to remove the malodorous gas. NH3as the main odor gas from intensive farm has been chosen as the abject of paper. Because the activated carbon has the advantages of being got easily and cheaply, rapid deamination reaction rate and high removal efficiency.So activated carbon is used to remove the malodorous gas derived from the intensive farms.In this paper, three kinds of (diameter:3mm) activated carbon from Taiyuan Xinhua Chemical Plant,Shanxi Fenyang Risheng Industrial Plant and Datong Tianzhao Activated Carbon Limited Company has been chosen as raw materials. The activated carbon from the Taiyuan Xinhua Chemical Plant has larger adsorption capacity than the other two kinds, in addition, its apparent pH value is lower than others and its content of acidic functional groups is higher than others too. So3-1activated carbon from the Taiyuan Xinhua Chemical Plant has been chosen as raw activated carbon in this paper. High-pressure hydrothermal method, impregnation method and combination of high-pressure hydrothermal method and impregnation method are used to modify the raw activated carbon in this paper. The adsorption efficiency of NH3of modified activated carbon has been evaluated in fixed bed. The results show that300℃is the best temperature to modify activated carbon in high-pressure hydrothermal process and in this condition the activated carbon has the largest adsorption capacity; Under the condition of impregnation content of citric acid and Cu(NO3)2about40%at solution temperature of20℃for three hours, the3-1activated carbon can be modified easily to adsorb NH3. If the3-1activated carbon has been modified using high-pressure hydrothermal method at first, then it has been treated by impregnation process, this modified activated carbon has higher adsorption efficiency of NH3than it is modified by other methods.Through investigating the operation conditions of NH3adsorption on modified activated carbon in fixed bed, it is concluded that the low temperature is in favor of the adsorption of NH3, the largest adsorption capacity is on30℃condition; The adsorption capacity of the modified activated carbon decreases with the increase of inlet concentration of NH3; NH3removal efficiency of modified activated carbon has been improved with the decrease of space velocity.The modified activated carbon is a re-generational sorbent for NH3removal. Through analyzing the regeneration methods and conditions, the result shows that if modified activated carbon is regenerated by N2,20%O2in N2and20%O2+15%H2O in N2the regenerated activated carbon has low efficiency for NH3adsorption. When the modified activated carbon is regenerated by solvent, it has higher efficiency for NH3adsorption than other methods, especially in the condition of being regenerated by Oxalic acid which has been shook for half an hour at the rate of160r/min in20℃. The many cycle of adsorption-regeneration for modified activated carbon by GS300firstly then by40%citric acid also have been investigated. It is concluded that with the increase of cycle of adsorption and regeneration, the adsorption rate and the adsorption capacity decreases.In this paper, the physical chemical structure for activated carbon has been charactered by FTIR, TPD, Boehm and BET methods. The results of Boehm method show that the more acidic functional groups have, the more NH3could be adsorbed by the modified activated carbon. The results of FTIR show that modification by high-pressure hydrothermal method and impregnation process for activated carbon can change the quantity of functional groups, thus ffect activated carbon to adsorb NH3. NH3adsorption process and regeneration process can change the number and type of carbon functional groups. The TPD characterization shows that modification for activated carbon can improve the surface acidity by high-pressure hydrothermal method, impregnation method and the combination method of the former two. And the surface basic acidity of fresh activated carbon is higher than the activated carbon after adsorption, and the surface basic acidity of fresh activated carbon is also higher than the activated carbon after regeneration. Specific surface area and specific pore volume characterization show that high-pressure hydrothermal method and combination method for activated carbon both can change the pore structure of the activated carbon and improve the ability of absorption of NH3. After the adsorption, the specific surface area, total pore volume, micropore area, micropore volume and average pore size become lower than before. Investigation of the change of micropore in pore structure of activated carbon shows that the micropore of activated carbon plays a vital role in adsorbing NH3.In summary, the adsorption of NH3from intensive farms by modified activated carbon has been discussed in detail in this paper. The adsorption conditions, structure of activated carbon and regeneration process also have been carefully investigated. It can provide theoretical foundation for industrialization. However, the mechanism for adsorption and regeneration is just a primary discussion, there is much work to do in future in order to find out NH3adsorption mechanism.