Study On Removing Ammonia-nitrogen In Wastewater Using Microwave-activated Carbon

Along with the development of industry and agriculture and the increase of population, a lot of ammonia nitrogen wastewater was produced. This wastewater which discharged into the rivers and lakes could cause many problems to the environment, such as eutrophication. At present, the treatment of ammonia-nitrogen wastewater mainly includes physical chemical and biological treatment method. However these methods show many shortcomings such as causing secondary pollution and complex operation. Especially when biological treatment method was used, much time was wasted, and this can’t meet the requirements of the development of industry. Therefore, to develop a new method which is economic and efficient in removing the ammonia nitrogen of water has important significance.Firstly, the technological conditions of ammonia-nitrogen wastewater treatment by microwave radiation were studied. The effects of pH, radiation time, initial concentration of wastewater, microwave setting temperature and microwave power on the treatment efficiency of ammonia-nitrogen wastewater were investigated. The influence of ammonia-nitrogen removal rate by microwave radiation and oil bath heating were compared. Results showed that microwave radiation was better for the treatment of ammonia-nitrogen wastewater than conventional heating, in which the initial pH of wastewater, microwave setting temperature and microwave power were important influencing factors.Secondly, the modification of activated carbon by H2SO4, NaOH, Na2SiO3·9H2O, NaCl, NaOH and Na2SiO3·9H2O together was studied. The effect of adsorption of ammonia-nitrogen by modified activated carbon from wastewater was examined. Static adsorption experiments indicated that the best effect of adsorption was achieved by activated carbon modified by NaOH, but when worked together with microwave, the activated carbon modified by NaOH and Na2SiO3·9H2O was better. So NaOH and Na2SiO3·9H2O was used together to modify activated carbon. The fitting of the adsorption isotherm curve told that the adsorption of ammonia-nitrogen by modified activated carbon fit in with the Langmuir adsorption model, and the adsorption dynamics fit in with pseudo-second-order kinetics equation. The optimum temperature of the adsorption was about 30℃.The treatment efficiency of ammonia-nitrogen wastewater by microwave and modified activated carbon together was studied at last. The effect of activated carbon dose, initial pH of wastewater, microwave radiation time and microwave setting temperature on the treatment efficiency of ammonia-nitrogen wastewater were investigated. Results showed that microwave setting temperature was an important influencing factor, and the wastewater initial pH almost had no affection on the treatment efficiency when microwave and modified activated carbon was used together to treat ammonia-nitrogen wastewater. The removal rate of 500 mg/L ammonia-nitrogen wastewater could reach 96% when the 15 g/L modified activated carbon was added into the wastewater and microwave radiation was 6 minutes. The used activated carbon was modified again after had been dried naturally, and was used to treat ammonia-nitrogen wastewater. The experiment was repeated 4 times, and the removal rate of ammonia-nitrogen wastewater could reach 95% or above. Finally, the treatment efficiency of different concentrations ammonia-nitrogen wastewater of Changlian Catalyst plant by microwave and modified activated carbon together also was studied, and we got good results. All the removal rate could reach 95% and above too. The concentration of ammonia-nitrogen wastewater could reach the emissions standards.