| Water is the material basis for people’s survival and development.In recent years, water pollution accidents occurred frequently whichs posed a serious threat to the safety of drinking water for people. The problem of sudden ammonia nitrogen pollution in source water is an important issue and a difficult problem that city water supply plant facing. Therefore, it is of great significance to develop a key emergency treatment to deal with sudden ammonia pollution. This technology has great significance to deal with the sudden ammonia pollution in the city water supply plant, and ensure the safety of drinking water. The biological method requires continuous operation and the management is difficult; chemical method may produce secondary pollution; however physical method has the advantages offast and effective, simple, no secondary pollution. The natural zeolite has good selective adsorption of ammonia, therefore using zeolite as the emergency treatment to solve ammonia pollution is the most suitable for the water supply plant.The research using microwave and NaCl to modify granular natural zeolite for dealing with ammonia nitrogen polluted source water in laboratory. Through single factor experiments, the effects of particle size, dosage, pH, time and initial concentration on the removal of ammonia nitrogen were study. The adsorption kinetics model and isothermal adsorption model were fitting. Combined with experimental date, mechanism and adsorption characteristics of ammonia adsorption by natural zeolite and modified zeolite was analyzed and discussed, obtained the following conclusions:(1) The experimental results show that the best experimental conditions for the natural zeolite removed ammonia nitrogen were zeolite particle size 0.5-1.Omm, dosage 6.0g, pH value 6.5, reaction time 60min whichs the removal rate of ammonia nitrogen was 34.54%, and ammonia nitrogen concentration reduced from 10mg/L to 6.55 mg/L.(2) The experimental results show that removal efficiency of ammonia by modified zeolite in different conditions can be concluded:NaCl+ microwave zeolite (N+MZ)> NaCl zeolite (NZ)> microwave+ NaCl zeolite (M+NZ)> NaCl microwave zeolite (M-NZ)> microwave zeolite (MZ)> natural zeolite (Z). The efficiency of N+MZ to removed ammonia nitrogen was the bestwhileremoval rate was 87.76%, and the residual ammonia concentration in solution was reduced to 1.22mg/L.(3) The pH value had a direct effect on modified zeolite on ammonia nitrogen removal efficiency. The pH value too high or too low is not conducive for modified zeolite to removed ammonia nitrogen. The suitable pH value was 6.5.(4) The process characteristic of adsorption of ammonia nitrogen by natural zeolite and modified zeolite were in accordance with the "rapid adsorption and slow balance", After fully modified NaCl solution, the zeolite reached adsorption equilibrium more quickly. The second-order kinetic equation was most suitable for the adsorption process of ammonia nitrogen by natural zeolite and modified zeolite. The adsorption process of ammonia nitrogen is not just controlled by inter particle diffusion but controlled by multiple steps.(5) With the increase of the initial ammonia nitrogen concentration, the adsorption capacity of natural zeolite and modified zeolite to ammonia nitrogen is increasing, and the isothermal adsorption curve was the same. The adsorption thermodynamic processesis more in line with Freundlich model rather than Langmuir model.(6) The presence of COD, P and cations has less influence on the removal of ammonia nitrogen by the NaCl fully modified zeolite, on the contrary it has a great influence on the removal of ammonia nitrogen from the zeolite without NaCl fully modified.The cationic effects of ammonia removal by natural zeolite was greater than the modified zeolite and the sequence was Mg2+>Ca2+>K+... |
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