| The condensed water in the evaporation process in the ammoniumnitrate industry contains a large amount of ammonium nitrate andammonium At present,there are no effective and economical methods forthe treatment of such wastewater In some companies the condensed waterwas discharged directly after diluting wim water and polluted theenvironment seriously The study on the effective treatment of the highconcentration ammonium nitrate wastewater has been paid great attentionboth at home and abroadThe use of reverse osmosis and electrodialysis technology to teat thehiconcentration ammonium nitrate wastewater was studied in this paperThe SW type of seawater desalination membrane was utilised for thereverse osmosis process and the SED type of chemical separationmembrane for electrodialysis process The influence of various operatingparameters such as the feed pressure,temperature,pH value and theconcentration of the wastewater on the treatment and that of the secondstage reverse osmosis were investigated in the reverse osmosis process Theresults show that the reinoval rate jncreases,with the jncrease of the feed pressure but decreases wim the increase of the the temperature The pHvalue seems to have little influence,while the rising of the concentration ofammonium nitrate in the feed leads to the removal rate drop Thewastewater containing 1 50 x 1 0~4mg/L of ammonium nitrate can beconcentrated to 8．05x 10。mg/L The permeate can be desaRed at average of1 18x10~5mg/L The removal rate of ammonium nitrate is up to 97 1％～95 3％in reverse osmosis circular process When the coefficient ofrecovery of the second stage of reverse osmosis is set to 85％,theconcentration of ammonium nitrate in permeate water is 5 lmg/L Theeffect of the feed flow rate,electricity curreut,temperature and the pHvalue of the wastewater has been studied in the electrodialysis process Theexperimental results show that the concentrated effect increases wim theincrease of the flow rate and of the current Nevertheless,increasing thetemperature leads to the decrease of both the concentrated effect and thevoltage The concentrated effect varies with the pH values and reachs amaximum at a pH value of 6 In this way,the wastewater containing1 50x 10。mg/L of ammonium nitrate can be concentrated to 8 03 x 10。mg/L．and desalted wastewate can be reduced to 2 41 x 10~3mg/L by usingelectrodialysis For the first stage of separation and concentration process,reverse osmosis technology is much advantageous over the electrodialysisas for as the concentrated effect and the energy consumption are concernedThe wastewater containing 8 0 x l 0。mg/L of ammonium nitrate can beconcentrated to 1 7 05 x 1 0~3mg/L．and the desaRed wastewater can bereduced to 4 10x10。mg/L by the second stage ofelectrodialysis concentrated to 17.05×10~4 mg/L, and the desalted wastewater can be reduced to 4.10×10~3 mg/L by the second stage of electrodialysis.After analyzing the experimental results of the two different treatmentprocesses,a new process was proposed to improve further the wastewatertreatment result by combining the reverse osmosis with the electrodialysisprocess:The first stage of reverse osmosis process is used to concentratethe wastewater to 8 00 x l 0。mg／L The electrodialysis process series arethen used to concentrate the wastewater further to 17 05x10。mg／L Andthe second stage of reverse osmosis process is used to desalt the permeatewater of the first stage of reverse osmosis to 5 1 mg／L In comparison withthe existing technology,the combination process of reverse osmosis andelectrodialysis proposed in this paper is advantageous on the treatment ofhigh concentration of ammonium nitrat wastewater Furthermore．it cansave more energy,reduce emissions and recover more resources Theresults obtained in this study are of significance in the treatment of highconcentration of ammonium nitzat wastewater in industries and its relatedtheoretical studies... |
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