The Study On Removal Nitrogen Of Spent Liquor Of T Acid Crystallization

With the development of China's textile industry and the increase of the industry of printing and dyeing,the requirement for dye raw materials and the high concentration of organic dye waste liquor are more and more.The spent liquor of T acid crystallization is accompanied by the production of H-acid has low biochemical degradation.It can be hardly treated by the traditional water treatment technology.For the pretreatment of spent liquor of T acid crystallization which have high concentration of organic matter and ammonia nitrogen,the removals of ammonia nitrogen and total nitrogen are compared between ammonia evaporation,Fenton oxidation and Fenton oxidation-ammonia evaporation.In view of the characteristics of spent liquor of the spent liquor of T acid crystallization,the pretreatment of ammonia nitrogen in high concentration is used by the method of ammonia evaporation.We investigate the effect of pH,temperature,reaction time and gas-liquid volume ratio on ammonia nitrogen removal rate.The results show that the removal rate of the ammonia nitrogen is increased in the ammonia evaporation with the increase of the effect of pH,temperature and gas-liquid volume ratio.The ammonia evaporation performe the highest removal of ammonia nitrogen which can achieve 94.47%at optimal conditions.We observe the first-order removal kinetics of ammonia nitrogen by evaporation ammonia method.The reaction rate constant k is 0.00463 min-1.The activation energy is 28.7036kJ/mol.Treating the spent liquor of T acid crystallization by Fenton oxidation has been investigated.The effects of key factors including doses on H2O2,H2O2/FeSO4 mole ratio,pH and reaction time on TOC,COD,UV254,ammonia nitrogen and total nitrogen removal rate are investigaded.The results show that it can be effective in achieving the organic matter removal.The removal of ammonia nitrogen and total nitrogen increased significantly after Fenton oxidation.Fenton is able to remove 74.51%COD,49.59%TOC,88.58%UV254,and the removal rates of ammonia nitrogen and total nitrogen are 17.22%and 15.29%.For the purpose of reducing the concentration of ammonia nitrogen and total nitrogen of spent liquor of T acid crystallization,which was pre-treated by complex extraction process,Fenton oxidation and ammonia evaporation was tested in order to create the favourable condition for the following biological treatment.The influence of Fenton oxidation,pH,gas-liquid volume ratio,temperature and reaction time on the removal efficiency of ammonia nitrogen and total nitrogen was investigated.The experimental results showed that the concentration of ammonia nitrogen was reduced by Fenton oxidation,which enhanced the removals of ammonia nitrogen and total nitrogen.It was found that the removal of ammonia nitrogen and total nitrogen increased with increasing pH,temperature and gas-liquid volume ratio.The removal of ammonia nitrogen exceeded 99%and total nitrogen exceeded 97%at optimal conditions.It was also found that ammonia removal rate of spent liquor of T-acid crystallization by evaporation followed the first-order kinetic equation and the reaction rate constant k was 0.00883 min-1.The activation energy was 8451.20 J/mol and the pre-exponential factor was 0.139 min-1.The ammonia evaporation has the following advantages:stable and reliable operation,high efficiency treatment,low capital investment and recover ammonia.It can effectively remove ammonia nitrogen and total nitrogen.It is concluded that ammonia evaporation is the effective and economical choice of treating spent liquor of T-acid crystallization containing high concentration of ammonia nitrogen and may be applied in industry.