Study On Adsorption And Slow Release Characteristics Of Ammonia Nitrogen In Anaerobic Fermentation Broth By Different Adsorption Materials

Anaerobic fermentation broth is the residue of agricultural waste after anaerobic fermentation.It has strong plant nutrition and insecticidal function because it is rich in a variety of nutrients and ammonia nitrogen.But now the anaerobic fermentation broth has been directly used to kill insects,which leads to the decrease of its insecticidal efficiency and the waste of other nutrients.Therefore,the adsorption of insecticidal components for efficient utilization is a research direction.In this study,three different adsorption materials were used:weak acid cation exchange resin,artificial zeolite and corn straw biochar.The adsorption capacity of adsorption materials under different conditions(adsorption material dosage,adsorption temperature,initial ammonia nitrogen concentration,adsorption pH,adsorption time)was studied by static adsorption method,and the adsorption process and type were determined by fitting isothermal adsorption equation and kinetic equation.The effects of adsorption of ammonia nitrogen by different materials in ammonium chloride solution and in anaerobic fermentation broth were compared,and the slow release study was also carried out.The results showd that:(1)When the addition of cation exchange resin reached 0.5 g,the increase of ammonia nitrogen adsorption tended to be smooth.The adsorption effect increased with the increase of temperature,and the adsorption capacity of the resin increased with the increase of ammonia nitrogen concentration,and tended to be stable after 1000 mg/L.The optimum pH value of adsorption is 7 with the adsorption capacity reaches the maximum 1.135 mg.The adsorption process accords with Langmuir isothermal adsorption equation and quasi-second-order kinetic equation.In the slow release of ammonia nitrogen,the higher the concentration of NaCl was,the faster the release rate of ammonia nitrogen is,and the more ammonia nitrogen is released.NaCl concentration can be selected according to the actual situation.In the process of adsorption of anaerobic fermentation broth by the resin,due to the interference of potassium ion,the adsorption effect of the resin on ammonia nitrogen decreased to only 4.8 mg,while it was 5.5 mg in NH4Cl solution.(2)The adsorption capacity of artificial zeolite to ammonia nitrogen increases with the increase of zeolite addition,initial ammonia nitrogen concentration and time.At lg,1000 mg/L and 80 min respectively,the growth of adsorption capacity basically reached the maximum,and then gradually tended to be flat.With the increase of pH value,the adsorption capacity increased at first and then decreased,the best pH value was 7,and the adsorption capacity reached 0.4684 mg.The adsorption process of ammonia nitrogen by zeolite accords with Langmuir isothermal adsorption equation and quasisecond-order kinetic equation.In the slow release of ammonia nitrogen,the release rate and release amount also increased with the increase of NaCl concentration.In the process of zeolite adsorbing ammonia nitrogen in anaerobic fermentation broth,also due to the influence of interference components,the adsorption effect decreased to only 3.15 mg,but it was 3.5 mg in NH4Cl solution.(3)Under different conditions(addition amount of biochar,time and pH),biochar),the maximum adsorption capacity of corn straw biochar to ammonia nitrogen was 0.033 mg,0.018 mg and 0.012 mg respectively,which was much lower than that of resin and zeolite,and basically has no adsorption capacity.There was basically no ability to adsorb ammonia nitrogen.