| Sulfadiazine(SD)is one of the most important sulfonamides,which are detected in environment every year,it is composed by pyrimidine ring,benzene ring,sulfur and nitrogen.Since the use of thie drug increased every year,a large number of drugs were found in our environment,this has brought great threat to ecology and human health,so the removal of sulfonamide in water has received increasing attention.In this paper,a new type of nano-biomarerial was prepared by using aerobic granular sluge as adsorbent to adsorbe titanium dioxide.the material was characterized and we studied titanium dioxide adsorption performance in aqueous solution and its toxicity to AGS.Besides,the removal of sulfadiazine and the formation of intermediate products were invertigated under UV irradiation.The Main contents and results are as follows:1.The aerobic granular sludge was successfully cultivated via increasing influent organic loading and aeration flux,along with added Ca2+ as core plus shortening settling time step by step in a SBR.The obtained granule sludge was tawny with the characteristics of compact structure,well setting property and high biological activity.The content of EPS increased in the process of granulation and the main components of EPS were PN and PS,which play a key role in the aggregation of microorganism and may be attributed to the formation of aerobic granule.The size,SVI was between 1 and 5 mm,40 mL/g.The removal efficiency of COD and NH4+-N reached more than 97%.2.The nano-biomarerial were produced by adding titanium dioxide into aerobic granular sludge in a SBR and characterized by SEM,EDS,CLSM.In addition,adsorption property was investigated for the removal of P25 from aqueous solution.Batch experiments were carried out to investigate the effect of contact time,P25 dosage,dispersant on adsorption.The results show that the adsorption process of P25 is more consistent with the pseudo-second-order kinetic model than the pseudo first order kinetics model,and the correlation coefficient is more than 0.999.The entire adsorption is affected by surface diffusion and internal diffusion of the particles,but mainly affected by surface diffusion.Subsequent desorption experiments found that little P25 fall off during the concussion process,indicating that P25 was more solid with the guanular sluge.Through the determination of PN,PS and dead cells in AGS,it was found that the increase of the concentration of titanium dioxide,more dead cells were found on the surface of AGS,which resulted in the decrease of PN and PS.When the concentration of P25 is over 100 mg/L,the impact on biological activity is great.3.UV light intensity and time in a certain number can promote the activity of heterotrophic bacteria in AGS,and will not cause much impact on AOB.The photocatalytic degradation of SD was promoted by UV irradiation,and some intermediate products were formed,including 2-AP and 4-APS,ammonia and sulfate.Among them,2-AP and 4-ABS were easy to inhibit the biology and 4-ABS was easy to be degraded.The remocal of ammonia is not affected after nanotitania loading on AGS,which was probably due to de formation of ammonia nitrogen during the degradation of SD.However,the degradation rate of SD was improved,one reason was that the intermediate 4-ABS produced by photodegradation was more biodegradable,and its inhibitory effect on biological was reduced,another reason was that titanium dioxide in the UV light produced free radicals to promote the oxidation of SD. |
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