| Cephalexin,a extensively used antibiotic,had been detected in many rivers,which is toxic to ecological health.It is very urgent to find an effective way to remove it.Activated carbon with high mesoporosity is an excellent adsorbent due to well-developed pore structure and can be used for the removal of cephalexin.However,the adsorption capacity of existing activated carbons for cephalexin so low that could't achieve a deep removel effect.So it will be of practical significance to develop a new activated carbon with higher adsorption capacity for cephalexin.Amygdalus pedunculata Pall.(AP)is a kind of shrub and had been planted widely in the northern desert area to prevent desertification.Its shell(APS)contains high carbon content,low impurities and has a large number of pores on its surface which is helpful for infiltration of activators,can be used to prepare activated carbon with high adsorption performance.In this paper,four APS-based activated carbons with high mesoporosity had been obtained by using steam and chemical reagents respectively.Their adsorption properties toward cephalexin were studied and compared.Finally,the effect of modification methods on the adsorption performance of activated carbons were discussed.Hope to provide reference for industrial production of activated carbon with high adsorption for antibiotic.Main research were as follows:1.Preparation of APS-based activated carbon with high mesoporosity by using steam.The effects of carbonization temperature,activation temperature,activation time,and steam consumption on the iodine value and methylene blue value and yield of activated carbon were discussed.The optimum conditions were as follows: carbonization temperature600°C,carbonization time 60 min,activation temperature 850 °C,activation time 60 min,steam/carbide weight ratio 6.At this condition,the specific surface area of activated carbon(AC-H850)was 1127 m2/g,the mesoporosity was 60.9%,the isoelectric point is 6.76.This study provides a new approach for the preparation of high mesoporosity activated carbon.2.Preparation of APS-based activated carbon with high mesoporosity by using KOH,Zn Cl2 and H3PO4 respectively.The effects of activation temperature and impregnation ratios on the iodine value and methylene blue value and yield of activated carbon were investigated.The result showed that AC-K4,900,AC-Zn1.5,600 and AC-P2,400 were prepared under optimal impregnation ratio and activation temperature,their specific surface area were 1665 m2/g,1810 m2/g and 1688 m2/g respectively,the mesoporosity were 68.8%,57.0% and 81.1%,the isoelectric point were 5.61,4.56,and 2.98 respectively.3.The adsorption properties of four activated carbons for cephalexin were studied,including effects factors and adsorption kinetics and adsorption isotherm models were investigated.The result showed that AC-H850,AC-K4,900,AC-Zn1.5,600,and AC-P2,400 all had great adsorption properties for cephalexin,and larger pore volume,higher mesoporosity and lower content of acidic oxygen-containing functional groups were favorable for cephalexin adsorption.The adsorption capacity was affected by the ionic strength,p H and temperature.Kinetics and isotherms datas had a great fit for pseudo-second-order kinetics model and Langmuir isotherm model respectively.The maximum adsorption capacity of activated carbons for cephalexin based on Langmuir model were: AC-K4,900(389.11 mg/g)> AC-H850(292.39 mg/g)> AC-Zn1.5,600(199.60 mg/g)> AC-P2,400(149.03 mg/g),and the adsorption capacity of first two activated carbons for cephalexin were significantly higher than that reported in the literature.Considering economic investment and ecological benefits,AC-H850 was a more excellent adsorbent.4.HNO3 and Fe(NO3)3 modified activated carbons were prepared by impregnation and their adsorption properties for cephalexin were studied.The results indicated that the adsorption capacity of activated carbons modified by HNO3 got weaker,but the adsorption capacity of AC-K4,900,AC-Zn1.5,600 and AC-P2,400 modified by Fe(NO3)3 were enhanced by8.2%,52.7% and 53.2% respectively,all were high-efficiency adsorbents for cephalexin. |
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