| A large amount of wastewater are produced in Purified terephthalic acid(PTA)refined section.Extraction-ultrafiltration-reverse osmosis-adsorbtion technology is developed by our research team for the preliminary treatment of wastewater.Firstly,PX,which is the raw material of PTA,is used to extract most organic matters from wastewater.Secondly,metal ions in the aqueous solution can be recycled successfully by appealing to ultrafiltration-reverse osmosis-adsorption craft.However,little PX is remained in water after extraction.As the major material of the reverse osmosis membrane,polyamide would be dissolved easily in PX and then the stabilization of the whole craft was seriously shortened.Therefore,selective adsorption PX technology from the wastewater before ultrafiltration-reverse osmosis may generate crucial significance of the industrial application of PTA wastewater treatment process.Zeolites were modified by iron ion-exchange with the best conditions,which were as followed:The concentration of FeCl3 was 0.1mol/L,and the temperatures of modifation and calcination were 25 ? and 700 ?,respectively.Meanwhile,the time of them were 12 hours and 2 hours,orderly.The relationship between the structure of the ZSM-5 and Fe-ZSM-5 zeolites were explored using modern analytical techniques,such as SEM/XRD/XRF and BET.Compared the zeolites modified by H+ with the Fe-ZSM-5,the selectivity factors of PX to Co2+and Mn2+ were improved from 1878.9,1995.2 to 4767.93,5483.86 in turn.Fe-ZSM-5 zeolite was used as the appropriate adsorbent,batch experiments were performed to elucidate the effects of parameters such as dosage of zeolite,adsorption time,temperature and pH,and contrast with ZSM-5 zeolite.The results indicated that Fe-ZSM-5 zeolite has better selective adsorption effect than ZSM-5 zeolite;the dosage of zeolite of 1 g/L is suitable;pH hardly affects the absorption of PX while Fe-ZSM-5 zeolite hardly absorb metal ion under a acid condition.And the adsorption of PX on Fe-ZSM-5 zeolites is a exothermic process while the adsorption of metal ion on Fe-ZSM-5 zeolites is a endothermic process;the adsorption of PX on the zeolites almost achieve a balance when adsorption time gets 50min.It is inexistence of competition adsorption between PX and Co2+?Mn2+,through a series of comparative tests.The adsorption thermodynamics and kinetics of PX on Fe-ZSM-5 zeolites were investigated completely and systematically.Compared with the Freundlich isotherm model,the Langmuir isotherm model agreed better with the experimental data.The adsorption of PX on Fe-ZSM-5 zeolite followed the pseudo-second-order rate expression.And the biggest adsorption capacity was 125.0mg/g.The Fe-ZSM-5 zeolite is successfully regenerated using the high temperature roasting.The particle adsorbent was made by Fe-ZSM-5 zeolite,pseudo-boehmite,active carbon,cellulose acetate fiber and HNO3.The factors,water/powder ratio and consumption of different powders,which would influenced the compressive strength,and adsorption capacity of shaped Fe-ZSM-5 zeolite were discussed.When the water/powder ratio was 0.36?0.38 mL/g,the consumption of Fe-ZSM-5 zeolite,pseudo-boehmite,active carbon and cellulose acetate are 70 wt%,10 wt%,15 wt%and 5 wt%respectively,what's more,the conerntration of HNO3 was 5 wt%.the shaped Fe-ZSM-5 zeolite with columnar construction of 2x3 mm,had better adsorptive property.The particle mechanical strength can reach to 83.05 N/cm,uner this condition,the equilibrium adsorption capacity of PX is 63.7 mg/g.The adsorption of PX on Fe-ZSM-5 zeolite in the fixed bed was studied as a function of space velocity at perspex tube of internal diameter 1.6 cm and 24 cm height with concentration of 50 mg/L.The result of fixed bed adsorption test indicate the suitable operation parameters were the space velocity of the solution of 2 mL/min with the columns of diameter 1.6 cm and 2.4 cm height,and the adsorption capacity can achieve 45.64 mg/g.Whose selectivity factors were better than commercial ZSM-5 partical and active carbon in the same condition. |
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