Study On Preparation And Adsorption Performance Of Tannic Acid-based Porous Materials

The development of the chemical,textile and pharmaceutical industries has made a remarkable contribution to the advancement of human technology and civilization.In recent years,environmental and ecological damage caused by industrial wastewater pollution has posed a challenge to sustainable human development.Tannic acid(TA)has been widely developed as an adsorption material for wastewater treatment.During more than a decade of research,problems such as adsorbent dissolution and environmentally unfriendly preparation processes have limited practical applications.To address the problems of TA adsorption materials,this study proposed an epoxy ring-opening method to cross-link TA with ethylene glycol diglycidyl ether(EGDE)under non-alkaline conditions and prepared microspheres for dye adsorption.The method was also applied to crosslinking-encapsulated modified carbon nanotubes(CNT)to remove dye and drug.The details are as follows:(1)In this study,TA-EGDE microspheres were prepared by a one-step method.The differences in morphology,stability and adsorption property of the microsphere were compared with different raw material compositions.The ideal molar ratio of phenolic hydroxyl and epoxy groups is 4:1.(2)The effects of pH,temperature,ionic strength and other factors on the methylene blue(MB)adsorption by TA-EGDE microspheres and microsphere stability were investigated.The results showed that the optimum adsorption pH was 9.The adsorption effect was enhanced by increasing temperature.The effect of ionic strength on adsorption was small.The microspheres have good stability under acid or alkaline conditions,and the weight loss rate of 72 hours is less than 5%.(3)The MB adsorption by the TA-EGDE microspheres was in accordance with quasi-second kinetic and the Langmuir model with a maximum adsorption capacity of 618.44 mg/g at 25℃.The adsorption process was entropy-driven,spontaneously occurring and heat-absorbing.The removal rate maintained above 92%after five adsorption/regeneration cycles.(4)Based on adsorption studies,TA-EGDE microspheres tend to remove positively charged dyes with small size.The MB was separated and recovered from two-component dye mixture by flow-through test(recovery efficiency>90%).It was revealed that the mechanism of selective adsorption mainly originated from the dye charge and molecular structure differences.(5)Tannic acid modified carbon nanotube adsorbent material(TACNT)was prepared by co-crosslinking method.The removal rates of common cationic dyes(methylene blue,methyl green,rhodamine B and neutral red)were greater than 90%.The flow-through adsorption of multiple mixed dyes achieved 100%continuous removal of cationic dyes.(6)TA-CNT has strong hydrophobic interaction to adsorb and remove tetracycline(TC).The adsorption capacity is 55 mg/g for TC,which is six time larger than that of TA-EGDE.