Study on preparation of low ash activated carbon by phosphoric acid method
Phosphoric acid activation is currently the main method for industrial production of biomass-based activated car-bon,but the higher ash content limits its application in high-end fields such as medicine and food.Based on this,the effect of activation conditions(temperature,time,etc.)and washing conditions(medium,acid concentration,temperature,etc.)on the ash content and properties of activated carbon was investigated by using wet phosphoric acid as the activator and waste wood chips as the carbon source,and the surface properties and microstructure of activated carbon were analyzed by using TG,FT-IR,XRD,SEM and TEM characterization.The results showed that insoluble phosphate was the main factor in the generation of activated carbon ash,and that the activated carbon ash,iodine and methylene blue values could be regulated by controlling the activated carbon preparation process and washing process.The optimal process conditions were activation temperature of 500℃,phosphoric acid concentration of 70%,acid to chip ratio of 2∶1,activation time of 60 min,N2 protec-tion,washing solution dosage of 100 mL,washing solution concentration of 20%,washing medium of H3PO4,washing tem-perature of 80℃and washing time of 60 min.The activated carbon prepared under these conditions had an ash content of 1.07%,iodine value of 1 241.4 mg/g,methylene blue value of 285 mg/g,specific surface area of 2 290 m2/g,indicating that the activated carbon prepared by this technology had the potential to be applied in high-end industries such as food and medicine.
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