Comparative study on characterization and adsorption properties of activated carbons by phosphoric acid activation from corncob and its acid and alkaline hydrolysis residues

•AC (SBET: 2033 m2/g or Vtot: 1.633 cm3/g) was prepared from KHR or AHR.•The KHR is more suitable to prepare well-developed mesopore AC than the AHR.•ACs with nearly the same liquid phase adsorption possess different pore structures.•ACs differ in pore size distribution though with more or less the same SBET and Vtot.

Four activated carbons were prepared from corncob, acid hydrolysis residue, alkaline hydrolysis residue and China fir sawdust respectively with phosphoric acid activation under the same process condition. TG/DTG-DSC analysis revealed that the addition of phosphoric acid decreased the pyrolysis rate while increased the temperature and the yield. The findings showed that the acid and alkaline hydrolysis residue from corncob were both suitable to prepare high performance activated carbon. Moreover, different micropore volume, mesopore volume and mean pore width existed although activated carbons possessed the similar BET surface area and total pore volume. In addition, the liquid phase adsorption and pore properties of activated carbons were contrasted to show that the pore structure varied from one to another though with more or less the same iodine number, methylene blue adsorption and decolorization of caramel. Compared to China fir sawdust, activated carbons from corncob, acid hydrolysis residue and alkaline hydrolysis residue were easily made with a high decolorization of caramel. FTIR results suggested that four activated carbons were found with hydroxyl and phosphorus groups.