Fig. 5
Reprinted with permission from Elsevier License Number: 5,601,360,125,916
SEM images of activated carbons prepared from paulownia wood chemically activated using different mass of phosphoric acid to wood powder ratios at 400 °C: (a) 1:1; (b) 2:1; (c) 3:1; (d) 4:1 [53].