Effect of ZnCl2 impregnation ratio on pore structure of activated carbons prepared from cattle manure compost: application of N2 adsorption-desorption isotherms

Activated carbons were prepared from cattle manure compost (CMC) by ZnCl 2 activation with various ZnCl 2 /CMC mass ratios. Based on the N 2 adsorption-desorption isotherms, mathematical models including the Dubinin-Radushkevich (DR) equation, the α s plot, and the Horvath-Kawazoe method were used to analyze the pore structural characteristics of the prepared activated carbons. It was found that for carbons possessing both micro-and mesopores, the DR method provided a more accurate estimation than the α s method for the extent of microporosity. The effect of the ZnCl 2 impregnation ratio on the pore structure was discussed using the DR method. The results revealed that pore evolution involved three distinct regions with increases in the amount of impregnated ZnCl 2 : raising the ZnCl 2 /CMC mass ratio from 0.00 to 0.50 resulted in a 19-fold increase in micropore volume (V me D ) but caused no change in the mesopore volume (V me D ); increasing the ZnCl 2 /CMC mass ratio from 0.50 to 1.00 led to an increment in V mi D of about 50% and in V me D of 170%; while raising the ratio from 1.50 to 2.50 caused a slight decrease in V mi D but a 200% increment in the value of V me D .