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

Abstract

Activated carbons were prepared from cattle manure compost (CMC) by ZnCl2 activation with various ZnCl2/CMC mass ratios. Based on the N2 adsorption-desorption isotherms, mathematical models including the Dubinin-Radushkevich (DR) equation, the αs 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 αs method for the extent of microporosity. The effect of the ZnCl2 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 ZnCl2: raising the ZnCl2/CMC mass ratio from 0.00 to 0.50 resulted in a 19-fold increase in micropore volume (Vme D) but caused no change in the mesopore volume (Vme D); increasing the ZnCl2/CMC mass ratio from 0.50 to 1.00 led to an increment in Vmi D of about 50% and in Vme D of 170%; while raising the ratio from 1.50 to 2.50 caused a slight decrease in Vmi D but a 200% increment in the value of Vme D.