Analysis of various experimental methods and preparation of mesoporous activated carbon powders from sawdust using phosphoric acid

A critical analysis of various reported experimental methods utilized for preparation of activated carbon using phosphoric acid was attempted to identify the right choice of experimental method. The various experimental methods were grouped into three major categories; of these, a two-stage activation process with the precursor exposed to preset furnace temperature in a self-generated atmosphere was identified to be a suitable method. Accordingly, activated carbon powders were prepared utilizing a two-stage activation process, covering the effect of activation time at 500°C with an impregnation ratio of 1.5. The samples were subjected to adsorption using methylene blue dye, and the adsorption capacity was found to increase with increase in activation time. An adsorption capacity greater than 400 mg/g of activated carbon shows highly developed pores, with pore size higher than 1.5 nm signifying its economical application to commercial liquid-phase adsorption processes. The adsorption isotherms were found to match well with the Langmuir isotherm model with correlation coefficient (r2) greater than 0.95 as compared to the Freundlich isotherm model with r2 less than 0.8.