Production of micro- and mesoporous activated carbon from paper mill sludge - I. Effect of zinc chloride activation

A series of micro- and mesoporous activated carbons were produced from pape r mill sludge using a modified carbonization methodology. N-2-adsorption is otherm data and mathematical models such as the D-R equation, alpha(s)-plot , and MP and BJH methods were used to characterize the surface properties o f the produced carbons. Results of the surface analysis showed that paper m ill sludge can be economically and successfully converted to micro- and mes oporous activated carbons with surface areas higher than 1000 m(2)/g. Activ ated carbons with a prescribed micro- or mesoporous structure were produced by controlling the amount of zinc chloride (ZnCl2) used during chemical ac tivation. Pore evolvement was shown to be most affected by the incremental addition of ZnCl2. Increasing the ZnCl2 to sludge ratio from 0.75 to 2.5 re sulted in a 600% increase in the mesopore volume. ZnCl2 to sludge ratios le ss than 1 and greater than 1.5 resulted in the production of micro- and mes oporous carbons, respectively. At a ZnCl2 to sludge ratio of 3.5, an activa ted carbon with a predominantly (80%) mesoporous structure was produced. Th e calculated D-R micropore volumes for activated carbons with the suggested microporous structure were in good agreement with those obtained from the a; method, while estimated micropore volumes from the cr, method deviated m arkedly from those obtained from the D-R equation for carbons with a predom inantly mesoporous structure. (C) 2000 Elsevier Science Ltd. All rights res erved.