Preparation of Mesoporous Activated Carbons by Chemical Activation of Acid- and Base-Pretreated Bamboos for Removal of Bulky Dye Molecules

Mesoporous activated carbons were prepared from three types of bamboo materials, i.e. non-pretreated, acid-pretreated and base-pretreated bamboos, by H3PO4 and ZnCl2 activation. Acid- and base-pretreatments of bamboo materials were performed using H2SO4 and NaOH, respectively, in order to alter bamboo components and enhance an activation effect. The change in bamboo components by acid- or base-pretreatment was examined by thermogravimetric analysis. The porous structure of prepared activated carbons was also characterized through N2 adsorption-desorption isotherms at －196℃. The results showed that the base-pretreatment of raw materials had the positive effect on mesopore development during H3PO4 and ZnCl2 activation processes, while such kind of effect by acid-pretreatment was observed only for ZnCl2 activation. The most mesoporous sample prepared from base-pretreated bamboo by H3PO4 activation with the impregnation ratio of 6 g/g showed the SBET, Vmeso and Dave values of 1380 m2/g, 1.54 cm3/g and 6.0 nm, respectively. The dye adsorption experiments were carried out through a batch test to evaluate each prepared activated carbon. Methylene blue and direct blue 71 were chosen as adsorbates. ZnCl2 activated carbons had the better adsorption capacity for methylene blue compared to H3PO4 activated carbons, which were not well-suited for the methylene blue adsorption probably due to their smaller SBET and positive charge on surface. The most mesoporous sample had the largest amount of direct blue 71 adsorption (0.97 mmol/g) among the all samples, suggesting that the prepared mesoporous activated carbons would be a valuable material for the removal of bulky dyes.