Investigation of sulfuric acid-treated activated carbon properties

Abstract

A granulated type of commercial activated carbon (GAC) with surface area of 828 m2/g was treated witha strong solution of sulfuric acid (98% wt.) at a temperature of 30 °C. The physicochemical and porous propertiesand the surface chemistry of the sorbents were investigated and compared in detail. It was established that the lowertemperatures of impregnation and the higher concentration of H2 SO4 solution resulted in the introduction of higherpercentages of sulfur-containing groups and smaller porosity loss. The results of EDS, FTIR, and XPS tests confirmedthe introduction of sulfone groups and acidic oxygenated ones, which increased the adsorbent affinity towards mercuryspecies available in the aqueous phase (pH 7) by 20%. It was found that acid-washing treatment helped to reduce theash content of GAC and cleaned its internal space; however, with the introduction of bulky H2 SO4 molecules intomicropores and narrow mesopores of GAC, the surface area and pore volume were reduced. The increase of mercuryadsorption capacity in spite of decreasing porosity after acid treatment shows that trapping in pores is not the onlymechanism involved in mercury adsorption.