Dye adsorption on biosolid adsorbents and commercially activated carbon

This study reused biosolids to manufacture adsorbents (S500 and S600) and used for Chrysophenine (CH) and Orange II adsorption. In addition, a commercially activated carbon (F820) was selected and used in dye adsorption to enable comparison of the dye adsorption characteristics of biosolid adsorbents and commercially activated carbon. The Boehm titration method allows determination of the oxygen surface functional groups. Results indicated that the distribution of the surface functional groups of the two biosolid adsorbents was similar in spite of the fact that they were pretreated under different pyrolytic temperatures. Only a small amount of quinoid-type group existed on the surface of biosolid adsorbents, but it contributed substantially to the surface functional group on F820. The sequence of BET surface area was S600 (813 m2/g) ≈ F820 (802 m2/g) > S500 (737 m2/g). The commercially activated carbon had a high micropore volume and possessed a significant pore volume increment at the pore diameter < 13 Å (a large pore volume peak in the vicinity of 9 Å). The pore volume of biosolid adsorbents was high in the vicinity of 500 Å (macropore) and 80 Å (mesopore). The sequence of CH adsorption capacity was S500 > S600 > F820 at different temperatures, indicating that the biosolid adsorbents were more suitable for CH adsorption than the commercially activated carbon. But for Orange II, the adsorption capacity of biosolid adsorbents was higher than F820 at 10 °C. When the adsorption temperature increases, the mass transfer increases and overcomes the adsorption energy barrier. Therefore, the Orange II molecule could transfer into micropores, and the adsorption capacity of F820 approached that of biosolid adsorbents. Moreover, the adsorption capacity of F820 could be higher than that of biosolid adsorbents at 60 °C.