Adsorption of Direct Yellow 12 onto Ordered Mesoporous Carbon and Activated Carbon

Mesoporous carbon CMK-3 was prepared using a mesoporous silica SBA-15 as the template, and the adsorption of aqueous direct yellow 12 (DY-12) on CMK-3 and commercial powdered activated carbon (PAC) was studied. X-ray diffraction, N 2 adsorption, and transmission electron microscopy results demonstrate that CMK-3 with ordered structure is a true replica of its template SBA-15. CMK-3 and PAC have comparable pore volumes, whereas CMK-3 mainly consists of mesopores, and PAC contains both micropores and mesopores. The adsorption of DY-12 over CMK-3 and PAC could be well-described by the Langmuir isotherm model. The maximum adsorption amounts of CMK-3 and PAC for DY-12 at 25 °C were found to be (303.0 and 161.3) mg·g −1, respectively, indicative of a substantially higher adsorption capacity of CMK-3 compared to that of PAC. DY-12 adsorption processes over CMK-3 and PAC obey pseudosecond-order kinetics. For DY-12 adsorption on CMK-3, the rate constants were (2.82·10 −4, 4.43·10 −5, and 9.77·10 −6 ) g·mg −1 ·s −1 at initial DY-12 concentrations of (17.7, 44.3, and 145) mg·dm −3, respectively. In the case of PAC, the rate constants were found to be (1.78·10 −5, 9.8·10 −7, and 6.7·10 −7 ) g·mg −1 ·s −1 at initial concentrations of (17.7, 44.6, and 339) mg·dm −3, respectively, reflecting much lower adsorption rates over PAC than those over CMK-3. Furthermore, the intraparticle diffusion of DY-12 over CMK-3 and PAC was elucidated using the Weber−Morris model. The present results clearly verify the importance of mesopores in the adsorption of aqueous DY-12.