Adsorption of humic acid to aminopropyl functionalized SBA-15

Humic acid is generally considered as one of ubiquitous pollutants in surface and ground water. In this study, aminopropyl functionalized SBA-15 adsorbents with varied aminopropyl contents were prepared via the co-condensation method and characterized by elemental analysis, X-ray diffraction, N2 adsorption, IR spectroscopy and zeta-potential measurements. The adsorption behaviors of the adsorbents for humic acid were investigated using batch experiments and adsorption kinetic tests. SBA-15 exhibited low humic acid adsorption amount. In contrast, substantially enhanced humic acid adsorption was observed over aminopropyl functionalized SBA-15 adsorbents. Humic acid adsorption over the adsorbents could be well described using Langmuir adsorption model and the maximum humic acid adsorption capacities were found to be 8.5, 72.5 and 117.6 mg g−1 for SBA-15, APTS-SBA-15-5% and APTS-SBA-15-10%, respectively. In addition, increasing solution pH led to monotonically decreased humic acid adsorption over aminopropyl functionalized SBA-15. Humic acid adsorption process over functionalized SBA-15 could be well described using pseudo-second-order kinetic model and HA adsorption was controlled by both external and intraparticle diffusion based on the fitting results using Weber–Morris model.