Characteristics of adsorption of rice-hull activated carbon

An experiment was conducted to compare the adsorption capacity and characteristics between activated carbon made of rice-hull(RHAC) and F-400 by Calgon to remove phenol, heavy metal and ammonia-nitrogen. While F-400 could not remove ammonia-nitrogen, RHAC was able to adsorb it. This is considered to be due to the ionic sorption capability of SiO2 remaining on the surface of RHAC. From the sorption equilibrium test, it was found that RHAC has higher adsorption capacity than F-400. In column tests, the slope of breakthrough curves of RHAC which represent the affinity of an adsorbent, was observed to be more gradual than F-400. This may be attributed to the inner diffusion of adsorbent once attached on macropores, into micropores well developed, with higher specific surface area of RHAC than F-400. For heavy metals, F-400 would remove chromium and lead but not cadmium, whereas RHAC was able to remove cadmium, lead but not chromium. This phenomenon is considered to have something to do with the distinct surface functional group of RHAC and the various surface charge densities of heavy metals tested.