Modeling of copper (II) removal by iron oxide-coated granular activated carbon

摘要

Although Fe oxides (includes oxide, hydroxide, and oxyhydroxie Fe minerals) are recognized as effective adsorbents or heavy metals, oxide adsorbent-based treatment processes have been limited by their small particle size. When present as a discrete mineral phase in wastestreams, Fe oxide particles are typically in a colloidal size range that is difficult to remove from aqueous solution. To overcome this limitation, some possible alternatives were described by Edwards and Benjamin (1989), Huang and Vane (1989), and Theis et al. (1992, 1994), who used sand or activated carbon as the supporting medium for iron oxide precipitates, or cemented iron oxide with a proprietary binding material.~(1-4) These adsorbents can solve the particle size problem associated with iron oxide for use in a column process with promising abilities for both cationic and anionic metals removal and recovery. For example, Edwards and Benjamin used iron oxide coated sand as an adsorbent filter media to treat several cationic metals (Cd, Cr, Cu, Ni and Pb) in a column~1. Huang and Vane prepared an Fe~(2+) treated activated caron to remove anionic As~(5+) from aqueous solution.~2 Finally, Theis et al. produced a granular Fe oxide adsorbent for treating cationic Cd and Pb, and anionic Cr metals in a mini-column process.~(3, 4) Because the capacity of these adsorbents for metals depends on the amount of iron oxide on the adsorbent surface, activated carbon would seem to have an advantage as a substrate because of its large surface area. Therefore, we present some results of our work with a composite adsorbent made from Fe oxide and granular activated carbon. A major objective of this work was to select an appropriate equilibrium model to describe the adsorption isotherm, and to show how a first or second order reaction or homogeneous surface diffusion models could be used to model the adsorption process in the batch system.