Column study of Cr (VI) adsorption onto modified silica–polyacrylamide microspheres composite

Adsorption of Cr (VI) from aqueous solution was studied using a continuous fixed bed column which is packed with a new micro-porous composite particle developed in this study. This composite particle is composed of silica porous particle in which acrylamide is polymerized within the pore regions of the silica particles. The composite particle was supposed to maintain the mechanical properties of polyacrylamide as efficient absorbent to serve appropriately in the continuous processes. In order to enhance the adsorption capacity of the composite particle, it was modified with ethylenediamine. Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR) and thermogravimetry analysis (TGA) was applied to characterize the adsorbent. It was shown that polyacrylamide itself within the pore region of silica particle is also porous possibly because of the evaporation of solvent during the drying process. The effect of various parameters such as feed concentration (50–200 mg/L), feed flow rate (3–10 mL/min) and sorbent amount (250–750 mg) on the breakthrough characteristics of the adsorption system was investigated appropriately. Two well-known column adsorption models, Thomas and Adams–Bohart models were applied to fitting the experimental data. The results showed that the Thomas model was suitable for the description of breakthrough curve at all experimental conditions, while Adams–Bohart model was suitable for an initial part of dynamic behavior of column.

► We have introduced a procedure for synthesis of silica–polyacrylamide composite.
► The capability of produced composite was investigated in removal of Cr (VI).
► The results showed a good capability for removal of Cr (VI) using the composite.
► Regeneration of composite after adsorption was done with 0.02 M NaOH successfully.