Arsenate and phosphate removal from water using Fe-sericite composite beads in batch and fixed-bed systems

Natural sericite clay was modified with iron-oxide and then the modified sericite was encapsulated into beads by employing the ionic gelation method to obtain Fe-sericite composite beads. The materials were fully characterized by N₂ adsorption–desorption isotherm, SEM-EDX, XRD, FT-IR and XPS analyses. Batch experiments showed that the composite beads showed a high uptake of As(V) and phosphate within a wide range of pH and the maximum sorption capacity determined by Langmuir isotherm were found to be 5.780 and 4.446 mg/g for As(V) and phosphate, respectively. The sorption kinetic data indicate that at least 12 h of contact time is necessary to attain the sorption equilibrium and intra-particle diffusion plays a significant role in the sorption process. The presence of background electrolyte (NaNO₃) or other heavy metals ions could not significantly affect the uptake of As(V)/phosphate by Fe-sericite composite beads. Furthermore, a fixed-bed column experiment has demonstrated that Fe-sericite composite beads could remove As(V) and phosphate up to acceptable level with a high breakthrough volume even under dynamic conditions. XPS analysis results indicate the successful sorption of As(V)/phosphate and it is assumed that these two pollutants formed an inner sphere complexes with iron oxide present in the composite beads.