Alginate hydrogel beads were impregnated with zinc oxide (ZnO) modified sepiolite clay and applied for the removal of congo red (CR) dye from its aqueous solution in batch and packed column systems.

A single pot microwave assisted process was employed for the synthesis of sepiolite-poly­(dimethylsiloxane) (SP-PDMS) nanohybrid for removal of Congo red (CR) dye from contaminated water in a batch process. The synthesized nanohybrids were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, confirming the nanohybrids formation. The structures of the nanohybrids were confirmed by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) while the specific surface area and pore size were determined by the Brunauer–Emmett–Teller (BET) method using N2 adsorption isotherms. The dye removal process was subjected to kinetic and equilibrium studies, the results of which showed that pseudo-first-order kinetics dominated the adsorption of CR onto the nanohybrid. The equilibrium data were analyzed using Freundlich, Langmuir, Tempkin, Dubinin–Radushkevich, and generalized isotherm models. The nanohybrids demonstrated favorable adsorption properties toward CR with the isotherm models fit in the order Generalized > Langmuir > Freundlich isotherm > Tempkin > Dubinin–Radushkevich. The maximum adsorption capacities (Q max) of 132.22, 167.45, and 85.33 mg g–1 were obtained for SP-PDMS1, SP-PDMS2, and SP-PDMS3, respectively. The removal efficiency was found to be 100% up to the fifth cycle. It was found that the synthesized nanohybrid can effectively remove 98% of CR dye from a given aqueous solution. The proposed synthesis is a simple and easily scalable process in the production of SP-PDMS nanohybrid for efficient removal of CR and water purification.

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