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An efficient adsorbent/catalyst Co and Fe-catalysts loaded on sepiolite (Co-Fe/sepiolite) was successfully prepared for high temperature gas flow catalytic reaction by a simple impregnation method. The impact of preparation conditions (such as pH value of impregnation solution, impregnation time, calcination temperature, and time) on catalytic activity was studied. We found that the catalytic activity of Co-Fe/sepiolite was strongly influenced by all the investigated parameters. The regeneration efficiency (RE) was used to evaluate the catalytic activity. The RE is more noticeable at pH 5.0 of impregnation solution, impregnation time 18 h, calcination temperature 650 °C, and calcination time 3 h. This Co-Fe/sepiolite has great adsorption capacity in absorbing dye. It is used for an adsorbent to adsorb dye from wastewater solution under dynamic adsorption and saturated with dye, then regenerated with high temperature gas flow for adsorption/oxidation cycles. The Co-Fe/sepiolite acts as a catalyst to degrade the dye during regeneration under high temperature gas flow. Hence, the Co-Fe/sepiolite is not only an adsorbent but also a catalyst. The Co-Fe/sepiolite is more stable than sepiolite when applied in the treatment of plant's wastewater. The Co-Fe/sepiolite can be reused in adsorption-regeneration cycle. The results indicate the usability of the proposed combined process, dye adsorption on Co-Fe/sepiolite followed by the catalytic oxidation in high temperature gas flow.

In this study, the impregnation synthesis of NiO/sepiolite and its application for dye removal during wastewater treatment is introduced. The NiO/sepiolite materials act as an adsorbent/catalyst. It comprises a unique combination of adsorption and high-temperature gas flow regeneration (the NiO/sepiolite acts as a catalyst at this stage, using regeneration rate as evaluation index of catalytic activity of NiO/sepiolite) in a single unit, in which the NiO/sepiolite was regenerated and reused for the next round adsorption of dye. An aqueous solution of methylene blue was used to evaluate the adsorption and regeneration performance of the adsorbent/catalyst. The regeneration rate reached 74% when the reaction time and temperature were 7 min and 350 °C, respectively. The effects of the regeneration temperature and volume fraction of O2 on the regeneration rate were investigated. And the regeneration reaction kinetics was provided. The combination of adsorptive and catalytic properties in the NiO/sepiolite composites received interesting results for removing refractory biodegradable organic pollutants. This work provides new insights for the removal of dye from wastewater using Ni catalysts supported on natural low-cost clay.