Ultra-Highly Efficient Removal of Methylene Blue Based on Graphene Oxide/TiO₂/Bentonite Sponge

An ultra-highly efficient Graphene Oxide/TiO₂/Bentonite (GO/TiO₂/Bent) sponge was synthesized using an in situ hydrothermal method. GO/TiO₂/Bent sponge with a GO mass concentration of 10% exhibited the highest treatment efficiency of methylene blue (MB), combining adsorption and photocatalytic degradation, and achieved a maximum removal efficiency of 100% within about 70 min. To further prove the ultra-high removal capacity of the sponge, the concentration of MB in water increased to ten times the original concentration. At so high a MB concentration, the removal rate was still as high as 80% in 90 min. The photocatalytic mechanism of GO/TiO₂/Bent sponge was discussed through XPS, PL and radicals quenching experiments. Here Bent can immobilize TiO₂ and react with a photo-generated hole to increase the amount of hydroxyl radical; effectively enhancing the degradation of MB.GO sponge enlarges the sensitivity range of TiO₂ to visible light by increasing the charge separation of TiO₂ and reducing the recombination of photo-generated electron-hole pairs. Additionally, GO sponge with an interconnected porous structure provides an effective platform to immobilize TiO₂/bent and makes them be easily recovered. The as-prepared sponge develops a simple and cost-effective strategy to realize the ultra-highly efficient treatment of dyes in wastewater.