Three-dimensional monolithic TiO2/ZIF-8/AgCl/Ag-based photocatalytic microreactor for efficient degradation of organic pollutants

Abstract

Photocatalytic degradation of organic pollutants based on solar light is regarded as an important strategy for addressing water scarcity issue. However, efficient utilization of light in this process requires careful optimization of the photocatalytic reactor layout to maximize the interaction between light, photocatalyst and reactant molecules. Herein, a three-dimensional monolithic photocatalytic microreactor, in which in-situ grown TiO2/ZIF-8/AgCl/Ag was distributed on the surface of polydopamine (PDA)-modified melamine sponge (MS), was developed. The structural and optical properties were examined using SEM, TEM, HRTEM, XRD, XPS, FT-IR, EIS and TPR characterizations. Methylene blue (MB) was selected as the pollutant model, and the results showed that the photocatalytic microreactor had the super-fast degradation ability of MB due to high specific surface area, synergistic effects caused by TiO2/ZIF-8/AgCl/Ag hybrid structure and enhanced light-matter interaction. A MB removal rate (99.99%) was obtained within 8 min under visible light irradiation. After six times recycling, the photocatalytic microreactor still showed high photodegradation ability (90%). The radical scavenging experiments and electron spin resonance analysis showed that ·O2-, h+ and ∙OH were the reactive groups that played a role in the reaction system, and then a possible catalytic mechanism of TiO2/ZIF-8/AgCl/Ag was proposed.