An easily-synthesized low carbon ionic liquid functionalized metal-organic framework composite material to remove Congo red from water

Abstract

Congo red (CR) is documented as a typical azo dye compound that is widely used for industrial activities such as papermaking, textiles, leather and additives production, making it a main component of COD contaminants in industrial wastewaters. Excessive releases of CR have resulted in adverse impacts on water environments and ecological systems due to its non-biodegradable, toxic and carcinogenic properties. Therefore, the removal of CR from water environments is of important for wastewater treatment. Previous studies have proved that metal-organic frameworks (MOFs) were feasible for CR adsorption, but less stable in water environments. Several functionalized materials have therefore been used to produce MOF-derived composite material for better performance. To simplify the synthesis processes and reduce the energy consumption, an ionic liquid (IL) was used in this study for the synthesis of [BMIM][PF₆]/ZIF-8 (BP/Z) composite material. The morphological structure of this material remained stable after the incorporation of IL. The equilibrium time of CR adsorption was 90 ​min with a maximum adsorption capacity of 1463 ​mg/g. Isotherm and kinetic studies revealed that the adsorption process was better described by Langmuir and pseudo-second-order model. Our results also presented that the IL/MOF composite material can be used within pH 5 and 6 with the presence of Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻ and SO₄²⁻. It was also proved that the novel IL/MOF composites in this study have great potential to adsorb and remove organic dyes from water.