Zeolitic imidazolate framework (AMCD-ZIF) functionalised membrane for the removal of dyes from water

Abstract

The chemical and thermal stability of zeolitic framework (ZIFs), in addition to the tunability of their functional groups renders them ideal candidates for water treatment applications. With the right functionality, ZIF particles can efficiently remove targeted contaminants from water. This, however, requires separating the particles from the suspension (through centrifugation or filtration) to recycle the ZIF particles after each treatment cycle. This time-consuming and costly process can be avoided by suspending the ZIF particles on solid support compatible with water treatment approaches. The design and preparation of a novel amine-carboxamide modified ZIF-8 (AMCD-ZIF) through the integration of mixed-linkers: 2-methylimidazole (MIM) and 4-amino-1H-imidazole-5-carboxamide (AMCD) in 1:1 ratio following a hydrothermal method, is reported in this study. Prepared and characterized AMCD-ZIF is used as a functionalizing agent to decorate the surface of electrospun polyvinyl chloride membranes (PVC-M). The functionalised electrospun membrane AMCD-ZIF/PVC-M is not only capable of microfiltration of aqueous molecules, due to the high porosity of the PVC-fibrous membrane, but also efficiently removing dyes from water due to the functionality introduced by the (AMCD-ZIF) at the surface of the membrane. Adsorption of aqueous organic dyes; malachite green (MG), methylene blue (MB), and direct blue 71 (DB) from water using the pristine AMCD-ZIF and membrane (AMCD-ZIF/PVC-M) were achieved. Both adsorbents resulted in the complete removal of aqueous MG in 30 min at ambient conditions and neutral pH. The adsorption capacity of MG is 2500 mg/g for AMCD-ZIF and 476 mg/g for AMCD-ZIF/PVC-M at ambient conditions. Adsorption efficiency of MG was maintained at approximately 100 % after six cycles of dye removal, without compromising the efficiency of the structure of AMCD-ZIF and AMCD-ZIF/PVC-M.