Synthesis and Characterization of Polysaccharide-MOF Composites for Environmental Remediation

Abstract

MOFs are porous co-ordination networks/polymers which are highly crystalline substances with enhanced porosity, large surface area and improved overall attributes. These cages comprise of metal ion clusters which serve as the secondary building units (SBUs). Based on the coordination geometry of the organic linkers with metal ions; their structure and unique attributes can vary accordingly. Zeolitic Imidazole Framework-8 (ZIF-8) have improved structural porosity, flexibility, surface functionality and crystalline nature making it feasible to be utilized in various applications including the gas storage, CO2 adsorption, alkane/alkene separation and the catalysis. The biodegradability, higher surface area, and flexible binding interaction between the cellulose and ZIF-8 have made it an ideal choice for the various water remediation applications. The poor wet chemistry of the ZIF8-Cellulose composite is reported previously as the cellulose swells and loose dimensional stability in aqueous media. To overcome this problem, the ZIF8-APTES-Cellulose composite is synthesized which have high hydrophobicity and aqueous stability. The wet chemistry is tested by measuring the water contact angle which is 139.5°. The FTIR analysis shows a significant peak at 450cm-1 confirming the Zn-N bond along with peaks at 1550cm-1, 1480 cm-1, 1080cm-1, and 1020 cm-1 confirming the N-H bending of APTES, C=N vibration, C-N vibration of imidazole and C-O vibration of the composite respectively. Moreover, XRD analysis of the composite shows characteristic peak positions at 7.3°, 10.3°, 12.7°, 18°, 22.7° and 35.02° confirming the presence of ZIF8, APTES and cellulose. The dye degradation efficiency for the composite is explored at different conditions such as pH, dose of adsorbent, and concentration of dyes to achieve the optimized results. The maximum efficiency for the degradation of Congo Red dye is achieved 95% with 4mg dose of adsorbent at pH 4.0. This study opens up avenue for the dye remediation of wastewater.