Synthesis of titanium based hetero MOF photocatalyst for reduction of Cr (VI) from wastewater

Abstract

Cr (VI) is one of the well-known toxic contaminant coming from leather tanning, metal finishing, textile industries etc. As per world health organization standard, limit for Cr (VI) in drinking water is 0.05 mg/l. In last few years, Metal organic framework (MOFs) based photocatalyst has find great interest for environmental remediation. In this work, titanium based MOFs NH2-MIL-125 and NTU-9 was integrated to make a hetero MOF NTU-9/NH2-MIL-125 (HMF) via refluxing method. It was characterized by XRD, TGA, FE-SEM, FT-IR, XPS, UV–vis (DRS) and PL etc. XRD indicates crystallinity and framework nature of all the synthesized MOFs. Thermal stability of HMF is improved to 520 °C in comparison to NTU-9. Diffuse reflectance spectra exhibit HMF having band gap of 2.2 eV absorbing up to 563 nm. BET surface area of NTU-9, NH2-MIL-125 and HMF were found to be 986, 1267 and 550 m²/g respectively indicating their microporous nature. In order to compare the photocatalytic activity, Cr (VI) solution was chosen a model wastewater. Because of more efficient charge separation, HMF is found to show better activity in comparison to both the contributing MOFs. Acidic condition favors the Cr (VI) reduction and HMF achieves 100% reduction within 90 min of visible light irradiation. In same time NTU-9 and NH2MIL-125 could exhibit only 35 and 55% reduction respectively. This study may give new direction to the study of hetero MOFs for environmental application.