Wheat straw cellulose based fluorescent probe cum bioadsorbents for selective and sensitive alleviation of uranium(VI) in waste water

Abstract

Twin functional ecofriendly fluorescent probe and bioadsorbents were fabricated from wheat straw (WS) for detection and alleviation of hazardous uranyl ions from wastewater. Cellulose nanofibers (CFs) were isolated from WS using alkaline steam explosion and were converted into cellulose dialdehyde (DCF) via selective oxidation followed by conversion to Fluorescent Schiff base cellulose fibres (FSCF) by condensation with L-Arginine, a natural amino acid. Fourier transform infra-red spectroscopy (FTIR), X-Ray Diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrometer (EDX) and thermo-gravimetric analysis (TGA) established formation of Schiff base evenly on CFs yielding robust, crystalline and thermally stable fibrous bioadsorbents. FCSF exhibited affinity for uranyl ions in presence of competing ions and linear increase in fluorescent intensity with concentration at 561 nm when excited at 279 nm in DMF with a low limit of detection (LOD) of 8.09 μM and binding constant of 10 M−1 m3. Under optimised conditions, adsorption studies revealed suitability of Pseudo-second order kinetics with maximum adsorption capacity of 192.7 mg g−1 and Langmuir isotherm confirming chemisorption of U(VI) ions. FSCF exhibited 97% adsorption efficiency after 5 cycles when tested for reusability. The results demonstrated potential application of FSCF for probing and removal of uranyl ions from wastewater.