Synthesis of quaternary nanocomposites for catalytic reduction of Cr(VI) to Cr(III) and its sensing

Abstract

Alginate/Carboxymethylcellulose/Dex/MnO2/g-C3N4 (Alg/CMC/Dex/MnO2/g-C3N4) sol crosslinked with Ca2+ composite gel was synthesized by dissipative convective process followed by freeze drying process and characterized by Fourier transform infra red spectroscopy(FT-IR), Thermogravimetric analysis (TGA), Powder X-ray diffraction (PX-RD), Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Brunauer-Emmett –Teller (BET) adsorption isotherm and Rheology. As synthesized composite was used electrochemical sensor for the detection of Cr(VI) by Cyclic Voltammetry in aqueous solutions over the range of 0.01 to 20.0 μg mL−1 with a detection limit of 0.63 ng mL−1 and 1.17 ng mL−1 respectively. The rheological behavior of the gel Alg/CMC/Dex/MnO2/g-C3N4/Ca showed elastic behavior dominating over viscous behavior with an increase of angular frequency sweep on account of showing gel like structures. The catalyst Alg/CMC/Dex/MnO2/g-C3N4/Ca reduced Cr(VI) to Cr(III) just in 1.20 min. in presence of 0.01 M NaBH4 which is due to its highest surface area among all as synthesized monoliths. The reduction of Cr (VI) became fast took only 26.63 s in presence of conc. H2SO4. The reaction kinetics became very fast when the catalyst amount is increased 0.006 g and the reaction cannot be measurable. The novelty of the catalyst Alg/CMC/Dex/MnO2/g-C3N4/Ca is that it does not need any acid or base to reduce Cr(VI) to Cr(III) in a minimum time reported.