Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe 3 O 4 ) were synthesized using chemical co-precipitation method at 80°C. The nanoparticles were characterized using UVvisible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K 2 Cr 2 O 7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

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Many oxidative and reductive processes have made extensive use of supported vanadium oxide catalysts. Understanding surface-active speciation and support interactions in these materials is critical to the development of heterogeneous catalysts. In this context, the vanadium incorporated on Mobil Composition of Matter No. 41 (V-MCM-41) catalysts were prepared with ethanol (AM) and without ethanol (NAM) at room temperature. The chemical and structural properties of the V-MCM-41 (AM) and V-MCM-41 (NAM) materials were studied by X-ray diffraction (XRD), N 2 physisorption, inductively coupled plasma-optical emission spectrometry (ICP-OES), diffuse reflectance UV−vis spectroscopy (DRUV−vis), temperature-programmed reduction with hydrogen (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), 51 V NMR analysis, and high-resolution transmission electron microscopy (HRTEM) analysis. The TEM images showed that the V-MCM-41(AM) sample pores were arranged radially with nanosized particles. Further, the elemental analysis reports confirmed that the majority of the vanadium species were successfully loaded onto the pristine siliceous materials. However, the local environment of the vanadium and support interaction was entirely different due to the influence of ethanol in the synthesis medium. The NMR and DRUV−vis results showed that the incorporated vanadium oxide species were highly dispersed on both catalysts with an octahedral coordination environment under hydrated conditions. The detailed investigation from the XPS analysis combined with the TPR results confirmed that the fraction of the V 5+ ion on the mesoporous nanospherical V-MCM-41 (AM) catalyst was significantly larger than the bulk V-MCM-41 (NAM) catalyst. The efficiency of catalysts was tested for diphenylmethane (DPM) oxidation reaction using CO 2 -free air as an oxidant, and catalytic experiments revealed that nanospherical V-MCM-41 (AM) showed a higher catalytic activity than bulk V-MCM-41 (NAM). Differences in catalytic activity were mainly encountered by the concentration of surface-active sites, which were influenced by the radial arrangements of nanospherical particles and the diffusion capability of vanadium oxides. The Raman and NMR studies also showed that a V 5+ ion in a distorted coordination environment with a terminal VO bond is required to activate the O 2 molecule for the selective oxidation reaction. The calculated activation energies for V-MCM-41 (AM) and V-MCM-41 (NAM) were found to be 15 and 35 kJ/mol, respectively. This research paves the way to developing the nanosized MCM-41 material for a variety of shape-selective reactions and storage applications.

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