A facile and green synthesis of CuO/NiO nanoparticles and their removal activity of toxic nitro compounds in aqueous medium.

In this present work, we report the green synthesis of mixed bimetal oxides (CuO/NiO) for the efficient reduction of toxic nitrophenols (NP, DNP and TNP) in aqueous medium. The CuO/NiO NPs were synthesized by green hydrothermal method combined calcination process. The physiochemical properties of the synthesized CuO/NiO NPs were systematically characterized by using XRD, XPS, FTIR, SEM, and HR-TEM techniques. The calcinated CuO/NiO NPs XRD pattern and SEM morphology show the high crystalline nature than the non-calcinated. Whereas, the XPS and FTIR results confirmed the formation of the metal oxide bonding and the interaction of the bimetals. The HR-TEM images showed the spherical crystals with average particle size about 25 nm. In addition, the SAED pattern confirmed the polycrystalline nature of CuO/NiO NPs. The catalytic reduction of nitro compounds to amino derivative was studied with reducing agent (NaBH4). The CuO/NiO NPs showed the high catalytic activity and completed the reduction reaction of NP, DNP and TNP with in 2, 5 and 10 min respectively. In addition, CuO/NiO NPS exhibited the excellent kinetic rate constant k value about 1.519, 0.5102, 0.4601 min-1 for NP, DNP and TNP respectively. Furthermore, the conversion product aminophenol was observed for these three nitro compounds. The proposed CuO/NiO NPs showed excellent crystal stability after the nitrophenol reduction reactions. An inexpensive CuO/NiO NPs is a promising catalysts for reduction of toxic nitro compounds to useful products in aqueous or non-aqueous medium.

Batch adsorption studies on surface tailored chitosan/orange peel hydrogel composite for the removal of Cr(VI) and Cu(II) ions from synthetic wastewater.

Elimination of heavy metals from wastewater has been a significant process to improve the aquatic source's quality. Various materials act as very effective adsorbents to remove heavy metals, which cause toxicity to plants and all other living organisms. Thus, the present work focuses on removing heavy metals chromium (Cr) and copper (Cu) ions containing wastewater using biodegradable and cost-effective chitosan-based hydrogel composite. The composite was prepared via chemical cross-linking of radical chitosan with polyacrylamide and N,N'-Methylene bisacrylamide and blended with orange peel. The synthesis of the adsorbent has been confirmed by using Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy - Energy dispersive X-ray analysis (SEM-EDAX) and X-ray diffraction (XRD) studies. The adsorption power of the composite of metal ions at different time, pH, adsorbent dosages, different metal ion concentrations were analyzed by using Atomic Absorption Spectroscopy (AAS). The results concluded that the optimum pH for Cr(VI) and Cu (II) were 4 and 5, contact time: 360 min, adsorbent dosage: 4 g, and initial metal ion concentration: 100 mg/L for each metal ions. The adsorption isotherm models follow the Freundlich model and pseudo-second-order kinetics. From the results, the adsorption capacity was observed to be 80.43% for Cr(VI) and 82.47% for Cu(II) ions, respectively.

A strategy to enhance the photocatalytic efficiency of α-Fe2O3.

The photocatalytic dye degradation of pure α-Fe2O3 and different concentration of Co doped α-Fe2O3 is explored. Facile hydrothermal method were employed to prepare pristine, 2% and 4% Co-Fe2O3 nanoparticles. Further, synthesized product confirmation studies were employed from X-ray diffraction, UV-vis spectrometry, Fourier-transform infrared, Raman, scanning electron microscope and transmission electron microscope studies. The rhombohedral nanoparticles developed were enhanced photocatalytic action. Photocatalytic dye degradation studies were analyzed for prepared three samples and the photocatalytic efficacy of the obtained photocatalysts was compared experimentally. Methylene blue dye was degraded under UV-light irradiation with 364 nm. The results showed that 4% Co doped α-Fe2O3 sample exhibited better dye degradation with 92% efficiency. The 4% doping of cobalt ions enhanced the photocatalytic property of Fe2O3 and is a good candidate for methylene blue dye degradation above 90%. In addition, strategy for photocatalytic efficiency enhancement was proposed.

Nitrile-calixarene grafted magnetic graphene oxide for removal of arsenic from aqueous media: Isotherm, kinetic and thermodynamic studies.

A novel adsorbent was developed based on nitrile functionalized calix [4]arene grafted onto magnetic graphene oxide (N-Calix-MGO) for remediation of arsenic (III) ions from aqueous media. The nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The effective parameters on adsorption efficiency such as pH, adsorbent dosage, contact time, initial concentration, and temperature were studied. The adsorption process was provided with a high removal efficiency up to (90%) at pH 6 which followed by IUPAC Type II pattern. The mathematical models of kinetics and isotherm validated the experimental process. The adsorption kinetic is followed pseudo-first-order model with R2 > 0.9. The adsorption equilibrium was well fitted on the Freundlich model (R2 ∼ 0.96) as compared Langmuir model (R2 ∼ 0.75). Hence, the Freundlich model suggested a multilayer sorption pattern with a physisorption mechanism for arsenic (III) uptake ono developed nanocomposite with a sorption capacity of 67 mg/g for arsenic. The Gibbs free energy (ΔG° < -20 kJ/mol) showed As(III) uptake ono N-Calix-MGO nanocomposite was the physical adsorption mechanism.