Volume 6, Issue 5

One step green synthesis of silver nanoparticles (AgNPs) from silver nitrate (AgNO 3 ) using Leucaena leucocephala seeds extract as the reducing agent at room temperature was performed. The bioreduced NPs were characterized by UV-vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. Qualitative information of major components in the seed extract was obtained through its phytochemical screening. The phytochemical data of L. leucocephala revealed the presence of terpenes, flavonoids, coumarins and sterols. The reaction was optimized for AgNO 3 , extract concentration and time duration for the reaction. The obtained NPs showed a characteristic UV peak of AgNPs at 420 nm. TEM and SEM images showed the spherical shaped NPs over which the extract coating was very prominent. The binding of L. leucocephala seeds extract onto NPs was tested using FTIR and TGA. The antifungal activity of the as-synthesized NPs against two fungal species, namely Phlebiopsis gigantea and Echinodontium taxodii , was studied. The antimicrobial effect of the as-synthesized NPs was ascertained against Escherichia coli and Staphylococcus aureus . The antioxidant potential of the AgNPs was tested with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging. Also, the sensitivity of the NPs towards Fe 3+ ions was tested in aqueous media.

The preparation of oligochitosan through the heterogeneous degradation of chitosan/H 2 O 2 combined with the homogeneous reaction of chitosan with H 2 O 2 under gamma radiation was studied. Oligochitosan with weight-average molecular weight (M w ) of less than 10 kDa could be efficiently prepared by gamma Co 60 irradiation of chitosan solution (4%) and hydrogen peroxide (0.5%) at doses ranging from 8 to 24 kGy. The M w , chemical structure, and the crystallinity of chitosan and oligochitosan were characterized by GPC, FT-IR, and XRD. The solubility and antioxidant activity of chitosan and of oligochitosan with the different molecular weights were investigated. Results showed that oligochitosan CS 5 (20 kGy) and CS 6 (24 kGy) have good solubility in the pH range of 3 to –11. The scavenge percentage of CS 5 against 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical is 99.2% in 90 min. The antioxidant activity of oligochitosan is effective in a short time period; therefore, it has potential application as an effective and natural antioxidant.

For the first time, aqueous leaf extract of Urtica dioica was used as a sustainable source of reducing and capping agents to synthesize iron nanoparticles (INPs). In this regard, zero-valent INPs were produced and entrapped in a biologic coating. INPs were characterized by transmission electron microscopy (TEM), particle size analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometer, vibrating sample magnetometer, thermogravimetric analysis (TGA), and differential TGA. Based on the results, the prepared INPs were completely composed of zero-valent iron atoms without any iron oxide impurities. Nanoparticles were spherical in shape with diameters ranging from 21 nm to 71 nm with a mean particle size of 46 nm. Particles were entrapped in a biologic coating which resulted in formation of complexes ranging from 117 nm to 605 nm. High zeta potential value of these complexes (−82.6 mV) and the presence of hydrophilic groups on the biologic coating provided a stable colloid system. Prepared INPs were non-crystalline (amorphous) having a low magnetization value of 0.14 emu/g. The prepared particles are of significant interest in a wide range of scientific and technical applications.

Silver nanoparticles (AgNPs) have widespread applications. Recently, the synthesis of NPs using plant extract has attracted much attention. In this study, with an easy and rapid process at room temperature, AgNPs were produced by the aqueous extract of dried Juglans regia green husk, which is considered as a waste. The first sign of AgNPs synthesis was the color change of the sample from light green to yellowish brown. In addition, the production of AgNPs was examined by UV-Vis spectroscopy, dynamic light scattering (DLS), energy dispersive X-ray (EDX), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The antibacterial effect of AgNP on Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus and anticoagulation activity were determined. Synthesized silver colloid had electromagnetic absorbance at approximately 450 nm. The hydrodynamic diameter of monodisperse AgNPs was approximately 67 nm. The face center cubic metallic silver, which was spherical in shape, was in the range 3–50 nm with the average size of 7 nm. The extract showed antioxidant activity against 1,1-diphenyl-2-picryl hydrazyl (DPPH). Phenolic compounds, tannins, flavonoids, reducing sugars, proteins, ascorbic acid and carotenoids existing in the extract acted as reducing agents. AgNPs may be capped by biomolecules having O-H, C=O, N-H and other stabilizing functional groups.

An effective adsorbent (Fe-La-AC) was synthesized by impregnating mixed solution ferric nitrate and lanthanum nitrate with activated carbon and heated by microwave to remove methylene blue (MB) from dye wastewater. The Fe-La-AC was characterized by N 2 adsorption, Fourier transform infrared spectroscopy, Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy. Moreover, the existence of Fe 3 O 4 leads to Fe-La-AC having magnetic properties, which makes it easily separated and recycled from dye wastewater in an external magnetic field. After modification, the following phenomena occurred: Brunauer-Emmett-Teller surface area, average pore diameter, and total pore volume decreased; graphitization degree decreased. In addition, the equilibrium isotherms and kinetics of MB adsorption on raw activated carbon and Fe-La-AC were examined. The equilibrium adsorption data indicated that the adsorption behavior followed the Langmuir isotherm, and the pseudo-second-order model matched well the kinetic data. The maximum adsorption capacity of Fe-La-AC is 261.10 mg/g, which increases by 26.38% as compared with raw activated carbon. According to these results, Fe-La-AC is a promising adsorbent for the removal of MB from dye wastewater.

In this paper, microwave regeneration of spent activated carbon saturated with organic compounds was investigated. It has been observed from the present experiments that the microwave regeneration temperature and time have significant influences on iodine adsorption value and yield of the regenerated activated carbon (RAC). The characteristics of the RAC were examined by Brunauer–Emmett–Teller (BET). The RAC has a greatly higher surface area (743.6~264.1 m 2 /g), total pore volume (0.54~0.22 cm 3 /g), and a relatively smaller average pore width (28.83~33.58 nm) compared to the spent catalyst. The separation mechanism for activated carbon and organic impurities was determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectrometer (EDS). It was a process in which the organic impurities were aggregated from the pore internal migration to the surface at low temperatures, and the organic impurities were completely decomposed as the temperature increased to 900°C for 40 min. Simultaneously, a hexagonal crystal structure material of ZnO was obtained.

The desulfurization of liquid fuels with deep eutectic solvent (DES) newly synthesized from inexpensive constituents of imidazole and tetrabutylammonium bromide salt was conducted via liquid-liquid extraction. The aim of the work is to lower the sulfur content of liquid fuels to below the environmental regulation using DES in a process with low energy requirement. A simulated fuel containing dibenzothiophene (DBT) and thiophene as representative refractory sulfur compounds and a commercial-grade diesel fuel were used for this work. Quantitative monitoring of sulfur compounds in the raffinate phase of the fuels was performed using high-performance liquid chromatography and energy-dispersive X-ray fluorescence techniques. The results of sulfur extraction showed that DBT and thiophene extraction efficiencies of 70% and 47%, respectively, could be achieved from the simulated fuel in a single run extraction. Similarly, 47% total sulfur removal from the commercial-grade diesel fuel was achieved with the solvent. The deep desulfurizations of the fuels were successfully achieved in four and five successive stages with the simulated fuel and the diesel fuel, respectively. The solvent was effectively regenerated after the extraction process with both fuels, thus allowing for its repetitive usage.

Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to experiment optimization of microwave drying zinc oxide leach residues (ZOLR). The effects of different factors involving temperature, drying time, material mass, material thickness and their interaction on moisture content and dehydration rate of ZOLR were investigated. Two second-order polynomial models for moisture content and dehydration rate of ZOLR were established by multivariate regression analysis. Analysis of variance shows that all independent variable and quadratic terms of the four factors have significant influence on moisture content and dehydration rate of ZOLR. The optimum drying conditions are as follows: temperature is 93.41°C, drying time is 15.9 min, sample mass is 77.91 g and material thickness is 17 mm. The predicted values of moisture content and dehydration rate were 10.98% and 1 g/min, which were close to experimental values 11±0.03% and 1±0.01 g/min under the optimal conditions. Infrared spectra analysis show that no chemical reactions took place in the process of microwave dying ZOLR and only a part of the absorbed water was removed in the sample.