A new approach to the remediation of heavy metal liquid wastes via off-gases produced by Klebsiella pneumoniae M426

When the off-gas from an aerobic culture of Klebsiella pneumoniae M426 grown in the absence of added heavy metals was passed through a solution of Hg(2+), Cd(2+), Pb(2+), or Cu(2+) a yellow-white (Hg), white (Cd, Pb), or blue (Cu) precipitate was formed. Metal removal from solution was >97% within 2 h at initial concentrations of (as metal): Hg, 8.5; Cd, 12.6; Pb, 7.8; Cu, 9.5 mg/mL. Mercury was removed from solution at pH 2 and in up to 1 M NaCl. Energy dispersive X-ray microanalysis (EDX) of the precipitates showed them to comprise metal, sulfur and carbon in the case of Hg, Cd, and Pb, and, in the case of Cd and Pb, also oxygen. The pH of the solution increased by 1-2 units at an initial pH of 7 and by 4-5 units at an initial pH of 2. In the case of cadmium and lead, the presence of crystalline metal carbonates and hydroxides was confirmed by X-ray powder diffraction (XRD) analysis and additional peaks were seen which could not be assigned to known compounds in the diffraction file database. In the case of copper, hydroxides, and a form of copper sulfate, were found. In the case of mercury the XRD patterns could not be assigned to any known compound, except for HgCl in the solution at the acidic initial pH. The absence of sharp peaks in the pattern for the Hg-precipitate was indicative of poorly crystalline, nanocrystalline or amorphous material. The unknown mercury compound, since it contained non-carbonate carbon, was suggested to be derived from a volatile organothiol in the gases evolved from the culture. Analysis of the culture head gas by GC-MS showed the presence of dimethyldisulfide as a likely precipitant. No sulfur compound was found using XRD analysis in the case of cadmium and lead, although EDX analysis suggested this as a major component and the lack of XRD pattern is evidence for a non-crystalline metal-organothiol. The exact chemistry of the new materials remains to be elucidated but metal precipitation via a biogenic organothiol is a potentially effective approach to the remediation of aggressive metal wastes.     

Lanthanum biosorption by a Pseudomonas sp.: equilibrium studies and chemical characterization

Lanthanum biosorption by a Pseudomonas sp. was characterized in terms of equilibrium metal loading, model fitting, kinetics, effect of solution pH, lanthanum–bacteria interaction mechanism and recovery of sorbed metal. Lanthanum sorption by the bacterium was rapid and optimum at pH 5.0 with equilibrium metal loading as high as 950 mg g⁻¹ biomass dry wt. Scatchard model and potentiometric titration suggested the presence of at least two types of metal-binding sites, corresponding to a strong and a weak binding affinity. The chemical nature of metal–microbe interaction has been elucidated employing FTIR spectroscopy, energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). FTIR spectroscopy and XRD analysis revealed strong involvement of cellular carboxyl and phosphate groups in lanthanum binding by the bacterial biomass. EDX and the elemental analysis of the sorption solution ascertained the binding of lanthanum with the bacterial biomass via displacement of cellular potassium and calcium. Transmission electron microscopy exhibited La accumulation throughout the bacterial cell with some granular deposits in cell periphery and in cytoplasm. XRD confirmed the presence of LaPO₄ crystals onto the bacterial biomass after La accumulation for a long period. A combined ion-exchange–complexation–microprecipitation mechanism could be involved in lanthanum accumulation by the biomass. Almost 98% of biomass-bound La could be recovered using CaCO₃ as the desorbing agent.     

Structural characterization,antioxidant and anticancer properties of gold nanoparticles synthesized from leaf extract (decoction) of Antigonon leptopus Hook. & Arn.

Tea is an aromatic beverage prepared by pouring boiling water over alleviated leaves of the tea plant. Tea prepared from the aerial parts of Antigonon leptopus has been traditionally used as remedy for cold, diabetes and pain in many countries. The gold nanoparticles (Au NPs) synthesized from powdered leaf extract (decoction) of A. leptopus were characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern and energy dispersive X-ray (EDX) analyses to define the formation of Au NPs. Further, the synthesized Au NPs were well characterized based on their strong surface plasmon resonance (SPR), crystalline nature, functional groups, size and dispersed shapes, purity and Bragg's reflections of face centered cubic (fcc) structure of metallic gold. The Au NPs showed higher free radical scavenging property when compared to the effect of leaf extract. Cytotoxicity study of synthesized Au NPs exhibited the growth inhibitory property at the concentration (GI₅₀) of 257.8 μg/mL in human adenocarcinoma breast cancer (MCF-7) cells after 48 h. Thus, the Au NPs synthesized from the Mexican creeper, A. leptopus revealed the important biological properties: as a free radical as well as anticancer agent. We conclude that the A. leptopus derived biological materials have promising potential as a source for the development of anticancer drug in future.     

The Tunable and Well-Controlled Surface Plasmon Resonances of Au Hollow Nanostructures by a Chemical Route

Au plasmonic hollow spherical nanostructures were synthesized by electrochemical reduction (GRR, the Galvanic Replacement Reaction) using Ag nanoparticles as templates. From UV-visible absorption spectroscopy, it was found that the surface plasmon resonance (SPR) of gold hollow spherical nanostructures first showed red shift and then blue shift. However, further addition of gold precursor (HAuCl₄) resulted into a red shift of SPR peak. The morphological changes from Ag nanoparticles to Au hollow nanostructures were assessed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX)analysis. The Mie Scattering theory based simulations of SPR of Au hollow nanostructures were performed which are in good agreement with the experimental observations. Based on the experimental observations and theoretical calculations, a complete growth mechanism for Au hollow nanostructures is proposed.     

Palladium and gold removal and recovery from precious metal solutions and electronic scrap leachates by Desulfovibrio desulfuricans

Biomass of Desulfovibrio desulfuricans was used to recover Au(III) as Au(0) from test solutions and from waste electronic scrap leachate. Au(0) was precipitated extracellularly by a different mechanism from the biodeposition of Pd(0). The presence of Cu²⁺ (∼2000 mg/l) in the leachate inhibited the hydrogenase-mediated removal of Pd(II) but pre-palladisation of the cells in the absence of added Cu²⁺ facilitated removal of Pd(II) from the leachate and more than 95% of the Pd(II) was removed autocatalytically from a test solution supplemented with Cu(II) and Pd(II). Metal recovery was demonstrated in a gas-lift electrobioreactor with electrochemically generated hydrogen, followed by precipitation of recovered metal under gravity. A 3-stage bioseparation process for the recovery of Au(III), Pd(II) and Cu(II) is proposed.Victoria S. Baxter-Plant – Deceased     

Green synthesis of ZnO hierarchical microstructures by Cordia myxa and their antibacterial activity

In this study, the leaves extract of Cordia myxa, has been used for the first time to synthesize zinc oxide (ZnO) hierarchical microstructures. The solution combustion method was employed as a self-sustaining reaction between zinc nitrate and the leaves extract. The surface properties of leaves mediated ZnO microstructures were determined by UV–Visible spectral analysis, Fourier transform infrared (FT-IR), Cold field emission-scanning electron microscopy (CFE-SEM), Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In addition, the effect of the leaves extract concentration on ZnO structures, size and surface properties was also studied. ZnO structures synthesized employing C. myxa were found to be hexagonal, triangular and round in shape which was determined using CFE-SEM. X-ray diffraction (XRD) analysis confirmed the crystalline nature of compounds. Furthermore, C. myxa mediated ZnO microstructures shows good bactericidal activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria.     

Synthesis of Silver and Gold Nanoparticles Using Cashew Nut Shell Liquid and Its Antibacterial Activity Against Fish Pathogens

This study reveals a green process for the production of multi-morphological silver (Ag NPs) and gold (Au NPs) nanoparticles, synthesized using an agro-industrial residue cashew nut shell liquid. Aqueous solutions of Ag⁺ ions for silver and chloroaurate ions for gold were treated with cashew nut shell extract for the formation of Ag and Au NPs. The nano metallic dispersions were characterized by measuring the surface plasmon absorbance at 440 and 546 nm for Ag and Au NPs. Transmission electron microscopy showed the formation of nanoparticles in the range of 5–20 nm for silver and gold with assorted morphologies such as round, triangular, spherical and irregular. Scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction analyses of the freeze-dried powder confirmed the formation of metallic Ag and Au NPs in crystalline form. Further analysis by Fourier transform infrared spectroscopy provided evidence for the presence of various biomolecules, which might be responsible for the reduction of silver and gold ions. The obtained Ag and Au NPs had significant antibacterial activity, minimum inhibitory concentration and minimum bactericidal concentration on bacteria associated with fish diseases.     

Macroscopic and microscopic variation in recovered magnesium phosphate materials: Implications for phosphorus removal processes and product re-use

Phosphorus (P) recovery and re-use will become increasingly important for water quality protection and sustainable nutrient cycling as environmental regulations become stricter and global P reserves decline. The objective of this study was to examine and characterize several magnesium phosphates recovered from actual wastewater under field conditions. Three types of particles were examined including crystalline magnesium ammonium phosphate hexahydrate (struvite) recovered from dairy wastewater, crystalline magnesium ammonium phosphate hydrate (dittmarite) recovered from a food processing facility, and a heterogeneous product also recovered from dairy wastewater. The particles were analyzed using “wet” chemical techniques, powder X-ray diffraction (XRD), and scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy (SEM–EDS). The struvite crystals had regular and consistent shape, size, and structure, and SEM–EDS analysis clearly showed the struvite crystals as a surface precipitate on calcium phosphate seed material. In contrast, the dittmarite crystals showed no evidence of seed material, and were not regular in size or shape. The XRD analysis identified no crystalline magnesium phosphates in the heterogeneous product and indicated the presence of sand particles. However, magnesium phosphate precipitates on calcium phosphate seed material were observed in this product under SEM–EDS examination. These substantial variations in the macroscopic and microscopic characteristics of magnesium phosphates recovered under field conditions could affect their potential for beneficial re-use and underscore the need to develop recovery processes that result in a uniform, consistent product.     

Physical, X-ray diffraction and scanning electron microscopic studies of uroliths

Identification of chemical constituents of calculus is important in the diagnosis and management of urolithiasis. The compositional variability of uroliths has different etiologies and requires various modes of treatment and prophylaxis. In the present study, we report the chemical compositional analyses of calculi recovered from buck and bullock by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) techniques and ultra-structure examination by scanning electron microscopy (SEM). XRD and EDX investigations conclusively established the chemical compositions of urinary calculi under investigation. The calculus from buck (sample I) had calcium oxalate monohydrate, a dominant salt phase and magnesium compound in significant amount. The calculus from bullock (sample II) had magnesium ammonium phosphate phase, with significant amount of calcium in apatite form and K+ ions. SEM study at higher magnification (X 1000) showed bipyramidal crystals in external zones of urolith (sample I). The struvite apatite calculus showed that basic unit of structure was lamination and the laminitis appeared to be made up of fine granules and high porosity. The bio-mineralization process of calculus formation was also studied, with a view to take preventive and therapeutic measures for amelioration of urinary stone diseases in animals and humans.     

Mycocrystallization of gold ions by the fungus Cylindrocladium floridanum

The size and morphology determines the thermodynamic, physical and electronic properties of metal nanoparticles. The extracellular synthesis of gold nanoparticles by fungus, Cylindrocladium floridanum, which acts as a source of reducing and stabilizing agent has been described. The synthesized nanoparticles were characterized using techniques such as UV–Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis (EDAX), and high-resolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical with an average size of 19.05 nm. Powder XRD pattern proved the formation of (111)-oriented face-centered cubic crystals of metallic gold. This microbial approach by fungus for the green synthesis of spherical gold nanoparticles has many advantages such as economic viability, scaling up and environment friendliness.     

Biorecovery of gold by Escherichia coli and Desulfovibrio desulfuricans

Microbial precipitation of gold was achieved using Escherichia coli and Desulfovibrio desulfuricans provided with H2 as the electron donor. No precipitation was observed using H2 alone or with heat-killed cells. Reduction of aqueous AuIII ions by both strains was demonstrated at pH 7 using 2 mM HAuCl4 solution and the concept was successfully applied to recover 100% of the gold from acidic leachate (115 ppm of AuIII) obtained from jewelry waste. Bioreductive recovery of gold from aqueous solution was achieved within 2 h, giving crystalline Au0 particles (20-50 nm), in the periplasmic space and on the cell surface, and small intracellular nanoparticles. The nanoparticle size was smaller (red suspension) at acidic pH (2.0) as compared to that obtained at pH 6.0 and 7.0 (purple) and 9.0 (dark blue). Comparable nanoparticles were obtained from AuIII test solutions and jewelry leachate.     

A Bacteriophage Mediated Gold Nanoparticles Synthesis and Their Anti-biofilm Activity

In the present study, gold nanoparticles (AuNPs) synthesis was carried out by using a rare bacteriophage which is morphologically similar to 7–11 phages of the C3 morphotype of tailed phage belonging to Podoviridae family as green route. Effect of various physiological parameters like pH, temperature and concentration of gold chloride salt on AuNPs synthesis was studied. The reaction mixtures have shown vivid colours at various physiological parameters. Phage inspired AuNPs were further characterized by using different techniques such as UV–Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and dynamic light scattering (DLS). DLS study revealed synthesis of various sizes of AuNPs in the range of 20–100 nm. SEM studies revealed synthesis of varied shaped AuNPs, viz., spheres, hexagons, triangles, rhomboids and rectangular etc. The presence of Au in the nanostructures was confirmed by EDS. The XRD pattern reflects the crystalline nature and nano size of AuNPs. These phage inspired AuNPs showed anti-bacterial activity against different bacterial pathogens. Anti-biofilm activity of AuNPs was evaluated on a glass slide. It was noticed that at 0.2 mM concentration of these AuNPs about 80% of biofilm formation by Pseudomonas aeruginosa, a human pathogen was inhibited. Thus, the phage inspired AuNPs synthesis could be potential therapeutic agents against human pathogens.     

Biosynthesis of extracellular and intracellular gold nanoparticles by Aspergillus fumigatus and A. flavus

Green chemistry is a boon for the development of safe, stable and ecofriendly nanostructures using biological tools. The present study was carried out to explore the potential of selected fungal strains for biosynthesis of intra- and extracellular gold nanostructures. Out of the seven cultures, two fungal strains (SBS-3 and SBS-7) were selected on the basis of development of dark pink colour in cell free supernatant and fungal beads, respectively indicative of extra- and intracellular gold nanoparticles production. Both biomass associated and cell free gold nanoparticles were characterized using X-ray diffractogram (XRD) analysis and transmission electron microscopy (TEM). XRD analysis confirmed crystalline, face-centered cubic lattice of metallic gold nanoparticles along with average crystallite size. A marginal difference in average crystallite size of extracellular (17.76 nm) and intracellular (26 and 22 nm) Au-nanostructures was observed using Scherrer equation. In TEM, a variety of shapes (triangles, spherical, hexagonal) were observed in both extra- and intracellular nanoparticles. 18S rRNA gene sequence analysis by multiple sequence alignment (BLAST) indicated 99 % homology of SBS-3 to Aspergillus fumigatus with 99 % alignment coverage and 98 % homology of SBS-7 to Aspergillus flavus with 98 % alignment coverage respectively. Native-PAGE and activity staining further confirmed enzyme linked synthesis of gold nanoparticles.     

Dopamine-Induced Growth of Au and Ag Nanoparticles on ITO Substrate and Their Application in PCPDTBT-Based Polymer Solar Cell

The direct attachment and growth of gold or silver nanoparticles (NPs) on indium tin oxide (ITO) surfaces was demonstrated using a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method by chemical reduction of the precursor metal salts with dopamine aqueous solution. Ag NPs on ITO substrate were approximately spherical with an average particle size of about 57 nm, but had a wide particle size distribution. Compared with Ag NPs, under the same 10 SILAR cycles, Au NPs have higher density packing and smaller average particle size of about 36 nm. XRD characterization and surface chemistry analysis confirmed the formation of Ag and Au NPs on ITO substrate with small amounts of dopamine-quinone adsorbed on the surface of them. Although Au NPs showed characteristic plasmon absorption, this did not result in performance enhancement in solar cell with the structure of ITO/ZnO/PCPDTBT:[6,6]-phenyl C₇₁/MoO₃/Ag because of the energy level mismatch between ZnO and dopamine molecules adsorbed on the surface of metal NPs.     

Enhanced surface plasmon resonance with the modified catalytic growth of Au nanoparticles

The catalytic growth of Au nanoparticles (AuNPs) has been employed in several analytical methods for improving the detection sensitivity, or integrated with the enzyme reactions for the quantitative detection of the respective substrates. However, the catalytic growth of Au nanoparticles do not work in some situations, such as surface plasmon resonance (SPR), electrochemistry, where metal matrices were used, because metal matrices used in these techniques, e.g. Au, are susceptible to metal deposition, which increased the background seriously. In this work, a SiO(2) layer was vapor-deposited on the gold film. The inhibition of metal deposition by this SiO(2) layer was investigated by SPR sensor. The results showed that the SiO(2) layer could avoid the deposition of metal on Au film. With the low background achieved by SiO(2)-coated Au films, sensitive detection of DNA hybridization using the catalytic growth of Au nanoparticles enhanced SPR was demonstrated. The work described here maybe helpful for the development of sensitive bioanalytical methods.     

Metal solubilization from metal-containing solid materials by cyanogenic Chromobacterium violaceum

Different cyanogenic bacterial strains (Chromobacterium violaceum, Pseudomonas fluorescens, Bacillus megaterium) were cultivated under cyanide-forming conditions in the presence of metal-containing solids such as nickel powder or electronic scrap. All microorganisms were able to form water-soluble metal cyanides, however, with different efficiencies. C. violaceum was able to mobilize nickel as tetracyanonickelate [Ni(CN)4(2-)] from fine-grained nickel powder. Gold was microbially solubilized as dicyanaoaurate [Au(CN)2-] from electronic waste. Additionally, cyanide-complexed copper was detected during biological treatment of shredded printed circuit boards scrap. Regarding the formation of tetracyanonickelate, C. violaceum was more effective than P. fluorescens or B. megaterium. Besides a few previous reports on gold solubilization from gold-containing ores or native gold by C. violaceum, the findings demonstrate for the first time the microbial mobilization of metals other than gold from solid materials and represent a novel type of microbial metal mobilization based on the ability of certain microbes to form HCN. The results might have the potential for industrial applications (biorecovery, bioremediation) regarding the treatment of metal-containing solids since metal cyanides can easily be separated by chromatographic means and be recovered by sorption onto activated carbon.     

Treatment of catechol bearing wastewater in an upflow anaerobic sludge blanket (UASB) reactor: sludge characteristics

This paper deals with the characteristics of anaerobic microbial granules grown in an UASB reactor treating catechol bearing synthetic wastewater (SWW). The specific methanogenic activity of the sludge showed an increase in trend with an increase in the organic loading rate and the catechol concentration in the SWW. The settling velocity of individual granules in the size range of 0.5-2.5mm was found to be in the range of 30-75mh(-1). The ash content in the sludge was 11.7% with a sludge volume index of 18-20mlg(-1). The inorganic elemental distribution within the granules showed a decrease except that for phosphorous and cobalt, which increased by approximately 12% and 18%, respectively, after the treatment of SWW. Scanning electron microscopy (SEM) coupled with electron disperse X-ray analysis showed an increase in the sulphur content by approximately 300% after the treatment of SWW. Surface mineral composition of the granules determined by XRD analysis indicated the existence of vuagnatite (CaAlSiO(4)(OH)). SEM observation of the granules showed the predominance of Methanosaeta and Methanobacterium type of species on the surface along with a variety of other species.     

Negative Poisson ratio of crystalline cellulose in kraft cooked Norway spruce

The tensile properties of kraft cooked Norway spruce were studied by tensile testing with in situ X-ray diffraction (XRD). Samples were of earlywood, cooked for varying times. The total lignin content of the samples was between 21.7% and 9.3%. Tensile tests with XRD were performed on wet samples, without XRD on dry samples. The tensile strength, the modulus of elasticity (MOE), and the elongation at fracture/yield were determined. X-ray diffraction was used to determine the microfibril angle (MFA) and the deformation of crystalline cellulose by monitoring the reflections 200 and 004. The (X-ray) Poisson ratio of crystalline cellulose was calculated, both before and after the yield point. The tensile strength and the MOE of the wet samples were significantly lower than in the dry samples. The tensile properties of dry samples were similar to dry earlywood samples of untreated Norway spruce. The MFA only showed notable changes due to strain when it was initially large, when a diminishing effect was observed. The Poisson ratio of crystalline cellulose was negative. The average values ranged between -0.26 and -1.17 before the yield point and between -0.86 and -1.05 after the yield point.     

Electron probe X-ray microanalysis of human skeletal muscle involved in rheumatoid arthritis

Summary Electron probe X-ray microanalysis in the scanning microscope was used to determine the elemental composition of muscle fibes from patients with rheumatoid arthritis (RA). Quantitative data concerning phosphorus, sulphur, chlorine and potassium were correlated to the fibre type by a routine method based on serial cryosectioning and histochemical staining of adjacent sections. Significantly lowered sulphur values were found in type II A and II B muscle fibres of RA patients as compared to those of healthy controls. Traces of gold were detected in muscles of two patients treated with gold salts. The basis and mechanism for the decreased sulphur content in RA muscles are so far unknown, but may depend on the decreased amount of sulphur-rich protein(s).     

Mycogenesis of gold nanoparticles using a phytopathogen <Emphasis Type="Italic">Alternaria alternata</Emphasis>

The development of an eco-friendly and reliable process for the synthesis of gold nanomaterials (AuNPs) using microorganisms is gaining importance in the field of nanotechnology. In the present study, AuNPs have been synthesized by bio-reduction of chloroauric acid (HAuCl₄) using the fungal culture filtrate (FCF) of Alternaria alternata. The synthesis of the AuNPs was monitored by UV–visible spectroscopy. The particles thereby obtained were characterized by UV, dynamic light scattering (DLS), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). Energy-dispersive X-ray study revealed the presence of gold in the nanoparticles. Fourier transform infrared spectroscopy confirmed the presence of a protein shell outside the nanoparticles which in turn also support their stabilization. Treatment of the fungal culture filtrate with aqueous Au⁺ ions produced AuNPs with an average particle size of 12 ± 5 nm. This proposed mechanistic principal might serve as a set of design rule for the synthesis of nanostructures with desired architecture and can be amenable for the large scale commercial production and technical applications.