Biosorbents for heavy metals removal and their future

Silver nanoparticles (NPs) have been the subjects of researchers because of their unique properties (e.g., size and shape depending optical, antimicrobial, and electrical properties). A variety of preparation techniques have been reported for the synthesis of silver NPs; notable examples include, laser ablation, gamma irradiation, electron irradiation, chemical reduction, photochemical methods, microwave processing, and biological synthetic methods. This review presents an overview of silver nanoparticle preparation by physical, chemical, and biological synthesis. The aim of this review article is, therefore, to reflect on the current state and future prospects, especially the potentials and limitations of the above mentioned techniques for industries.

/pdf/synthesis-of-silver-nanoparticles-chemical-physical-and-2arg54gdmv.pdf

Synthesis of silver nanoparticles: chemical, physical and biological methods.

http://fac.ksu.edu.sa/sites/default/files/Abdel-Raouf%20et%20al%2C2012.pdf

Microalgae and wastewater treatment.

Biogenic synthesis of nanoparticles: A review

Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30–17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

/pdf/synthesis-and-biological-characterization-of-silver-1gpnjonquc.pdf

Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica.

1. A Brief Introduction to Phytoplanktons.- 2. Physico- Chemical Environment of Aquatic Ecosystem.- 3. Phytoplanktons and Primary Productivity.- 4. Community Pattern Analysis.- 5. Case Study.- 6. Glossary.- 7. Bibliography.

An Introduction to Phytoplanktons: Diversity and Ecology

Chlorella ellipsoidea and Chlorococcum infusionum , promising microalgae for biodiesel feedstock production, were treated with ethylenediaminetetraacetate (EDTA) and phosphorous to induce stress which was then followed by flow cytometry to study the enhanced intracellular neutral lipid content. Treatment resulted in up to a threefold increase in total lipid content of Chlorella (41.8±1.9% at 16 days of incubation period) and more than twofold increases in Chlorococcum (31.3±1.0%at 18 days of incubation period) under phosphorous starvation in the culture. It was observed that maximum biomass yields in Chlorella and Chlorococcum were 1.56±0.06 and 2.17±0.12 g/L at 1.5 g/L of phosphorous after 20 and 18 days of incubation periods, respectively. The qualitative analyses of neutral lipid bodies under stress conditions were performed by confocal microscopy and revealed bright golden-yellow lipid droplets in stress exposed cells. Significant increase of monounsaturated fatty acids under the nutrient limited conditions was suitable to produce biodiesel. The maximum biomass (g/L) and lipid content (% dry cell weight) at different stresses showed significant results ( Ρ < 0.05) by single-factor Analysis of Variance (ANOVA) followed by Duncan's Multiple Range Test (DMRT).

/pdf/efficacy-of-edta-and-phosphorous-on-biomass-yield-and-total-56s3q943o9.pdf

Efficacy of EDTA and Phosphorous on Biomass Yield and Total Lipid Accumulation in Two Green Microalgae with Special Emphasis on Neutral Lipid Detection by Flow Cytometry

Bioreduction of Au3+ to Au0 and subsequent synthesis of gold nanoparticles using three cyanobacterial strains Leptolyngbya tenuis, Coleofasciculus chthonoplastes, and Nostoc ellipsosporum was investigated. The optimized condition for maximum gold nanoparticle synthesis was determined as 20 mg cyanobacterial biomass per 100 mL of 15 mg L−1 Au3+ solution as inoculum size at pH 5. At the onset of nanoparticle synthesis (up to 3 h) increased activity of catalase, ascorbate peroxidase, super oxide dismutase, and malondialdehyde content along with rapid loss of pigments and protein content (1–72 h) indicated gold toxicity at cellular level. Associated changes in thallus morphology were also significant. Nostoc biomass produced spherical- to irregular-shaped nanoparticles with diverse sizes and small number of nanorods. On the other hand, Coleofasciculus showed nanoparticle synthesis at extracellular medium which was either absent in Nostoc or very low in Leptolyngbya. Biosafety analysis by MTT assay using peripheral blood mononuclear cells (PBMC), two cancer cell lines viz. T cell acute (T-ALL) and human acute lymphoblastic leukemia (MOLT-4) and antibacterial effect against Pseudomonas aeruginosa and Staphylococcus aureus showed no toxic effect of synthesized gold nanoparticles.

Gold (III) bioreduction by cyanobacteria with special reference to in vitro biosafety assay of gold nanoparticles

Green synthesis is a significant process for non-toxic metal nanoparticle production employing plant materials. In the present investigation we reported an environmentally friendly method for gold-silver nano-alloy biosynthesis using a cyanobacterial strain, Lyngbya majuscula as bio-reagent. On exposure of Lyngbya thallus to equimolar solution of gold and silver (1 mM, pH 4) for 72 hrs and subsequent pink coloration of the experimental biomass indicated the nanoparticle synthesis. Extracted nanoparticles showed a distinct single plasmon band at 481 nm and further EDX analysis confirmed the presence of both the metals Au and Ag in nano-alloy form. It was also observed from TEM study that all the synthesized particles were spherical in nature with a size range of ~5-25 nm. The SEM pictures of the metal treated biomass confirmed the intra and extracellular nano-alloy formation. The XRD analysis of particle loaded biomass revealed that the 2θ values appeared at 38.2°, 44.5°, 64.8°and 77.8° that were indexed at (111), (200), (220) and (311) lattice planes. Presence of different functional groups viz. N-H, C=C, C–O, C=O on the surface of nanoparticles were recorded by FTIR. Overall, this technique requires low energy and less manufacturing cost for metal alloy biosynthesis.

Cyanobacteria mediated green synthesis of gold-silver nanoalloy

The
bioaccumulation of 198Au radionuclide, by Rhizoclonium riparium
a member of Chlorophyceae has been studied. It has been observed that
accumulation of gold on Rhizoclonium is almost pH independent and
slightly higher at basic pH. Accumulation of gold was studied with 198Au
radiotracer, 0.1, 1 and 5 ppm concentrations of gold. It has been concluded
from the biochemical analysis that the gold accumulation is due to adsorption
in the cellulose and not in protein, fat and carbohydrate. Accumulated gold was
recovered when washed with conc. HNO3.

Ruma Pal

Papers

An Introduction to Phytoplanktons: Diversity and Ecology

Efficacy of EDTA and Phosphorous on Biomass Yield and Total Lipid Accumulation in Two Green Microalgae with Special Emphasis on Neutral Lipid Detection by Flow Cytometry

Gold (III) bioreduction by cyanobacteria with special reference to in vitro biosafety assay of gold nanoparticles

Cyanobacteria mediated green synthesis of gold-silver nanoalloy

Preconcentration of 198Au in a green alga, Rhizoclonium