We biosynthesized iron oxide nanoparticles with four different pH in the solution to see its influence in the oxides obtained. This method allowed for generating aggregates of 1–10 nm, and under optimal conditions (pH=10) we could control the size in the range of 1–4 nm. With the purpose to analyze the biosynthesized iron oxide clusters we employed electron transmission microscopy techniques. Because the biosynthetic method with alfalfa has been used, the presence of the biomass, which is dense and within which are contained the nanoparticles, makes their observation difficult. Using the HAADF (Z contrast) technique it is possible to locate the nanoparticles, which are then characterized using EDS and HRTEM.

Electron microscopy characterization of biosynthesized iron oxide nanoparticles

Remediation and recycling of chromium from tannery wastewater using combined chemical–biological treatment system

This article presents a review of the main physical, chemical, electrochemical, and biological technologies used for treating heavy metals in the wastewater of industrial processes and in synthetic aqueous solutions which could be applied to leachate from landfills. This paper outlines the generalities, operating principles, and modifications made to the technologies described. It discusses and assesses which of these have better removal rates and higher levels of efficiency in minimizing the heavy metal concentrations contained in leachates, such as mercury, chromium, lead, nickel, and copper among others. The first part of the document presents the so-called conventional technologies, such as chemical, physical, and electrochemical treatment. These have been used to treat different wastewater, especially industrial waste, operating adequately from the technical topic, but with high costs and the secondary products’ production. The second part exposes biological treatments tend to be most widely used due to their versatility, effectiveness, and low cost, when compared with traditional technologies. It is important to note that there is no single treatment and that each of the technologies reviewed has different heavy metal decontamination rates. All technologies search to reduce concentrations of heavy metals to values that are safe for the natural resources where they are discharged or disposed, thereby complying with the regulatory limits regulated in each of the regions.

Technologies applicable to the removal of heavy metals from landfill leachate.

Total reflection X-ray fluorescence spectrometric determination of elements in water hyacinth from the Lerma River

Nanomaterials are widely used in health and biomedical applications, however, only a few studies investigate their toxic effects.  The present report signifies a contribution to the study of the toxic effects of silver nanoparticles on   E. coli cells, which is a model organism of anthropogenic pollution. The toxicity of nanoparticles depends on their chemical and surface properties, shape and size. Nanoparticles that have the same chemical composition but different shapes or sizes might have different effects on cells. In this work, Ag nanoparticles  were biosynthesized with an Eichhornia crassipes biomass, and it was demonstrated for the first time, that the amounts of hydrolysable tannins in this plant, are directly related to the size, shape, structure and composition of the Ag nanoparticles ; furthermore, the toxic effect was studied using E. coli cell culture. The EC was divided in three sections, i.e. roots, stems and leaves. Particle aggregation seems to be influenced by the amount of tannins present in the biomass. For each plant part, the amounts of hydrolysable tannins were determined, the highest amounts of these chemicals were present in the leaves, and hence these Ag nanoparticles dissolutions were used for the nanotoxicity experiments. . The cytotoxicity  of Ag nanoparticles in a suspension was tested using the Ag nanoparticles synthesized with leaves, against Escherichia Coli ATCC 25992 where the concentration that inhibited 100% of bacterial growth, was 5 mg/L in contrast with a commercial solution which needed 10mg/L of Ag. For the most part, the Ag nanoparticles  seemed to be of a nearly spherical shape, although on closer examination were determined to be mainly polyhedral.  Leaves biomass, produced mainly quantum dot nanoparticles with sizes below 10 nm and the Ag nanoparticles were mostly AgO. The cytotoxicity of Ag NPs in a suspension tested using the Ag nanoparticles on E. coli was highly effective towards inhibition of bacterial growth.

https://jns.kashanu.ac.ir/article_43375_696d418a7514f9b75189b526a7831851.pdf

Nanotoxicity for E. Coli and Characterization of Silver Quantum Dots Produced by Biosynthesis with Eichhornia crassipes

The bio-reduction method is reported as a part of a complimentary self-sustained technology, where bioremediation and metal particle production are related. The use of the characterization methods in this self sustainable technique open the expectative to be used for several other elements and with other plants, which will be discussed. However, the particular case of Mn nanoparticles involves an important option to generate nanoparticles in the range of 1-4 nanometers with a well controlled size and with a structure based on an fcc-like geometry for the smallest clusters and with more complex arrays for cluster greater than four shells, which involves magnetic moments significantly related to their atomistic configuration. At the same time, the use of the characterization methods establishes the dependence of the nanoparticle's size on the pH conditions used during the synthesis; small clusters in the range of 1-2 nm were generated using pH = 5, and it was shown that for the smallest aggregates, simple polyhedron shapes are stable.

Synthesis and characterization of Mn quantum dots by bioreduction with water hyacinth.

Inorganic Nanoparticles Induced Naturally in Water Hyacinth: Structural and Chemical Study

Production of different compounds can generate large amounts of hazardous wastes which are dangerous to the environment and human health. The disposal or treatment of hazardous liquid waste rich in heavy metals like silver (Ag), mercury (Hg) and chromium (Cr) is difficult due to the strong acidity and toxicity which usually present in these contaminants. For this study, several research works were reviewed in order to obtain an efficient and viable treatment in time and removal efficiency. A series of chemical precipitations were evaluated for efficiency in the reduction of heavy metals in liquid waste. The precipitation of all three metals lasted 30 minutes and after treatment the wastewater presented concentrations of 0.064 mg·L-1 Ag, 0.010 mg·L-1 Hg and 0.048 mg·L-1 Cr, with a standard pH (7.5-8.5); with removal efficiencies of 94.31% for Ag, 99.99% for Hg and 98.17% for Cr.

/pdf/ag-hg-and-cr-precipitation-for-recycling-derived-of-16ukjtus77.pdf

Pedro Avila-Pérez

Papers

Synthesis and characterization of Mn quantum dots by bioreduction with water hyacinth.

Inorganic Nanoparticles Induced Naturally in Water Hyacinth: Structural and Chemical Study

Ag, Hg and Cr Precipitation for Recycling Derived of Hazardous Liquid Waste