Luis Cumbal

Polymer supported inorganic nanoparticles: characterization and environmental applications

Abstract Nanoscale Inorganic Particles (NIPs) and their agglomerates offer excellent opportunities conducive to selective removal of a wide array of target compounds from contaminated water bodies. For example, (i) hydrated Fe(III) oxides or HFO particles can selectively sorb dissolved heavy metals like zinc, copper or metalloids like arsenic oxyacids or oxyanions; (ii) Mn(IV) oxides are fairly strong solid phase oxidizing agents; (iii) magnetite (Fe 3 O 4 ) crystals are capable of imparting magnetic activity; (iv) elemental Zn o or Fe o are excellent reducing agents for both inorganic and organic contaminants. Very high surface area to volume ratio of these nanoscale particles offers favorable sorption and/or reaction kinetics. However, applications of NIPs in fixed-bed columns, in-situ reactive barriers and in similar flow-through applications are not possible due to extremely high pressure drops. Also, these NIPs are not durable and lack mechanical strength. Harnessing these inorganic nanoparticles and their aggregates appropriately within polymeric beads offers new opportunities that are amenable to rapid implementation in the area of environmental separation and control. While the NIPs retain their intrinsic sorption/desorption, redox, acid–base or magnetic properties, the robust polymeric support offers excellent mechanical strength, durability and favorable hydraulic properties in the flow-through systems. This paper discusses at length the preparation, characterization and environmental applications of two classes of polymer supported nanoparticles: (i) Hydrated Fe(III) Oxide (HFO) dispersed polymeric exchanger and their As(III), As(V), and heavy metals removal properties; (ii) Magnetically Active Polymeric Particles (MAPPs). The polymer supported nanoparticles are reusable and can be easily reprocessed over many cycles of operation.

One century of arsenic exposure in Latin America: a review of history and occurrence from 14 countries.

The global impact on public health of elevated arsenic (As) in water supplies is highlighted by an increasing number of countries worldwide reporting high As concentrations in drinking water. In Latin America, the problem of As contamination in water is known in 14 out of 20 countries: Argentina, Bolivia, Brazil, Chile, Colombia, Cuba, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Peru and Uruguay. Considering the 10 μg/L limit for As in drinking water established by international and several national agencies, the number of exposed people is estimated to be about 14 million. Health effects of As exposure were identified for the first time already in the 1910s in Bellville (Córdoba province, Argentina). Nevertheless, contamination of As in waters has been detected in 10 Latin American countries only within the last 10 to 15 years. Arsenic is mobilized predominantly from young volcanic rocks and their weathering products. In alluvial aquifers, which are water sources frequently used for water supply, desorption of As from metal oxyhydroxides at high pH (>8) is the predominant mobility control; redox conditions are moderate reducing to oxidizing and As(V) is the predominant species. In the Andes, the Middle American cordillera and the Transmexican Volcanic Belt, oxidation of sulfide minerals is the primary As mobilization process. Rivers that originate in the Andean mountains, transport As to more densely populated areas in the lowlands (e.g. Rímac river in Peru, Pilcomayo river in Bolivia/Argentina/Paraguay). In many parts of Latin America, As often occurs together with F and B; in the Chaco-Pampean plain As is found additionally with V, Mo and U whereas in areas with sulfide ore deposits As often occurs together with heavy metals. These co-occurrences and the anthropogenic activities in mining areas that enhance the mobilization of As and other pollutants make more dramatic the environmental problem.

Arsenic in volcanic geothermal fluids of Latin America

Numerous volcanoes, hot springs, fumaroles, and geothermal wells occur in the Pacific region of Latin America. These systems are characterized by high As concentrations and other typical geothermal elements such as Li and B. This paper presents a review of the available data on As concentrations in geothermal systems and their surficial discharges and As data on volcanic gases of Latin America. Data for geothermal systems in Mexico, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Ecuador, Bolivia, and Chile are presented. Two sources of As can be recognized in the investigated sites: Arsenic partitioned into volcanic gases and emitted in plumes and fumaroles, and arsenic in rocks of volcanic edifices that are leached by groundwaters enriched in volcanic gases. Water containing the most elevated concentrations of As are mature Na-Cl fluids with relatively low sulfate content and As concentrations reaching up to 73.6 mg L⁻¹ (Los Humeros geothermal field in Mexico), but more commonly ranging from a few mg L⁻¹ to tens of mg L⁻¹. Fluids derived from Na-Cl enriched waters formed through evaporation and condensation at shallower depths have As levels of only a few μg L⁻¹. Mixing of Na-Cl waters with shallower meteoric waters results in low to intermediate As concentrations (up to a few mg L⁻¹). After the waters are discharged at the ground surface, As(III) oxidizes to As(V) and attenuation of As concentration can occur due to sorption and co-precipitation processes with iron minerals and organic matter present in sediments. Understanding the mechanisms of As enrichment in geothermal waters and their fate upon mixing with shallower groundwater and surface waters is important for the protection of water resources in Latin America.

Abiotic As(III) Oxidation by Hydrated Fe(III) Oxide (HFO) Microparticles in a Plug Flow Columnar Configuration

Scientific evidence pertaining to selective sorption of As(V) species or arsenates and As(III) species or arsenites onto Fe(III) oxide microparticles is widely available in the literature. Practical implications of this phenomenon are well recognized for both natural and engineered systems. The previous investigations to this effect have clearly established that such selective sorption processes are accompanied by formation of inner-sphere complexes between the surface functional groups of Fe(III) oxides and As(V) or As(III) species in question. Although thermodynamically favorable, oxidation of As(III) or arsenite by Fe(III) oxides has not been reported to date. Experimental studies for all such investigations were, however, carried out in continuously stirred batch reactors. The results of the present study confirm that, in a plug flow configuration with stationary Fe(III) oxide microparticles in a column, aqueous-phase As(III) undergoes near-complete conversion to As(V) at neutral to slightly alkaline pH. The stationary phase consists of porous polymeric particles within which submicron hydrated Fe(III) oxide particles have been irreversibly dispersed. As the mobile liquid phase slowly percolates through the stationary column, each As(III) solute progressively binds to a multitude of Fe(III) sorption sites favoring As(III) oxidation. The resulting As(V) and Fe(II) are subsequently sorbed onto iron oxide particles. The plug flow configuration of the system allows thousands of contacts with Fe(III) sorption sites for each As(III) molecule, thus enhancing As(III) oxidation in accordance with law of mass action effect. Also, the absence of Fe(II) in the aqueous phase offers highest possible oxidizing environment near the HFO sorption sites. The reactor configuration approximating plug flow is postulated to be the major contributor for As(III) oxidation by Fe(III) oxide microparticles. This observation may have major ramifications for arsenic-containing groundwater percolating through iron-rich soil. At acidic pH, conversion of As(III) to As(V) is, however, much less pronounced due to unfavorable thermodynamics.

Sonochemical Synthesis of Silver Nanoparticles Using Starch: A Comparison

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature.

Green synthesis of silver nanoparticles using Andean blackberry fruit extract

Green synthesis of nanoparticles using various plant materials opens a new scope for the phytochemist and discourages the use of toxic chemicals. In this article, we report an eco-friendly and low-cost method for the synthesis of silver nanoparticles (AgNPs) using Andean blackberry fruit extracts as both a reducing and capping agent. The green synthesized AgNPs were characterized by various analytical instruments like UV–visible, transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The formation of AgNPs was analyzed by UV–vis spectroscopy at λmax = 435 nm. TEM analysis of AgNPs showed the formation of a crystalline, spherical shape and 12–50 nm size, whereas XRD peaks at 38.04°, 44.06°, 64.34° and 77.17° confirmed the crystalline nature of AgNPs. FTIR analysis was done to identify the functional groups responsible for the synthesis of the AgNPs. Furthermore, it was found that the AgNPs showed good antioxidant efficacy (>78%, 0.1 mM) against 1,1-diphenyl-2-picrylhydrazyl. The process of synthesis is environmentally compatible and the synthesized AgNPs could be a promising candidate for many biomedical applications.

One pot phytosynthesis of gold nanoparticles using Genipa americana fruit extract and its biological applications.

In this article, rapid one pot synthesis of gold nanoparticles (GNPs) using an eco-friendly extract of Genipa americana L. fruit is described. Electrospray ionization mass spectrometry (ESI-MS) and Fourier transform infrared (FTIR) spectroscopic studies demonstrated that small molecules such as genipin, genipaol, geniposide and ranolazine can act as reducer as well as stabilizers. The monodispersed, spherical GNPs were further characterized by UV-vis spectroscopy at λmax=535 nm, transmission electron microscopy (TEM), dynamic light scattering (DLS) and X-ray diffraction (XRD) analysis. This synthetic approach offers a greener and alternate route to the preparation of GNPs free from toxic chemical components and stable for 6-7 months under room temperature. The green synthesized GNPs showed weak antioxidant efficacy against 1,1-diphenyl-2-picrylhydrazyl and no cytotoxicity against A-549 and HeLa human cancer cell lines, from lung and cervix. This study opens a new industrial scope of G. americana fruit in nanoscience and as surface modified GNPs can be developed into a successful drug carrier for future pharmaceutical products.

Green Approach for Fabrication and Applications of Zinc Oxide Nanoparticles

Zinc oxide nanoparticles (ZnO-NPs) are known to be one of the multifunctional inorganic compounds which are widely used in everyday applications. This study aims to fabricate ZnO-NPs using grapefruit (Citrus paradisi) peel extract with particle size ranging from 12 to 72 nm. Structural, morphological, and optical properties of the synthesized nanoparticles have been characterized by using UV-Vis spectrophotometer, TEM, DLS, and FTIR analysis. They show the significant photocatalytic degradation efficiency (>56%, 10 mg/L, 6 h) against methylene blue and antioxidant efficacy (≥80% for 1.2 mM) against 1,1-diphenyl-2-picrylhydrazyl. From the results obtained it is suggested that green ZnO-NPs could be used effectively in environmental safety applications and also can address future medical concerns.

Lantana camara berry for the synthesis of silver nanoparticles

ABSTRACT Objective To synthesize the silver nanoparticles (AgNPs) by reduction of silver ions into nano silver, using ripened berry extract of Lantana camara and evaluate its antioxidant activity against 1, 1-diphenyl-2- picrylhydrazyl. Methods The prepared AgNPs were characterized by visual, UV-visible spectrophotometer, dynamic light scattering and transmission electron microscopy with selected area electron diffraction. Results Transmission electron microscopy and dynamic light scattering analysis confirmed the AgNPs are spherical and 75.2 nm average sized. Selected area electron diffraction analysis supports that the obtained nanoparticles were in crystalline form. In addition, the antioxidant efficacy of prepared AgNPs was found to be higher than berry extract against 1, 1-diphenyl-2- picrylhydrazyl. Conclusions From the results obtained it is suggested that surface modified AgNPs at lower concentration, showed higher antioxidant activity than berry extract against 1, 1-diphenyl-2- picrylhydrazyl and could be used effectively in future ethno pharmacological concerns.

In vitro evaluation of silver nanoparticles cytotoxicity on Hepatic cancer (Hep-G2) cell line and their antioxidant activity: Green approach for fabrication and application.

In this article, biosynthesis of silver nanoparticles (AgNPs) using Andean Mora (Rubus glaucus Benth.) leaf has been reported. Different analytical techniques including UV-vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used for the characterization of AgNPs. The initial appearance of color change with the intense surface plasmon resonance (SPR) bands around 440-455 in UV-visible spectra revealing the formation of AgNPs. The TEM image showed the AgNPs to be anisotropic, quasi-spherical in shape with sizes in the range of 12-50nm. On the other hand, XRD studies revealed the formation of face-centered cubic structure for AgNPs. The surface modified AgNPs showed no cytotoxicity at the concentration ranging from 0.01μM to 1.0μM on the Hepatic cancer (Hep-G2) cell line and observed antioxidant efficacy >70% at the concentration 0.05mM/0.20mL against 1, 1-diphenyl-2-picrylhydrazyl. From the results obtained it is suggested that AgNPs could be used effectively in future drug delivery systems and other biomedical concerns.