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# Nanotechnology and Water Treatment: Applications and Emerging Opportunities. Critical Reviews in Microbiology, 34(1): 43-69

Department of Microbiology and Plant Pathology, University of Pretoria, South Africa.
(Impact Factor: 6.02). 02/2008; 34(1):43-69. DOI: 10.1080/10408410701710442
Source: PubMed

ABSTRACT

Nanotechnology, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for treatment of surface water, groundwater, and wastewater contaminated by toxic metal ions, organic and inorganic solutes, and microorganisms. Due to their unique activity toward recalcitrant contaminants and application flexibility, many nanomaterials are under active research and development. Accordingly, literature about current research on different nanomaterials (nanostructured catalytic membranes, nanosorbents, nanocatalysts, and bioactive nanoparticles) and their application in water treatment, purification and disinfection is reviewed in this article. Moreover, knowledge regarding toxicological effects of engineered nanomaterials on humans and the environment is presented.

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Available from: Jacques Theron, Apr 11, 2014
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• "They have also been suggested as a good sorbent for the remediation treatment of contaminated sediments or wastewaters [3] [4]. "
##### Article: Effect of carbon nanotubes on Cd(II) adsorption by sediments
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ABSTRACT: With increasing production and application, carbon nanotubes (CNTs) will enter into the environment in significant masses in upcoming years. CNTs have great potential to disturb the bioavailability and toxicity of other contaminants because of their high and strong adsorption capacity. This study investigated the influence of CNTs on the Cd(II) adsorption behavior by sediment–CNTs mixture at different CNTs/sediments ratios. The results showed that the adsorption kinetic data were well described by the pseudo-second-order model, and the pseudo-second-order rate constant (k2) decreased from 0.122 to 0.070 g/(mg min) with increasing CNTs/sediments ratios from 0% to 10%. Because of the different functional groups in CNTs (carboxyl groups, pKa = 2.81) and sediments (humic acid, pKa = 5.83), the removal efficiencies of Cd(II) by CNTs increased at pH 3.0, while the removal efficiencies of Cd(II) by sediments increased significantly at pH 5.7. The adsorption capacity of Cd(II) increased by the CNTs polluted sediments with ascending CNTs/sediments ratios. Cd(II) adsorption by sediments–CNTs mixture is a spontaneous (ΔG○ < 0), endothermic, and physical reaction (ΔH○ < 41 kJ/mol). Moreover, the spontaneity of the Cd(II) adsorption by sediment–CNTs mixture decreased, as indicated by less negative ΔG○ values, with increasing CNTs/sediments ratios. This is among the first study to investigate the effect of CNTs on metal adsorption by sediments. The results indicate CNTs released into sediments would change the adsorption behavior of Cd(II) by sediments and then alter the potential risk of Cd(II) and CNTs in sediments.
Full-text · Article · Mar 2015 · The Chemical Engineering Journal
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• "There is a general interest in the study of plasma-liquid interactions within the scientific community for an array of applications, including but not limited to biomedicine and biological disinfection [1] [2] [3] [4] [5] [6], chemical disinfection [7] [8] [9], and agricultural applications. [10] [11] In order to successfully realize these applications and develop mature technologies, the basic science underlying these coupled plasma gas-liquid systems must be well understood. "
##### Article: Momentum, Heat, and Neutral Mass Transport in Convective Atmospheric Pressure Plasma-Liquid Systems and Implications for Aqueous Targets
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ABSTRACT: There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 $\mu$m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results from this study include the presence of a 10 K temperature drop in the gas boundary layer adjacent to the interface that arises from convective cooling and water evaporation. Accounting for the resulting difference between gas and liquid bulk temperatures has a significant impact on reaction kinetics; factor of two changes in terminal aqueous species concentrations like H$_2$O$_2$, NO$_2^-$, and NO$_3^-$ are observed if the effect of evaporative cooling is not included.
Full-text · Article · Feb 2015 · Journal of Physics D Applied Physics
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• "The AgNPs prepared using green methods have high surface area, a smaller size and high dispersion and show a strong bactericidal and antibiotic activity. The AgNPs have several important applications in the field of antimicrobial agents, capable of purifying drinking water, degrading pesticides and killing human pathogenic bacteria [7] [8] [9] [10] . Many recent reports were published on biosynthesis of AgNPs using plant latex [11- 13] , natural rubber latex [14] [15] , plant extract or by the whole plant showing promising biological activities [6] [16] , such as cytotoxic and antimicrobial activities. "
##### Article: Antimicrobial activity of latex silver nanoparticles using Calotropis procera
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ABSTRACT: Objective: To synthesize silver nanoparticles by green methods using serum latex of Calotropis procera at 80 OC and evaluate them against bacteria, dermatophytes and phytopathogenic fungi comparing with the activity of untreated latex. Methods: The synthesis of silver nanoparticles was performed by mixing 3% latex serum extract with the same volume of silver Nitrate (2 mM) solution in round flask and heating in water bath at 80 OC. Characterization of silver particles were determined using UV-visible spectrophotometer, transmission electron microscopy (TEM), X-ray diffraction (XRD), and fourier transform infra-red spectroscopy (FTIR). The antimicrobial activity of the green synthesized LAg-NPs was determined against bacteria, dermatophytes and phytopathogenic fungi and compared to the crude untreated latex by agar well diffusion methods. Results: Biosynthesis of latex silver nanoparticles was successfully obtained by green method. The formation of silver nanoparticles has been confirmed by UV–visible, TEM microscopy, X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). TEM analysis showed that synthesized silver nanoparticles (LAg-NPs) are highly stable spherical shaped particles, well dispersed with a diameter ranged from 4 up to 25 nm and an average size of 12.33 nm. LAg-NPs showed strong antibacterial activity against Gram –ve bacteria (E. coli, Pseudomonas aeruginosa and Serratia sp.) and antifungal activity against (Trichophyton rubrum, Candida albicans and Aspergillus terreus). Conclusions: It can be concluded that serum latex of Calotropis procera was found to display strong potential for the synthesis of silver nanoparticles as antimicrobial agents through rapid reduction of silver ions (Ag+ to Ag0). The green synthesized LAg-NPs were found to show higher antimicrobial efficacy than crude latex.
Full-text · Article · Nov 2014 · Asian Pacific Journal of Tropical Biomedicine