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Membrane-Based Technologies for the Removal of Toxic Pollutants
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Sanchita Patwardan, Rajesh W. Raut, Nilesh S. Wagh, Jaya Lakkakula
A hybrid silver nanoparticle grafted CNTs polymer-based membrane was constructed to remove refractory pollutants like oil in order to decrease the COD of a water body. A solution containing CNTs and acrylic acid was ultrasonicated in an acetone solvent for 10 minutes. The resultant solution was set aside for a few hours at a high temperature of 750C after the addition of benzoyl peroxide (BPO). The polymeric CNTs membrane was separated from the solution and dehydrolysed overnight. On the other hand, tollens reagent was prepared by sonicating a mixture of silver nitrate and ammonia to obtain a brownish ppt. Sodium dodecyl sulfate was introduced into a poly-acrylic acid solvent followed by the addition of tollens reagent with constant agitation. The resultant mixture was centrifugated by adding formaldehyde. The pellet form silver impregnated polymer-based CNT was rinsed with ethyl alcohol before filtering it through a polyvinylidene fluoride membrane to obtain a final silver fabricated PAA/CNT membrane. Transmission electron microscopy was used to evaluate the morphology of the modified CNTs. The average diameter of the membrane was found to be approximately 40 nm with a uniform thickness of 1 µm. The membrane was highly efficient with a high water flux of 3,000 L/m−2 h−1 bar−1 due to its higher adsorption of bacteria, specifically E.coli, and excellent oil-water separation potential. This hydrophobic, multifunctional membrane can be applied on an industrial scale where oil is produced as a major pollutant (Gu et al. 2016).
Fabrication of Nanomaterials
Published in C. Anandharamakrishnan, S. Parthasarathi, Food Nanotechnology, 2019
R. Preethi, Leena Maria, J.A. Moses, C. Anandharamakrishnan
It is a one-step method, a synthesis of nanoparticles with a controlled size, which is environmentally green due to the use of non-toxic chemicals. The chemical reaction of Tollens’ reagent consists of ammonia and silver nitrate, by an aldehyde group producing silver particles. However, the formation of silver nanoparticles depends on several factors including temperature, pH, and the concentration of substrate (aldehydes or ketones), water activity (aw), moisture, and time. Saccharides used as a reducing agent, in the presence of ammonia, produce a nanoparticle film or hydrogel with a size of 50–200 nm particles. In the modified Tollens method, oleic acid is used a stabilizer and glucose as a reducing agent under the UV radiation attribute-controlled size of particles. A trace amount of aldehyde flavor compounds can be detected and screened based on Tollens-process-synthesized silver nanoparticles (Basiuk and Basiuk, 2015; Ayob et al., 2001). AgNps composites were fabricated using biopolymer xylan as the stabilizing and reducing agent with the Tollens agent under microwave irradiation. The fabricated silver nanoparticles act as a selective and sensitive detector of heavy metals in water treatment (Ta et al., 2018).
Polyols for Polyurethane Production
Published in Eric J. Goethals, Telechelic Polymers: Synthesis and Applications, 2018
David J. Sparrow, David Thorpe
Carbohydrates, particularly sucrose, starch and its derivatives, are extensively used as polyol starters, because of their ready availability and low cost. One limitation is that reducing sugars, i.e., compounds that reduce Tollens’ reagent or Fehling’s solution, undergo cara-melization and decomposition, and hence are unsuitable in the conventional base catalyzed propylene oxide addition processes. Consequently, reducing sugars can only be used in acid-catalyzed processes or alternatively must first be converted into a nonreducing form, for example by hydrogenation (e.g., glucose to sorbitol) or by methanolysis (e.g., glucose to methylglucoside). Sucrose, which is the largest volume, bulk produced, pure organic chemical, is a nonreducing sugar. Its low cost and high hydroxyl functionality make it an ideal candidate and it is by far the most widely used rigid foam polyol starter. Carbohydrate polyols are claimed to offer a major technical advantage in giving rigid foams with improved and stablized char when subjected to fire. An excellent review of sugars in polyurethanes has been published.159
Biosynthesis, antimicrobial spectra and applications of silver nanoparticles: current progress and future prospects
Published in Inorganic and Nano-Metal Chemistry, 2022
Nimisha Tehri, Amit Vashishth, Anjum Gahlaut, Vikas Hooda
The viruses are nucleoprotein particles. The proteins constituting capsid of viruses act as highly reactive surface to interact with metal ions.[99] The exploration of viruses to carry out biosynthesis of nanoparticles is growing rapidly in recent years. However, it is in the stage of development for silver nanoparticles. The biosynthesis of silver nanoparticles (2–9 nm) from tobacco mosaic virus (TMV) has been reported by Yang et al.[67] The principle of biosynthesis reported in this study was found to be associated with TMV coat proteins subunits that are known to contain serine, aspartic acid, tyrosine and cysteine. These amino acids contain different functional groups like thiol, carboxyl and hydroxyl which usually play the role of reducing agent for Ag+ ions reduction. Secondly, under increased alkaline conditions i.e., >10 pH due to Tollens’ reagent used in this study, coat proteins (which generally remain stable up to pH 10) get disassemble to soluble proteins or peptides that behave as reducing and stabilizing agent for the formation of silver nanoparticles.
Sensitive determination of arginine based on hydrogen bonding by a surface plasmon resonance (SPR) sensor
Published in Instrumentation Science & Technology, 2020
A method for producing a silver film which uses glucose in order to reduce the Tollens’ reagent was used during the preparation steps which are shown in Figure 2b,c. Soaking the beaker with aqua regia solution and thoroughly rinsing with water was performed before the addition of the reaction solution. The following steps were carried out in order to obtain the Tollens' reagent.
One-step fabrication of recycled Ag nanoparticles/graphene aerogel with high mechanical property for disinfection and catalytic reduction of 4-nitrophonel
Published in Environmental Technology, 2019
Yi Zhang, Jia-Cheng E. Yang, Ming-Lai Fu, Baoling Yuan, Kiran Gupta
Among these candidates, GA has been being considered as an ideal supporter for its unique characteristics including continuously interconnected porous structure, enhanced transport property, superior mechanical flexibility and low mass density. Hence, the composite constituted by GA and Ag NPs can be expected to exhibit extensive advantages for disinfection and degradation in water treatment. Finding a facile method for effectively loading Ag NPs onto GA with high elastic mechanical property and chemical stability still faces great challenges [28–31]. Kwon and Lee et al. reported a step-wise method by firstly preparing graphene oxide (GO) and Ag NPs doped carbon spheres (AgCS), respectively, then inducing reduction and gelation of a mixture of GO and AgCS in an oil bath for the formation of G/AgCS hydrogel, and finally the G/AgCS aerogel was obtained by freeze drying hydrogel [28]. Li et al. reported an energy intensive method to fabricate high-quality three dimensional (3D) GA/Ag using γ-ray irradiation in isopropanol/water solution [31]. Zhu et al. fabricated a 3D porous reduced GO aerogel decorated with Ag NPs composite on a glass carbon electrode (GCE) by dropping the suspension of GO and AgNO3 onto the GCE, then freeze drying and further reducing it with N2H4 [29]. Obviously, these preparation processes suffer from tedious procedures, vast time and energy consumption. Very recently, Miao and Liu et al. utilized ammonium hydroxide to reduce and assemble Ag NPs onto the nitrogen doped GA by a one-step method [30]. In this reaction, ammonium hydroxide firstly reacted with Ag+ to form Tollens’ reagent dispersing in GO solution and then reduced Tollens’ reagent to Ag NPs loaded on GA homogeneously. The only defect is that the composite showed poor elastic mechanical property, probably due to the lack of effective binding agent. Compared with ammonium hydroxide, Methylamine (MA) not only can react with Ag+ to form Tollens’ reagent, but also can reduce the Tollens’ reagent to Ag NPs. In addition, MA may act as an effective agent to bond with the epoxy group of GO for fabrication of Ag NPs/GA with better elastic mechanical strength for the formation of high-molecular polymer [32]. It can be expected that MA could act as a multirole agent for assembly of Ag NPs/GA composite with better elastic mechanical property as well as other endowed performances.