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Chemical Treatment
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
Donald B. Aulenbach, Béla G. Lipták, Thomas J. Myron
In OR reactions, electrons are transferred from the oxidized molecules to the reduced molecules. The reducing agent donates the electrons and is oxidized in the process. The donated electrons are accepted by the reduced chemical. An example of such a process is the reduction of chromium by ferrous ions. Here, the ferrous ions reduce the chromium from its soluble hexavalent form to an insoluble trivalent form, while the iron is oxidized as shown in the following: Cr+6+3Fe+2→Cr+3+3Fe+3
Calix-Assisted Fabrication of Metal Nanoparticles
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
Anita R. Kongor, Manthan K. Panchal, Vinod K. Jain, Mohd Athar
As the name suggests, this method involves reduction of ions from its variable oxidation state (Ag+ or Au3+) to zero oxidation state (Ag° or Au°) with the help of reducing agents. Some commonly used reducing agents are citrate, borohydride, and elemental hydrogen. The major issue is controlling the growth of the nanoparticles and preventing them from agglomerating. This may arise when the chemical reactions are not complete leaving unwanted reactant on the product. Thus, nowadays, interest has been raised for the chemical reduction of inorganic salts in the presence of both reducing as well as stabilizing/coating agent for the preparation of well-dispersed nanoparticles. There exists no chance of aggregation when a stabilizing agent is used; hence, better stability for durable applications can be achieved. By varying the concentrations of reductant and stabilizer, uniformly sized nanoparticles can be synthesized. A better uniformity of the nanoparticles can be used for applications especially in medicine.
Synthesis and Characterisation of Carbonaceous Materials
Published in Ramendra Sundar Dey, Taniya Purkait, Navpreet Kamboj, Manisha Das, Carbonaceous Materials and Future Energy, 2019
Ramendra Sundar Dey, Taniya Purkait, Navpreet Kamboj, Manisha Das
Chemical reduction of GO is one of the brilliant processes used to produce rGO and graphene in mass quantities. The reduction of graphene oxide is generally achieved using reducing agents such as hydrazine and its derivatives, NaBH4, hydroquinone, sulfur compounds, metal/acid, etc. or by hydrothermal and solvothermal protocols [32,37–46]. The majority of reducing agents are either toxic or explosive and are difficult to handle for large-scale production. Moreover, most of the available methods are time consuming (6–48 hours) at room temperature or they require high temperatures [46]. The reduction of GO by metal/acid, including Fe/HCl, Al/HCl, Zn/H2SO4, Zn/HCl, etc. has drawn tremendous attention due to the fast reduction and high degree of reduction obtained [10]. Chemical reduction of GO using Zn metal and mineral acid at room temperature is rapid (2 hours) and does not involve the use of any other toxic reagents [10].
Modelling and optimisation of hardness in citrate stabilised electroless nickel boron (ENi-B) coatings using back propagation neural network – Box Behnken design and simulated annealing – genetic algorithm
Published in Transactions of the IMF, 2021
M. Vijayanand, R. Varahamoorthi, P. Kumaradhas, S. Sivamani
An electroless nickel bath is composed of the nickel ion source, complexing agent, reducing agent and stabiliser. Nickel chloride or sulphate is used as the source for metal deposition. Complexing agents stabilise the solution by preventing the excess free metal ion concentration and also act as a pH buffer. The function of the reducing agent is to reduce the metal ions by providing electrons. Nickel ion reduction using hypophosphite gives nickel-phosphorus alloys, and that reduced using dimethylamine borane (DMAB) or sodium borohydride provides nickel-boron alloys. Sodium borohydride has higher reduction efficiency among the discussed reducing agents.7 Stabilisers prevent the breakdown (decomposition) of a solution by masking the active nuclei.8,9
Graphene in wearable textile sensor devices for healthcare
Published in Textile Progress, 2022
Md Raju Ahmed, Samantha Newby, Wajira Mirihanage, Prasad Potluri, Anura Fernando
The most popular wet chemical method is delamination within a suitable solvent through an ultrasonication process (Hummers & Offeman, 1958). This method, called the Hummers’ method, involves treating graphite with sodium nitrate, sulfuric acid, and potassium permanganate mixture. Several investigations have been done to improve this method. One group eliminated sodium nitrate to prevent the toxic nitrous gas as a by-product (Marcano et al., 2010); at the same time, another resulted in higher oxidation and an excellent yield when phosphoric acid was added to the mixture. However, generally, the quality of reduced GO greatly depends on how well the reducing agents work along with other parameters such as temperature (Dimiev & Tour, 2014). Over the past few years, several attempts have been made to explore different reduction methods of GOs (Pei & Cheng, 2012). Currently, the most common reducing agents used in chemical reduction are sodium borohydride (NaBH4), hydrazine (N2H4), hydriodic acid (HI), and dimethylhydrazine (I. K. Moon et al., 2010; Pei, Zhao, Du, Ren, & Cheng, 2010; Shin et al., 2009; Stankovich et al., 2006). Sodium-ammonia (Na-NH3) can also be used to reduce GO to give a higher level of efficiency (Feng, Cheng, Zhao, Duan, & Li, 2013). This process involves taking GO that has been dispersed in liquid ammonia (NH3), adding sodium (Na) metal pieces to it, and plunging the mixture in a dry ice-acetone bath for 30 minutes. The resulting GO offered a high carbon-oxygen level of 16.61, low resistance at 350/sq., and a very high mobility rate of 123cm2/Vs.
Facile, controllable, chemical reduction synthesis of copper nanostructures utilizing different capping agents
Published in Inorganic and Nano-Metal Chemistry, 2020
Mohamed F. El-Berry, Sadeek A. Sadeek, Ahmed M. Abdalla, Mostafa Y. Nassar
During the chemical reduction reaction, the metal ions (Mn+) are chemically reduced to a zero-valent form of the metal (M0). The crystallization of the metal nanoparticles occurs in two major steps: nucleation and crystal growth. In the chemical reduction method, the main function of the reducing agent is to provide electrons to ions to reduce them into atoms, which later are developed into particles by nucleation and crystal growth steps. Various reducing agents are used in the chemical reduction method such as hydrazine,[30] ascorbic acid,[31] formaldehyde,[32] isopropyl alcohol,[33] and sodium borohydride.[34] Most reactions are carried out in water for the purposes of mass production, cost, and environmental consistency of the Cu products. However, using water as a solvent for the chemical reduction synthesis of Cu nanoparticles is a great challenge, compared with the synthesis of Au or Ag nano-powders.[20,35,36] This can be attributed to that Cu is less chemically stable than Cu(II) and Cu(I) oxides; thus, a major problem is the usual occurrence of surface oxidation during its synthesis. Recently, some approaches for preventing oxidation during the synthesis of Cu nanoparticles have been proposed.[37] The most popular strategies include the replacement of the aqueous system with a non-aqueous system and the use of protecting agents to resist the surface oxidation of Cu nanoparticles.