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Biosynthesized Metal Nanoparticles in Bioremediation
Published in Vivek Kumar, Rhizomicrobiome Dynamics in Bioremediation, 2021
Jaison Jeevanandam, Yiik Siang Hii, Yen San Chan
Recently, nanosized silver particles (AgNPs) are extensively under research due to their exceptional electronic, catalytic and antibacterial properties. This has led AgNPs to be widely used as biosensors, catalysts, in surface-enhanced spectroscopy and in active energy devices (Tran et al. 2013). However, it is noteworthy that the AgNPs are widely utilized as nanocatalyst in environmental remediation applications. AgNPs possess capability to degrade harmful pollutants such as heavy metals, pesticides and dyes (Isa and Lockman 2019). Dyes are broadly used in textiles and poor management in wastewater treatment cause these effluents to be discharged into water bodies. These effluents generally consist of various toxic compounds, which include heavy metals, acids, and alkalis, that pose great risks to aquatic life and humans. Therefore, it is important to remediate wastewater to minimize the damage to the environment (Carvalho and Carvalho 2017). Herein, Singhal and Gupta (2019) utilized disposed sheet of X-ray extracted silver for AgNPs’ fabrication. The ability of these AgNPs in discoloring dyes were tested against five azo dyes that are soluble in water, namely evans and methylene blue, congo red, eriochrome black T and methyl orange. In their study, individual dyes were treated in static condition with AgNPs at room temperature and the experiment was carried for 90 mins. Results obtained showed that AgNPs were able to degrade all dyes by ~96–99%, except eriochrome black T.
Activation, Initiation, and Growth of Electroless Nickel Coatings
Published in Fabienne Delaunois, Véronique Vitry, Luiza Bonin, Electroless Nickel Plating, 2019
Esteban Correa, Alejandro Alberto Zuleta Gil, Juan G. Castaño, Félix Echeverría
Alkaline cleaning is a procedure that involves the use of alkaline solutions (usually pH > 11) containing sodium (Staia et al. 1997; Czagány et al. 2017; Belakhmima et al. 2017; Oliveira et al. 2017) or potassium hydroxide (Goettems et al. 2017). Such alkaline solutions are used in compositions that vary from 30 to 120 g/L NaOH or KOH (ASTM B322-99 2014) at temperatures ranging between 60°C and 90°C (Olarewaju Ajibolam et al. 2015; Oliveira et al. 2017; Staia et al. 1997; Czagány et al. 2017). Solutions containing mixtures of sodium hydroxide (50 g/L), sodium carbonate (30 g/L), sodium phosphate (30 g/L) (Wang et al. 2018; Fayyad et al. 2018), and sodium silicate (Xie et al. 2016) are also commonly used. Due to the pH of the solutions, alkaline cleaning has the advantage of preventing the dissolution of the substrate during the process, which is why it is one of the most commonly used methods for cleaning low-, medium-, and high-carbon steels. Some of the conventional cleaning methods for this type of substrates are specified in ASTM B183 (ASTM B183-18 2018).
Hydrogen Economy, Geothermal and Ocean Power, and Climate Change
Published in Roy L. Nersesian, Energy Economics, 2016
An acid donates hydrogen ions, and when dissolved in water, the balance between hydrogen ions and hydroxide ions shifts toward more hydrogen ions, which makes the solution more acidic. A base is a substance that accepts hydrogen ions. When dissolved in water, the balance between hydrogen ions and hydroxide ions shifts in favor of hydroxide ions, making the solution basic or alkaline. The range of pH values is between 0 and 14, with the pH of distilled water at 7.0, a neutral point. Basic or alkaline solutions have pH values above 7 to as high as 14, whereas acidic solutions have pH values below 7 to as low as 0. A kitchen drain cleaner has high pH values, whereas battery acid has low pH values, both depending on their strength.114 Each unit of a pH scale represents a factor of 10 in a substance being more basic or acidic.115 A change of 0.1 in pH value represents about a 25 percent change in strength of an acid or base. The addition of carbon dioxide in seawater forms a mixture of bicarbonate and carbonate and hydrogen ions, the latter associated with carbonic acid, whose strength is dependent on sea water temperature and alkalinity. One-third of anthropomorphic carbon dioxide is absorbed by land and oceans, and oceans alone absorb about one-quarter of anthropomorphic carbon dioxide. About one-half of absorbed carbon dioxide is retained in the upper 400 meters of the ocean depth and the remaining half penetrates deeper waters from an internal ocean circulation driven by differences in density and by winds. Changes in pH in deep ocean depths are expected to lag changes in surface pH by a few centuries.
Development of environmentally and economically sustainable delamination process for spent lithium-ion batteries
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Tushar Maske, Sandeep Anwani, Ravi Methekar
Solvent dissolution, heat treatment, alkali dissolution, and deep eutectic solvents are common methods used for delamination of the untreated cathode material (UCM) from the cathode electrode. In the solvent dissolution method (SDM), the UCM is delaminated from the aluminum foil by dissolving the polyvinylidene fluoride (PVDF) binder in a solvent such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAC), or N, N-dimethylformamide (DMF), etc. (He et al. 2015; Wu et al. 2023). Despite being a time-consuming process, the main advantage of this method lies in the low energy consumption for delamination of the cathode electrode materials (He et al. 2021). On applying high-temperature, PVDF gets decomposed causing the delamination of UCM in heat treatment method (Raj et al. 2022). Hydrogen fluoride (HF) and other hazardous gases are produced as a consequence of this procedure and these emissions have a negative impact on the ecosystem (Wang et al. 2019a). The inertness of NaOH toward UCM selectively dissolves the aluminum foil into the alkali solution in the alkali treatment method (Senćanski et al. 2017). It would be harmful to aquatic plants and animals if the alkaline wastewater generated after alkali treatment was discharged directly (Zhao et al. 2019). Although high temperatures are needed in the deep eutectic solvent for melting and dissolving the PVDF binder, better delamination efficiencies were achieved (Tran et al. 2019; Wang et al. 2019b). The primary detriment of this approach is the expensive nature of the solvent.
A review of the role of pre-treatment on the treatment of food waste using microbial fuel cells
Published in Environmental Technology Reviews, 2022
Hirra Zafar, Nicolas Peleato, Deborah Roberts
Chemical pre-treatments aim to modify the biological and physicochemical properties of the substrate through chemical reactions. In MFCs, most of the chemical pre-treatments (˃80% studies) were done on wastewater sludge, and only a few articles employed chemical pre-treatment of food waste. Alkaline pre-treatment uses bases such as sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), and aqueous ammonia (NH3.H2O). Alkali pre-treatment causes biomass swelling, which increases the internal surface area of the biomass and reduces the crystallinity of the cellulose. Acid pre-treatment involves the use of hydrochloric acid (HCl), hydrogen peroxide (H2O2), sulfuric acid (H2SO4), and acetic acid (CH3COOH) to hydrolyze hemicellulose and other biopolymers to render them more susceptible to microbial or enzymatic degradation [82, 93–96]. Acid pre-treatment can also be used to solubilize complex biopolymers such as lignocellulosic biomass and therefore increase the hydrolysis rates to improve contact with enzymes.
Recovery of Cobalt, Nickel and Copper Compounds from UHT Processed Spent Lithium-ion Batteries by Hydrometallurgical Process
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Thanh Tuan Tran, Hyun Seung Moon, Man Seung Lee
Application of precipitation to the direct manufacture of copper compounds from aqua regia solution is very difficult. Therefore, these solutions are often neutralized by adding alkaline solution like NaOH solution (Castro and Martins 2009). As a result, a large amount of wastewater is also generated along with increasing consumption of chemicals. Therefore, it is better to separate Cu(II) from the aqua regia stripping solution without changing the acidity of the stripping solution. For this purpose, solvent extraction of Cu(II) was tried in this work. Since Cu(II) exist as CuCl3− and CuCl42- in strong HCl solution, Aliquat 336 was selected for the selective extraction of these complexes over HCl and HNO3 according to ion exchange mechanism. Our experimental results showed that 99.4% Cu(II) was extracted from the stripping solution through three stages cross-current extraction by 1.0 moL·L−1 Aliquat 336 in kerosene with 15%(v/v) octanol as a modifier (see Figure 3). Besides, there was a decrease in the concentration of hydrogen ions after the extraction of Cu(II) from 5.5 to 5.0 mol·L−1, which can be attributed to co-extraction of HCl or HNO3 into Aliquat 336 (Le, Son and Lee 2019). Extraction reaction of Cu(II) by Aliquat 336 can be represented as: