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General Types of Contaminated Site Restoration Methods and Technologies
Published in Kofi Asante-Duah, Management of Contaminated Site Problems, 2019
SEAR is conducted by injecting a surfactant solution into the contaminated zone while simultaneously extracting water to maintain hydraulic control over the movement of the surfactant solution and the mobilized contaminants (Figure 12.10). In this process, a solution of surfactants (which are the primary ingredient of many soaps and detergents) is injected into the subsurface containing NAPLs. The surfactants increase the effective aqueous solubility of the NAPL contaminant; indeed, they can achieve a significant reduction in the interfacial tension between the NAPL and water phases, so that NAPL removal is greatly accelerated. Hydraulic control of the surfactant and NAPL is maintained by using higher pumping rates at the extraction wells than at the injection wells, and by the selective placement of water injection wells. (By the way, it is noteworthy that the surfactants used in SEAR are nontoxic, food grade, and biodegradable. Salts, and sometimes alcohols, may be added to adjust the surfactant properties that is, to improve the uptake of NAPL, or the hydraulic properties, such as the viscosity of the surfactant solution.) Surfactant flooding is followed by water flooding to remove residual contaminants and injected chemicals. Conventional wastewater treatment technologies may then be used to process the extracted effluent so long as surfactant foaming can be controlled, via the addition of an anti-foaming agent.
Process aids and additives for latices and thermoplastics
Published in David R. Karsa, Surfactants in Polymers, Coatings, Inks and Adhesives, 2020
Selection of a suitable foam control agent to overcome all these problems may at first seem difficult and it is not surprising that most commercially available defoamers and antifoams contain many components. Although the terms ‘defoamer’ and ‘antifoam’ are often used interchangeably, strictly a ‘defoamer’ (or ‘defoaming agent’) is used to break down foam that is already present, whereas an ‘antifoam’ (or ‘antifoaming agent’) is used to prevent foam formation. The latter is usually the most cost-effective means of chemical control.
Biomanufacture
Published in John M. Centanni, Michael J. Roy, Biotechnology Operations, 2016
John M. Centanni, Michael J. Roy
Fermentation to produce biotechnology products is performed in a fermenter, a closed and sealed glass or stainless steel vessel with a series of portals, stirring devices, and tubes entering the chamber (Figure 6.6). To begin the fermentation process, one must have raw materials of the highest quality, including a growth medium, gasses, a seed of recombinant bacterial or fungal organisms, and a means to control the process. Seed material, formed of billions of organisms that are capable of active division, is derived from a vial of WCB that has been expanded in a flask containing the defined medium. This is called the inoculum. The environment inside the vessel is controlled by human intervention or, when on auto-pilot, by a microprocessor. The fermentation process is initiated once all ingredients and the seed have been added together in the vessel and the fermenter has been closed and sealed. Once the environment inside the chamber is optimal, the cells replicate and are active manufacturers of the recombinant protein product. The chamber is typically stirred or otherwise agitated in an effort to evenly distribute gasses (particularly oxygen), nutrients, organisms, and, if secreted, the recombinant protein product. As stirring and movement of gasses may cause foaming, addition of antifoaming agent, a chemical designed to reduce microbubble formation, is often helpful. High shear stress and foaming contribute to protein denaturation and as such is avoided whenever possible. Cell growth and product production are monitored by taking samples from the chamber, and critical measurements, such as pH, gas tension, and osmolality are measured by probes placed directly in the chamber. This in-process testing allows the operator to follow the progress and correct variables if deviation from the specified limits is required. For example, if pH drops out of range, sodium hydroxide may be added to raise the pH, thus getting the fermentation system back into an optimal pH range.
Chemical footprint of textile and apparel products: an assessment of human and ecological toxicities based on USEtox model
Published in The Journal of The Textile Institute, 2020
Figure 6 shows that the ChF for human toxicity of antifoaming agent is approximately 1.29 × 10−10 cases, and thus, it is the major contributor among the above-mentioned chemical materials and accounts for 99.39% of the total human toxicity. During the dyeing process, antifoaming agent is generally used to eliminate the dyestuff of the foam and the fabric floating knot. By replacing the foaming agent molecules on the foam surface with antifoaming agent molecules, a liquid film with a low strength can be formed to damage the foam (Shang, 2010). However, when antifoaming agent works, it produces a pollutant, that is, dimethyl siloxane, reaction product with silica of a large ChF for human toxicity, causing the potentially toxic effects of antifoaming agent on the human body.
Hydro-distillation of spent lubricating oil and characterization of the product
Published in Petroleum Science and Technology, 2020
Siladeniol, dimethyl (C2H8O2Si) and Cyclotetrasiloxane octametyl which are silicon derivatives identified, could have resulted from dimethyl poly siloxanes (C2H6OSi)n which is an anti-foaming agent (Ikhajiagbe et al. 2013) prominent in lubricating oil formulations. The presence of hydroxyl group in some of the compounds identified might be due to the moisture added to the lubrication oil during usage or from the hydrolytic reaction resulting from water added during the recovery process in this study. The Methyl-2-phenyl-5-(1,4-dihydropyridin-4-ylidene)-1,3dioxan-4,6-dione with C16 is the highest number of carbon chain compound present in the portion, signifying occurrence of fragmentation because lubricating oil generally contains carbon range of C17 - C35 (Abro et al. 2013).
High yield production of lipid and carotenoids in a newly isolated Rhodotorula mucilaginosa by adapting process optimization approach
Published in Biofuels, 2023
Ravi Gedela, Ashish Prabhu, Venkata Dasu Veeranki, Pakshirajan Kannan
Batch fermentation was carried out in a 5 L stirred bioreactor (Sartorius, B-LITE) with 2 L working volume using MM and MSM medium as mentioned in Section 2.3. The reactor was inoculated with 10% (v/v) pre-inoculum. The pH was maintained at 6.0 using 5 M NaOH or 5 M H2SO4, other parameters such as temperature, agitation speed and aeration are maintained at 30 °C, 180 rpm, and 1.0 L/min, respectively. Silicone oil is used as an antifoaming agent for reducing foaming during the course of the reaction.