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Electrochemical remediation for contaminated soils, sediments and groundwater
Published in Katalin Gruiz, Tamás Meggyes, Éva Fenyvesi, Engineering Tools for Environmental Risk Management – 4, 2019
Permeable reactive barriers (PRBs) have been extensively used for the remediation of inorganic and organic pollutants in groundwater. PRBs are built by digging a trench in the path of flowing groundwater and then filling it with a selected permeable reactive material. As the contaminated groundwater passes through the PRB, organic contaminants may be degraded or sequestered, inorganic contaminants are sequestered, and clean groundwater exits the PRB. Reactive materials commonly considered include iron filings, limestone, hydroxyapatite, activated carbon, and zeolite. Monitoring data from several field PRB projects showed that high-concentration dissolved inorganic species flowing through the PRB tend to precipitate and clog the reactive material. In addition, the reactivity of the material used in the PRB may decrease. Coupling electrokinetics with PRBs has been found to eliminate clogging of the PRB system caused by mineral precipitation and improve the long-term performance of PRBs. More research is needed towards developing combined electrokinetic-PRB systems to induce favorable geochemical conditions within the PRB as needed during the course of the remediation process (Weng, 2009).
Occupational Health and Safety
Published in Terry Jacobs, Andrew A. Signore, Good Design Practices for GMP Pharmaceutical Facilities, 2016
Reactive materials are those that tend to react spontaneously, react vigorously with air or water, be unstable to shock or heat, generate toxic gases, or explode. There are a variety of different types of reactive materials that can be used in a pharmaceutical manufacturing facility and its associated laboratory spaces, including oxidizers, peroxides and peroxide formers, water-reactive materials, and flammable metals. Although many of the hazards associated with the handling and use of reactive materials can be reduced through prudent work practices by the end users, some important design considerations can be incorporated into the facility design.
Combustion of a rapidly initiated fully dense nanocomposite Al–CuO thermite powder
Published in Combustion Theory and Modelling, 2019
I. Monk, M. Schoenitz, E. L. Dreizin
Thermites comprising mixed powders of a metal fuel, such as aluminium and a metal oxide oxidiser, e.g. oxide of iron, copper, molybdenum, etc., have high reaction enthalpies, but the heat release occurs relatively slowly, limiting their applications to welding [1–3] and a rather narrow area of custom heat sources [4]. Efforts have been made to increase their reaction rates by increasing their reactive interface area, mostly by using nano-sized mixed metal fuel and oxidiser particles and by preparing fully-dense nanocomposite structures [5–8]. The rates of combustion for such nanocomposite thermites increased substantially extending their potential applications to explosives [9], pyrotechnics [10], and propellants [11]. The reaction is accelerated mostly due to reduced ignition delays and/or lower temperatures at which the thermal runaway leading to high-temperature combustion occurs. It was reported, however, that the nano-particle based materials rapidly sinter upon heating, losing their original nanostructure [12,13]. The sintering creates larger particles forming upon ignition of a nanothermite, in which fuel and oxidiser are no longer mixed on the nanoscale, resulting in respectively long particle burn times [14]. Similarly, particle burn times measured for fully-dense, micron-sized nanocomposite aluminium-based reactive material powders ignited by a CO2 laser beam were found to be longer than for the pure aluminium particles with the same dimensions [15]. The latter result was also explained by the loss of particle nanostructure immediately after ignition, when the metal fuel melts.
Enhanced reactivity by energy trapping in shocked materials: reactive metamaterials for controllable output
Published in Combustion Theory and Modelling, 2022
Donald Scott Stewart, Kibaek Lee, Alberto M. Hernández
For the materials, we use a predictive (previously proven) reactive flow model for the explosive, and well-tested material models for the inert. The multi-material code ALE3D [3] (similar to [2]), was used to generate the simulations discussed in the remainder of the paper. In Section 2, we discuss the general concept of a reactive metamaterials that can be engineered for controllable output of the explosive system. We note that a large contrast in the shock impedance of the explosive matrix and the inert material generates shock reflections that retain kinetic energy in a region, that later can be used to increase the pressure and temperature and hence reactivity of the reactive material. In Section 3, we describe the geometrical configurations and corresponding models for the matrix explosive and material models subcomponents that represent a realisable design. In Section 4 we describe the results for two limiting cases: The shocking of high impedance particles and void collapse embedded in and the explosive matrix materials and how the energy of reflection and collapse is redistributed back to the explosive matrix. This section highlights two basic responses of shock reflection and shocked void collapse, to set the stage for understanding the results from our base line simulations that follow. In Section 5 we describe the baseline simulations for larger arrays of embedded particles/void in the matrix explosive. Five cases of shock initiation of the system of explosives, particles and voids are simulated. It is demonstrated that particles can trap energy in layers. The mechanisms of reactive flow within the particle test bed is examined in detail, in the limit of strong shocks. Section 6 has a discussion and concluding remarks.