Browse Topic: Inorganic chemicals

Items (15)
Objective Method to Quantify Ecological Toxicity between Friction Materials2017-01-24959/17/2017
California and Washington recently passed legislation to limit certain constituents in brake pad friction materials. As part of the California (CA) legislation enacted in 2010, brake pad manufacturers need to perform an alternative assessment to identify potentially safer environmental and toxicological choices for future friction material production. Copper, chromium VI-salts, lead, cadmium, mercury, and other compounds have been identified as potentially unsafe to the environment. This paper contains the methodology behind an objective and comprehensive alternative assessment to quantify the ecological impact of friction materials. Utilizing raw material specific Chemical Abstracts Service (CAS) numbers and their associated toxicological reference values (TRVs), this newly defined method estimates the total toxicological impact of finished friction materials on both the environment and on a human carcinogenic level to allow the manufacturer to screen greener alternatives. Utilizing chemical specific TRVs such as the lethal concentration 50% (LC50), median effective concentration 50% (EC50), and the median effective reproductive concentration 50% (ErC50), this method quantifies ecological impact characteristics of brake pad friction material. In the same regard, the carcinogenic properties of each chemical are evaluated, placed into groupings based on their carcinogenic potential as evaluated by the International Agency for Research on Cancer (IARC) and are utilized to generate comparative carcinogenic ratings. The methodology is best utilized as a relative comparison between multiple uncompressed friction formulations in order to create greener friction material for the future.
Visser, Andrew M.Severnak, Scott
Optimization of a Magnetically Agitated Photocatalytic Reactor for Water Recovery2005-01-29957/11/2005
NASA will require a safe and efficient method for water recovery on long-term space missions. Photocatalysis represents a promising solution for part of a system designed for recovery of water from humidity condensate, urine, and shower waste. It eliminates the need for chemical oxidants that are dangerous and difficult to transport, and the considerable energy consumption of distillation. In terms of decreasing the equivalent system mass (ESM) with respect to these alternative technologies, considerations for the volume, mass, cooling and crew time are also important. This photocatalytic reactor generates the oxidant in the form of hydroxyl radicals and valence band holes by exposing silica-titania composite particles with a barium ferrite core to ultraviolet light. The magnetic core of the catalyst allows for separation, confinement, and agitation. This agitation, accomplished with a sinusoidal signal fed solenoid, allows greater mass transfer and improves mineralization of organics. In addition, fixed magnets strategically placed above the reactor confines the catalyst to where it receives maximum UV exposure. The composite catalyst, irradiated by an 8-watt 254 nm lamp, was able to decrease the 10 mg/L initial phenol concentration by an average of 92.2% after one hour. Although the frequency of the signal fed to the solenoid did not appear to have an impact on the extent of photodegradation (10-80 Hz), there was a strong correlation with the ball milling process. Building upon pioneering work of Mazyck and Drwiega (04-ICES 2404), this promising option for water recovery has been optimized with improvements in magnetic field, reactor design, and catalyst synthesis.
Kostedt, William L.Mazyck, David W.Wu, Chang-YuChadik, Paul
Modeling Ammonia Removal in Biofilters: Physical and Chemical Calibration9815917/13/1998
The use of air treatment biofilters for the control of trace air contaminants in advanced life support (ALS) systems is currently being investigated by the Waste Processing and Resource Recovery team of the New Jersey - NSCORT (NASA Specialized Center of Research and Training). Ammonia (NH3) was selected as a model compound because it presents special challenges to the sustained operation of a biofilter; additionally, ammonia' is a contaminant of concern to ALS. The special challenges that NH3 removal presents to biofilter operation are due to (dynamic changes in the biodegradation environment which result from the accumulation of ammonia and its metabolic (biotransformation) products. This accumulation degrades the quality of the environment eventually limiting and eliminating the desired biological activity. This paper contains inform&ion on the development of a mathematical model for a nitrifying biofilter. The model presented takes into account the physical (advective and diffusive transport), chemical (acid-base chemistry and vapor-liquid equilibrium), and biochemical (biodegradation stoichiometry and kinetics) nature of the system. This model is being developed to provide a better understanding of the system dynamics than can be achieved through experimentation alone and to take the first step toward the development of a biofilter simulation model which may be used in system studies and for biofilter design and control. The work completed to date includes calibration and development of the physical and chemical aspects of the model. The calibration results indicate that the experimental biofilter acts as a plug flow reactor with a small amount of mechanical dispersion (D = 0.325cm2/s) and that the rate limiting step for mass transfer of ammonia into the biofilter media appears to be diffusion through the aqueous phase.
Russell, James F.Cowan, Robert M.Joshi, Jitendra A.
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