391 research outputs found
Chapter 7 Extraterrestrial Environment
Get PDFAbstract This chapter deals with some aspects of the extraterrestrial environment, which is relevant—directly or indirectly—to human development. Space waste is an emerging problem that poses serious threats to human activities in space and is approached at several different angles. The next subject is relevant to the greenhouse effect, and starting from the analysis of planetary evolution and climate principles takes the reader to a journey around the solar system discussing the amazing marvels and mysteries of greenhouse effects on other terrestrial moons and planets: Mars, Venus, Pluto, Titan, and Triton. Finally, the implications and potential uses of humble but magic extraterrestrial hydrated minerals are addressed. This chapter is not an ordinary one but demonstrates lessons that can be learned by studying our neighborhood that one day we may call home
Martian aqua : occurrence of water and appraisal of acquisition technologies
No full textThe production of water through in-situ resource utilization (ISRU) will be necessary for a sustainable human presence on Mars. Accessible water on Mars occurs as ice (pure and mixed with regolith), bounded water in the regolith (adsorbed and in hydrated minerals) and vapor in the atmosphere. Harvesting water from the atmosphere appears to be relatively challenging than obtaining it from the regolith. However, the potential landing sites for human exploration are unlikely to have easy access to near-surface ice of any form, while utilization of the atmosphere can be accomplished almost anywhere. Extensive research has been conducted on atmospheric water vapor, which is ubiquitous and renewable, yet provides only a thin water source across the planet. This paper provides an overview of water availability on Mars, investigates the volatiles (CO2, H2O) phase equilibria in the atmosphere-surface system of the planet, and compares water harvesting from the atmosphere to obtaining water from the regolith. The findings indicate that while atmospheric water harvesting does not appear to be feasible to serve as the primary water source, it might have potential to become a supplementary, decentralized clean water supply. Atmospheric water harvesting systems on Mars require more power and energy, but they offer greater simplicity and flexibility compared to water extraction from the regolith. This approach could prove valuable in regions where water extraction from the regolith is infeasible or as a temporary backup in the event of a primary water system failure. Such a distributed water harvesting method might enhance the resilience and flexibility of water supply systems for future human Mars missions and settlements. Ultimately, any technology developed for extraterrestrial environments can have important applications on Earth
Adsorption Ion Exchange And Catalysis Design Of Operations And Environmental Applications
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Modeling of ion exchange of Pb2+ in fixed beds of clinoptilolite
No full textIon exchange of Pb2+ on natural clinoptilolite in fixed bed and batch operations has been studied and simple models on experimental data have been applied. The operations are conducted at ambient temperature, an initial concentration of 0.01 N and at pH 4. Paterson's model is used to describe batch kinetics, the Langmuir isotherm is used to correlate equilibrium data and a solid diffusion controlled process is used to describe the fixed bed operation. The evaluated operating capacity is in the range of 0.21-1 meq/g and the diffusion coefficient is in the range of (0.07-5.4) × 10 -12 m2/s. The experimental results obtained put the basic theory under question. According to these experiments, the capacity and diffusion coefficient in fixed bed systems are flow dependent and different from those measured in the batch-reactor systems. This could be explained if the type of experimental setup influenced both the equilibrium isotherm and the system behavior. © 2003 Published by Elsevier Inc
Experimental study of zeolitic diffusion by use of a concentration-dependent surface diffusion model
Full text linkSurface diffusivity in adsorption and ion exchange processes is probably the most important property studied expensively in the literature but some aspects, especially its dependence on solid phase concentration, is still an open subject to discussion. In this study a new concentration-dependent surface diffusion model, equipped with a flexible double selectivity equilibrium relationship is applied on the removal of Pb2+, Cr3+, Fe3+ and Cu2+ from aqueous solutions using a natural zeolite. The model incorporates the Chen-Yang surface diffusivity correlation able to deal with positive and negative dependence with surface coverage. The double selectivity equilibrium relationship successfully represents the experimental equilibrium data, which follow Langmurian isotherm type for Pb2+, sigmoidal for Cr3+ and Fe3+ and linear for Cu2+. The concentration-dependent surface diffusion model was compared with the constant diffusivity surface diffusion model and found to be moderately more accurate but considerably more useful as it provides more insights into the diffusion mechanism. The application of the model resulted in an average deviation of 8.56 ± 6.74% from the experimental data and an average solid phase diffusion coefficients between 10−9 and 10−10 cm2/s. The results showed that the diffusion of metal ions in the zeolite structure is unhindered following the surface diffusion mass transfer mechanism
Automotive shredder residue (ASR) : a rapidly increasing waste stream waiting for a sustainable response
Full text linkRecycling scrapped cars plays an important role in reducing pollution by decreasing the amount of waste that ends up in landfills. Directive 2000/53/EC regulates the management of ELVs. ELVs are collected and dismantled to remove the battery, tyres, fluids and any parts that can be re-used and the wreck is shredded. The metallic parts are separated by physical processes and recovered as ferrous scrap and nonferrous metals, all of which is recycled. The 25% remainder is the automotive shredder residue (ASR), which is composed mainly of plastics, contaminated with any metallic and other parts that could not be separated. This is often disposed of in landfills as solid urban waste and is not recycled. ASR generation in EU is approximately 2-2.5 million tonnes /year, constituting 10% of total hazardous waste in the EU. The study suggests that recovery rates for ELVs set in the EU Directive on end-of life vehicles will not be met until the volume of the ASR is further reduced. Treatment of the ASR focuses on recovering any useable materials, reducing the volume of the ASR to cut down on the quantity that will end up in landfill, and recovering the energy from the petrochemical content of the plastics. Up-to-date there are 8 post-shredder technologies (PST) used or potentially used for the treatment of auto shredder residues (ASR). The aim of this study is to give an overview of what problem the ASR presents to modern society and what the options are for processing this waste into recovered products or materials, or energy, with a minimum of useless by-products for which landfilling is the only route
Investigating the inhibitory effect of cyanide, phenol and 4-nitrophenol on the activated sludge process employed for the treatment of petroleum wastewater
Get PDFAbstract In this work, the inhibitory effect of cyanide, phenol and 4-nitrophenol on the activated sludge process was investigated. The inhibition of the aerobic oxidation of organic matter, nitrification and denitrification were examined in batch reactors by measuring the specific oxygen uptake rate (sOUR), the specific ammonium uptake rate (sAUR) and the specific nitrogen uptake rate (sNUR) respectively. The tested cyanide, phenol and 4-nitrophenol concentrations were 0.2–1.7 mg/L, 4.8–73.1 mg/L and 8.2–73.0 mg/L respectively. Cyanide was highly toxic as it significantly (>50%) inhibited the activity of autotrophic biomass, heterotrophic biomass under aerobic conditions and denitrifiers even at relatively low concentrations (1.0–1.7 mgCN−/L). The determination of the half maximum inhibitory concentration (IC50) confirmed this, since for cyanide IC50 values were very low for the examined bioprocesses (25 mg/L) for the tested bioprocesses since appreciable concentrations were required to accomplish significant inhibition. The autotrophic bacteria were more sensitive to phenol than the aerobic heterotrophs. The denitrifiers were found to be very resistant to phenol
Variable diffusivity homogeneous surface diffusion model and analysis of merits and fallacies of simplified adsorption kinetics equations
Full text linkAdsorption and ion exchange phenomena are encountered in several separation processes, which in turn, are of vital importance across various industries. Although the literature on adsorption kinetics modeling is rich, the majority of the models employed are empirical, based on chemical reaction kinetics or oversimplified versions of diffusion models. In this paper, the fifteen most popular simplified adsorption kinetics equations are presented and discussed. A new versatile variable-diffusivity two-phase homogeneous diffusion model is presented and used to evaluate the analytical adsorption models. Aspects of ion exchange kinetics are also addressed
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