Assessment and modelling of chromium release in minerals processing waste deposits

The minerals processing industry is by far the largest generator of mineral solid wastes, which are commonly stored in large scale landfill deposits. The potential environmental impact of these is directly linked to the time-dependent process of leachate generation within these deposits. Rainwater draining through the porous matrix of a deposit creates a slowly moving aqueous environment within the deposit. Heavy metal species that may be contained in trace amounts in the waste material can be mobilised into the aqueous phase by various chemical reactions and be transported by mechanisms of diffusion and convection to the base of the deposit and from there further into the surrounding environment. Laboratory assessment methods aim to provide indicators to the leachate generation potential of a particular waste material, often based on "worst case" assumptions, but generally fail to offer a meaningful appreciation of the time-dependent leach behaviour of the material in a full scale deposit. This is to a large part due to the lack of a thorough description - in terms of a rigorous mathematical model - of the leachate generation process itself. Such a model is developed in the present work, building on an existing model for heap leaching, which, conceptually, is very similar to the leachate generation process. The model is based on the continuity equation formulated for reaction-diffusion processes at the level of an individual porous particle and for convection-dispersion transport at the bulk level. This is combined with a number of reaction models, both kinetic rate expressions and thermodynamic equilibrium models, to describe the release process of individual species at the solid liquid interface and also within the aqueous phase. The model has been translated in the WASTESIM computer code within which waste iv Abstract material and disposal scenario are characterised by a number of parameters, such as those describing reaction modes and constants, particle size and pore diffusion effects as well as bed transport and saturation. The program was found to be a versatile tool for modelling a wide range of multi-species, multi-reaction deposit and batch leach scenarios. However, for modelling real waste materials the model parameters have to be established from a systematic laboratory investigation. An assessment methodology is proposed which aims to combine lysimeter studies with bench scale leach and physico- chemical characterisation experiments to enable determination of all model parameters entirely on the basis of laboratory experiments and validate them at this level against the results from independent lysimeter studies with the modelling tool. It is argued that, if all model parameters are validated at the laboratory scale in this way, modelling of full scale scenarios involving the same waste material can be conducted with some confidence. This approach has been put to the test with two waste materials from the ferro-alloy industry - a furnace emission control dust and a smelter slag. The contaminant species of particular interest for both these materials was chromium, especially Cr(VI), and therefore it was the release behaviour chromium on what much of the work presented herein has focused. The aqueous and environmental chemistry of chromium is extensively reviewed and, as a side aspect, the long-term atmospheric oxidation of Cr(III) to Cr(VI) has been positively identified by experimental work with a third chromium-containing waste material. The two test materials have been subjected to intensive characterisation in terms of column and batch leach experiments, adsorption studies, column tracer studies and physical characterisation experiments. The results are carefully interpreted with a view to establishing a complete set of parameters to simulate the leachate generation behaviour with respect to chromium species in a deposit scenario. It is demonstrated Abstract V that the modelling tool can in fact also be used for the interpretation of batch leach data through curve fitting exercises. For both materials the WASTESIM code, calibrated with parameters established entirely through the laboratory experimentation, has been used to simulate the leach curves of two independent lysimeter experiments, which are then compared to the measured data. In both cases the modelled and measured curves compared reasonably well and in most regards discrepancies can be explained by insufficient characterisation in the bench-scale experiments. The overall approach is therefore seen as valid in principle, but it is acknowledged that further experimental work and model development would be needed to take account of the remaining discrepancies. Two aspects were found to be particularly significant. The first relates to slow reaction mechanisms, which may go unnoticed in short-term laboratory experiments, but may become significant in full scale deposits given their long life-span. The slow atmospheric oxidation of chromium is a point in case. The second aspect relates to the hydro-dynamic characterisation of flow through unsaturated beds. Both model and laboratory assessment methods are insufficiently developed to account for effects such as dead pore diffusion and a distribution of flows. Recommendations for further development work should focus on these two aspects and on expansion of the approach to heavy metal species other than chromium. It is hoped that the modelling and assessment methodology will ultimately find welcome application in the environmental risk assessment of mineral processing waste disposal operations

Textile materials

In this specialised publication, the reader will find research results and real engineering developments in the field of modern technical textiles. Modern technical textile materials, ranging from ordinary reinforcing fabrics in the construction and production of modern composite materials to specialised textile materials in the composition of electronics, sensors and other intelligent devices, play an important role in many areas of human technical activity. The use of specialized textiles, for example, in medicine makes it possible to achieve important results in diagnostics, prosthetics, surgical practice and the practice of using specialized fabrics at the health recovery stage. The use of reinforcing fabrics in construction can significantly improve the mechanical properties of concrete and various plaster mixtures, which increases the reliability and durability of various structures and buildings in general. In mechanical engineering, the use of composite materials reinforced with special textiles can simultaneously reduce weight and improve the mechanical properties of machine parts. Fabric- reinforced composites occupy a significant place in the automotive industry, aerospace engineering, and shipbuilding. Here, the mechanical reliability and thermal resistance of the body material of the product, along with its low weight, are very relevant. The presented edition will be useful and interesting for engineers and researchers whose activities are related to the design, production and application of various technical textile materials

Characterization and Modelling of Composites, Volume II

Composites have been increasingly used in various structural components in the aerospace, marine, automotive, and wind energy sectors. Composites’ material characterization is a vital part of the product development and production process. Physical, mechanical, and chemical characterization helps developers to further their understanding of products and materials, thus ensuring quality control. Achieving an in-depth understanding and consequent improvement of the general performance of these materials, however, still requires complex material modeling and simulation tools, which are often multiscale and encompass multiphysics. This Special Issue is aimed at soliciting promising, recent developments in composite modeling, simulation, and characterization, in both design and manufacturing areas, including experimental as well as industrial-scale case studies. All submitted manuscripts will undergo a rigorous review and will only be considered for publication if they meet journal standards

Design and fabrication of optical fibre long period gratings for CO₂ sensing

This thesis investigated the repeatability of the overwrite long period grating (LPG) fabrication method and highlighted the advantage it offers in its ability to tune spectral features thus allowing the manufacture of bespoke sensors. Moreover, LPGs with periods ranging from 100 - 200 μm were written and a novel technique for mapping the transmission data was presented. This method gave a unique overview into the period mediated evolution of attenuation features, which, when designing LPGs that operate at the sensitive phase matching turning point, is invaluable. Further exploration into the overwrite method revealed that the UV irradiation duty cycle used in the fabrication of LPGs was found to influence the presence of harmonics, where a duty cycle of 25% maximised coupling to 2nd order transmission features. LPGs which possessed these additional spectral features within a small wavelength range (600 - 1000 nm) were assessed for their suitability in performing multi-parameter sensing. Ionic liquids were explored as an LPG COThis thesis investigated the repeatability of the overwrite long period grating (LPG) fabrication method and highlighted the advantage it offers in its ability to tune spectral features thus allowing the manufacture of bespoke sensors. Moreover, LPGs with periods ranging from 100 - 200 μm were written and a novel technique for mapping the transmission data was presented. This method gave a unique overview into the period mediated evolution of attenuation features, which, when designing LPGs that operate at the sensitive phase matching turning point, is invaluable. Further exploration into the overwrite method revealed that the UV irradiation duty cycle used in the fabrication of LPGs was found to influence the presence of harmonics, where a duty cycle of 25% maximised coupling to 2nd order transmission features. LPGs which possessed these additional spectral features within a small wavelength range (600 - 1000 nm) were assessed for their suitability in performing multi-parameter sensing. Ionic liquids were explored as an LPG COThis thesis investigated the repeatability of the overwrite long period grating (LPG) fabrication method and highlighted the advantage it offers in its ability to tune spectral features thus allowing the manufacture of bespoke sensors. Moreover, LPGs with periods ranging from 100 - 200 μm were written and a novel technique for mapping the transmission data was presented. This method gave a unique overview into the period mediated evolution of attenuation features, which, when designing LPGs that operate at the sensitive phase matching turning point, is invaluable. Further exploration into the overwrite method revealed that the UV irradiation duty cycle used in the fabrication of LPGs was found to influence the presence of harmonics, where a duty cycle of 25% maximised coupling to 2nd order transmission features. LPGs which possessed these additional spectral features within a small wavelength range (600 - 1000 nm) were assessed for their suitability in performing multi-parameter sensing. Ionic liquids were explored as an LPG CO₂ sensitive coating. It was shown that these materials demonstrate a refractive index change upon exposure to CO₂ which was maintained following mechanical stabilisation using a gelling agent. A coating system for applying the gelled ionic liquid to the surface of an optical fibre was developed and techniques to improve the coating deposition were explored. The sensor demonstrated an 8 nm wavelength shift in response to 20% CO₂, which was reversible by reducing the partial pressure of CO₂ for 25 min.sensitive coating. It was shown that these materials demonstrate a refractive index change upon exposure to CO₂ which was maintained following mechanical stabilisation using a gelling agent. A coating system for applying the gelled ionic liquid to the surface of an optical fibre was developed and techniques to improve the coating deposition were explored. The sensor demonstrated an 8 nm wavelength shift in response to 20% CO₂, which was reversible by reducing the partial pressure of CO₂ for 25 min. sensitive coating. It was shown that these materials demonstrate a refractive index change upon exposure to CO₂ which was maintained following mechanical stabilisation using a gelling agent. A coating system for applying the gelled ionic liquid to the surface of an optical fibre was developed and techniques to improve the coating deposition were explored. The sensor demonstrated an 8 nm wavelength shift in response to 20% CO₂, which was reversible by reducing the partial pressure of CO₂ for 25 min

From electrode manufacturing to Li-ion battery testing, modeling & simulation, toward new generation electric vehicle

..

Strategies for rapid seismic hazard mitigation in sustainable infrastructure systems

The goal of this study is to design and evaluate economic and rapid seismic retrofit strategies for relatively small rehabilitation projects for steel structures consistent with the tenets of sustainable design. The need to retrofit existing structures in earthquake prone regions may arise directly from the problem of aging and deteriorating conditions, recognition of the vulnerability of existing infrastructure, from updates in seismic code requirements, or changes in building performance objectives. Traditional approaches to seismic hazard mitigation have focused reducing the failure probabilities, consequences from failures, and time to recovery. Such paradigms had been established with little regard to the impact of their rehabilitation measures on the environment and disruptions to occupants. The rapid rehabilitation strategies proposed here have sustainability benefits in terms of providing a more resilient building stock for our communities as well as minimizing environmental and economical impacts and social consequences during the rehabilitation project. To achieve these goals, a unique approach to design supplemental systems using tension-only elements is proposed. In this design approach undesirable global and local buckling are eliminated. Two rapid rehabilitation strategies are presented. The first is a bracing system consisting of cables and a central energy dissipating device (CORE Damper). The second is a shear wall system with the combined use of thin steel plate and tension-only bracing. Analytical studies using both advanced and simplified models and proof-of-concept testing were carried out for the two devices. The results demonstrated stable, highly efficient performance of the devices under seismic load. Preliminary applications of the CORE damper to the retrofitting of a braced steel frame showed the ability of the system to minimize soft story failures. Both techniques can be implemented within a sustainability framework, as these interventions reduce the seismic vulnerability of infrastructure, are low cost, utilize materials and fabrication processes widely available throughout the world, can be handled by unskilled labor and carried out with minimal disruptions to the environment. The approach taken in this study can provide a road map for future development of sustainability-based rehabilitation strategies.Ph.D.Committee Co-Chair: DesRoches, Reginald; Committee Co-Chair: Leon, Roberto T.; Committee Member: Craig, James I.; Committee Member: Goodno, Barry; Committee Member: White, Donald W

Seasonal power peaking and the diffusion of demand-side technologies : modelling socio-economic & technical dynamics in the Greek Islands

Imperial Users onl

1991 OURE report, including the 1st Annual UMR Undergraduate Research Symposium -- Entire Proceedings

The Opportunities for Undergraduate Research Experiences program began in 1990. The aims were to enrich the learning process and make it more active, encourage interaction between students and faculty members, raise the level of research on the campus, help recruit superior students to the graduate program, and support the notion that teaching and research are compatible and mutually reinforcing. Chancellor Jischke made available an annual budget of $50,000 to support the program. As the papers herein attest, the OURE program is achieving its goals — UMR graduates have performed research on an enormous variety of topics, have worked closely with faculty members, and have experienced deeply both the pleasures and frustrations of research. Several of the undergraduates whose papers are included are now graduate students at UMR or elsewhere. Others, who have not yet graduated, are eager to submit proposals to the next OURE round. I am sure all involved join me in expressing gratitude to Chancellor Jischke for inaugurating the program. The first section of this volume is made up of papers presented at the first annual UMR Undergraduate Research Symposium, held in April 1991. Joining the UMR undergraduates in the Symposium were students from other colleges and universities who had participated in an NSF- sponsored summer program of research on parallel processing conducted by the UMR Computer Science Department

Project based-learning based on I-STEM (Islamic, Science, Technology, and Mathematics) to facilitate the development of geometric critical thinking skills of first middle students

In line with the 21st century, mathematics learning innovations continue to be developed to facilitate students' critical thinking skills by adjusting the context of their religious life. The purpose of this study is to provide ideas that teachers can do to implement Project Based Learning (PjBL) with a STEM (I-STEM) approach that is used to facilitate the development of students' critical thinking skills. The pattern of integration that is designed lies in the flat plane geometry material with the integration of the verses of the Koran and the internalization of Islamic values, with the hope of being able to create meaningful learning activities for students. This research is a qualitative research with library research. Data collection techniques are carried out through reviewing the literature, both from articles, books, and other documents that can be used to describe theories and information needed in research. The data analysis technique used is content analysis (content analysis). The results of this study are the I-STEM-based PjBL syntax includes 1) basic questions (integration with the verses of the Koran presented in the LKPD); 2) designing project plans (miniature Kaaba); 3) draw up a project completion schedule; 4) monitor project progress; 5) test project results (and compare with other problems); and 6) evaluate the learning experience. I-STEM-based PjBL was developed to facilitate the development of students' critical thinking skills through syntax and LKPD which were developed adapted to the context of Islamic life and the Koran at the junior high school level

Project based-learning based on I-STEM (Islamic, Science, Technology, and Mathematics) to facilitate the development of geometric critical thinking skills of first middle students

In line with the 21st century, mathematics learning innovations continue to be developed to facilitate students' critical thinking skills by adjusting the context of their religious life. The purpose of this study is to provide ideas that teachers can do to implement Project Based Learning (PjBL) with a STEM (I-STEM) approach that is used to facilitate the development of students' critical thinking skills. The pattern of integration that is designed lies in the flat plane geometry material with the integration of the verses of the Koran and the internalization of Islamic values, with the hope of being able to create meaningful learning activities for students. This research is a qualitative research with library research. Data collection techniques are carried out through reviewing the literature, both from articles, books, and other documents that can be used to describe theories and information needed in research. The data analysis technique used is content analysis (content analysis). The results of this study are the I-STEM-based PjBL syntax includes 1) basic questions (integration with the verses of the Koran presented in the LKPD); 2) designing project plans (miniature Kaaba); 3) draw up a project completion schedule; 4) monitor project progress; 5) test project results (and compare with other problems); and 6) evaluate the learning experience. I-STEM-based PjBL was developed to facilitate the development of students' critical thinking skills through syntax and LKPD which were developed adapted to the context of Islamic life and the Koran at the junior high school level