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Rare earth elements (REEs) are valuable raw materials which are in great demand in modern high technology industries. Developing methods to produce/recover REEs from waste is significant to the national security of any developed country. This study was focused on investigating the use of supercritical CO2 (sCO2) to extract REEs from anthracite acid mine drainage (AMD). Four different mine drainage water source locations at Blaschak Coal Corp. in Pennsylvania, USA were selected for sample collection. An extraction process was developed and demonstrated for two of those water sources containing the highest concentration of REEs. A method involving metal ion coagulation, their dissolution from the sludge into a concentrated aqueous HNO3 solution, complexation with organic ligands and sCO2 extraction was developed to recover REEs from AMD. Specifically, sodium aluminate (NaAlO2) was used as the coagulant to concentrate REEs from the AMD into a solid precipitate. Consequently, over 99% of the REEs in AMD is concentrated in the remaining sludge. During the coagulation process, the effects of pH and NaAlO2 concentration on REE precipitation were investigated. Fuming nitric acid (HNO3) was used to digest the pre-concentrated sludge and tributyl phosphate (TBP) was used to form REE/TBP/HNO3, a non-polar complex with selected REEs, specifically, cerium (Ce), lanthanum (La) and neodymium (Nd). HNO3 concentration and organic/aqueous phase ratio were considered as the variables to improve complexation efficiency. Dynamic extraction experiments using sCO2 and REE/TBP/HNO3 solutions were then conducted at optimal conditions of 60 °C and 20 MPa. The overall REE extraction efficiencies are found to increase with the atomic number of the REE. As a result, the average overall REE extraction efficiencies of 41.8%, 40.1% and 58.2% for Ce, La and Nd, respectively, are obtained. The potential improvements in the overall extraction efficiency are also discussed.

The challenging problem of conducting fully Bayesian inference for the reaction rate constants governing stochastic kinetic models (SKMs) is considered. Given the challenges underlying this problem, the Markov jump process representation is routinely replaced by an approximation based on a suitable time discretisation of the system of interest. Improving the accuracy of these schemes amounts to using an ever finer discretisation level, which in the context of the inference problem, requires integrating over the uncertainty in the process at a predetermined number of intermediate times between observations. Pseudo-marginal Metropolis-Hastings schemes are increasingly used, since for a given discretisation level, the observed data likelihood can be unbiasedly estimated using a particle filter. When observations are particularly informative an auxiliary particle filter can be implemented, by employing an appropriate construct to push the state particles towards the observations in a sensible way. Recent work in state-space settings has shown how the pseudo-marginal approach can be made much more efficient by correlating the underlying pseudo-random numbers used to form the likelihood estimate at the current and proposed values of the unknown parameters. We extend this approach to the time-discretised SKM framework by correlating the innovations that drive the auxiliary particle filter. We find that the resulting approach offers substantial gains in efficiency over a standard implementation., Comment: 22 pages

Mercury (Hg) is one of the major airborne emissions from coal combustion sources. Mercury emissions can be a serious pollution issue that is harmful to human health. Activated carbon (AC) is one of the most promising sorbents for Hg adsorption to date. Due to its high cost of chemical preparation, an affordable alternative activated carbon with a high Hg-capturing capacity would be beneficial to environmental security. This study focused on investigating the use of anthracite coal-based activated carbon (ACAC) prepared by a chemical activation method to remove elemental Hg from simulated flue gas. An activation process was developed by evaluating different carbonization temperatures, reagent/coal mass ratios and treating environments. The sample with the highest surface area was selected for synthesizing a bromide-impregnated ACAC. The ACAC sample prepared with KOH at a carbonization temperature of 800 °C, KOH/anthracite mass ratio of 1:1, and activated in an N2 environment yielded a surface area of 527.43 m2/g. Mercury adsorption experiments using synthesized ACAC in simulated flue gas were conducted at two different temperatures, 20° and 100 °C, with exposure times of 2.5 and 1 h, respectively. The kinetic adsorption capacity was found to increase with decreasing temperature. Specifically, at the Hg-laden gas temperature of 20 °C, with 2.5 h exposure time, the adsorbent can achieve the maximum adsorption capacity of 476.51 μ g/g. The bromide-impregnated ACAC was also investigated under two different temperatures of 20 °C and 100 °C and exposure of 5 h. The adsorption capacity of the bromide-impregnated ACAC was found to be higher at elevated temperatures.

It has long been acknowledged that understandings of risk are influenced by external or ‘objective’ assessments, and by internal or ‘subjective’ value judgements. In-depth research has been undertaken on how lay people perceive climate change and related risks, whereas work on expert opinions is more limited. This paper reports on 22 ‘expert’ interpretations elicited through a mental models approach, and encapsulated in a ‘meta’-influence diagram, denoting three conceptualisations of danger in relation to climate change: (i) human influence upon the climate system; (ii) impacts upon natural and human communities; and (iii) threat to the status quo, especially in the form of mitigation measures and related costs. These conceptualisations raise questions about how experts bring to bear their knowledge, values and understanding of climatic and social systems in articulating such discourses. This paper also discusses the implications of such diverse perspectives on managing climate change.

The optimal postremission treatment for elderly patients with acute myelogenous leukemia (AML) is presently unknown, but recent studies report the feasibility of autologous stem cell transplantation in this population. To better understand the long-term outcome of autologous transplantation in AML patients ≥60 years of age, we evaluated high-dose chemoradiotherapy preparative conditioning followed by transplantation of peripheral blood progenitor cells procured after a single cycle of cytarabine-based consolidation chemotherapy as postremission therapy in 27 patients aged 60 to 71 years (median age, 65 years) with newly diagnosed AML in first complete remission (CR). The median follow-up from CR for all patients was 13.6 months (range, 6.0-123.1 months). The median follow-up from remission for surviving patients was 81 months (range, 41.4-123.1 months). Seven patients are alive in continuous CR, 19 died from relapse, and 1 died as a result of treatment-related infection. Leukemia-free survival and overall survival are 10.3 and 13.4 months, respectively. Actuarial leukemia-free and overall survival at 3 years are 25% ± 9% and 28% ± 9%, respectively. Our results demonstrate that autologous transplantation of peripheral blood progenitor cells is well tolerated and feasible for patients ≥60 years of age with AML in first CR. Future investigation should focus on a randomized study evaluating a larger group of elderly patients in first CR comparing autologous stem cell transplantation with conventional cytarabine-based consolidation chemotherapy to identify the optimal postremission therapy.