Thermodynamic and Kinetic study of the removal of Cu2+ and Pb2+ ions from aqueous solution using Fe7S8 nanomaterial

In the present study, pyrrhotite (Fe7S8) was investigated for the removal of Pb2+ and Cu2+ ions from aqueous solution. The Fe7S8 material was prepared through a solvothermal method and was characterized using XRD. The average particle size for the nanomaterial was determined to be 29.86 ± 0.87 nm using XRD analysis and Scherrer\u27s equation. Batch studies were performed to investigate the effects of pH, time, temperature, interfering ions, and the binding capacity of Pb2+ and Cu2+ ions to the Fe7S8 nanomaterial. During the pH profile studies, the optimum pH for the binding of Pb2+ and Cu2+ was determined to be pH 5 for both cations. Isotherm studies were conducted from which the thermodynamics and binding capacities for both Cu2+ and Pb2+ were determined. The binding capacity for Pb2+ and Cu2+ binding to the Fe7S8 were determined to be 0.039 and 0.102 mmol/g, respectively at 25°C. The thermodynamic parameters indicated a ΔG for the sorption of Pb2+ ranged from 5.07 kJ/mol to -2.45 kJ/mol indicating a non-spontaneous process was occurring. Whereas, the ΔG for Cu2+ ion binding ranged from 9.78 kJ/mol to -11.23 kJ/mol indicating a spontaneous process at higher temperatures. The enthalpy indicated an endothermic reaction was occurring for the binding of Pb2+ and Cu2+ to the Fe7S8 nanomaterial with ΔH values of 55.8 kJ/mol and 153.5 kJ/mol, respectively. Furthermore, the ΔS values for the reactions were positive indicating an increase in the entropy of the system after metal ion binding. Activation energy studies indicated the binding for both Pb2+ and Cu2+ occurred through chemisorption

Isotropic Wavelets: a Powerful Tool to Extract Point Sources from CMB Maps

It is the aim of this paper to introduce the use of isotropic wavelets to detect and determine the flux of point sources appearing in CMB maps. The most suited wavelet to detect point sources filtered with a Gaussian beam is the Mexican Hat. An analytical expression of the wavelet coefficient obtained in the presence of a point source is provided and used in the detection and flux estimation methods presented. For illustration the method is applied to two simulations (assuming Planck Mission characteristics) dominated by CMB (100 GHz) and dust (857 GHz) as these will be the two signals dominating at low and high frequency respectively in the Planck channels. We are able to detect bright sources above 1.58 Jy at 857 GHz (82% of all sources) and above 0.36 Jy at 100 GHz (100% of all) with errors in the flux estimation below 25%. The main advantage of this method is that nothing has to be assumed about the underlying field, i.e. about the nature and properties of the signal plus noise present in the maps. This is not the case in the detection method presented by Tegmark and Oliveira-Costa 1998. Both methods are compared producing similar results.Comment: 6 pages. Accepted for publication in MNRA

The combination of geomatic approaches and operational modal analysis to improve calibration of finite element models: a case of study in Saint Torcato church (Guimarães, Portugal)

This paper present a set of procedures based on laser scanning, photogrammetry (Structure from Motion) and operational modal analysis in order to obtain accurate numeric models which allows identigying architectural complications that arise in historical buildings. In addition, themethod includes tools that facilitate building-damage monitoring tasks. All of these aimed to obtain robust basis for numerical analysis of the actual behavior and monitoring task. This case study seeks to validate said methodologies, using as an example the case of Saint Torcato Church, located in Guimãres, Portugal

3D printing part orientation optimization: discrete approximation of support volume

In three-dimensional (3D) printing, due to the geometry of most parts, it is necessary to use extra material to support the manufacturing process. This material must be discarded after printing, so its reduction is essential to minimize manufacturing time and cost. An important parameter that must be defined before starting the printing process is the part orientation, which has repercussions on the quality, deposition path, and post-processing among others. Usually, the user sets up this parameter arbitrarily, so this paper takes advantage of it on optimization techniques and proposes an approximation of the volume be covered by the support material, which depends directly on the angle of the part to be printed and its geometry. Among mono-objectives optimization strategies, this work focuses on five of them. Their performance is compared by two metrics: support volume and execution time. Then, the best result is compared with commercial software

Lessons from the operation of the "Penning-Fluorescent" TPC and prospects

We have recently reported the development of a new type of high-pressure Xenon time projection chamber operated with an ultra-low diffusion mixture and that simultaneously displays Penning effect and fluorescence in the near-visible region (300 nm). The concept, dubbed `Penning-Fluorescent' TPC, allows the simultaneous reconstruction of primary charge and scintillation with high topological and calorimetric fidelity

Benchmarking Bipedal Locomotion: A Unified Scheme for Humanoids, Wearable Robots, and Humans

In the field of robotics, there is a growing awareness of the importance of benchmarking [1], [2]. Benchmarking not only allows the assessment and comparison of the performance of different technologies but also defines and supports the standardization and regulation processes during their introduction to the market. Its importance has been recently emphasized by the adoption of the technology readiness levels (TRLs) in the Horizon 2020 information and communication technologies by the European Union as an important guideline to assess when a technology can shift from one TRL to the other. The objective of this article is to define the basis of a benchmarking scheme for the assessment of bipedal locomotion that could be applied and shared across different research communities.European Commission Seventh Framework Program, and COS