Molecular diffusion of CF\u3csub\u3e3\u3c/sub\u3eSF\u3csub\u3e5\u3c/sub\u3e in pure water and artificial seawater

We have experimentally determined the diffusion coefficient for trifluoromethyl sulfur pentafluoride (CF3SF5) in pure water and artificial seawater over a temperature range of − 2.0 °C to 30.0 °C. A working gas standard containing known concentrations of CF3SF5 and sulfur hexafluoride (SF6) was prepared. The working standard was allowed to diffuse across a water barrier, stabilized with agar gel, and the diffused gas was swept into a gas chromatograph with an electron-capture detector to measure the resulting gas mixing ratio. The mixing ratios for both CF3SF5 and SF6 were measured to determine the diffusivity for each species. The diffusion coefficient for SF6 was determined during these experiments as a check against existing literature values and to validate our experimental setup. The experimental data were fit to the Arrhenius equation to yield the following equations DCF3SF5 = 0.0015 exp (-12.9/RT) and DSF6 = 0.037 exp (-19.8/RT), where R is the gas constant in units of kilojoules per mole per kelvin and T is the temperature in kelvin. At the mean temperature of the ocean, 18 °C, DCF3SF5 = 7.02 × 10-6 ± 9.9% and DSF6 = 1.03 × 10-5 ± 13.8 % cm2/s. The diffusion coefficients for SF6 matched the literature data within 4.3% for all temperatures

Exploring the Reductive Pathway for the Hydrometallurgical Production of Copper from Chalcopyrite

The high demand for copper is coinciding with a sharp decline in the grade of copper reserves, and as a result, copper scarcities are expected to arise in the coming decades. In this work, a transformative hydrometallurgical process is being developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The focal point of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite may be reduced directly by the cathode of an electrochemical reactor, which is monitored by atomic absorption spectroscopy (AAS), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The efficiency of the electrochemical reaction is optimized by adjusting the electrode materials, applied current density, and reactor design. Chalcopyrite may also be reduced by reaction with the vanadium (II) ion, which circumvents engineering challenges associated with slurry electrodes but requires the separation and electrochemical regeneration of the vanadium (II) ion. A preliminary technoeconomic analysis suggests that both reduction pathways may be competitive with the pyrometallurgical standard for copper production. The performance of vanadium redox flow batteries (VRFBs) is hindered by the diffusion and migration of the vanadium species across the separator, however the migration of vanadium species has not been accurately measured or characterized with values of the transference numbers. In this work, models based on dilute solution theory and concentrated solution theory are developed to introduce the dimensionless ratio of migration to diffusion (M/D) to the literature. It is shown that transference numbers may be measured with high accuracy and precision for experiments conducted in the migration-dominated regime. An experimental procedure is designed to measure vanadium crossover as a function of current density for vanadium-containing electrolytes of various state of charge (SOC), state of discharge (SOD), and sulfuric acid concentration. Model-guided design of experiment is used to estimate the transference number of the vanadium species in Nafion 117 with minimal uncertainty related to unknown or unmeasured physical properties. Markov Chain Monte Carlo simulations are used to quantify the relative uncertainties of the transference number estimates to be less than five percent, consistently. The transference number estimates are related to faradaic efficiency loss and capacity fade of working VRFBs operating in the migration-dominated regime. The technique used in this work may be generalized to measure salt transference numbers in novel electrochemical systems and membrane separators to inform their rational design

Voltage Induced Variation of Solid Acid Catalyst Acidity

In biomass decomposition, acid groups catalyze the degradation of cellulose to form glucose. Liquid phase acid catalysts are commonly used for biomass conversion; however solid acid may be a more cost-effective approach since they obviate the need for dilute acid pretreatment. Currently, the required acidity of solid acid catalysts to hydrolyze cellulose is unknown. Here, we attempt to develop an electrochemical technique that effectively varies the acidity of solid acid catalysts. We applied voltage offsets to acidic SAMs at varying pH levels and characterized the fraction of protonated acid groups with EIS. The results indicated that SAMs degraded under the experimental conditions, and therefore, the factors that contributed to the stability of SAMs were investigated

Sonification of Chemical Engineering Data

Chemical Engineering concepts are generally taught using visual learning methods, which may hinder students that prefer alternate learning methods. The purpose of this study was to determine whether auditory learners benefit from auditory-based feedback. Multiple steady states (MSS) and PID control were presented through auditory means by sonifying temperature and heat output data streams. Twenty-three students completed a survey to determine their preferred learning modes, an assignment that presented MSS and PID control through auditory means, and a post-survey to assess whether they learned the material from the auditory component of the assignment. The data suggested that auditory learners benefit from auditory-based feedback, though the results were not statistically significant

The Reductive Leaching of Chalcopyrite by Chromium(II) Chloride for the Rapid and Complete Extraction of Copper

Abstract A hydrometallurgical process is developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The unique feature of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite reduction by chromium(II) ion is described for the first time and superior kinetics are shown. At high concentrate loadings of 39, 78, and 117 g L−1, chalcopyrite reacted completely within minutes at room temperature and pressure. The XRD, SEM‐EDS, and XPS measurements indicate that chalcopyrite reacts to form copper(I) chloride (CuCl). After the reductive treatment, the mineral products are leached by iron(III) sulfate to demonstrate the complete extraction of copper. The chromium(II) ion may be regenerated by an electrolysis unit inspired by an iron chromium flow battery in a practical industrial process