Effect of moisture on the radon exhalation rate from soil, sand and brick samples collected from NWFP and FATA, Pakistan

A series of experiments were carried out to study the effectof the moisture content on the radon exhalation rate from soil,sand and brick samples that were collected from the North WestFrontier Province and Federally Administered Tribal Areas ofPakistan, using CR-39-based radon dosimeters. After processing,samples were prepared by adding 15, 30 and 45% moisture contents(by weight) and were placed in plastic containers. The dosimeterswere installed in it at heights of 25 cm above the surface ofthe samples. These containers were then hermetically sealedand the dosimeters were exposed to radon for 60 to 65 days.After exposure, CR-39 detectors were etched in 25% NaOH at 80°Cfor 16 h, and track densities were counted. From the measuredtrack densities, exhalation rate was determined using two differentapproaches. Maximum average radon exhalation rates of 385 ±86, 393 ± 31 and 362 ± 36 mBq m^–2 h^–1were observed at 30% moisture content from soil, sand and bricksamples, respectively. A slight decrease in exhalation ratewas observed in all samples at moisture content of 45%. Accordingto the t-test, change in the exhalation rate as a function ofhumidity is significant at 95% confidence level.     

Facile CO2 Separation in Composite Membranes

CO₂ emission from anthropogenic sources has raised worldwide environmental concerns and hence proficient energy paradigm has tilted towards CO₂ capture. Membrane technology is one of the efficient technologies for CO₂ separation since it is environmentally friendly, inexpensive, and offers high surface areas. Various approaches are discussed to improve membrane performance focusing mainly on permeability and selectivity parameters. Different types of fillers are incorporated to reach the Robeson's upper bound curve. In this review, polymer‐inorganic nanocomposite membranes for the separation of CO₂, CH₄, and N₂ from various gas mixtures are comprehensively discussed. Metal organic frameworks (MOFs) and ionic liquid (ILs) mixed‐matrix membranes are also considered.     

Annealing and Test Temperature Dependence of Tensile Properties of UNS N04400 Alloy

Effects of annealing and test temperatures on the tensile behavior of UNS N04400 alloy have been examined. The specimens were annealed at 800, 1000, and 1200 °C for 4 h under vacuum in a muffle furnace. Stress-strain curves of the specimens were obtained in the temperature range 25-300 °C using a universal testing machine fitted with a thermostatic chamber. The results indicate that the yield strength (YS), ultimate tensile strength (UTS), and percentage elongation of the specimens decrease with increase of annealing temperature. By increasing the test temperature, the YS and UTS decrease, whereas the percentage elongation initially decreases with increase of test temperature from 25 to 100 °C and then increases with further increasing the temperature up to 300 °C. The changes in the tensile properties of the alloy are associated with the post-annealing microstructure and modes of fracture.     

Effects of Plasma Nitriding on the Tensile Properties of Al-Mg-Si

Effects of plasma nitriding on the tensile behavior of Al-Mg-Si alloy were investigated in this study. The specimens were nitrided at 70?W input pulsed DC power at 1?mbar pressure of nitrogen for 4?h using glow discharge plasma. The formation of aluminum nitride layer on the specimen's surface was confirmed by the XRD analysis. Stress-strain curves of both un-nitrided and nitrided specimens were obtained using Universal Testing Machine. The comparison of these curves reveals that yield stress, ultimate tensile stress, percentage elongation, and stress relaxation rate decrease after plasma nitriding. The changes in the tensile properties after nitriding have been correlated with the changes in the microstructure of the specimens as observed using scanning electron microscope.     

Biotechnological recycling of critical metals from waste printed circuit boards

Critical metals are key raw materials for new generation clean energy production. The extraction of critical metals often follows the difficult processing of primary ores and they are many times recovered as the companion metals. With the depletion of primary reserves, the focus has now shifted to processing the urban mines, like electronic (e-)waste. Among the different types of e-waste, the waste printed circuit boards (WPCBs) are the major reservoir of high-value critical metals and are usually treated by the traditional pyro- and/or hydro-metallurgical techniques. However, the application of microbial activities in metals recycling is rapidly emerging as a green technology in comparison to smelter or chemical processing. The application of microorganisms (bacteria/fungi) in WPCBs’ recycling is being increasingly explored in order to meet the parallel objectives of resource recovery and pollution mitigation. Therefore, the present article assesses the current frontiers in bioleaching of critical metals from WPCBs and contains discussions on process fundamentals, challenges, and perspectives. The applicability of microbial recycling of WPCBs at a higher scale in terms of a circular economy and urban mining notion, the techno-economic analysis, and environmental sustainability in comparison to the chemical processing route are also discussed. © 2020 Society of Chemical Industry     

Valorization of solid waste biomass by inoculation for the enhanced yield of biogas

Clean Technologies and Environmental Policy - The current work reports experimental outcomes about anaerobic digestion (AD) of the organic fraction of catering solid waste to produce biogas and...