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Carleo, I., Gandolfi, D., Barragan, O., Livingston, J. H., Persson, C. M., Lam, K. W. F., et al. (2020). The Multiplanet System TOI-421*. Astron. J., 160(3), 23 pp.
Abstract: We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P-b = 5.19672 +/- 0.00049 days, a mass of M-b = 7.17 +/- 0.66 M-circle plus, and a radius of R-b = R-circle plus, whereas the outer warm Neptune, TOI-421 c, has a period of P-c = 16.06819 +/- 0.00035 days, a mass of M-c = 16.42(-1.04)(+1.06)M(circle plus), a radius of R-c = 5.09(-0.15)(+0.16)R(circle plus), and a density of rho(c) = 0.685(-0.072)(+0.080) cm(-3). With its characteristics, the outer planet (rho(c) = 0.685(-0.0072)(+0.080) cm(-3)) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly alpha transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.
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Mejia, H. F. G., Toledo-Alarcon, J., Rodriguez, B., Cifuentes, J. R., Porre, F. O., Haeger, M. P. L., et al. (2022). Direct recycling of discarded reverse osmosis membranes for domestic wastewater treatment with a focus on water reuse. Chem. Eng. Res. Des., 184, 473–487.
Abstract: The recycling of discarded membranes (end-of-life) represents a relevant alternative for sustainability of reverse osmosis (RO) desalination plants in the context of circular economy. This work evaluated the feasibility of using discarded commercial RO membranes in the treatment of domestic secondary wastewater to obtain water with a certain standard quality. Crossflow filtration tests were conducted to evaluate desalination and wastewater filtration performance at different operating pressures on RO membranes discarded from desalination plans at different working positions (primary M1; secondary M2). The standard manufacturer desalination tests showed a superior performance on M1 membranes, in terms of rejection (similar to 25 LMH, 97%), compared to M2 (similar to 33 LMH, 50%); both having a lower performance than a standard membrane (38 LMH +/- 15%; 99.6%). The failure is sufficient for discarding due to loss of lifespan. Moreover, in wastewater filtration tests using the secondary clarifier outlet effluent from a WWTP at different working pressures, both types of membranes were shown to be effective, with degrees of performance highly dependent on the working pressure. Thus, the operating values of permeate flux/salt rejection were between 56 and 59 LMH/ 96-97% for 600 psi: 33-34 LMH/ 94-96% for 300-psi and in the range of 10-11 LMH/ 90-94% for 80-psi test. Surface characterization of the membrane showed a pressure-related increase in fouling and bacterial adhesion post-filtration. Finally, the operating performance was verified in M1 wastewater filtration at 300 psi over long times (14 h), yielding stable and promising values (similar to 27 LMH; 96%). The permeate obtained has a low concentration of fecal coliforms (< 2 MPN/ 100 mL, 99.99% removal) and meets local standards for irrigation and drinking water in terms of conductivity, phosphorus and nitrogen concentration in treated water. (c) 2022 Institution of Chemical Engineers.
Keywords: Desalination; RO membranes; Discarded; Secondary wastewater; Water scarcity
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Zuniga-Barra, H., Toledo-Alarcon, J., Torres-Aravena, A., Jorquera, L., Rivas, M., Gutierrez, L., et al. (2022). Improving the sustainable management of mining tailings through microbially induced calcite precipitation: A review. Miner. Eng., 189, 107855.
Abstract: Mining activities offers evident potential economic benefits for mineral rich countries. However, mining operations can produce a series of environmental impacts. Many of them are associated with the generation and management of tailings. Biogeochemical processes have potential to modify the properties of particulate solids, such as tailings. Microbial induced calcite precipitation (MICP) is probably the most studied biogeochemical process. It promotes calcite precipitation, as a result of biological activity of different microorganisms. Available research indicates that MICP is a tool that has the potential to contribute to a more sustainable management of tailing deposits. Indeed, MICP have been reported as a technology suitable for removal and/or immobilization of heavy metals, creation of impermeable barriers, prevention of soil liquefaction and control of windblown dust emissions. However, several challenges still need to be addressed to enable relible full-scale implementation, requiring research in the near future. These are consideration of the particular chemical composition of tailings, reduction of urea requirements, determination of optimal reagents dosage, evaluation of the long term stability of the treatment and calculation of costs associated to ecah particular application.
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