Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms

Removal of Trichloroethylene by Clay Modified with Cationic Surfactant in Aqueous Solutions: Equilibrium, Kinetic, and Thermodynamic Study

Trichloroethylene (TCE) is commonly found in ground water, and it may serve as a major source of many types of cancers such as kidney, liver, lymphatic glands, and spinal cord. In the present research, TCE uptake from aqueous media by montmorillonite (Mt) modified by tetradecyl trimethyl ammonium bromide (TTAB) surfactant was explored. Firstly, the characteristics of raw and modified montmorillonite (raw-Mt and TTAB-Mt) were analyzed by SEM, FTIR, XRD, and XRF instruments. Then, the sorption process was evaluated as a function of different factors such as surfactant loading rate, pH, ionic strength, contact time, sorbent dosage, TCE concentration, temperature, and regeneration agent. The maximum TCE sorption by the modified clay was obtained at surfactant loading rate of 120 cation exchange capacity of the clay. The maximum removal efficiency of TCE by the modified clay was 99.6 at pH 5 and 30 min contact time. The findings also exhibited that the isotherm and kinetic sorption followed the Freundlich and pseudo-second-order models, respectively. It can be concluded that TTAB-Mt, as a cheap, abundant, non-toxic, and environmental friendly adsorbent can be considered to remove TCE in aqueous phase

Modern fiber laser beam welding of thenewly-designed precipitation-strengthened nickel-base superalloys

In thepresentresearch,themodern fiber laserbeamweldingofnewly-designedprecipitation- strengthened nickel-basesuperalloysusingvariousweldingparametersinconstantheatinputhasbeen investigated.Fivenickel-basesuperalloyswithvariousTiandNbcontentsweredesignedandproduced by VacuumInductionMeltingfurnace.The fiber laserbeamweldingoperationswereperformedin constant heatinput(100Jmm2) anddifferentweldingpowers(400and1000W)andvelocities(40and 100mms1) using6-axisanthropomorphicrobot.Themacro-andmicro-structuralfeatures,weld defects, chemicalcompositionandmechanicalpropertyof3.2mmweldmentswereassessedutilizing optical andscanningelectronmicroscopesequippedwithEDSanalysisandmicrohardnesstester.The results showedthatweldingwithhigherpowerscancreatehigherpenetration-to-widthratios.The porosity formationwasincreasedwhentheweldingpowersandvelocitieswereincreased.Noneofthe welds displayedhotsolidification andliquationcracksin400and1000Wweldingpowers,butliquation phenomenon wasobservedinalltheheat-affectedzones.WithincreasingtheNbcontentofthe superalloystheliquationlengthwasincreased.Thechangingoftheweldingpowerandvelocitydidnot alter thehardnesspropertyofthewelds.ThehardnessofweldsdecreasedwhentheTicontentdeclined in thecompositionofsuperalloys.Finally,the400and1000W fiber laserpowerswithvelocityof40and 100mms1 havebeenofferedforhotcrack-freeweldingofthethinsheetofnewly-designed precipitation-strengthenednickel-basesuperalloys

Decreased Serum Selenium Levels of COVID-19 Patients in Comparison with Healthy Individuals

Background: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is the cause of the COVID-19 pandemic and is the cause of increased mortality, especially among elderly patients and those who have severe complications, such as chronic pulmonary obstruction, hypertension, diabetes, and cancer. Nutrition, especially micronutrients, plays an important role in reducing mortality and complications from COVID-19 because micronutrients strengthen our immune system and nutritional status is an important factor that affects the outcome of patients with COVID-19. Among micronutrients, selenium has an important effect on both intrinsic and acquired immunity. Host selenium deficiency affects the viral genome and increases the virulence of viruses. We have investigated the serum selenium levels in COVID-19 patients and healthy control individuals. Methods: A total of 50 patients with COVID-19 infection were included in this study. During hospitalization, 13 patients died (non-survivor group) and 37 patients recovered (survivor group). We assessed the serum selenium levels in 50 COVID-19 patients and 50 healthy individuals by Agilent SpectrAA-240 Z atomic absorption spectrometer. Results: The serum selenium level was significantly lower in COVID-19 patients (77. 8 ± 13.9 μg/L) as compared to healthy control individuals (91.7 ± 16.7 μg/L), but there was no significant difference between the survivor and non-survivor groups. Also, there was no significant relationship between serum selenium levels and laboratory findings of COVID-19 patients. Conclusions: These results suggest that decreased serum selenium levels may be a risk factor for the COVID-19 infection, but there was no significant relationship between selenium and severity and mortality of COVID-19 disease. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature