Microwave-Assisted Synthesis of Nitrogen and Sulphur Doped Graphene Decorated with Antimony Oxide: An Effective Catalyst for Oxygen Reduction Reaction

In this study, we report on the facile synthesis of a novel electrocatalysts for the oxygen reduction reaction (ORR), based on reduced graphene oxide (RGO), functionalized with metallic and non-metallic elements. In particular, thanks to a fast one-pot microwave-assisted procedure, we induced, in the RGO graphene lattice, a combined doping with nitrogen and sulphur, and the simultaneous decoration with antimony oxide nanocrystals. The multi-doped–decorated material shows enhanced catalytic performance towards ORR, with respect to common nitrogen- or sulphur-doped carbon-based materials. The presence of co-doping is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analysis. The detailed electrochemical characterization shows the simultaneous effects of dopant atoms on the catalytic behavior. In particular, the importance of nitrogen and sulphur atoms in driving the oxygen absorption, together with the role of antimony in enhancing the electrochemical performance toward the ORR, are discussed.

Radiative Transfer Model Simulations for Ground-Based Microwave Radiometers in North China

Ground-based microwave radiometer profilers (MWRPs) are widely used to provide high-temporal resolution atmospheric temperature and humidity profiles. The quality of the observed brightness temperature (TB) from MWRPs is key for retrieving accurate atmospheric profiles. In this study, TB simulations derived from a radiative transfer model (RTM) were used to assess the quality of TB observations. Two types of atmospheric profile data (conventional radiosonde and ERA5 reanalysis) were combined with the RTM to obtain TB simulations, then compared with corresponding observations from three MWRPs located in different places in North China to investigate the influence of input atmospheric profiles on TB simulations and evaluate the quality of TB observations from the three MWRPs. The comparisons of the matching samples under clear-sky conditions showed that TB simulations derived from both radiosonde and ERA5 profiles were very close to the TB observations from most of the MWRP channels; however, the correlation was lower and the bias was obvious at 51.26 GHz and 52.28 GHz, which indicates that the oxygen absorption component in the RTM needs to be improved for lower-frequency temperature channels. The difference in location of the radiosonde and MWRP sites affected the TB simulations for the water vapor channels, but had little impact on temperature channels that are insensitive to humidity. Comparisons of both simulations (ERA5 and Radiosonde) and the corresponding TB observations from the three sites indicated that the water vapor channels observation quality for the MWRP located in southern Beijing needs improvement. For the two types of profile data, ERA5 profiles have a more positive effect on TB simulations in the water vapor channels, such as enhanced consistence, reduced bias and standard deviation between simulations and observations for those MWRPs located away from the radiosonde station. Therefore, hourly ERA5 data are an optimal option in terms of compensating for limited radiosonde measurements and enhancing the monitoring quality of MWRP observations within 24 h.

Packing size effect on the liquid circulation property in an external-loop packed bubble column

Packing size effects on the fluid dynamics in an external-loop packed bubble column with Raschig rings of three different effective diameters (5, 14 and 41 mm) in the riser were investigated. The overall gas holdup, liquid circulating velocity and gas-liquid mass transfer coefficient were respectively measured by volume expansion method, tracer-response method and dynamic oxygen-absorption technique. CFD simulation with the Euler-Euler two-fluid method was used to predict the liquid circulating velocity by treating the packing as a porous medium. Compared to the empty column, the gas holdup was found to increase with the presence of packing, however, the liquid circulating velocity and gas-liquid mass transfer coefficient may increase or decrease. Specifically, the gas holdup increases with the decrease of packing size, while the liquid circulating velocity is on the contrary, which induces the maximal gas-liquid mass transfer rate at packing diameter of 14 mm.

Study on Preparation of Oxygen Carrier Using Copper Slag as Precursor

Copper slag, an important by-product of the copper smelting process, is mainly composed of 2FeO SiO2, Fe3O4, and SiO2. Due to the sufficient metal oxides, copper slag is regard as a potential oxygen carrier (OC), which can be applied in chemical looping technology. This research proposed to use the granulated copper slag particles as precursor to produce oxygen carrier. Through this method, waste heat of the high-temperature slag can be fully recovered, eliminating the complicated copper slag pretreatment process. In this paper, the reactivity of granulated copper slag after redox calcination was studied by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM), the highest reactivity occurred at 1,000°C. In addition, the oxygen release and absorption performance of OC were tested in thermal-gravimetric (TG). According to theoretical calculations, the mass loss caused by oxygen release accounts for 70.57% of the total loss and the mass reached by 4.2% at 1,000°C in oxygen absorption experiment. The copper slag modified through calcining in redox condition was proved to be a promising oxygen carrier in chemical looping process. Furthermore, the performance research on OC also provided theoretical references for the operating paraments of OC circulating between air reactor and fuel reactor in practical chemical looping processes.

Study on the Effect of Polysulfide Content on the Micromorphology and Spontaneous Combustion Characteristics of Coal

This paper aimed to study the effect of the polysulfide content on the micromorphology and spontaneous combustion characteristics of coal, in order to develop more targeted prevention and treatment strategies. To this end, this study selected the method of mixing different sulfides with very low sulfur content raw coal to prepare the coal samples to be tested. Various parameters, such as true density, porosity, micromorphology, and oxygen uptake of the different sulfur samples, were tested. The results reveal that sulfide had a certain expansion effect on the coal body and improved the pore structure of coal, and the porosity increased with the increase of the sulfur content. After adding iron (II) disulfide (FeS2) and iron (II) sulfide (FeS) powder to the original coal sample, the number of fine particles on the surface increased significantly. After increasing the oxidation temperature, the lamellar structure disintegrated, and the massive coal body was broken into several fine particles, which promoted the spontaneous combustion of coal. Polysulfide promotes the low-temperature oxygen absorption of coal and shortens the natural firing period of coal. FeS has a slightly greater effect on increasing the tendency of coal to spontaneously combust and shortening the shortest natural firing period of coal. Before the addition of FeS2 and FeS to the coal samples, the coal production amount was not much different below 80–90°C, and then, the gap gradually widened. Under the same temperature condition of coal, carbon monoxide (CO) production basically occurred first as the sulfur content increased. When FeS2 and FeS were added, the sulfur content of the coal samples was 3 and 4%, respectively, and the production of CO and ethene (C2H4) was the largest. Although the peak areas of aliphatic hydrocarbon, aromatic hydrocarbon, hydroxyl group, and carbonyl group in the coal samples with FeS were different, they all reached their maximum value when the sulfur content was 4%.

Evaluation of the Potential of Modified Calcium Carbonate as a Carrier for Unsaturated Fatty Acids in Oxygen Scavenging Applications

Modified calcium carbonates (MCC) are inorganic mineral-based particles with a large surface area, which is enlarged by their porous internal structure consisting of hydroxyapatite and calcium carbonate crystal structures. Such materials have high potential for use as carriers for active substances such as oxygen scavenging agents. Oxygen scavengers are applied to packaging to preserve the quality of oxygen-sensitive products. This study investigated the potential of MCC as a novel carrier system for unsaturated fatty acids (UFAs), with the intention of developing an oxygen scavenger. Linoleic acid (LA) and oleic acid (OA) were loaded on MCC powder, and the loaded MCC particles were characterized and studied for their oxygen scavenging activity. For both LA and OA, amounts of 20 wt% loading on MCC were found to provide optimal surface area/volume ratios. Spreading UFAs over large surface areas of 31.6 and 49 m2 g−1 MCC enabled oxygen exposure and action on a multitude of molecular sites, resulting in oxygen scavenging rates of 12.2 ± 0.6 and 1.7 ± 0.2 mL O2 d−1 g−1, and maximum oxygen absorption capacities of >195.6 ± 13.5 and >165.0 ± 2.0 mL g−1, respectively. Oxygen scavenging activity decreased with increasing humidity (37–100% RH) and increased with rising temperatures (5–30 °C). Overall, highly porous MCC was concluded to be a suitable UFA carrier for oxygen scavenging applications in food packaging.

Penurunan Kecemasan melalui Senam Prolanis Pada Lansia

Indonesia has reached the phase of the old structured country because it has an elderly population which reaches 9.27% ​​of the total population. Problems experienced were increasing due to the prevalence in the elderly due to decrease capability of physical and mental. Prolanist exercises a form of physical exercise that was overcoming adversity in the elderly. This study aimed to study the effect of prolanist exercises on anxiety in the elderly in the working area of ​​the Sumberbaru Health Center. The design of this study was pre-experimental with a total sampling technique with a total sample of 29 prolanist members. Analysis of the data used was a paired t-test statistical test. The results obtained before prolanis exercises most of the elderly were at mild anxiety levels, with an average HARS score of 19.76. After prolanis exercises the elderly anxiety almost half are in the level of mild anxiety, with an average HARS score of 18.10. Based on statistical tests with a significance level of α = 0.05, the results obtained p value 0,000. Because the value of p <α (0.05), Ho was rejected. So there was an effect prolanist exercises for anxiety the elderly at the Sumberbaru Health Center. Prolanis exercises activities created social interaction between the elderly so that the elderly cannot feel isolated. Prolanis exercises also increase oxygen absorption, pain management, and trigger endorphins to created a sense of calm thereby reducing anxiety in the elderly.

The antioxidative-activity stability of aloe vera (Aloe vera var. chinensis) instant during storage

Aloe vera contains a phenolic compound that has bioactive activity. Previous research showed that microencapsulation of aloe vera powder with maltodextrin as an encapsulation agent produced instant aloe vera with high antioxidative activity. The problem was the hygroscopic instant caused rapid moisture and oxygen absorption during storage, therefore decreasing the instant aloe vera antioxidative activity periodically. The aim of this research was to evaluate the antioxidative activity stability of instant aloe vera during storage. The processing of instant aloe vera through a reconstituted aloe vera powder with water with a ratio of 1:120 and then added with 2.5% maltodextrin as the encapsulating agent. The solution was then inserted into a spray dryer with an inlet temperature of 130oC, an outlet temperature of 103oC, and the flow rate of the solution is 350.0 mL/h. The resulted instant aloe vera was divided into 15 packs with a weight of 25 g, and each sample was wrapped with polyethylene plastic film with 0.80 mm thickness and then was stored at 25oC with a relative humidity of 75%. The sample was conducted in triplicate. The moisture content, and antioxidative activity that was based on the ability to capture 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical (RSA) and lipid peroxidation inhibition were analyzed every week until the critical condition was achieved at a moisture level of 12%. The research showed that the radical scavenging activity (RSA) and lipid peroxidation inhibition of instant aloe vera before storage were 16.34±1.22% and 39.33±1.68%, respectively, whereas in the critical condition the RSA was 3.63±0.04% and the lipid peroxidation inhibition was 22.31±0.02%. Based on their antioxidative activity, the appropriate storage time of instant aloe vera was about 12 weeks in polyethylene plastic film of 0.08 mm thickness