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The removal of rare earth elements in mineral processing wastewater is highly desirable but still challenging. In this study, three bimetallic Prussian blue analogues (PBA) and six corresponding oxides are prepared by co-precipitation and calcination methods, and then utilized to adsorb aqueous Yb(III) solution. The results of XRD, SEM, BET, and XPS indicate the successful synthesis of all the adsorbents. Among them, three PBA-oxide samples (PBO-800) exhibit the superior adsorption capacities (˃250 mg/g). The adsorption processes of Yb(III) are in accordance with the pseudo-second-order kinetic model and Langmuir model, simultaneously showing the spontaneous and endothermic thermodynamics. Moreover, PBO-800 can be reused after alkaline solution regeneration with less than 10% degradation after five consecutive adsorption-desorption cycles. More importantly, PBO-800 exhibits the impressive separation selectivity of Yb(III) and most light rare earth ions (e.g., 5.51 of Yb/La, 4.03 of Yb/Pr), as well as the selectivity of Yb(III) and alkali metal ions (e.g., 300.5 of Yb/Na, 256.2 of Yb/Ca). According to the characterization analysis and DFT calculation, the adsorption mechanism of Yb(III) by PBO-800 is mainly attributed to the strong interaction between the abundant active-oxygen sites and Yb(III), and the significant electrostatic attraction.

The electrified cleaning agent requires a moderate volatilization rate, low ozone-depleting substances value, non-flammable, non-explosive and other characteristics. This study performed a whole life cycle assessment on a hydrocarbon-based electrified cleaning agent. The life cycle model is cradle-to-grave, and the background data sets include power grid, transportation, high-density polyethylene, chemicals, etc. The analysis shows that the global warming potential (GWP) of the life cycle of 1 kg of electrified cleaning agent is 2.08 kg CO2 eq, acidification potential (AP) is 9.49E-03 kg SO2 eq, eutrophication potential (EP) is 1.18E-03 kg PO43-eq, respirable inorganic matter (RI) is 2.13E- 03 kg PM2.5 eq, ozone depletion potential (ODP) is 4.91E-05 kg CFC-11 eq, photochemical ozone formation potential (POFP) is 2.89E-02 kg NMVOC eq, ionizing radiation-human health potential (IRP) is 3.16E-02 kg U235 eq, ecotoxicity (ET) is 2.69E-01 CTUe, human toxicity-carcinogenic (HT-cancer) is 4.32E-08 CTUh, and human toxicity-non-carcinogenic (HT-non cancer) is 2.31E-07 CTUh. The uncertainty of the results is between 3.46-9.95%. The four processes of tetrachloroethylene production, D40 solvent oil production, tetrachloroethylene environmental discharge during product use, and electricity usage during product disposal have substantial effects on each LCA indicator, so they are the focus of process improvement. Changes in power consumption during production and transportation distance of raw materials have little effect on total carbon emissions. Compared with the production process of single-solvent electrified cleaning agent tetrachloroethylene and n-bromopropane, the production of the electrified cleaning agent developed in this study has its own advantages in terms of carbon footprint and other environmental impact indicators. Carbon emissions mainly come from the power consumption of each process, natural gas production and combustion, and other energy materials for heating. It is recommended to use renewable raw materials instead of crude oil to obtain carbon credits based on geographical advantages, and try to use production processes with lower carbon emissions, while the exhaust gas from the traditional production process is strictly absorbed and purified before being discharged.

Herein, chemical activation of chitosan gel by KNO3 to prepare nitrogen-doped carbon. The sol-gel method enabled the activation agent KNO3 to be evenly dispersed in the carbon precursor, thereby ge...

Highly active and low-cost catalytic electrodes for oxygen evolution reaction (OER) are always crucial for obtaining clean hydrogen energy via large-scale electrolytic water splitting. Herein, endowing the nickel-iron phosphide (NiFeP) nanoprisms with the tunable electronic structures have been carried out by tailoring the energy level of d-band in our study. The bimetallic synergistic effect efficiently accelerates the formation and cleavage rates of M O bonding, enabling the greatly improved OER catalytic performance after doping Fe into Ni2P. The large surface area benefiting from the porous architecture also facilitates more contact between electrocatalyst and alkaline electrolytes, resulting in an advanced OER activity. Therefore, NiFeP can drive the OER process with a low potential of 258 mV at a current density of 10 mA cm−2 and a Tafel slope of 46 mV dec−1 in 1.0 M KOH solution. The present work provides the bimetallic phosphide nanoprism electrocatalyst with the tailored electronic structure for further application relevant to renewable energy exploration.

Microalgae are a renewable source of dietary supplements, bioactive compounds, and potential energy. Once harvested, the microalgal medium is dewatered to form a slurry for downstream processing. This article outlines a process design for pumping the microalgae slurry. The pump requirements for delivering the Chlorella slurry with 5, 10 or 20 wt% solids at one tonne per hour (1,000 kg/h) and 10 bar were calculated. The 5 wt% microalgae slurry is a Newtonian fluid with a viscosity of 1.95 mPaA—s. The 10 wt% and 20 wt% microalgae slurries are non-Newtonian fluids, whose viscosity depends on the shear rate (g). The viscosity of 10 wt% and 20 wt% microalgae slurries is 1.504 (g = 50 s -1 )/1.155 (g = 100 s -1 ) and 1.844 (g = 50 s -1 )/1.219 (g = 100 s -1 ) mPaA—s, respectively. The pump power requirements are mainly governed by the delivery pressure. The effect of the pipe length and the number of elbows is negligible. The effective power of the pump is calculated as 0.267-0.275 kW. To fulfill this duty, a ZGB type single-stage single-suction centrifugal slurry pump can be selected, which would provide enough shear rate to reduce the viscosity of the microalgae slurry and give required shaft power. Citation: Li, J., Qu, Y., Gong, Y., Yang, C., Yang, B., Liu, P., Zhang, B., and Ding, Y. (2020). Process Design of Microalgae Slurry Pump. Trends in Renewable Energy, 6(3), 234-244. DOI: 10.17737/tre.2020.6.3.00120

Development of sustainable routes to synthesize precious metal supported catalysts is of great importance because of their wide applications in the catalysis field. This paper reported a controllable and recyclable cation-assisted reduction route to fabricate a palladium nanoparticle supported catalyst. At 323 K, highly dispersed Pd/Al2O3-CARM was prepared through introducing M2+ (M = Mn, Zn or Cu) ions to promote the reduction of H2PdCl4 in ethylene glycol–water solution, and the residual filtrate after preparation could be recycled to prepare Pd/Al2O3 catalysts. A turnover frequency of 300 × 102 h−1 was obtained for Pd/Al2O3-CARMn in solvent-free aerobic oxidation of benzyl alcohol to benzaldehyde.

First-row non-precious metal-based catalysts are widely studied and recognized as potential substitutes for precious metal-based catalysts in the oxygen evolution reaction (OER) for hydrogen generation but their application remains challenging. In this study, a unique class of Co-Fe selenide hollow nanospheres (CoSe@FeSe2) is well-designed through a facile hydrothermal method. The in situ formed hybrid composites possess numerous interfaces allowing partial electron transfer via O2- bridges to optimize the adsorption feature of the reaction intermediates, *OH, *O, and *OOH, on the catalysts. The collected surface valence band spectra evidence the optimization of the intermediate adsorption and active sites. The as-synthesized CoSe@FeSe2 exhibits excellent OER activity with a low overpotential of 281 mV to drive a current density of 10 mA cm-2 and a low Tafel slope of 34.3 mV dec-1 in an alkaline electrolyte. Additionally, the advanced catalyst also shows super stability with negligible current density decay after 12 h. This work presents a prototype for the fabrication of highly efficient electrocatalysts using an electronic engineering strategy.

Nitrogen-doped porous carbon materials are a new type of electrode material with safety, nontoxicity, high conductivity and good electrochemical performance, which have recently attracted extensive attention due to its wide application in supercapacitors. In this work, carbon-based materials named ZBK-[Formula: see text] were prepared (where [Formula: see text] represents the different ratios of KNO3 used in the synthesis), using the nitrogen-containing organic molecule benzotriazole as a carbon and nitrogen source, and ZnCl2 and KNO3 as activators. These materials were mixed and heated at 350∘C for 1[Formula: see text]h and 750∘C for 2[Formula: see text]h under N2 to prepared porous carbon materials with a higher nitrogen content. The result had shown that material (ZBK-4) had a larger specific surface area (2292.47[Formula: see text]m2/g) and higher nitrogen and oxygen contents (4.88%[Formula: see text]N and 5.99% O). At the current density of 1[Formula: see text]A/g, the specific capacitance of ZBK-4 was 300[Formula: see text]F/g, indicating good rate capability. In addition, the specific capacitance of the material after 8000 cycles remained at 93.05%, indicating good cycle stability. Therefore, these experimental results have confirmed that the obtained nitrogen-doped porous carbon material has good electrochemical performance, and good prospects for application in the field of supercapacitors.

Advanced space materials are important to support the development of space technology. Their performance restricts the development of spacecraft to a great extent. However, the space environments encountered by spacecraft in orbit will lead to the degradation of material properties. The stability of the material in the space environment directly affects the performance level and service life of spacecraft. For the space radiation effects on space materials, a method to determine ground test parameters using depth-dose profile simulation is presented. By using this method, a ground test of the effects of space radiation environment in medium earth orbit for 8 years on carburized films was performed. The solar absorptance, infrared emittance, and surface resistivity of the test samples were measured. The results showed that the solar absorptance of the material changed significantly after irradiation, decreased by 10.3%, the infrared emittance decreased by 0.033, and the surface resistivity decreased slightly. The SEM photos indicated that the surface of the sample became rougher and there were more small holes. The XPS results indicated that the chemical bonds in the surface of samples changed under combined irradiation, and the C==O bond changed to C—O bond.

With the rapid development of artificial intelligence (Al) technology, machine understanding math word problems (MWPs) has received growing attention. However, existing methods of automatic understanding MWPs are hardly integrated into cognitive intelligent systems used for individual learning. To address the integration problem, this paper firstly clarified the relationship between understanding MWPs and discourse comprehension. According to the trait of discourse comprehension models, the existing methods were divided into knowledge schema-based methods and mental processing-based methods. Then we shortly presented the construction-integration model and proposed a conceptual framework for machine understanding MWPs. The proposed conceptual framework was established from long and short-term memory, cognitive computing services, formal representation models, and human-computer interaction. Finally, we draw a conclusion that integrating cognitive models of human understanding discourse into the process of machine understanding MWPs is conducive to developing a humanized cognitive intelligence system for personalized learning.

Nickel ion exchanged MCM-41 samples with different Si/Al ratios and Ni-ZSM-5/MCM-41 were prepared and used to catalyze ethylene oligomerization which was performed in a fixed bed model (T = 523 K, P = 2 MPa). A temperature programmed desorption of ammonia (NH3-TPD) method was employed to quantitatively determine the acid strength distribution of Ni-MCM-41 samples with different Si/Al ratios and Ni-ZSM-5/MCM-41. The TPD spectrum was analyzed by an interrupted-TPD method with desorption-control (dc-method) to obtain the desorption activation energy of ammonia, which can be used as acid strength scale for the purpose of correlation with catalytic activity. A quantitative relationship between catalyst acidity and catalytic activity was established by a Bronsted type equation. The site with desorption activation energy of ammonia E = 124 kJ mol−1 was found as the most suitable site for ethylene oligomerization. An approximate linear relationship is obtained between the activity of the ethylene oligomerization reaction and the acid amount corresponding to the acid site with E = 124 kJ mol−1.

Carbonate esters and esters were commonly used as solvents, reaction carrier, and additives in organic synthesis, the pharmaceutical industry, and processing industries. Vapor–liquid equilibrium (V...

Presently, many regeneration processes of waste lubricating oil, such as catalytic hydrogenation, are available. However, some of these processes are highly costly and not suitable for Chinese economic conditions, and some may produce contaminated impurities such as acid slag, which cannot meet environmental protection requirements. This study aims to develop a green process for the regeneration of waste lubricating oil into a base oil, which should meet the requirements of green chemistry, have the characteristics of simple operation, low cost, less pollution and high recovery rate, and turn wastes into renewable resources. The new process developed via this research has three stages. First, mechanical and large particle impurities in the waste lubricating oil were removed by pretreatment. Second, most of the colloid and asphaltene were removed by thermal extraction and sedimentation. Finally, the activated bleaching earth was used to further purify the waste lubricating oil. The performance evaluation of the finally obtained lubricating base oil conformed to the standard of the HVI-100 lubricating oil. The total recovery rate of the process was about 63.5%. Citation: Wu, J., Li, B., Wang, W., Yang, S., Liu, P., Yang, C., and Ding, Y. (2019). Green Refining of Waste Lubricating Oil: A China Perspective. Trends in Renewable Energy, 5, 165-180. DOI: 10.17737/tre.2019.5.2.0084

A novel titanosilicate zeolite was synthesized by a sequential treatment of ERB-1 with deboronation and atom-planting method to develop an epoxide catalyst. The Fourier transform infrared (FTIR) an...

Corresponding H- and Ni-form MWW zeolites were synthesized and compared to investigate the influences of the acidity strength and the synergetic effect of bifunctional sites on the catalytic performance for ethylene oligomerization and aromatization. The acidities of ERB-1 and MCM-22 zeolites with an MWW structure were adjusted via deboronation and desilication to synthesize MCM-56 and ITQ-1. The physicochemical properties of the catalysts were measured via XRD, EDS, EPMA, N2 sorption, SEM, FT-IR, pyridine adsorption FT-IR, NH3-TPD, XPS and H2-TPR studies. The effects of the acid strength and Ni/acid site ratio on the product distribution were studied at 523 and 723 K, which are two typical optimal reaction temperatures for oligomerization and aromatization, respectively. According to the characterization and catalytic performance results from this series of catalyst zeolites with similar structures and different acid sites, a fundamental mechanism involving different elementary steps for ethylene oligomerization and aromatization was proposed to explain the synergetic effect of acid and Ni sites on bifunctional MWW zeolites. The synergetic effect impact relating to different acid strength MWW zeolite structures shows that Ni ions on weak acidity zeolites are superior for ethylene conversion and determine the Anderson–Schultz–Flory product distribution at 523 K, and strong acid sites on MCM-22 are preponderant for ethylene conversion and dominate the product distribution at 723 K. Ni species are not only favorable for the dimerization of α-olefins at 523 K, but also for dehydrogenation, leading to the generation of aromatics at 723 K. Increasing zeolite acidity strength produces an obviously positive effect on the production of aromatics.

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The solubility of a solid in a given solvent is decided jointly by its thermodynamic stability and the solute-solvent intermolecular forces. The melting point and enthalpy of melting of 1,9‑Nonanedioic acid as well as its heat capacities at solid and melt state were determined by DSC. The solubilities of 1,9‑Nonanedioic acid in ethanol, acetone, acetic acid and ethylene glycol were measured at temperatures from 276 to 337 K. The solubilities in the four solvents at constant temperature are in the order of ethanol > acetic acid > acetone > ethylene glycol while the temperature dependence is in the opposite order. The experimental solubility data were correlated with the van't Hoff, Wilson and the λh equations with the measured melting properties. The three models with optimized parameters are all able to reproduce the experimental data well, among which the λh equations has lowest average standard deviation and seems to be more consistent with the experimental data. Thermodynamic analysis of the obtained model parameters shows that the dissolution of 1,9‑Nonanedioic acid in the four solvents are all endothermic and mainly driven by the enthalpy change of the solution. The positive excess enthalpy of mixing the 1,9‑Nonanedioic acid melt and the solvent indicates the solute-solvent intermolecular interactions are dominated by repulsive forces.

Regardless of online or offline learning, there are operational difficulties in “facing all students”, and it is very difficult to pay attention to the “individual differences” between students. As we all know, students are developing people. During the teaching process, students' mentality, knowledge, and abilities will change, which may shouldn't be taken into account by static grouping. In this study, neural network model was used to construct the mapping relationship between students' characteristics and heterogeneous grouping, and the trained model was used to predict the grouping position at the next moment. This dynamic grouping algorithm can ensure that every student is in a heterogeneous group for a long time. Finally, we propose a heterogeneous dynamic grouping teaching pattern.

The COVID-19 outbreak in early 2020 brought online learning to the forefront of education. Scholars in China and abroad have conducted many studies on online learning during the pandemic, but only a few have performed quantitative comparative analysis on this topic during and before the outbreak. The current paper presents social network analysis of a course hosted on China’s MOOC platform “icourse163”. Specifically, this study aimed to uncover (1) variations in the scale of online learning amid COVID-19; (2) the characteristics of online learning interaction during COVID-19; and (3) teachers’/teaching assistants’ authority over online learning before, during, and after COVID-19. Results revealed that the scale of online learning interaction increased greatly during the pandemic but was not effectively maintained once the outbreak was under control. Online learning interaction became more frequent during the pandemic and more effective thereafter. The roles of teachers/teaching assistants in online learning during the pandemic were not as noteworthy as expected.

With the development of the digital age, “digital learning and innovation” is becoming more and more important in the core literacy of information technology discipline. Through the elaboration of relevant concepts, this paper explores the connotation and concrete performance of “digital learning and innovation” literacy of senior high school students, and then obtains its three manifestations: the collection and management of digital learning resources, the adaptation of digital environment, the application and innovation of digital learning resources. On this basis, a questionnaire survey was designed to understand the status of “digital learning and innovation” literacy of high school students in S Middle School of Anhui Province, and the data results were analysed. It was found that senior high school students generally have this literacy, but some students still have some problems and need teachers’ timely guidance. Therefore, this study further proposes strategies for achieving high school students’ “digital learning and innovation” literacy to assist teachers in reminding students of “digital learning and innovation literacy” in teaching.

Mental models have been deeply concerned by researchers and practitioners since it plays a crucial role in problem-solving. In this study, we proposed mental models for random sampling word problems. On basis of the proposed mental models, we further performed a mental simulation with a rule-based mental reasoning method and a template-based approach to generate human-style explanations. And then we established an experiment on a prototype intelligent tutoring system. Experimental results showed that: the proposed mental models were available for most random sampling word problems; and a solution with human-style explanations to the problem encoded in mental models was produced effectively by means of mental reasoning. Based on these results, we concluded that our mental models can be used to encode essential information for solving random sampling word problems effectively, and it is profitable to take mental models into account when developing intelligent tutoring systems.