Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Life cycle optimization oriented to sustainable waste management and circular economy: A review
No full textLife cycle optimization (LCO) is an effective decision-making method combining life cycle assessment and optimization, which is capable of adjusting system configurations to meet specified sustainability goals. This study analyzed the status quo of LCO studies related to sustainable waste management and the circular economy. Most studies have focused on simultaneously optimizing environmental and economic objectives, whereas few have considered social impacts. Greenhouse gas emissions is the most commonly used environmental indicator in optimization, followed by the endpoint single-score indicator. A static deterministic model is often employed to formulate an LCO problem, while uncertainty and dynamic models are less frequently applied but cause concerns. To deal with multi-objective optimization, the epsilon-constraint method and non-dominated sorting genetic algorithm are popular. Waste LCO has been mainly applied to macro system planning, such as integrated municipal solid waste management systems, biowaste supply chains, waste-to-energy systems, and waste-to- resource networks, aiming to determine optimal waste allocation, facility capacity/location, technology choice, etc. It is occasionally used in optimizing process structure, operating conditions, blending ratio of feedstocks, and product development. Future research should focus on exploring the integration of more environmental and social indicators into multi-objective optimization, modeling under uncertainty, dynamic LCO, process and product optimization, and addressing the lack of multi-scale studies
Guangdong Pro-vincial Key Laboratory of New and Renewable Energy Research and Development[E439kf1201]
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Metal incorporated into magnetic hybrid covalent organic framework for high selective uptake of scandium ion
No full textThe growing demand for rare-earth elements (REEs) has led to the development of sustainable methods and materials for separating and recovering these critical metals (CM). Herein, metal was incorporated into a covalent organic framework (COF) via the solvothermal method for selective capture and uptake of scandium. The incorporation of metals into hybrid magnetic COF@COF materials has not been studied for CM's selective capture or recovery. The hybrid metal incorporated (MI-COF@COF) material shows good stability, fast kinetic, excellent selectivity, high affinity, and an enhanced adsorption capacity for scandium uptake (294.1 mg g(- 1), corresponding to 99.6 % adsorption efficiency), and robust reusability. The regression coefficient of the pseudosecond-order model achieves a higher value (R-2 = 0.999) and an equilibrium capacity of 53.5 mg g(- 1) with 98.5 % adsorption efficiency within 5 min. Notably, scandium is effectively separated with an efficiency of 94.0 % from red mud-leached solution in the presence of interfering ions. Aside from scandium, incorporating other metals into hybrid materials paved the way for economically feasible metal incorporation for targeted selective capture
Effect of particle size, water saturation, inorganic salt and methane on the phase equilibrium of CO2 hydrates in sediments
No full textUnderstanding the thermal stability of gas hydrate in complex marine geological environment is of importance to hydrate-based carbon sequestration. In this work, the factors affecting the equilibrium of CO2 hydrate in ocean sediments, including quartz sands, inorganic salts and gas impurities were quantitatively measured in a temperature range from 273 to 283 K and a phase equilibrium model of hydrate was established. To reveal the distribution in pore structure, the micro-morphologies of hydrate-bearing sediments were measured by cryo-SEM. Results showed that reduction of initial water saturation, addition of NaCl and CH4 were found to have inhibitory effect on CO2 hydrate equilibrium. Initial water saturation reduced the equilibrium temperature by the capillary pressure, but only 0.3-0.7 K temperature depression was observed as the water saturation reduced to 5 %. About 5.7 K in the average temperature depression was found by the addition of 10 wt% NaCl and 24 mol% CH4. NaCl and CH4 influenced the hydrate equilibrium by changing the water activity and chemical potential of hydrate water lattice. SEM images showed that the hydrate formed in pores of quartz sand had porous surface and coated the sand particles like a layer of cells which are 5-20 mu m in diameter, suggesting the hydrate layer exists between the liquid and gas phase. Based on the van der Waals-Platteeuw model, a hydrate equilibrium model was developed. The model provided a good prediction of the hydrate equilibrium in the presence of quartz sand, NaCl and CH4 with an averaged deviation of +/- 4.2 %, which had the potential to be applicated in more complexed ocean sedimentary environment
Enhanced electrochemical performance of ZrTe-Mn<sub>2</sub>O<sub>3</sub> nanocomposite electrocatalyst for HER and OER in alkaline medium
No full textElectrochemical energy conversion in renewable-energy technologies relies on the OER and HER towards next-generation fuels. Herein, we have coupled zirconia telluride (ZrTe) and manganese oxide (Mn2O3) nanosheets heterointerfaces by a facile hydrothermal method, which are engineered on stainless steel substrate (ZrTe-Mn2O3/SS). The physical properties, including crystallinity, phase purity, morphology, conductivity, and chemical interacted states of the developed composite, are systematically investigated by XRD, HRTEM, I-V, and XPS. The XPS observation showed unique redox properties of hydrogen peroxide species on the ZrTe-Mn2O3 catalyst and the oxidation state of Zr and Mn that was more easily changed in the ZrTe-Mn2O3 electrocatalyst compared with the pristine catalysts. The very decent electrochemical performance of the catalyst activation step (Mn3+-> Mn4+ and Zr2+-> Zr4+ oxidations) observed from electrochemical cyclic voltammetry (CV) and linear sweep voltammetry (LSV) studies that are tested in the alkaline environment. Concerning higher bifunctional activity for ZrTe-Mn2O3, the current density of 10 mA cm(-2) is revealed only at a lower overpotential of 244 mV and Tafel slope of 48 mV/dec toward better OER. At the same time, composite material also exhibited a minimal overpotential of 61 mV toward HER to attain 100 mA/cm(2). It was also found that introducing a connection of ZrTe with Mn2O3 improves the precise surface area and exposes more multi-active sites for easy transfer of electrons. In addition, it maintains excellent long-term stability for almost 110 hrs through chronoamperometry, which leads to no activity loss and further represents higher OER/HER activity in industrial applications. We conclusively demonstrate that the first-time reported research provides valuable insights attributed to the defective structure, porous nature, and covalently bridging between atomic-level heterogeneous interfaces, favouring rapid electron transfer process activation for continuously produced O-2 and H-2 gas bubbles
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