Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Key Research Program of Fron-tier Sciences, Chinese Academy of Sciences (CAS)[ZDBS-LY-SLH041]
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Isolation and characterization of ureolytic calcifying bacteria from methane hydrate-bearing marine sediments for bio-cementation application
No full textIn bio-calcification, microbes precipitate calcium carbonate (CaCO3), forming versatile solid substances that promotes eco-friendly materials and reduce carbon emissions. Marine bacteria can generate bio-cements to strengthen dikes and combat coastal erosion. However, the role of marine bacteria in generating bio-cements for enhancing coastal structures and combating erosion is not fully understood. This study investigates the potential of CaCO3 precipitating bacteria isolated from methane hydrate-bearing marine sediments. Five calcifying marine bacteria were isolated using Christensen's urea agar from marine sediments collected from Gawadar coastal, Pakistan. Bacterial strains induced CaCO3 precipitation producing urease enzymes. Strains were identified as Pseudomonas putida, Bacillus altitudinis, Vibrio sp., Bacillus sp., and Vibrio plantisponsor. Energy-dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray diffraction were applied for the identification and differentiation of calcite and vaterite precipitates. The growth of isolates and precipitation potential were observed optimum at 5% NaCl and pH 9.5-11. Bacillus altitudinis (ST4SD3) and Bacillus sp. (ST4SD1) produced more soluble Ca2+ (8532.53 mg/l and 7581.98 mg/l) as compare to other isolates at higher pH 10 and pH 11, favorable for CaCO3 precipitation. It is concluded that marine ureolytic bacteria possess significant potential for bio-cementation, which can stabilize methane hydrate-bearing sediments, improve soil properties, protect coastal regions from erosion, and crucial in the methane cycle, a greenhouse gas. We recommend further exploration of such bacteria's applications in marine construction and sediment stabilization to enhance the robustness and longevity of coastal infrastructures. Furthermore, such bacteria could also be beneficial in extracting gas from unconsolidated methane hydrates containing sediments
A study on the thermochemical conversion characteristics of biomass mixed blast furnace slag catalyst coupled in supercritical CO2/H2O atmosphere
No full textTo reduce excessive CO2 in the environment and reutilize waste blast furnace slag, thermochemical reduction methods have become a focus of attention. The waste blast furnace slag as the catalyst, thermochemical conversion of biomass and its mixed catalyst under supercritical CO2 (scCO2)/scCO2 mixed H2O atmosphere were compared to explore the best CO2 consumed condition. The composition and thermal stability of the raw materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometer (XRF), thermogravimetric analysis (TGA) and simultaneous thermal analysis (STA), while gas chromatograph (GC), gas chromatography mass spectrometer (GC-MS), scanning electron microscope (SEM), brunauer emmette teller (BET), fourier transform infrared spectrometer (FT-IR) and X-ray diffractometer (XRD) were used to analyze the properties of the products. As a result, the scCO2 atmosphere increased the consumption of CO2 during the reaction process compared to the N2 atmosphere. Under the scCO2 mixed H2O atmosphere, the addition of the catalyst resulted in the highest H2 yield of 5.90 +/- 0.01 mol/kg, led to an increase in HE from 58.17 % to 69.16 %, and also greatly facilitated the phenolic hydroxyl groups-OH and carboxyl groups C=O on the solid products to be detached from the aromatic ring. The specific surface area of the biomass reached the optimum value of 240.83 m2/g in the CHE7 when the characteristic peaks 002 and 100 intensities displayed high stack height and lateral dimensions
An alternative amino acid leaching of base metals from waste printed circuit boards using alkaline glutamate solutions: A comparative study with glycine
No full textOver the last decade, glycine has received significant attention as a green lixiviant, given its benign nature and selectivity. However, its application in leaching waste printed circuit boards faces limitations in production capacity. To address this challenge, the present study introduces alkaline glutamate (Glut) leaching as an alternative method. The glutamate leaching was found highly selective to Cu, Zn and Pb, and under the optimised conditions, 85.1 % Cu, 88.0 % Zn and 61.5 % Pb were extracted. Comparative analysis with glycine leaching revealed significant advantages of glutamate leaching. Glycine leaching with > 2 % solids resulted in limited Cu extraction and considerable Cu loss (30-65 %), due to the precipitation of oversaturated cupric glycinate. In contrast, 5 times higher solids content (10 %) could be accommodated in glutamate leaching. Furthermore, the Cu concentration in the leachate of alkaline glutamate leaching was found to be more than double that from glycine leaching (21.0 vs. 9.9 g/L)
Ultrasonic assisted in-situ synthesis of photocatalytic ZnO on PVDF membrane surface for fouling degradation
No full textAnimal carcasses can be harmlessly treated through high-temperature and high-pressure hydrolysis, resulting in the production of bioactive polypeptides. The polypeptides can be effectively separated from other impurities by ultrafiltration (UF) membranes technology. However, membrane fouling is inevitable during filtrating process, which significantly impacts their lifespan and economic efficiency. In this study, the photocatalyst ZnO nanoparticles on the PVDF membrane surface (PVDF/Zn) were fabricated to degrade foulant. Firstly, tannic acid (TA) was blended into the membrane to provide coordination sites to fix Zn2+. Then, ZnO nanoparticles was synthesized exclusively on the membrane surface under ultrasonic assistance, where the ultrasonic energy generated by the cavitation bubbles was excluded by the pore size. Chemical composition and morphology characterization were conducted to prove the successful synthesis of ZnO on the membrane surface. The PVDF/Zn membrane demonstrated a flux of 42 L m- 2h- 1 and a rejection of 97 % when filtering BSA solution, with a flux recovery rate (FRR) of 80 % after photocatalytic degradation. During the treatment of high-temperature and high-pressure hydrolyzed animal carcass solution (HHAS), the FRR exceeded 90 %, effectively separating impurities from polypeptides. This work provides a novel approach to enhancing the efficiency of treating HHAS and offers new insights into the preparation of photocatalytic membranes
Synergistic effect of carbon molecular sieve and alkali metal nitrate on promoting intermediate-temperature adsorption of CO2 over MgAl-layered double hydroxide
No full textThe development of intermediate-temperature adsorbents with high CO2 adsorption capacity is crucial for the tandem integration with CO2 hydrogenation catalyst, aimed at enhancing economy viability and minimizing energy consumption in Carbon capture, utilization and storage (CCUS). Although certain porous carbon materials (PCM) have been employed to enhance CO2 adsorption capability of layered double hydroxide (LDH), there remains an urgent necessity to identify more cost-effective and efficient PCM alternatives. Herein, alkali metal nitrates ((Li0.3Na0.18K0.52)NO3, hereafter referred to as LiNaK) modified layered double hydroxide (LDH)/carbon molecular sieve (CMS) composite (LiNaK-LDH/CMS) as promising adsorbents for CO2 capture was reported. The effects of CMS addition and nitrate loading, the calcination and adsorption temperature, as well as the cycling stability were investigated systematically. The results revealed that the CO2 capture capacity of the LiNaKmodified layered double oxide (LDO)/CMS composite (30 mol%LiNaK-LDO/CMS15%)-incorporating with 15 wt% CMS addition and 30 mol% nitrate loading-achieved a remarkable CO2 adsorption capacity of 1.32 mmol/g at 300 degrees C due to the synergetic interactions between CMS and nitrate; this represents nearly a sevenfold enhancement compared to initial LDO performance. Moreover, the 30 mol%LiNaK-LDO/CMS15% adsorbent also demonstrated commendable cyclic stability after ten adsorption/desorption cycles, retaining over 85 % of its initial adsorption capacity within half of adsorption time. Based on both obtained adsorption performance and characterization data from the adsorbents, a pre-adsorption enhancing CO2 intermediate-temperature adsorption mechanism over LiNaK-LDH/CMS composite through air calcination processes is proposed. This study significantly advances LDH-based adsorbent for future research into CO2 intermediate-temperature adsorption
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