School of Water, Energy and Environment (SWEE)

Permanent URI for this community

https://dspace.lib.cranfield.ac.uk/handle/1826/8737

Browse

Browsing School of Water, Energy and Environment (SWEE) by Publisher "ACS"

Now showing 1 - 9 of 9
  • Thumbnail Image
    ItemOpen Access
    Bioaccumulation of Hg in rice leaf facilitates selenium bioaccumulation in rice (Oryza sativa L.) leaf in the Wanshan mercury mine
    (ACS, 2020-02-26) Chang, Chuanyu; Chen, Chongying; Yin, Runsheng; Shen, Yuan; Mao, Kang; Yang, Zhugen; Feng, Xinbin; Zhang, Hua
    Mercury (Hg) bioaccumulation in rice poses a health issue for rice consumers. In rice paddies, selenium (Se) can decrease the bioavailability of Hg through forming the less bioavailable Hg selenides (HgSe) in soil. Rice leaves can directly uptake a substantial amount of elemental Hg from the atmosphere, however, whether the bioaccumulation of Hg in rice leaves can affect the bioaccumulation of Se in rice plants is not known. Here, we conducted field and controlled studies to investigate the bioaccumulation of Hg and Se in the rice-soil system. In the field study, we observed a significantly positive correlation between Hg concentrations and BAFs of Se in rice leaves (r2 = 0.60, p < 0.01) collected from the Wanshan Mercury Mine, SW China, suggesting that the bioaccumulation of atmospheric Hg in rice leaves can facilitate the uptake of soil Se, perhaps through the formation of Hg-Se complex in rice leaves. This conclusion was supported by the controlled study, which observed significantly higher concentrations and BAFs of Se in rice leaf at a high atmospheric Hg site at WMM, compared to a low atmospheric Hg site in Guiyang, SW China.
  • Thumbnail Image
    ItemOpen Access
    Can a paper-based device trace COVID-19 sources with wastewater-based epidemiology?
    (ACS, 2020-03-23) Mao, Kang; Zhang, Hua; Yang, Zhugen
    A recent outbreak of novel coronavirus pneumonia (COVID-19) caused by SARS-CoV-2 infection has spread rapidly around the globe, with cases now confirmed in 130 countries worldwide. Although public health authorities are racing to contain the spread of COVID-19 around the world, the situation is still grim. About 158 111 confirmed cases and 5946 cumulative deaths (81 059 confirmed cases and 3204 cumulative deaths from China) have been reported around the globe as of March 15, 2020. Some clinical cases have found that some carriers of the virus may be asymptomatic, with no fever, and no, or only slight symptoms of infection. Without the ability to screen these asymptomatic patients quickly and effectively, these unsuspecting carriers have the potential to increase the risk of disease transmission if no early effective quarantine measures are implemented. Therefore, to trace unknown COVID-19 sources, fast and accurate screening of potential virus carriers and diagnosis of asymptomatic patients is a crucial step for intervention and prevention at the early stage.
  • Thumbnail Image
    ItemOpen Access
    Clay swelling: role of cations in stabilizing/destabilizing mechanisms
    (ACS, 2022-01-17) Chen, Wen L.; Grabowski, Robert C.; Goel, Saurav
    The stepwise hydration of clay minerals has been observed repeatedly in studies, but the underlying mechanism remains unclear. Previous numerical studies confirmed the presence of one-water layer (1W) and two-water layer (2W) hydration states. However, the undisturbed transition between these hydration states has never been captured. Using molecular dynamics simulation, this study (i) simulated for the first time the free 1W–2W transition during clay hydration and (ii) identified the underlying mechanism to be the detachment of cations from the clay surface and the formation of a shell of water molecules around the cation. The swelling dynamics of clay was found to be affected by the clay charge, clay mineralogy, and counterions through complex cation–clay interactions, cation hydration capacity, and cation migration rate.
  • Thumbnail Image
    ItemOpen Access
    CO2 capture performance of gluconic acid-modified limestone-dolomite mixtures under realistic conditions
    (ACS, 2019-07-10) Wang, Ke; Gu, Feng; Clough, Peter T.; Zhao, Pengfei; Anthony, Edward J.
    Calcium Looping (CaL) technology has become one of the most attractive ways to capture CO2 from fossil fuel power plants. However, with increasing numbers of cyclic reactions, the CO2 capture capacity rapidly decreases. To address this shortcoming, limestone-dolomite mixtures modified by gluconic acid were explored to prepare highly effective, MgO-stabilized, CaO sorbents that exhibited a high and stable CO2 capture capacity over multiple cycles. The sorbents were all tested over 10 carbonation-calcination cycles and were performed under realistic CaL conditions (calcination in a high CO2 concentration). The results of this research have demonstrated that the inhomogeneous composition that occurs between CaO and MgO - caused by the small CaO crystallite size, porous texture, nanosheet (~100 nm thick) morphology - provides sufficient void space for the volume expansion during carbonation to mitigate the effects of repeated cycle sintering and retain structural stability. A MgO content as low as 10 mol% was able to ensure a superior CO2 capture performance with a fast carbonation rate, high CO2 carrying capacities and remarkable stability. Furthermore, these sorbents retained a conversion (above 90%) over multiple cycles following a recarbonation step
  • Thumbnail Image
    ItemOpen Access
    Effect of seawater, aluminate cement and alumina-rich spinel on pelletised CaO-based sorbents for calcium looping
    (ACS, 2019-06-26) Morona, Lorena; Erans, María; Hanak, Dawid P.
    Calcium looping (CaL) is considered as an emerging technology to reduce CO2 emissions in power generation systems and carbon-intensive industries. The main disadvantage of this technology is reactivity decay over carbonation/calcination cycles due to sintering. The main objective of this study was to evaluate the performance of novel sorbents for CaL. Three types of pelletized CaO-based sorbents for CO2 capture were developed by adding aluminate cement, aluminate cement with seawater, or alumina-rich spinel to calcined limestone. Different concentrations of seawater in deionized water solutions were tested: 1, 10, 25, and 50 vol %. All samples were tested in a thermogravimetric analyzer (TGA) under two different calcination conditions: mild (N2 atmosphere and 850 °C during calcination) and realistic (CO2 atmosphere and 950 °C during calcination). The samples were characterized using SEM and EDX. Aluminate cement CaO-based sorbents exhibited better performance in the TGA tests (25% conversion after 20 cycles achieved by limestone and 35% with aluminate cement CaO-based pellets, under mild conditions, and 11% conversion after 20 cycles with limestone compared to 15% utilizing aluminate cement CaO-based pellets, under realistic conditions). However, doping had a negative effect on the reactivity of the sorbent. Moreover, alumina rich spinel CaO-based sorbents showed the worst performance.
  • Thumbnail Image
    ItemOpen Access
    Interactions between organic model compounds and ion exchange resins
    (ACS, 2019-07-22) Finkbeiner, Pascal; Moore, Graeme; Tseka, Tebogo; Nkambule, Thabo; De Kock, Lueta-Ann; Jefferson, Bruce; Jarvis, Peter Robert
    Ion exchange (IEX) can successfully remove natural organic matter (NOM) from surface water. However, the removal mechanism is not well understood due to the complexity and variability of NOM in real source waters as well as the influence of multiple parameters on the removal behaviour. For example, this includes the physicochemical properties of the NOM and IEX resin, and the presence of competing anions. Model compounds with a range of physical and chemical characteristics were therefore used to determine the mechanisms of NOM removal by IEX resins. Fifteen model compounds were selected to evaluate the influence of hydrophobicity, size and charge of organic molecules on the removal by ion exchange, both individually and in mixtures. Three different resins, comprising polystyrene and polyacrylic resin of macroporous and gellular structure, showed that charge density (CD) was the most important characteristic that controlled the removal, with CD of >5 meq mgDOC-1 resulting in high removal (≥89%). Size exclusion of compounds with high MW (≥8 kDa) was evident. The hydrophobicity of the resin and model compound was particularly important for removal of neutral molecules such as resorcinol, which was best removed by the more hydrophobic polystyrene resin. Relationships were identified that provided explanations of the interactions observed between NOM and IEX resin in real waters.
  • Thumbnail Image
    ItemOpen Access
    Large-area and clean graphene transfer on gold-nanopyramid-structured substrates: implications for surface-enhanced Raman scattering detection
    (ACS, 2022-03-16) Wu, Heping; Niu, Gang; Ren, Wei; Yang, Zhugen; Xu, Qihang; Dai, Liyan; Jiang, Luyue; Zhai, Shijie; Zhao, Jinyan; Zhang, Nan; Zhao, Libo; Jiang, Zhuangde; Zhao, Gang
    The transfer of large-area and clean graphene to arbitrary substrates, especially to those with raised nanostructures, represents a great challenge. Polymer-based supporting layers generally lead to organic residues, while graphene transfer using alternative supporting materials like paraffin suffers from breaking and thus limits the transfer area. We demonstrated an improved poly(methyl methacrylate) (PMMA)/paraffin double layer, enabling the large-area transfer of graphene with high cleanliness and high coverage (81%) onto gold nanopyramid (AuNP)-structured substrates. The impact of supporting layers including single PMMA or paraffin and mixed PMMA/paraffin was clarified. The properties of graphene on AuNPs were theoretically and experimentally examined in detail. Raman spectra show a polarization-dependent D peak due to the folding of large-curvature graphene. The graphene on AuNPs shows a slightly tensile strain and provides extra surface-enhanced Raman scattering (SERS) with an enhancement factor of ∼20 times. These findings open a pathway to extend the applications of transferred graphene on raised nanostructures in many fields, such as SERS detection, catalysis, biosensors, light-emitting diodes, solar cells, and advanced transparent conductors.
  • Thumbnail Image
    ItemOpen Access
    Preparation and characterization of lime/coal ash sorbents for sequential CO2 and SO2 capture at high temperature
    (ACS, 2021-06-23) Zhao, Zhenghui; Wu, Yinghai; Patchigolla, Kumar; Anthony, Edward J.; Oakey, John; Chen, Hongwei
    Extensive research has been done on Ca-based sorbents as a promising way to capture CO2 and SO2 from power plants. Considerable effort has also been directed toward maintaining sorbent activity by means of sorbent modification to deal with activity decay with repeated CO2 capture cycles. Based on the principle of “treating waste with waste” and inspired by the idea that a pozzolanic reaction can enhance the surface area, this paper presents a method of hydrothermal synthesis of lime and coal ash. A small amount of CaSO4 or NaOH was added during the hydration process and the mixture was stired for several hours at about 90oC. The synthesized samples were then characterised by scanning electron microscopy, nitrogen adsorption/desorption spectroscopy and X-ray diffraction. The activity of the synthesized sorbent for CO2 and SO2 capture were then tested in a thermogravimetric analyser. The treated samples demonstrate longer-lasting performance for CO2 cyclic capture, albeit with a slightly reduced capture ability compared to pure lime in the first few cycles due their lower CaO content (25~81% versus 98%). The sample with lime/ash mass ratio of 45:5 showed higher CO2 capture ability after three cycles and much greater stability in terms of their activity. The main product of the pozzolanic reaction is CaSiO3, which has a network structure, whose development is related to the ratio of CaO/coal ash, hydration duration and the amount of CaSO4 and NaOH additives. After high temperature calcination, a new phase, namely Ca3Al2O6 is believed to serve as a skeleton preventing sintering in repeated capture cycles. After experiencing multiple cycles, the synthesized sorbents also have a high SO2 capture capacity. A small amount of added NaOH decreases the cyclic CO2 carrying capacity of the synthesized sorbent but enhances SO2 carrying capacity dramatically. The explanation for this is that the sulphation reaction is controlled not only by gas diffusion but also by solid-state ion diffusion. Na+ ions generate more crystal lattice defects which can accelerate the ion diffusion rate in the product layer, and consequentially enhance overall SO2 carrying capacity.
  • Thumbnail Image
    ItemOpen Access
    Reaction mechanism and kinetics of the sulfation of Li4SiO4 for high-temperature CO2 adsorption
    (ACS, 2021-07-02) Yuan, Weiyang; Chen, huzhen; Qin, Changlei; Hanak, Dawid P.; Zhou, Xu
    CO2 adsorption is an important approach to control the excessive CO2 emission from energy and industrial plants and mitigating the greenhouse effect. As an acknowledged high-temperature adsorbent, Li4SiO4 shows advantages in capturing a large amount of CO2 with a fast reaction rate and excellent cyclic stability. However, its CO2 adsorption capacity would be significantly affected by the flue gas impurities, such as SO2 and O2. The underlying reaction mechanism of such impurities and Li4SiO4 is still unclear. For this reason, this work studied the reaction path and kinetics between Li4SiO4 and SO2 through experiments, thermodynamic calculations, and characterizations. The results showed that Li4SiO4 reacts with SO2 to produce Li2SiO3 and Li2SO4 in the presence of O2 at 500–700 °C and forms Li2SiO3 and Li2SO3 in the absence of O2 at 500–682 °C. Furthermore, this study revealed a very low activation energy of 7.47 kJ/mol for Li4SiO4 sulfation in the presence of O2 in the kinetic-controlled stage, and the value goes up to 249.7 kJ/mol in the diffusion-controlled stage. These results will provide valuable references for the industrial applications of CO2 adsorption by Li4SiO4.