Guangzhou Institute of Geochemistry
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Zirconia on acid-treated halloysite as an efficient catalyst for conversion of mono-saccharides to 5-hydroxymethylfurfural
No full textAn acidic catalyst was designed for catalyzing conversion of fructose into 5-hydroxymethylfurfural through a two-step approach. First, the textural features and acidity of halloysite nano clay were improved via acidtreatment. Secondly, zirconia, an acidic catalytic species, was synthesized through a simple procedure and immobilized on the acid-treated halloysite, resulting in an effective catalyst with increased acidity. Analysis of the catalyst confirmed that both acid-treatment and the incorporation of zirconia enhanced the acidity of the catalyst and improved its activity. To optimize the yield of the product, Response Surface Method was used and the effects of various reaction variables were studied. According to the results, yield of 93 % of the product was achieved within 60 min at 80 degrees C by using 25 wt% of the catalyst. The kinetic study showed that the activation energy was 61.6 kJ/mol. Thermodynamic parameters were determined to be 70 kJ/mol for enthalpy, -60 J/mol for entropy, and 91.5 kJ/mol for Gibbs free energy, respectively. Notably, the catalyst demonstrated high recyclability with minimal leaching of zirconia. In addition to its effectiveness in catalyzing the conversion of fructose, the catalyst exhibited efficient performance in the conversion of other monosaccharides
Evolution of alkaline magmas and enrichment of rare earth elements: Insights from the geochemistry of apatite in the Saima alkaline igneous complex, Liaodong Peninsula, China
No full textRare earth element (REE) mineralization related to alkaline magmas is an important source of REEs, and some deposits are enriched in heavy REEs (HREEs). However, the mechanisms of HREE enrichment in alkaline igneous rocks are unclear. In this study, we conducted petrographic, U-Pb geochronological, and in situ elemental and isotopic analyses of apatite in the Saima alkaline igneous complex, Liaodong Peninsula, China, the aim was to constrain the HREE geochemical behavior during alkaline magma evolution. The Saima complex consists of hornblende-pyroxene syenite, biotite syenite, syenite, nepheline syenite, and lujavrite (in order of magmatic evolution). Apatite U-Pb geochronology has yielded Late Triassic (hornblende-pyroxene syenite: 223 f 5 Ma; biotite syenite: 220 f 3 Ma; syenite: 219 f 6 Ma; nepheline syenite: 219 f 10 Ma) ages. Apatite in the hornblende-pyroxene syenite, biotite syenite, and syenite has similar geochemical compositions and textures, contains melt inclusions, and is classified as type I apatite that formed in a purely magmatic system. Two types of apatite occur in the nepheline syenite. The type II apatite has high Sr/Y and non-chondritic Y/Ho ratios, contains melt inclusions and scarce fluid inclusions, and is formed in a H2O-saturated magmatic system. The type III apatite is characterized by abundant fluid inclusions and has higher Sr contents, Th/U ratios, and 147Sm/144Nd ratios than the other apatite types. It has lower light REE (LREE) contents and higher HREE contents as compared with the type II apatite and is formed by the reaction of type II apatite with Cl-rich fluids. The calculated REE patterns of the equilibrium melt, based on Dapatite- melt values, are different from the corresponding whole-rock geochemical data. This finding, combined with the results of a Rayleigh fractionation model, indicates that a crystal mush accumulation model can explain the generation of the Saima complex. The enrichment of volatile components (e.g., H2O) and crystal accumulation during the evolution of the magma mush were key controls on the anomalous HREE enrichment in the evolved rocks of the complex
The development of a pull-apart basin in response to collision of the irregular South China continental margin with Indochina
No full textThe collision of Indochina and South China has played a significant role in shaping the current tectonic configuration of ics are still debated. To better constrain the development and nature of the collision, we conducted a study of the Shiwandashan basin in the southwestern South China block that employed integrated basin analysis methods including detrital zircon prov similar to 200 km long and 60 km wide, and features a V-shaped cross-sectional profile. Our study reveals that the Lopingian Series in the basin thickens rapidly from the northwestern and southeastern edges toward the center of the basin. The formation of the basin appears to have been influenced by intense compressive strike-slip faults during the Lopingian Epoch. However, the sedimentary structures within the basin also display characteristics consistent with an extensional setting, including slump deposits and soft-sediment deformation, along with rapid depositional rates and abrupt changes in depositional facies. Furthermore, Lopingian to Early Triassic igneous rocks within the basin exhibit geochemical signatures that are indicative of an extensional setting. Provenance analyses reveal two distinct source areas controlled by basin contains detrital zircons dating from 297 Ma to 253 Ma, with a peak of 270 Ma, while a similar detrital zircon age peak is not found in the southeastern part of the basin. These findings suggest the coexistence of extensional and compressive structures and distinct sediment sources during the Lopingian. Our analysis provides new insights into the tectonic evolution of the Shiwandashan basin and suggests that it may have been a pull-apart basin influenced by the diachronous collision of the Indochina block with the irregular margins of the South China block
Electrochemically enhanced adsorption of perfluorooctanoic acid (PFOA) on CuO-CNTs composite electrodes
No full textWith the intensification of the global freshwater crisis, seawater desalination has emerged as a vital approach for obtaining freshwater resources. However, the presence of persistent pollutants in seawater poses new challenges to the desalination process. Among these, perfluorooctanoic acid (PFOA) has garnered significant attention due to its stability, bioaccumulative nature, and potential toxicity. While multi-walled carbon nanotubes (CNTs) exhibit high adsorption capacity, their effectiveness in PFOA removal remains limited. To address this, we synthesized copper oxide-modified CNTs (CuO-CNTs) and fabricated electrodes using a straightforward coating technique for electrochemically assisted PFOA adsorption. Our results demonstrate that CuO-CNTs electrodes achieved a 1.26-fold increase in the initial electrosorption rate and a 2.04-fold improvement in removal efficiency, reaching 89.25 % at 0.6 V compared to CNTs. The maximum electrosorption capacity also increased 1.69- fold at 0.6 V relative to 0 V. Furthermore, studies on adsorption mechanism and various ion strengths/ ion types/ pH provide important references for optimizing electrosorption technology in desalination. These findings contribute to improving the efficiency and effectiveness of contaminant removal during desalination, thereby enhancing the quality of desalinated water
High-temperature structural disorders stabilize hydrous aluminosilicates in the mantle transition zone
No full textHydrous aluminosilicates are important deep water-carriers in sediments subducting into the deep mantle. To date, it remains enigmatic how hydrous aluminosilicates withstand extremely high temperatures in the mantle transition zone. Here we systematically investigate the crystal structures and chemical compositions of typical hydrous aluminosilicates using single-crystal X-ray diffraction, electron probe microanalyzer, and nanoscale secondary ion mass spectrometry. These single crystals are synthesized at 15.5-22.0 GPa and 1400-1700 degrees C, featuring pervasive structural disorders. In particular, Al and Si atoms extensively occupy new tetrahedral and octahedral sites that are nominally vacant in their ordered counterparts. High temperature activates disorders leading to variable local crystal structures and more hydrogen incorporation into the crystal structure. This result suggests that the order-to-disorder transition holds the key to the high thermal stability of hydrous aluminosilicates, significantly affecting the water cycle in the deep mantle
Modulating interfacial electron transfer in hydrothermal carbon/ humboldtine to achieve superior heterogeneous Fenton reactivity and H2O2 utilization efficiency
No full textThe strategic enhancement of interfacial electron transfer dynamics between carbon and iron, coupled with the improvement of H2O2 ' s effective decomposition, is imperative for achieving significant progress in the field of iron-carbon-based heterogeneous Fenton catalysis. This study prepared a novel Fenton catalyst, namely hydrothermal carbon/humboldtine (HTC/Hum), where Fe(III) was totally reduced to Fe(II) during catalyst preparation process due to the highly effective electron transfer between carbon and iron. Consequently, HTC/Hum exhibits exceptional Fenton catalytic performance, which would achieve 100 % degradation of Bisphenol A (BPA) within 5 min, outperforming conventional carbon-iron materials by increasing BPA degradation and H2O2 utilization efficiency by 230-400 and 18-24 times, respectively. Density functional theory (DFT) calculations also indicated that the energy barrier for HO center dot escaped from HTC/Hum is significantly lower than the conventional catalysts. Xray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical analysis all demonstrated that the electron transfer from carbon to iron also occurred continuously in the HTC/Hum system during the Fenton reaction, facilitated by electrons from defects and persistent free radicals in HTC, promoting the redox cycle of Fe(III)/Fe(II). This study presents a novel strategy enhancing electron transfer and H2O2 utilization, with promising applications in environmental remediation
Nontarget screen and identify sulfate and sulfonate surfactants in personal care products using UHPLC-Q-Orbitrap-HRMS based on fragmentation characteristics and sulfur isotopologue pattern
No full textSulfate and sulfonate compounds are extensively used as anionic surfactants in personal care products (PCPs), which might pose adverse potential to human health. However, available research mostly identified certain subsets of sulfated and sulfonated surfactants based on target analysis. In this study, we developed a comprehensive nontarget strategy for identification of sulfated and sulfonated surfactants in PCPs using UHPLC-HRMS supplemented by an in-lab R script based on characteristic fragment ions and sulfur isotope patterns. A total of 20 sulfate and 12 sulfonate surfactants of confidence level 3 and above were identified in the range of alkyl chain length from C12 to C26 with 0-7 ethoxy groups and molecular weights of 200-600 Da in the PCP samples. The sulfates included 4 alkyl sulfates and 16 alkyl ether sulfates. In addition to commonly reported 4 alkyl benzene sulfonates, this study identified eight sulfonate surfactants for the first time, which were 3 alkyl sulfonates, 3 methyl ammonium sulfonates, and 2 bis-sulfonate sulfonates in the PCPs. Interestingly, 22 sulfate and sulfonate compounds were identified in the negatively labeled PCP samples which were not supposed to contain sulfate and sulfonate surfactants. The results demonstrated robustness of the developed nontarget analyzing strategy in identifying and characterizing sulfate and sulfonate surfactants and consequently providing guidance for management and regulation of chemical addition in PCPs to ensure safe use
Radiocarbon Fingerprinting Black Carbon Source History in the Himalayas
No full textBlack carbon (BC) is considered as an important contributor to the Himalayan glaciers melt in the past few decades. However, the long-term source apportionment of BC remains unclear. Here we present the first radiocarbon (14C)-based annual variation of BC source apportionment in an ice core spanning the period of 1959-2012 drilled from the Southeastern Tibetan Plateau, a receptor site of South Asia outflow. We find fossil fuel combustion is a major contribution (73% +/- 5%), yet the biomass burning fraction (& fnof;biomass) has grown from 24% +/- 4% to 30% +/- 4% since 1990. Intriguingly, we further find the & fnof;biomass demonstrating a robust correlation with South Asian wildfires linked to climate oscillations. Thus, for mitigating BC impacts on Himalayan glaciers, South Asia's transition from fossil fuels to clean energy is a more efficient and urgent strategy than reducing residential biomass burning
Mid-Late Holocene coral calcification dynamics: deciphering climatic and environmental effects
No full textOver the past four decades, a marked decrease in coral calcification has occurred across the world's tropical reefs, closely linked to climate change and the impact of human activity. However, how natural and human-induced factors influence coral calcification remains unclear due to limited understanding of the geological past. This study addresses this gap by investigating the calcification parameters of 82 Porites corals from the northern South China Sea, with growth periods covering distinct climatic epochs during the Mid-Late Holocene, including the Holocene Climate Optimum, 4.2 ka BP event, Medieval Climate Anomaly, Little Ice Age and Current Warm Period. Our findings show a gradual increase in coral skeletal density towards the present, and varied linear extension and calcification rates between warm and cold phases and between pre- and post-industrial periods. This suggests that temperature plays a pivotal role in controlling coral calcification, with contingent influences from volcanic activity and solar radiation. Notably, the linear extension and calcification rates were significantly reduced during the Current Warm Period, suggesting a surpassing impact of contemporary human activities over the natural variability on coral calcification. This raises concerns about the future prospects of coral reefs in the face of ongoing climate change and increasing impact of human activity
Distribution of bacterial 3-OH-FAs in Chinese saline lakes and its implication for paleoclimate reconstruction
No full textMicrobial communities in saline lakes are sensitive to environmental changes and showed promise for paleoclimate reconstruction. However, how the Gram-negative bacterial communities and their related membrane lipids, 3-hydroxy fatty acid (3-OH-FA), adapt to salinity change is still unclear. Here, we report the potential impacts of salinity and pH on 3-OH-FA distributions, based on saline lake samples, including lacustrine sediments and surrounding soils, collected from the Balikun Lake of the Xinjiang Province and 12 shallow lakes of the Inner Mongolia Province, China. Our results revealed that 3-OH-FAs in saline lakes are mainly derived from in situ production. The 3-OH-FA distributions are sensitive to salinity and pH variations. Specifically, in brackish lakes (< 30 parts per thousand), salinity and pH dominated the distribution of 3-OH-FAs. However, in hypersaline lakes, salinity predominated the 3-OH-FA distributions. Moreover, multiple linear regression has been used to explore the potential salinity proxies based on 3-OH-FAs. The result revealed the promising potential of using 3-OH-FAs for paleoenvironment reconstruction, which provides alternative tools for investigating the paleoclimate changes in saline environments