The Experts below are selected from a list of 4179 Experts worldwide ranked by ideXlab platform
Yulong Ding - One of the best experts on this subject based on the ideXlab platform.
-
sodium nitrate Diatomite composite materials for thermal energy storage
Solar Energy, 2017Co-Authors: Guanghui Leng, Cenyu Yang, Haisheng Che, Li Cong, Yulong DingAbstract:Abstract The work reported in paper concerns the use of Diatomite to form-stabilise sodium nitrate, a phase change material (PCM) for medium temperature thermal energy storage applications. The composite was found to be able to retain up to 70% of the nitrate salt. X-ray diffraction (XRD) analyses suggested an excellent chemical compatibility between Diatomite and the salt. Scanning electron microscope (SEM) analyses demonstrated an even distribution of the salt within the Diatomite structure. Differential scanning calorimetry (DSC) measurements showed that melting temperature of the material was approximately 307.8 °C with a latent heat of 115.79 kJ/kg. Mechanical characterization of the composite material showed a compressive strength of the composite materials as high as 22.17 MPa. The composite materials were found to have a fairly low thermal conductivity of ∼0.5 W/m K and an addition of graphite could give a substantial thermal conductivity enhancement (∼6-fold with an additional of 10 wt% graphite).
-
sodium sulfate Diatomite composite materials for high temperature thermal energy storage
Powder Technology, 2015Co-Authors: Guanghui Leng, Hui Cao, Geng Qiao, Yunfeng Dai, Yelong Zhang, Yulong DingAbstract:This work explores the use of sodium sulfate and Diatomite to formulate composite materials for high temperature thermal energy storage applications. Sodium sulfate in the composite functions as a phase change material (PCM) and Diatomite as a structural skeleton for shape stabilization. It is found that sodium sulfate and Diatomite have an excellent chemical compatibility with the PCM melting temperature at around 880 degrees C It is shown that the composite containing 45% Diatomite gives an optimal formulation in terms of energy density, salt leakage and mechanical strength. The results also suggest that the composite with the optimal formulation has an application window of 890-980 degrees C Failures occur to the composite materials at temperatures above 1000 degrees C. (C) 2014 Elsevier B.V. All rights reserved.
Gustavo Garcia - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of zeolite y from Diatomite as silica source
Microporous and Mesoporous Materials, 2016Co-Authors: Gustavo Garcia, Edga Cardenas, Saul Cabrera, Jonas Hedlund, Johanne MouzoAbstract:Abstract Bolivian Diatomite was successfully used as a silica source for the synthesis of zeolite Y. Prior to synthesis, the Diatomite was leached with sulfuric acid to remove impurities and aluminum sulfate was used as an aluminum source. The raw materials were reacted hydrothermally at 100 °C in water with sodium hydroxide and different Na2O/SiO2 ratios were investigated. The final products were characterized by scanning electron microscopy, X-ray diffraction, gas adsorption and inductively coupled plasma-atomic emission spectroscopy. Diatomites originating from different locations and therefore containing different types and amounts of minerals and clays as impurities were investigated. After optimization of synthesis time, zeolite Y with low SiO2/Al2O3 ratio (3.0–3.9) was obtained at a high yield for high alkalinity conditions (Na2O/SiO2 = 0.85–2.0). Lower Na2O/SiO2 ratios resulted in incomplete dissolution of Diatomite and lower yield. Nevertheless, decreasing alkalinity resulted in a steady increase of the SiO2/Al2O3 ratio in zeolite Y. Consequently, it was possible to synthesize almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 for a Na2O/SiO2 ratio of 0.6, albeit at a low yield. In this respect, Diatomite enables the synthesis of high silica zeolite Y and behaves similarly to colloidal silica in traditional syntheses, with both sources of silica having in common a high degree of polymerization. Interestingly, the presence of minerals and clays in the starting Diatomite had marginal effects on the outcome of the synthesis. However, their dissolution resulted in presence of calcium and magnesium in the zeolite Y crystals. Finally, overrun of all investigated compositions resulted in the formation of zeolite P nucleating and growing onto dissolving zeolite Y crystals, which was shown to be triggered when aluminum was completely depleted at high alkalinity.
Guodong Sheng - One of the best experts on this subject based on the ideXlab platform.
-
new insights into the primary roles of Diatomite in the enhanced sequestration of uo22 by zerovalent iron nanoparticles an advanced approach utilizing xps and exafs
Applied Catalysis B-environmental, 2016Co-Authors: Guodong Sheng, Xiangke Wang, Pengjie Yang, Yanna Tang, Yuying HuangAbstract:Abstract In the current paper, nanoscale zero-valent iron (NZVI) was immobilized onto the negatively-charged Diatomite to obtain a novel composite (NZVI-D) for the enhanced sequestration of uranyl (U(VI)) in water. The as-synthesized NZVI-D was characterized by SEM, TEM and XRD in detail, and better dispersion of NZVI on Diatomite surface was observed, as compared with bare NZVI. The efficiency of U(VI) sequestration by NZVI-D was compared with that of commercial iron and bare NZVI. It was found that NZVI-D exhibits the best efficiency in U(VI) sequestration, showing obvious synergistic effect between Diatomite adsorption and NZVI reduction. The primary roles were further revealed by complementary macroscopic and spectroscopic studies. XPS results indicated that reduction of highly toxic and mobile UO22+ into less toxic and mobile UO2 could be enhanced using Diatomite-supported NZVI. EXAFS analysis demonstrated that Diatomite could react as a scavenger for insoluble products like UO2, and thus more reactive sites could be used for U(VI) reduction. Besides, Diatomite play multiple roles on pH buffering and preventing NZVI from aggregating and as adsorbent of Fe(II) produced in-situ during reaction for further U(VI) reduction. This study opens a new avenue for the practical application of NZVI and NZVI-D in environmental remediation.
-
characterization of Diatomite and its application for the retention of radiocobalt role of environmental parameters
Journal of Environmental Radioactivity, 2012Co-Authors: Guodong Sheng, Huaping Dong, Yimin LiAbstract:Abstract Clay minerals have been extensively studied because of their strong sorption and complexation ability. In this work, Diatomite was characterized by using acid–base titration. Retention of radionuclide 60 Co(II) from aqueous solution by sorption onto Diatomite was investigated by using batch technique under various environmental conditions such as pH, ionic strength, humic acid (HA), fulvic acid (FA), and temperature. The results indicated that the sorption of Co(II) onto Diatomite was strongly dependent on pH. At low pH value, the sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na + /H + on Diatomite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH value. The D–R model fitted the sorption isotherms better than the Langmuir and Freundlich models. The thermodynamic parameters (Δ H 0 , Δ S 0 and Δ G 0 ) calculated from the temperature-dependent sorption isotherms suggested that the sorption of Co(II) was an endothermic and spontaneous process. In addition, Diatomite showed higher sorption capacity than that of lots of the sorbents reported in the literatures we surveyed. From the results of Co(II) removal by Diatomite, the optimum reaction conditions can be obtained for the maximum removal of Co(II) from water. It is clear that the best pH values of the system to remove Co(II) from solution by using Diatomite are 7–8. Considering the low cost and effective disposal of Co(II)-contaminated wastewaters, the best condition for Co(II) removal is at room temperature and solid content of 0.5 g/L. The results might be important for assessing the potential of practical application of Diatomite in Co(II) and related radionuclide pollution management.
-
adsorption of pb ii on Diatomite as affected via aqueous solution chemistry and temperature
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009Co-Authors: Guodong Sheng, Suowei Wang, Yunhui Dong, Xiangke WangAbstract:Abstract To better understand the application of Diatomite as an adsorbent for the removal of Pb(II) from heavy metal-contaminated water, in this paper, Diatomite was used to adsorb Pb(II) from aqueous solution under various conditions. The results demonstrated that the adsorption of Pb(II) was strongly dependent on ionic strength at pH 7.0, and the adsorption at high pH values was mainly dominated via inner-sphere surface complexation. The presence of HA/FA showed great influence on Pb(II) adsorption on Diatomite. The adsorption of Pb(II) on Diatomite was dependent on foreign ions (herein K+, Na+, ClO4−, NO3− and Cl−) in solution at pH 8.0. The thermodynamic parameters (i.e., ΔH°, ΔS°, ΔG°) were evaluated from the temperature dependent adsorption isotherms. The results indicated that the adsorption process of Pb(II) on Diatomite was spontaneous and endothermic in nature.
-
sorption properties of th iv on the raw Diatomite effects of contact time ph ionic strength and temperature
Applied Radiation and Isotopes, 2008Co-Authors: Guodong Sheng, Jun Hu, Xiangke WangAbstract:Abstract Diatomite has a number of unique physicochemical properties and has diversified industrial uses. Natural Diatomite has been tested as a potential sorbent for the removal of Th(IV) from aqueous solutions. The results indicate that sorption of Th(IV) is strongly dependent on ionic strength at pH 3. Outer-sphere complexation or ion exchange may be the main sorption mechanism of Th(IV) to Diatomite at low pH values, whereas the sorption of Th(IV) at pH>3 is mainly dominated by inner-sphere complexation or precipitation. The competition for Th(IV) between aqueous or surface adsorbed anions (e.g., herein ClO4−, NO3− and Cl−) and surface functional groups of Diatomite is important for Th(IV) sorption. The thermodynamic data (ΔH0, ΔS0, ΔG0) are calculated from the temperature-dependent sorption isotherms. The results suggest that sorption process of Th(IV) on Diatomite is spontaneous and endothermic.
Johanne Mouzo - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of zeolite y from Diatomite as silica source
Microporous and Mesoporous Materials, 2016Co-Authors: Gustavo Garcia, Edga Cardenas, Saul Cabrera, Jonas Hedlund, Johanne MouzoAbstract:Abstract Bolivian Diatomite was successfully used as a silica source for the synthesis of zeolite Y. Prior to synthesis, the Diatomite was leached with sulfuric acid to remove impurities and aluminum sulfate was used as an aluminum source. The raw materials were reacted hydrothermally at 100 °C in water with sodium hydroxide and different Na2O/SiO2 ratios were investigated. The final products were characterized by scanning electron microscopy, X-ray diffraction, gas adsorption and inductively coupled plasma-atomic emission spectroscopy. Diatomites originating from different locations and therefore containing different types and amounts of minerals and clays as impurities were investigated. After optimization of synthesis time, zeolite Y with low SiO2/Al2O3 ratio (3.0–3.9) was obtained at a high yield for high alkalinity conditions (Na2O/SiO2 = 0.85–2.0). Lower Na2O/SiO2 ratios resulted in incomplete dissolution of Diatomite and lower yield. Nevertheless, decreasing alkalinity resulted in a steady increase of the SiO2/Al2O3 ratio in zeolite Y. Consequently, it was possible to synthesize almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 for a Na2O/SiO2 ratio of 0.6, albeit at a low yield. In this respect, Diatomite enables the synthesis of high silica zeolite Y and behaves similarly to colloidal silica in traditional syntheses, with both sources of silica having in common a high degree of polymerization. Interestingly, the presence of minerals and clays in the starting Diatomite had marginal effects on the outcome of the synthesis. However, their dissolution resulted in presence of calcium and magnesium in the zeolite Y crystals. Finally, overrun of all investigated compositions resulted in the formation of zeolite P nucleating and growing onto dissolving zeolite Y crystals, which was shown to be triggered when aluminum was completely depleted at high alkalinity.
Shuili Zheng - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of nano tio 2 Diatomite composite and its photocatalytic degradation of gaseous formaldehyde
Applied Surface Science, 2017Co-Authors: Guangxi Zhang, Yongwei Dua, Shuili ZhengAbstract:Abstract The TiO2/Diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO2 nanopartilces anchored on the surface of Diatomite with Ti–O–Si bonds between Diatomite and TiO2. The photodegradation of gaseous formaldehyde under UV irradiation by the TiO2/Diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO2/Diatomite composite exhibited better photocatalytic activity than pure TiO2, which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO2/Diatomite composite shows great promising application foreground in formaldehyde degradation.
-
characterization and improved solar light activity of vanadium doped tio2 Diatomite hybrid catalysts
Journal of Hazardous Materials, 2015Co-Authors: Guangxi Zhang, I Wang, Xue Leng, Shuili ZhengAbstract:Abstract V-doped TiO2/Diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol–gel method. The Diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/Diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V4+ ions substituted to Ti4+ sites. The 0.5% V-TiO2/Diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/Diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V4+ ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals O2–, while V5+ species presented on the surface of TiO2 particles in the form of V2O5 contributed to e––h+ separation. In addition, due to the combination of Diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.
-
a novel method for purification of low grade Diatomite powders in centrifugal fields
International Journal of Mineral Processing, 2013Co-Authors: Xiaoping Yang, Guangxi Zhang, Shuili Zheng, Ray L FrosAbstract:Abstract This study presented a novel method for purification of three different grades of Diatomite from China by scrubbing technique using sodium hexametaphosphate (SHMP) as dispersant combined with centrifugation. Effects of pH value and dispersant amount on the grade of purified Diatomite were studied and the optimum experimental conditions were obtained. The characterizations of original Diatomite and derived products after purification were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and specific surface area analyzer (BET). The results indicated that the pore size distribution, impurity content and bulk density of purified Diatomite were improved significantly. The dispersive effect of pH and SHMP on the separation of Diatomite from clay minerals was discussed systematically through zeta potential test. Additionally, a possible purification mechanism was proposed in the light of the obtained experimental results.
-
preparation and thermal energy storage properties of paraffin calcined Diatomite composites as form stable phase change materials
Thermochimica Acta, 2013Co-Authors: Yuzhong Zhang, Shuili Zheng, Yuri Park, Ray L FrosAbstract:Abstract A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined Diatomite through the fusion adsorption method. In this study, raw Diatomite was purified by thermal treatment in order to improve the adsorption capacity of Diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined Diatomite. The prepared paraffin/calcined Diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined Diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined Diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.