scholarly journals Sol-Gel Processes in Micro-Environments of Black Shale: Learning from the Industrial Production of Nanometer-Sized TiO2 Polymorphs

2019 ◽  
Vol 3 (1) ◽  
pp. 28
Author(s):  
Hans-Martin Schulz
Keyword(s):  
Black Shale ◽  
Industrial Production ◽  
Sol Gel ◽  
Low Ph ◽  
Ionic Exchange ◽  
Geochemical Processes ◽  
Pore Waters ◽  
Surrounding Matrix ◽  
Geochemical Reactions ◽  
Bulk Scale

Micro-environments in black shale are reactors for geochemical reactions that differ from the bulk scale. They occur in small isolated pores of several 10 s to 100 s of nanometers without or with limited ionic exchange by diffusion to the surrounding matrix. The example of the formation of titania polymorphs brookite (and anatase) in black shale demonstrates that pH < 4 of the pore waters or lower must prevail to enable dissolution of Ti-bearing precursors followed by the precipitation of these metastable solids. Comparably low pH is applied during the industrial production of nanometer-sized brookite or anatase by sol-gel methods. The process parameters during industrial production such as low pH, negative Eh, or low ionic strength (to promote agglomeration) allow a comparison with parameters during geochemical processes leading to titania formation in black shale. Sol-gel processes are suggested herein as key geochemical processes in micro-environments of black shale in order to understand the formation of single brookite crystals or agglomerates on a nanometer scale.

Control of Hierarchically Ordered Positive and Negative Replicas of Wood Cellular Structures by Surfactant-Directed Sol-Gel Mineralization

2002 ◽  
Vol 726 ◽  
Author(s):  
Yongsoon Shin ◽  
Jun Liu ◽  
Li-Qiong Wang ◽  
Jeong Ho Chang ◽  
William D. Samuels ◽  
...  
Keyword(s):  
Silicic Acid ◽  
Cell Walls ◽  
Cellular Structure ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Silica Particles ◽  
Low Ph ◽  
Cellular Structures ◽  
Inner Surface

AbstractWe here report the synthesis of ordered ceramic materials with hierarchy produced by an in-situ mineralization of ordered wood cellular structures with surfactant-templated sol-gel at different pH. At low pH, a silicic acid is coated onto inner surface of wood cellular structure and it penetrates into pores left, where degraded lignin and hemicellulose are leached out, to form a positive replica, while at high pH the precipitating silica particles due to fast condensation clog the cells and pit structures to form a negative replica of wood. The calcined monoliths produced in different pHs contain ordered wood cellular structures, multi-layered cell walls, pits, vessels well-preserved with positive or negative contrasts, respectively. The surfactant-templated mineralization produces ordered hexagonal nanopores with 20Å in the cell walls after calcination.

Molecular Building Blocks in Low PH Silicon Sol-Gels: A Silicon-29 NMR Study

1988 ◽  
Vol 121 ◽  
Author(s):  
Larry W. Kelts ◽  
Nancy J. Armstrong
Keyword(s):  
Sol Gel ◽  
Building Blocks ◽  
Low Ph ◽  
Tetraethyl Orthosilicate ◽  
Compact Ring ◽  
Molar Ratios ◽  
Molecular Building Blocks ◽  
Nmr Study ◽  
Ring Structures ◽  
Silicon Sol

ABSTRACTHigh field Silicon-29 NMR is used to study the structural intermediates in tetramethyl and tetraethyl orthosilicate (TMOS and TEOS) low pH sol-gel reactions. Linear oligomers as well as ring components of various sizes are identified and their evolution in the sols is followed. Differences in the number of compact ring structures are related to differences in gel times. Reactions are followed for various silicon alkoxide:water:acid molar ratios.

Synthesis and Characterizations of Titanium Tungstophosphate Nanoparticles for Heavy Metal Ions Removal

2016 ◽  
Vol 257 ◽  
pp. 187-192 ◽  
Author(s):  
Mohamed Ali Ghanem ◽  
Nezar H. Khdary ◽  
Abdullah M. Almayouf ◽  
Mabrook A. Salah
Keyword(s):  
Metal Ions ◽  
Surface Area ◽  
Self Assembly ◽  
Sol Gel ◽  
Bet Surface Area ◽  
Ionic Exchange ◽  
Characteristic Structure ◽  
X Ray ◽  
Heavy Metal Ions Removal ◽  
Metal Ions Removal

Ionic exchange of multi-components titanium tungstophosphate nanoparticles (TiWP-NPs) were prepared using sol-gel reaction of titanium isoperoxide and tungestophosphoric acid (TPA) in presence of CTAB surfactant. The X-ray, BET and TEM characterizations showed that the nanoparticles exhibit the characteristic structure of titanium tungstophosphate and a BET surface area of 74 ± 3 m2/g was achieved. The TPA has shown an effect on the self-assembly process and maintains the TPA content to minimum would be beneficial for obtaining higher surface area of TiWP nanoparticles. Metal ions adsorption of Cu(II), Pb(II) or Cd(II) using the resulting titanium tungstophosphate nanparticles materials is investigated and up to 95% removal percentage was achieved. Using this method, nanoparticles of ionic exchange titanium tungstophosphate can be synthesized in the form of powder and amenable to mass production.

Nano-Mg/Al hydrotalcite: Physicochemical Characterization and Removal of As(III) from Aqueous solutions

2014 ◽  
Vol 1616 ◽  
Author(s):  
E. Ramos-Ramírez ◽  
N. L. Gutiérrez-Ortega ◽  
G. Rangel-Porras ◽  
G. Herrera-Pérez
Keyword(s):  
Adsorption Isotherm ◽  
Aqueous Solutions ◽  
Natural Waters ◽  
Arsenic Removal ◽  
Sol Gel ◽  
Physicochemical Characterization ◽  
Chemical Characterization ◽  
Kinetic Studies ◽  
Isotherm Models ◽  
Ionic Exchange

ABSTRACTArsenic is one of the most toxic elements that can be found. Arsenic is mainly emitted by the copper, lead and zinc production, in agriculture as pesticides and herbicides. Two forms of arsenic are common in natural waters: arsenite (AsO33−) and arseniate (AsO43−), referred to as As(III) and As(V). The nano-Mg/Al-hydrotalcites present ionic exchange and adsorbent capacities. In this work, the physic-chemical characterization of nano-Mg/Al-hydrotalcites and his arsenic removal capacityis described. The solids were synthesized by the sol-gel method with Mg/Al=2 and 3 ratio. The solids and their thermal treated products were characterized by XRD, FTIR, DTA, TGA and N2 adsorption. The solids were used as adsorbents As(III) in aqueous solutions. Adsorption isotherm studies of As(III) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherm models. The As(III) adsorption isotherm data fit best to the isotherm Freundlich model. The maximum As(III) uptake capacity by nano-Mg/Al-hydrotalcites and the heated solids were determined using the Freundlich equation and were found to 547.46, 660.15, 799.88 and 739.12 mg As(III)/g HT-Mg/Al=2, HT-Mg/Al=3, HT-Mg/Al=2 at 350°C and HT-Mg/Al=3 at 350°C respectively. In the kinetic studies using 40 mg/L concentration of As(III) solutions was obtained an excellent removal capacity in contact times less at one minute.

scholarly journals Malonate and Carrot Root Respiration

1952 ◽  
Vol 5 (1) ◽  
pp. 64 ◽  
Author(s):  
Vera F Hanly ◽  
KS Rowan ◽  
JS Turner
Keyword(s):  
Organic Acid ◽  
Root Respiration ◽  
Direct Evidence ◽  
Succinic Dehydrogenase ◽  
Low Ph ◽  
Ionic Exchange ◽  
Carrot Root ◽  
Fermentation Products ◽  
Acid Cycle ◽  
Enzyme Systems

Following a review of earlier work with malonate as an enzyme and respiration inhibitor, direct evidence is provided of the existence in carrot root tissue of cytochrome oxidase and succinic dehydrogenase (S.D.). Malonate is clearly effective as an inhibitor of carrot root respiration only at low pH. Its effects at higher pH are, however, fully described and discussed. It is postulated that in this tissue a significant part of the respiration is mediated by enzyme systems not inhibited by malonate, KCN, or CO; that the remainder, whose activity is varied by wounding and aging, and by ionic exchange and uptake, involves an organic acid cycle of the Krebs type. The effects at low pH and low concentration of malonate (O.005-0.02M) may be explained as due to inhibition of succinic dehydrogenase only; under these conditions self reversal of inhibition, and reversal by addition of succinate, are both possible. At higher concentrations ( O.04-0.05M ) and low pH, malonate is assumed to inhibit not only S.D. but other enzymes concerned in pyruvate oxidation; this explains the lack of self reversal, lack of reversal by added succinate, and the failure to demonstrate accumulation of succinate in poisoned tissue; under these conditions, when inhibition is to the basal level, the RQ. is high, presumably because pyruvate is diverted to form fermentation products.

scholarly journals Green Synthesis and Characterization of High-Purity Monodispersed Cupric Oxide (CuO) Nanopowder

2019 ◽  
Vol 801 ◽  
pp. 351-356
Author(s):  
Yuan Teng Foo ◽  
Li Ting Foo ◽  
Ladan Shahcheragh ◽  
Bahman Amini Horri ◽  
Babak Salamatinia
Keyword(s):  
Green Synthesis ◽  
High Purity ◽  
Cupric Oxide ◽  
Sol Gel ◽  
Synthesis Method ◽  
Ionic Exchange ◽  
Synthesis Conditions ◽  
Calcination Temperatures ◽  
Optimum Synthesis ◽  
Exchange Material

In this study, high quality monodispersed nanocrystalline cupric oxide (CuO) nanopowder was prepared through novel sol-gel green synthesis method, assisted by sodium alginate (Na-ALG) as the green ionic exchange material. The morphology and structural properties of CuO nanopowders synthesized with and without the incorporation of extrusion dripping, at different Na-ALG solution concentrations and calcination temperatures, were studied using thermalgravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. Optimum synthesis conditions were identified, resulting in high-purity, monodispersed nanocrystalline CuO powder in the range of 9.92 – 12.4 nm, which could have a promising future in various applications.

pH-Sensitive Polymers for Novel Conformance-Control and Polymer-Flood Applications

2010 ◽  
Vol 13 (06) ◽  
pp. 926-939 ◽  
Author(s):  
Suk Kyoon Choi ◽  
Mukul M. Sharma ◽  
Steven L. Bryant ◽  
Chun Huh
Keyword(s):  
Polymer Solution ◽  
Polymer Concentration ◽  
Injection Pressure ◽  
Low Ph ◽  
Ph Sensitive ◽  
Solution Viscosity ◽  
Conformance Control ◽  
Polymer Flood ◽  
Geochemical Reactions ◽  
Acidic Conditions

Summary Novel conformance-control and polymer-flood applications that exploit the pH sensitivity of partially hydrolyzed polyacrylamide (HPAM) are proposed. The key feature of this process is the injection of the HPAM solution under acidic conditions. The low pH makes polymer molecules coil tightly, resulting in a very low polymer-solution viscosity. This allows the polymer solution to be injected into the reservoir at a substantially reduced injection pressure. Once injected, the acid reacts with the formation minerals to cause a spontaneous pH increase, uncoiling the polymer chains and causing a large increase in solution viscosity. Such a viscosity-control scheme can be exploited for placement of a concentrated polymer solution in high-permeability zones, where it later viscosifies to divert subsequently injected fluids (in-depth conformance control), or to reduce the high pressure drop near the wellbore during polymer injection (injectivity improvement). Extensive laboratory experiments were systematically performed and interpreted to evaluate the novel applications of pH-sensitive HPAM. The evaluations require (a) quantification of steady-shear viscosities, (b) characterization of geochemical reactions with acids, and (c) transport evaluation of HPAM solutions in cores. Rheological measurements show that shear viscosities of HPAM solution have a pronounced, but reversible, dependence on pH. The peak pHs observed in several shut-ins guarantee that spontaneous geochemical reactions can return the polymer solution to its original high viscosity. The use of a weak acid is the key. Coreflood results show that the HPAM solution under acidic conditions can be propagated through cores with much higher mobility than at neutral pH. However, low-pH conditions increase adsorption (polymer loss) and require additional chemical cost (for acid). The optimum injection formulation (polymer concentration, injection pH) will depend on the specific reservoir mineralogy, permeability, salinity, and injection conditions.

scholarly journals Analysis of Ionic-Exchange of Selected Elements between Novel Nano-Hydroxyapatite-Silica Added Glass Ionomer Cement and Natural Teeth

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3504
Author(s):  
Imran Alam Moheet ◽  
Norhayati Luddin ◽  
Ismail Ab Rahman ◽  
Sam’an Malik Masudi ◽  
Thirumulu Ponnuraj Kannan ◽  
...  
Keyword(s):  
Sol Gel ◽  
Glass Ionomer Cement ◽  
Energy Dispersive ◽  
Elemental Distribution ◽  
Ionic Exchange ◽  
One Pot ◽  
X Ray ◽  
Tooth Structure ◽  
Edx Analysis ◽  
Natural Teeth

One of the foremost missions in restorative dentistry is to discover a suitable material that can substitute lost and damaged tooth structure. To this date, most of the restorative materials utilized in dentistry are bio-inert. It is predicted that the addition of nano-HA-SiO2 to GIC matrix could produce a material with better ion-exchange between the restorative material and natural teeth. Therefore, the aim of the current study was to synthesize and investigate the transfer of specific elements (calcium, phosphorus, fluoride, silica, strontium, and alumina) between nano-hydroxyapatite-silica added GIC (nano-HA-SiO2-GIC) and human enamel and dentine. The novel nano-hydroxyapatite-silica (nano-HA-SiO2) was synthesized using one-pot sol-gel method and added to cGIC. Semi-quantitative energy dispersive X-ray (EDX) analysis was carried out to determine the elemental distribution of fluorine, silicon, phosphorus, calcium, strontium, and aluminum. Semi-quantitative energy dispersive X-ray (EDX) analysis was performed by collecting line-scans and dot-scans. The results of the current study seem to confirm the ionic exchange between nano-HA-SiO2-GIC and natural teeth, leading to the conclusion that increased remineralization may be possible with nano-HA-SiO2-GIC as compared to cGIC (Fuji IX).

scholarly journals Can pH and electrical conductivity monitoring reveal spatial and temporal patterns in wetland geochemical processes?

2013 ◽  
Vol 10 (1) ◽  
pp. 699-728 ◽  
Author(s):  
P. J. Gerla
Keyword(s):  
Electrical Conductivity ◽  
Organic Carbon ◽  
Dominant Role ◽  
Computer Code ◽  
Quality Data ◽  
Geochemical Processes ◽  
Spatial And Temporal Patterns ◽  
Water Quality Data ◽  
Wide Range ◽  
Geochemical Reactions

Abstract. Carbonate reactions and equilibria play a dominant role in the biogeochemical function of many wetlands. The US Geological Survey PHREEQC computer code was used to model geochemical reactions that may be typical for wetlands with water budgets characterized by: (a) input dominated by direct precipitation, (b) interaction with groundwater, (c) variable degrees of reaction with organic carbon, and (d) different rates of evapotranspiration. Rainfall with a typical composition was progressively reacted with calcite and organic carbon at various rates and proportions using PHREEQC. Contrasting patterns of the results suggest that basic water quality data collected in the field can reveal differences in the geochemical processes in wetlands. Given a temporal record, these can signal subtle changes in surrounding land cover and use. To demonstrate this, temperature, pH, and electrical conductivity (EC) were monitored for three years in five large wetlands comprising 48 sample sites in northwest Minnesota. EC and pH of samples ranged greatly – from 23 to 1300 μS cm−1 and 5.5 to 9. The largest range in pH was observed in small beach ridge wetlands, where two clusters are apparent: (1) low EC and a wide range of pH and (2) higher pH and EC. Large marshes within a glacial lake – till plain have a broad range of pH and EC, but depend on the specific wetland. Outlying data typically occurred in altered or disturbed areas. The inter-annual and intra-wetland consistency of the results suggests that each wetland system hosts characteristic geochemical conditions.

Sign in / Sign up

Export Citation Format

Share Document